Both sides previous revision
Previous revision
Next revision
|
Previous revision
|
electrical:12v:drop-in_lifepo4 [2023/12/17 20:23] frater_secessus [and that Sterling video] |
electrical:12v:drop-in_lifepo4 [2025/05/04 14:19] (current) frater_secessus [drawbacks of lithium] |
[draft] | ====== Drop-in Lithium (LiFePO4) ====== |
| |
| ===== TL;DR ===== |
| |
| * the most common lithium chemistry for 'dwellers is LiFePO4 (LFP hereafter), an extremely stable version of Li-Ion. |
| * there are two basic types of LFP batteries: **drop-in** (pre-made retail batteries) and DIY (built from components by the user) |
| * LFP must not be charged in freezing temperatures. |
| * drop-in LFP have electronics (BMS) for to help prevent damage to the cells. |
| * most "problems" reported by LFP owners are user error / misunderstanding, not actual problems with the battery. Read the manual! |
| |
| |
| [[opinion:frater_secessus:pareto|about these summaries]] |
| |
| |
| |
| ===== overview ===== |
| |
[[lifestyle:words_of_wisdom|Words of Wisdom]]: "Pricing of lithium-ion batteries is slowly changing from obscenely expensive to only moderately unaffordable..." -- Rob Beckers((https://www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/)) | |
| |
| |
====== Drop-in Lithium (LiFePO4) ====== | |
| |
> [[https://amzn.to/3AL6Vn0|{{ https://m.media-amazon.com/images/I/61+q6waDSsL._AC_UL320_.jpg?125}}]] | > [[https://amzn.to/3AL6Vn0|{{ https://m.media-amazon.com/images/I/61+q6waDSsL._AC_UL320_.jpg?125}}]] |
"Drop-in" batteries are pre-built LiFePO4 (LFP) lithium (Li) batteries that are more or less the same size and voltage as lead-chemistry 12v batteries.((6S lead nominal voltage is 12.0v; 4S LiFePO4 voltage is 12.8v)) 100Ah is the most common capacity, but larger and smaller batteries do exist. | "Drop-in" batteries are pre-built LiFePO4 (LFP) lithium (Li) batteries that are more or less the same size and voltage as lead-chemistry (Pb((Lead is //Pb// on the periodic table. Lithium is //Li//)) hereafter) 12v batteries.((6S lead nominal voltage is 12.0v; 4S LiFePO4 voltage is 12.8v)) 100Ah is the most common capacity, but larger and smaller batteries do exist. |
| |
The other approach to lithium is **DIY**((do it yourself)), where one selects cells, BMS, and other components and builds it themselves. That topic is beyond the scope of this article. People interested in DIY might want to read the [[https://diysolarforum.com/forums/diy-lifepo4-battery-banks.22/|DIY LiFePO4 Battery Banks subforum]] over on DIY Solar. You can also see the [[electrical:12v:lifepo4_batteries_thread|Lithium Battery Summary]] article for high points of a debate on lithium suitability for long term use. | The other approach to lithium is **DIY**((do it yourself)), where one selects cells, BMS, and other components and builds it themselves. That topic is beyond the scope of this article. People interested in DIY might want to read the [[https://diysolarforum.com/forums/diy-lifepo4-battery-banks.22/|DIY LiFePO4 Battery Banks subforum]] over on DIY Solar. You can also see the [[electrical:12v:lifepo4_batteries_thread|Lithium Battery Summary]] article for high points of a debate on lithium suitability for long term use. |
| |
The [[https://diysolarforum.com/|DIY Solar Forums]] are a good place to check for updated info, as well as links to teardown reviews and disassembly videos where the internal component quality has been given a detailed review. | The [[https://diysolarforum.com/|DIY Solar Forums]] are a good place to check for updated info, as well as links to teardown reviews and disassembly videos where the internal component quality has been given a detailed review. |
===== Drop-in lithium benefits ===== | |
| |
* Drop-ins are ready to use. Buy it, install it. | |
| |
| ===== benefits of lithium ===== |
| |
===== Drop-in lithium limitations ===== | * LFP has very low internal resistance, so they will display less [[electrical:12v:voltage_sag|voltage sag]] and can charge/discharge at up to 1[[electrical:12v:battery_capacity|C]], or 100A for a 100Ah bank. Note that for longevity reasons this is often restricted to 0.5C, or 50A for a 100Ah battery.((even lower C-rates like 0.2C are optimal for longevity)) |
| * If treated properly LFP can have many times the cycle life of Pb.((treated improperly they can suffer a sudden death)) |
| * LFP are not vulnerable to [[electrical:12v:psoc|partial states of charge]] like Pb. If anything they //prefer// sitting at PSoC. |
| * LFP charges more efficiently than Pb, so less charging power is wasted. Solar charging in particular will act larger than it is. |
| * flat voltage curve - stable voltage over much of its state of charge |
| * very little reduction of capacity at higher discharge rates compared to lead((there is a non-Peukert mechanism that starts to attenuate apparent capacity at very high C rates)) |
| * Li batteries (Li) have greater energy density than lead (Pb), so are smaller for a given capacity. They are also much lighter for the same capacity. |
| |
* Drop-in batteries are typically "black boxes" with no practical way tell what is going on inside. Some do have bluetooth or other methods to interact with the insides. | **Specific to drop-ins:** ready to use; no building required. |
* Drop-ins are not always repairable. Some, like SOK metal-cased batteries are reportedly repairable. | |
* Drop-ins are very expensive compared to [[electrical:12v:lifepo4_batteries_thread|DIY lithium]] | |
| |
| ===== drawbacks of lithium ===== |
| |
===== overall lithium benefits ===== | * Li has (historically at least) been relatively expensive up front. Prices started plummeting somewhere around 2024. |
| * Li cells need a [[#bms_functions|BMS]] to protect them from damage.((some DIYers run Li "barefoot" (without a BMS) )) For example, Li can be damaged by overvoltage, undervoltage, charging below freezing (32F), etc. Some batteries have low-temp cutoff and/or internal heating to address the cold-charging limitation. Most Drop-in Lithium batteries will have a BMS integrated into them, but raw cells do not. |
| * Li can be **damaged** by long duration at full charge or high voltage, or high ambient temperatures |
| * the flat voltage curve makes gauging SoC by voltage extremely challenging, and battery "gauges" designed for lead chemistry batteries will not work. An amp-counting [[electrical:12v:battery_monitor|battery monitor]] will be more useful with Li. |
| * LFP's nominal 12.8v is slightly higher than PB's nominal 12.0v. This can cause subtle misbehavior on components that are [[electrical:12v:alternator#gotchas|expecting a specific trigger voltage]]. |
| |
* Li batteries (Li) have greater energy density than lead (Pb), so are smaller for a given capacity. They are also much lighter for the same capacity. | **Specific to drop-ins:**: can be "black boxes" with no practical way tell what is going on inside. Some do have bluetooth or other methods to interact with the insides. Of course, lead batteries are black boxes, too. Although technical folks would be curious to know the inner workings, it is not a given that Normal People require that information. |
* Li batteries have very low internal resistance, meaning they can charge/discharge at up to 1[[electrical:12v:battery_capacity|C]], or 100A for a 100Ah bank. Note that for longevity reasons this is often restricted to C/2, or 50A for a 100Ah battery. | |
* If treated properly Li can have many times the cycle life of Pb.((treated improperly they can suffer a sudden death)) | |
* Li batteries are not vulnerable to [[electrical:12v:psoc|partial states of charge]] like Pb. If anything they //prefer// sitting at PSoC. | |
* flat voltage curve - stable voltage over much of its state of charge | |
* very little reduction of capacity at higher discharge rates compared to lead((there is a non-Peukert mechanism that starts to attenuate apparent capacity at very high C rates)) | |
* much less voltage sag under heavy loads | |
| |
| |
| |
===== overall lithium limitations ===== | ===== choosing a drop-in LFP battery ===== |
| |
* Li is relatively expensive | There are many factors here which only you will be able to assess. |
* Li cells need a [[#bms_functions|BMS]] to protect them from damage.((some DIYers run Li "barefoot" (without a BMS) )) For example, Li can be damaged by overvoltage, undervoltage, charging below freezing (32F), etc. Some batteries have low-temp cutoff and/or internal heating to address the cold-charging limitation. Most Drop-in Lithium batteries will have a BMS integrated into them, but raw cells do not. | |
* Li can be **damaged** by long duration at full charge or full discharge. | ==== voltage ==== |
* the flat voltage curve makes gauging SoC by voltage extremely challenging, and battery "gauges" designed for lead chemistry batteries will not work. An amp-counting [[electrical:12v:battery_monitor|battery monitor]] will be more useful with Li. | |
| Most 'dwellers will use **12v (12.8v) LFP banks**. Higher voltages are available but the use cases that require those voltages are beyond the scope of this article. |
| |
| |
| ==== capacity ==== |
| |
| If you are **replacing a lead-chemistry bank** whose capacity met needs, you can find the equivalent in LFP by multipying the lead capacity by 0.625. For example, if your 200Ah lead bank met needs it would require ~125Ah of LFP to replace it. |
| |
| If you are **starting from scratch** (no existing battery bank) it's a bit of math like any other bank: |
| |
| * [[electrical:12v:dailypowerrequirements|daily power requirements]] x [[electrical:autonomy|days of autonomy]] / usable percentage((80% in the case of LFP)) |
| |
| Example: if you needed 1,500Wh/day and wanted two days of autonomy, you would require 3,750Wh of LFP.((~293Ah)) (1,500Wh x 2 days / .8 usable) |
| |
| |
| ==== BMS features and specs ==== |
| |
| Roughly from most common to least common: |
| |
| |
| === low cell voltage discharge cutoff === |
| |
| LFP cells can be damaged by undervoltage. Discharge is typically disabled when one or more cells drops to ~2.625v (~10.5v for the pack) |
| |
| If the BMS has shut down due to low voltage/SoC it usually requires external voltage to "wake" it. Connect another battery, start the vehicle if [[electrical:12v:alternator|alternator charging]] is present, [[electrical:12v:self-jumpstarting|self-jumpstart]], etc. Read the battery manual for specifics. |
| |
| |
| === high cell voltage charge cutoff === |
| |
| |
| LFP cells can be damaged by overvoltage. Charging is typically disabled when one or more cells rises to ~3.65v (~14.6vv for the pack) |
| |
| === high temperature charge/discharge cutoff === |
| |
| LFP cells can be damaged by use at high temperatures, so the BMS will disable use at extreme temperatures. |
| |
| |
| === charge/discharge overcurrent cutoff === |
| |
| |
| The BMS will have stated charge/discharge limits. They may be the same or different; when they are different the discharge current limit is usually higher than the charge current limit. Examples in a 200Ah battery might be: |
| |
| * 200A charge, 200A discharge |
| * 100A charge, 150A discharge |
| * etc |
| |
| Note that **just because you can charge/discharge at higher rates doesn't mean you have to or that you should**. Generally speaking LFP prefers current to stay around 0.2C (40A for our 200Ah example) for longevity and cell balance. Also if you will only ever need to discharge at 75A then a 200A BMS is not required. |
| |
| |
| === low temperature (~freezing) charge cutoff === |
| |
| [not present in all BMS] |
| |
| LFP cells are damaged by charging when the cells are at ~freezing temperatures.((discharging too, but the limits are much colder)) |
| |
| Lack of **low temperature cutoff** is not necessarily a deal-breaker. Maybe you live in a hot location. Maybe your chargers have low temperature cutoff. Maybe you externally warm your battery. |
| |
| [[opinion:frater_secessus:self-heated_lifepo4|externally warmed vs. self-heated LiFePO4]] |
| |
| |
| |
| === cell balancing === |
| |
| The shape of the voltage curve((flat in the middle and suddenly sharp at high and low states of charge)) can **the cell to leave the flat middle first to "run away" from the others, voltage-wise**. Example of mild imbalance when charging to 14.0v: |
| |
| Cell #1 - 3.500 |
| Cell #2 - 3.502 |
| Cell #3 - 3.518 <- runner |
| Cell #1 - 3.480 <- lagger |
| |
| In this case the voltage adds up to 14.0v (good) but some cells are out of whack with the others (bad). The difference between the highest and lowest cell voltage is 38mV;; this difference is called the voltage //delta//. The pattern would exaggerate as charging continues until one cell (probably #3) trips the BMS' cell overvoltage charging protection. Triggering charge/discharge protection before the battery is completely charged/discharged reduces the **apparent capacity** of the battery.((the cells may have their rated capacity but we can't use it all because of imbalance)) |
| |
| Various //balancing// schemes exist to try to hold back runners. Note: [[electrical:12v:drop-in_lifepo4#an_approach_to_greater_longevity|Gentler charging]] and discharging also tends to improve cell balance. |
| |
| **Passive balancing** is the most common BMS cell balancing strategy, present in most drop-in BMS.((if the specs say the BMS has cell balancing but does not give details then it uses passive balancing.)) The BMS identifies the runner[s] and dissipates some of their charging current((or capacity, if balancing without charging is enabled)) with a small resistor. This dissipation reduces the voltage to slow or stop the runner. Passive balancing are usually quite low, perhaps able to bleed off 60mA-100mA. It might take a very long time to balance -- wildly imbalanced cells might require [[opinion:frater_secessus:lifepo4_charging_voltage|a temporary change in charging setpoints]]. |
| |
| Passive balancing is total loss: the excess is converted to heat in the resistor. |
| |
| **Active balancing** is less common but can usually balancing cells faster and to closer tolerances. The general approach is like Robin Hood -- take from the rich (overvoltage cells) cells and give to the poor (undervoltage cells). |
| |
| |
| [[https://amzn.to/4daK0ok|{{ https://m.media-amazon.com/images/I/511zR8+q9xL._AC_UY218_.jpg?100}}]] |
| The most common active balancer is the double-tiered capacitor type like [[https://amzn.to/4daK0ok|the Heltec]]. |
| |
| |
| Capacitive balancing wastes less power since most of the excess is transferred to the low cell[s]. There are efficiency losses involved (~50%((https://www.ti.com/download/trng/docs/seminar/Topic%202%20-%20Battery%20Cell%20Balancing%20-%20What%20to%20Balance%20and%20How.pdf))) but it's far less than the 100% loss of passive balancing. The main drawbak of capacitive balancers is the current spec (like 5A) only occur at huge deltas; the rest of the time the balancing current is much lower. |
| |
| In theory inductive active balancers would get around this delta/current relationship. [as of this writing in 2024 I know of no drop-ins that use inductive active balancers - secessus] |
| |
| |
| |
| |
| |
| === Bluetooth === |
| |
| [not present in all BMS] |
| |
| Bluetooth((or other interface like a cable jack)) so an app can monitor (and possibly interact with) the BMS. Tech hobbyists typically want to know everything that is going on under the hood. It is debatable whether or not Normal People would benefit from visibility into the inner workings. |
| |
| |
| === heater control === |
| |
| [less common] |
| |
| BMS in batteries with [[electrical:12v:drop-in_lifepo4#self-heating_batteries|a self-heating function]] trigger the heating when they sense that cell temps are at some defined setpoint. |
===== charging ===== | ===== charging ===== |
| |
Lithium can famously accept huge amounts of current; this does not mean it is //good// for it to do so. | Lithium can famously accept huge amounts of current; this does not mean it is //good// for it to do so. |
| |
* Maximum((max for our drop-ins; EV packs can have much greater throughput)) - 1C (100A for 100Ah battery) | * Absolute maximum((max for our drop-ins; EV packs can have much greater throughput)) - 1C (100A for 100Ah battery) |
* Manufacturer recommendation - ≤0.5C (≤50A for 100Ah battery) | * Manufacturer recommended maximum - ≤0.5C (≤50A for 100Ah battery) |
* cycle rating (longest life) - 0.2C (20A for 100Ah battery) | * recommended / cycle rating (longest life) - 0.2C (20A for 100Ah battery) |
| |
Lithium does not have a minimum charging current in the lead-battery sense. Charge as slow as you like. | Lithium does not have a minimum charging current in the lead-battery sense. Charge as slow as you like. |
| |
| If you choose to end Absorption based on current, you might start out with [[electrical:12v:battery_capacity|0.05C]] and see where that gets you. Adjust as needed. |
| |
=== voltage === | === voltage === |
- verify that charging completes as expected. If cell voltages are visible verify their balance is improving. | - verify that charging completes as expected. If cell voltages are visible verify their balance is improving. |
- optional: start moving back up by 0.05v or 0.1v increments if desired, watching as in step 2 above. Example: 13.8v, then 13.85v, then 13.9v, etc. **There is little reason to charge >14.0v (3.5Vpc)**. | - optional: start moving back up by 0.05v or 0.1v increments if desired, watching as in step 2 above. Example: 13.8v, then 13.85v, then 13.9v, etc. **There is little reason to charge >14.0v (3.5Vpc)**. |
| |
| |
| |
==== an approach to greater longevity ==== | ==== an approach to greater longevity ==== |
| |
> Bottom line, stay within the manufacturer recommended specs, and you should be fine, go beyond that (more conservative) and you should be extra fine. -- [[https://diysolarforum.com/threads/sok-206ah-battery-concerns.32368/post-397575|Dzl]] | |
| >> ... the reactions that cause [LiFePO4] aging are strongly correlated with voltage - David Howey, Professor of Engineering Science at the University of Oxford((https://youtu.be/1LygMkJpN6Q?si=MiLB6m-QUjPSzcs8&t=2372)) |
| |
| >> Bottom line, stay within the manufacturer recommended specs, and you should be fine, go beyond that (more conservative) and you should be extra fine. -- [[https://diysolarforum.com/threads/sok-206ah-battery-concerns.32368/post-397575|Dzl]] |
| |
[//Fine// vs //Extra Fine// is like //normal driving// vs //hypermiling//; getting big MPG numbers is possible but requires forethought and a willingness to alter one's own driving style. -- secessus] | [//Fine// vs //Extra Fine// is like //normal driving// vs //hypermiling//; getting big MPG numbers is possible but requires forethought and a willingness to alter one's own driving style. -- secessus] |
| |
| |
| ===== waking lithium batteries ===== |
| |
| Lithium banks can go dormant at low voltages in order to protect themselves: |
| |
| - the BMS turns off the DISCHARGE channel to keep cell voltage from going any lower |
| - so the battery internally has ~11.0v or whatever but does not pass that voltage to the terminals on the outside of the battery case |
| - which means smart chargers don't see battery voltage |
| - and think there's a problem so they won't start(("too smart for their own good")) |
| |
| What we need is a //dumb// charging source to get the party restarted. Another battery. Power supply. Charger with a "wake LiFePO4" mode, vehicle starter battery, etc. |
| |
=====self-heating batteries===== | If you want to use the starter battery there are several possibilities: |
| |
Lithium cannot be charged in freezing temps. We can either: | * Rigs with IGN-triggered relays can briefly turn the key to ACC then back off.((don't leave it on ACC long or the dead Li will suck power from the starter battery. Either turn ACC off again or actually start the vehicle.)) |
| * Rigs with voltage-sensing relays will have to actually start the engine or press a manual override switch to activate the VSR and wake the lithium bank. |
| * Rigs with diode- or FET-based isolators would start the engine to spin the alternator and get power flowing through the isolator to the sleeping lithium |
| * If you have no other options you can remove either the starter battery or house battery and locate them so a pair of jumper cables can connect them. |
| |
- cut off charging in the chargers; and/or | |
- warm the batteries, either internally (self-heating) or externally (typically with warming mats). | |
| |
| |
Self-heating is convenient, and does not require lithium- or temperature-aware chargers. The downsides are: | |
| |
* typically substantially more $$$ than warming pads | |
* can miss out on charging opportunities. Not a big deal with smaller solar-only setups, but can really hamper alternator or big solar. | |
| |
| |
==== how self-heating batteries work ==== | |
| |
The last issue is a function of how they work. | |
| |
- When the BMS detects dangerously-low temps it deactivates charging to the battery cells | |
- any charging power is sent to the internal warming pads, typically ~50w | |
- when the BMS detects the temps are ok it turns the charging back on. The warming may be switched off, or may continue to warm the battery further to a given temp setpoint. | |
| |
==== how this could cause a missed charging opportunity ==== | |
| |
Imagine a half-hour drive on a freezing morning with a 50A [[electrical:12v:b2b|DC-DC charger]].((Doesn't have to be DC-DC but it makes the math easier because charging current is more stable.)) You could pump 25Ah((minus the energy it took to hold temp overnight)) into an externally-warmed battery, or you could use the alternator to run the 50W internal heater and get 0Ah replaced. | =====self-heating batteries===== |
| |
With only small solar the Wh consumed overnight and Wh not produced in the morning might be a breakeven. | [see [[opinion:frater_secessus:self-heated_lifepo4|self-heating vs DIY warming]]] |
| |
| |
| |
Charging Li at very high rates may also strain the [[electrical:12v:alternator|alternator]]. | Charging Li at very high rates may also strain the [[electrical:12v:alternator|alternator]]. |
| |
| ==== myth: you can't use a combiner to charge batteries of different chemistries ==== |
| |
| There are two different challenges here: |
| |
| - **different resting voltages** - if the lead rests at 12.8v and LiFePO4 at 13.6v then when charging stops the lead batt could put a drain on the li batt. The [[electrical:12v:alternator#combiners|charging relay]]((or [[electrical:12v:b2b|DC-DC]])) is primarily there to stop house loads from draining the starter battery, but this separation also means **the starter battery cannot drain the house battery**.((unless self-[[electrical:12v:self-jumpstarting|jumpstarting]])) ((note, however, [[electrical:12v:alternator#gotchas|a gotcha with VSRs]])) |
| - **acceptable charging voltages** - the alternator voltage needs to be acceptable (not necessarily //optimal//) to both batteries. Read on. |
| |
| === acceptable charging voltage ranges === |
| |
| We can assume **the alternator voltage is acceptable to the starter battery** because the manufacturer designed that system.((and we can observe that the vehicle starts on demand)). So we only have think about whether or not the alternator voltage is acceptable to the house bank. And remember that lithium chemistries don't need to be fully charged [[electrical:12v:psoc|the way lead batteries do]]. |
| |
| For the following thought experiment we will use some a typical alternator output voltage of 14.2v and house bank charging voltage [[electrical:solar:charge_controller_setpoints|setpoints]] ("Absorption" or "Boost" voltage, Vabs); check your vehicle's alternator voltage and battery manufacturer charging specs to make your actual decision. |
| |
| ^ Chemistry ^ Acceptable Vabs ^ Optimal Vabs ^ |
| | Gel | 14.0v - 14.3v | 14.2v | |
| | AGM | 14.2v - 14.5v | 14.4v | |
| | Flooded | 14.4v - 14.8v | 14.6v | |
| | LiFePO4 | 13.6v - 14.4v | 14.2v((this is a matter of some debate. LFP mfg charging recommendations are often [[opinion:frater_secessus:lifepo4_charging_voltage|quite high]] - secessus)) | |
| |
| |
| Let's think about some combinations. In all these cases [[electrical:12v:alt_and_solar#how_alternator_charging_helps|alternator charging is extremely useful]] for [[electrical:12v:charging#bulk_stage|Bulk stage charging]] but may not be sufficient on its own: |
| |
| * **easy to meet charging requirements by alternator alone** |
| * starter battery + LiFePO4. Charging LFP at 14.2v is a good balance between moderate voltage and charging time. Lithium is not affected by [[electrical:12v:psoc|partial states of charge]] so you can charge as little or much as you want. Caveat: alternator charging should be [[electrical:12v:alternator#disabling_alternator_charging|disabled]] if you drive long enough to reach your desired state of charge. Specifically, LFP should not be held at high voltage after reaching full charge. |
| * **unlikely to meet charging requirements by alternator alone** - could theoretically meet charging by alternator alone //if// given sufficient time. Unfortunately most people don't drive enough hours ((typically 5-6 hours from 50% SoC)) to complete Absorption; [[electrical:12v:psoc|incomplete charging damages lead batteries]]. less one is driving for many hours each day it is unlikely that there will be sufficient time to complete Absorption. For this reason solar or other long-duration charging source is often [[electrical:12v:alt_and_solar#how_solar_helps|added to handle Float and late Absorption]]. |
| * starter battery + AGM. 14.2v from the alternator is in the acceptable range, but just barely. Extremely long Absorption would be required and adding solar is highly recommended. |
| * starter battery + Gel. The alternator is putting out the exact Vabs spec'd by the manufacturer. Caveat: gel can be damaged (electrolyte cavitated) by excess current. Ensure your setup charges withing the mfg current specs. |
| * **Useful but impossible((practically)) to meet charging requirements by alternator alone ** - cannot reach Vabs in any case. Solar is nearly mandatory, although DC-DC charging will do it if one is driving many hours a day. |
| * starter battery + flooded. Alternator charging is useful for Bulk stage (shoving Ah into the bank) but it cannot meet the minimum Vabs. |
| |
| |
| |
==== myth: you have to charge Li to 100% ==== | ==== myth: you have to charge Li to 100% ==== |
* going into a period where you will need max capacity | * going into a period where you will need max capacity |
* to perform a capacity test | * to perform a capacity test |
* to reset the BMS amp/SoC counter | * to [[electrical:12v:battery_monitor#drift_and_reset|reset the BMS amp/SoC counter]] |
* to top-balance cells((to the degree this works)) | * to top-balance cells((to the degree this works)) |
| |
| ==== myth: lithium batteries draw the full current until they are almost full ==== |
| |
| |
| * both lead and li chemistry charge acceptance [[electrical:12v:directcharginglfp#current_demands_of_dc-dc_chargers_vs_isolators|will taper]] when charged by a [[electrical:12v:alternator|relay/isolator]], and |
| * both will charge ~at [[electrical:12v:b2b|a DC-DC charger]]'s rated output until Absorption voltage is reached |
| |
| If we observed closely we //would// see some differences: the LFP taper is shaped a bit differently, and that lead Absorption tends to start earlier and last longer. |
| |
==== myth: if you don't charge to 14.4v the cells won't balance ==== | ==== myth: if you don't charge to 14.4v the cells won't balance ==== |
| |
* in cyclic use (like offgrid) ~13.8v (3.45Vpc) is sufficient to reach 100% with some absorption, without antagonizing cell balance. | * in cyclic use (like offgrid) ~13.8v (3.45Vpc) is sufficient to reach 100% with some absorption, without antagonizing cell balance. |
* when on shore power (like on a power pedestal) voltages as low as 13.4v will slowly bring the bank up to 100% SoC. | * when on shore power (like on a power pedestal) voltages as low as 13.6v will slowly bring the bank up to 100% SoC. |
| |
Overcharging lithium to run the cell balancers is like driving up to every red light at 100mph in order to trigger the ABS. It's //causing// the problem in order to //solve// the problem. | Overcharging lithium to run the cell balancers is like driving up to every red light at 100mph in order to trigger the ABS. It's //causing// the problem in order to //solve// the problem. |
| |
| |
Lithium doesn't need Absorption [[electrical:12v:charging#absorption_stage|in the way lead does]]. In some circumstances, however, an Absorption duration can help match [[electrical:solar:charge_controller_setpoints|charging setpoint]] expectations to [[electrical:depth_of_discharge|state of charge]] reality. | Lithium doesn't need Absorption [[electrical:12v:charging#absorption_stage|in the way lead does]].((lead needs complete Absorption to stay healthy)) In some circumstances, however, an Absorption duration can help match [[electrical:solar:charge_controller_setpoints|charging setpoint]] expectations to [[electrical:depth_of_discharge|state of charge]] reality. |
| |
Most charts and tables showing voltage v. SoC assume moderate rates of charge like 0.2[[electrical:12v:battery_capacity|C]] (20A per 100Ah of capacity). At that rate the charts are reasonably accurate. | Most charts and tables showing voltage v. SoC assume moderate rates of charge like 0.2[[electrical:12v:battery_capacity|C]] (20A per 100Ah of capacity). At that rate the charts are reasonably accurate. |
Here is the order of operations: | Here is the order of operations: |
| |
- Read and understand your Li battery manufacturer's charging specs((if you are adventurous and want maximal life read and understand what the Li cells actually need)) | - Read and understand your Li battery manufacturer's charging specs. |
| - if you want to maximize life from your bank consider [[electrical:12v:drop-in_lifepo4#an_approach_to_greater_longevity|charging less aggressively]] |
- Read and understand the charger's specs and functionality | - Read and understand the charger's specs and functionality |
- decide whether the charger can charge to mfg specs | - decide whether the charger can charge to the way you (or the manufacturer) wants |
| |
Armed with a full understanding, here is one approach to thinking about lead battery charger setpoints for lithium banks: | Armed with a full understanding, here is one approach to thinking about lead battery charger setpoints for lithium banks: |
* **Absorption voltage** (Vabs) - whatever charging voltage your battery manufacturer recommends.((see the section on longevity in this article)) | * **Absorption voltage** (Vabs) - whatever charging voltage your battery manufacturer recommends.((see the section on longevity in this article)) |
* **Absorption duration** - whatever the battery manufacturer recommends, typically 0 to 20 minutes.((charging voltages ≥14.0v typically require no absorption duration at all)) | * **Absorption duration** - whatever the battery manufacturer recommends, typically 0 to 20 minutes.((charging voltages ≥14.0v typically require no absorption duration at all)) |
* **Float voltage** (Vfloat) - Something like 13.4v((3.35vpc)) is a good compromise. See the discussion on float below. | * **Float voltage** (Vfloat) - Something like 13.3v-13.4v((3.35vpc)) is a good compromise. See the discussion on float below. |
* **Absorption reconnect** - this voltage is the setpoint below which Absorption(("boost" in Renogy/EpEver nomenclature)) is restarted. Normally in a solar configuration Vfloat is held until sun goes down, solar conditions otherwise deteriorate, or a load is applied that is more than the solar can support. Start with a value like 13.2v and see how your system behaves. Adjust as needed. | * **Absorption reconnect** - this voltage is the setpoint below which Absorption(("boost" in Renogy/EpEver nomenclature)) is restarted. Normally in a solar configuration Vfloat is held until sun goes down, solar conditions otherwise deteriorate, or a load is applied that is more than the solar can support. Start with a value like 13.2v and see how your system behaves. Adjust as needed. |
* **Equalize voltage** (Veq) - Li does not require equalization. If it cannot be disabled in the controller it is common to set Veq the same as Vabs so it becomes a non-issue.((some folks who charge to lower voltages like 13.6v may use Veq to raise bank voltage into the 14s for various purposes. See the section on longevity.)) | * **Equalize voltage** (Veq) - Li does not require equalization. If it cannot be disabled in the controller it is common to set Veq the same as Vabs so it becomes a non-issue.((some folks who charge to lower voltages like 13.6v may use Veq to raise bank voltage into the 14s for various purposes. See the section on longevity.)) |
* **Equalize duration** - zero, or as low as the controller will allow. Will make no practical difference when Veq is set to Vabs. | * **Equalize duration** - zero, or as low as the controller will allow. Will make no practical difference when Veq is set to Vabs. |
* **Temperature compensation** - Lead needs different charging voltages at different temperatures but Li does not. Change setting to **0**mV/cell.((lead defaults are something like -4mV/cell)) | * **Temperature compensation** - Lead needs different charging voltages at different temperatures but Li does not. Change setting to **0**mV/cell.((lead defaults are something like -4mV/cell)) |
| |
| Note: if you are willing to pay minimal attention, even a single-voltage power supply or [[electrical:12v:alternator#combiners|relay]] would work. Stop charging if/when the voltage hits your desired setpoint. |
| |
==== myth: you shouldn't Float lithium ==== | ==== myth: you shouldn't Float lithium ==== |
Neither of these is true for Li, which dislikes sitting at 100% SoC and has vanishingly-low self-discharge rates.((but see [[https://www.technomadia.com/2020/06/what-killed-our-rv-lithium-batteries-8-5-years-of-lifepo4/|this cautionary tale]] about add-on balancers depleting/killing a $4,000 bank)) So **with lithium Float is used for a different purpose**, as a **voltage floor**. It is a voltage below which the charger shouldn't let the bank fall while charging is present. Without Vfloat (or a very low one) the bank would charge then fall until reaching the "re-bulk" setpoint.((when a fresh charge cycle begins)). After initial charging loads would run off the battery instead of the charging source. Having a sane Vfloat allows Li to "relax" after charging while retaining the desired amount of Ah/Wh capacity. | Neither of these is true for Li, which dislikes sitting at 100% SoC and has vanishingly-low self-discharge rates.((but see [[https://www.technomadia.com/2020/06/what-killed-our-rv-lithium-batteries-8-5-years-of-lifepo4/|this cautionary tale]] about add-on balancers depleting/killing a $4,000 bank)) So **with lithium Float is used for a different purpose**, as a **voltage floor**. It is a voltage below which the charger shouldn't let the bank fall while charging is present. Without Vfloat (or a very low one) the bank would charge then fall until reaching the "re-bulk" setpoint.((when a fresh charge cycle begins)). After initial charging loads would run off the battery instead of the charging source. Having a sane Vfloat allows Li to "relax" after charging while retaining the desired amount of Ah/Wh capacity. |
| |
What Vfloat setpoint should actually be is a matter of some discussion and experimentation. Each setup (and use case) is different, but in general((and using nominal 12v math)) | What Vfloat setpoint should actually be is a matter of some discussion and experimentation. Each setup (and use case) is different, but we can start with some ballpark assumptions:((and using nominal 12v math)) |
| |
| |
* <13.4v will allow the bank to settle below 100% | * <13.4v will allow the bank to settle below 100% |
* 13.4v will hold the bank near whatever SoC it was charged to. If in doubt, this is a good default for solar charging.((When charging from shore power 13.4v will eventually charge and hold at 100% SoC, which may be undesirable)) | * ~13.4v will hold the bank near whatever SoC it was charged to. If in doubt, this is a good default for solar charging.((When charging from shore power 13.4v will eventually charge and hold at 100% SoC, which may be undesirable)) |
* >13.4v will continue to charge the bank beyond the SoC it was charged to during Absorption. This may be useful if the Vabs value is set intentionally low. | * >13.4v will continue to charge the bank beyond the SoC it was charged to during Absorption. This may be useful if the Vabs value is set intentionally low. |
| |
| |
If you cannot set a Float within the confines of the Li profile then leverage the USER or GEl profile, modifying as described in the previous section. | If you cannot set a Float within the confines of the Li profile then leverage the USER or GEL profile, modifying as described in the previous section. |
==== myth: you must use DC-DC for alternator charging Li ==== | ==== myth: you must use DC-DC for alternator charging Li ==== |
| |
Depends on the battery, the alternator, the use case, and even the [[electrical:12v:alternator|combiner]]. For example, [[https://www.youtube.com/watch?v=VY2b71zoyvg|Battle Born says]] this about direct-charging lithium: | If you have been successfully charging an AGM bank through a relay then an LFP bank of similar rated capacity will likely charge similarly. The actual results depend on the battery, the alternator, the use case, and even the [[electrical:12v:alternator|combiner]]. |
| |
| [[https://www.youtube.com/watch?v=VY2b71zoyvg|Battle Born says]] this about direct-charging lithium: |
| |
>> Yes, you can. Under most circumstances you don't even need to modify your system. | >> Yes, you can. Under most circumstances you don't even need to modify your system. |
| |
They do recommend [[electrical:12v:alternator#lithium-specific|a BIM]] or [[electrical:12v:b2b|DC-DC charger]] //for banks >300Ah//. | They do recommend [[electrical:12v:alternator#lithium-specific|a BIM]] or [[electrical:12v:b2b|DC-DC charger]] //for banks >300Ah//. |
| |
| If not already present, a small switch to [[electrical:12v:alternator#disabling_alternator_charging|disable the combiner]]((same goes for [[electrical:12v:b2b|DC-DC chargers]])) at will is a good idea. |
| |
| |
=== testing your isolator with Li === | === testing your isolator with Li === |
| |
see [[electrical:12v:directcharginglfp#assessing_your_setup_for_direct_alternator_charging|this section]] | see [[electrical:12v:directcharginglfp#assessing_your_own_setup_for_direct_alternator_charging|this section]] |
| |
==== but that Victron video ==== | ==== but that Victron video ==== |
| |
- Li doesn't like to be held at 100% State of Charge for long periods | - Li doesn't like to be held at 100% State of Charge for long periods |
- In practice a solar-charged bank doesn't bounce between Float and Absorption during the course of a day | - In practice a solar-charged bank doesn't bounce between Float and Absorption during the course of a day((unless a heavy enough load pulls Vbatt down to the re-Bulk setpoint)). |
| |
The 2nd point takes a bit of explaining. A [[electrical:solar:charge_controller|solar charge controller]] completes Absorption then falls to into Float where it will remain as long as the sun((and system capacity)) cooperates. Absorption //can// be re-triggered if voltage falls below the Absorption Reconnect setpoint, but that setpoint is even lower than Vfloat. If that happens the solar charging has already been overtasked and we will get a "microcycle" during that day in any case if the sun comes back. | The 2nd point takes a bit of explaining. A [[electrical:solar:charge_controller|solar charge controller]] completes Absorption then falls to into Float where it will remain as long as the sun((and system capacity)) cooperates. Absorption //can// be re-triggered if voltage falls below the Absorption Reconnect setpoint, but that setpoint is even lower than Vfloat. If that happens the solar charging has already been overtasked and we will get a "microcycle" during that day in any case if the sun comes back. |
| |
| |
===== BMS functions ===== | |
| |
Lithium cells can hurt themselves if left unsupervised. A BMS (Battery Management System) is device that tries to keep them out of trouble. It's like a fence around the yard that won't prevent skinned knees but should keep the kids out of the street where they could get really hurt. | |
| |
Drop-in Lithium batteries all have a BMS integrated inside of them, so there is typically less to worry about. However, not all of them will have the same protection features so do your research carefully. | |
| |
Typical BMS protections may include: | |
| |
==== Charging cut-off ==== | |
| |
Charging is disabled for a few different reasons: temperature extremes, high cell voltage, overcurrent. | |
| |
People who camp in cold weather may want to select a battery that has "low temperature cut-off", which disables charging near freezing.((Lithium is permanently damaged by charging below freezing)). The belt-and-suspenders solution is both low temperature cutoff and a way to keep the batteries warm. Some pricier batteries have internal heating, or you may [[https://diysolarforum.com/threads/lifepo4-heating-pad-for-cold-temperatures.5/page-26|DIY a heater]]. | |
| |
Note that the BMS overcurrent protection kicks in only at the limit, typically 1[[electrical:12v:battery_capacity|C]] (100A for a 100Ah battery). See the section on the [[:#an_approach_to_greater_longevity|benefits of even gentler charging]]. | |
| |
| |
==== discharge cut-off ==== | |
| |
Discharge is disabled for similar reasons as charging: extremes in temperature, cell voltage, or current. | |
| |
The low temperature discharge cut-off is typically much lower (like -20C) than for charging. | |
| |
=== wake-up === | === wake-up === |
| |
This issue occurs because the charging and discharging channels are separately controlled. When the battery is too low the discharge channel is disabled which means battery voltage is not exposed to the outside world. The charging channel remains active but the charger doesn't know that. "Jumping" the battery works because the jumper cables are not looking for voltage. | This issue occurs because the charging and discharging channels are separately controlled. When the battery is too low the discharge channel is disabled which means battery voltage is not exposed to the outside world. The charging channel remains active but the charger doesn't know that. "Jumping" the battery works because the jumper cables are not looking for voltage. |
==== cell balancing ==== | |
| |
{{ https://www.researchgate.net/profile/Afshin-Izadian/publication/273161090/figure/fig2/AS:288782403944449@1445862498996/Experimental-OCV-SOC-curve-for-LiFePO4-battery-cell-under-testing.png?150}} | |
Cell balancing attempts to keep all the cells in the same voltage ballpark. The method used in most drop-ins is //passive balancing//, which applies a small amount of braking a bit on runaway cells.((//Active balancing//, more complex and expensive, takes current from the highest and gives it to the lowest.)) | |
| |
| ===== Brands and specs ===== |
| |
The image on the right shows the LFP voltage curve: a //lower knee// (below ~3.2v) on the left, a wide, flat section in the middle, then the //upper knee// (~3.4v) on the right. //Between the knees// the voltage stays relatively flat and cells stay in relative balance. The first cell[s] that hits a knee will race in that direction ahead of the others. | [The market moves so fast that this section was badly outdate. This version is more general. Please verify stats and specs before ordering. - secessus] |
| |
This matters because voltage extremes, high or low, are not good for the cell. Cell imbalance can change effective capacity, since a wayward cell could trigger cell voltage BMS protection before the bank is fully charged or discharged. | |
| |
| |
Consider these two batteries, using made up round numbers to illustrate the point. Cells are arranged in [[electrical:12v:parallel_serial|series]] so the volts add up: | |
| |
* balanced((it will never be this perfect)) | |
* overall battery voltage = **13.6v** | |
* cell 1 = 3.400v | |
* cell 2 = 3.400v | |
* cell 3 = 3.400v | |
* cell 4 = 3.400v | |
* unbalanced((greatly exaggerated)) | |
* overall battery voltage = **13.6v** | |
* cell 1 = 3.**300**v | |
* cell 2 = 3.400v | |
* cell 3 = 3.400v | |
* cell 4 = 3.**500v** <-- a "passive" balancer will try to slow this one down((an "active" balancer would steal from the rich (#4) and give to the poor (#1)) | |
| |
In both cases the overall battery voltage is 13.6v, but in the unbalanced battery cell #1 is lagging (reducing capacity) and cell #4 is too high. The balancer will attempt to rein in #4 but the effect is tiny. Using a typical balancing current of 50mA, if you are charging at 20A that means the cells are receiving 5A except cell #4 which gets only 4.95A, about a 1% difference. Tiny balancing currents and the propensity of cells to race away explains why balancing is so gradual. | |
| |
| |
=== minimizing cell imbalance === | |
| |
It is more practical to minimize imbalance than to try to rebalance them after the fact. Here are some approaches: | |
| |
| |
* discharging gently, maybe a max of C/2 | |
* charging gently (minimum current needed to get the battery charged in the amount of time available). 50mA only makes a 1% difference when charging at 20A but 4% difference at 5A. | |
* charging voltages closer to 13.6v than to 14.4v.((the batt will eventually reach 100% State of Charge (SoC) when charged at 13.6v)). | |
* charging to a lower SoC, like 85%-95% instead of 100%. | |
| |
| |
| |
==== bluetooth ==== | |
| |
Some batteries have BMS with bluetooth or other forms of connectivity. With these you would be able to see more information, like individual cell balance, statistics, setting and the status of any protections. | |
| |
| |
| |
| |
===== Brands and specs ===== | |
| |
The most popular drop-ins at various price points appear to be: | The most popular drop-ins at various price points appear to be: |
| |
* premium - Battle Born | * premium - [[https://amzn.to/3LV85DI|Battle Born]], Lithionics |
* moderate - SOK | * midrange - [[https://amzn.to/3YxGPTh|SOK]], Epoch. And there are companies like SunFunKits that will [[https://www.sunfunkits.com/category/3/pre-built-batteries|build LFP batteries with the customer's choices of options]]. |
* inexpensive - Chins and Ampere Time (no cutoff) or Weize (cold cutoff) | * inexpensive - [[https://amzn.to/4cfU5Pm|Li Time]] (was Ampere Time), [[https://amzn.to/4dwItZr|Weize]], [[https://amzn.to/4fwJhiQ|Power Queen]], [[https://amzn.to/4cgSKIj|Roypow / Power Urus]], etc |
| |
Charge/discharge rates are expressed in [[electrical:12v:battery_capacity|C]]. Heated models typically shunt charging current to the internal warmer until the battery comes up to safe temp.((some run the warmer and rely on the BMS to release charging cutoff when safe to charge.)) | |
| |
[Please verify stats and specs before ordering. This is a best-effort listing but things change fast in this segment - secessus] | |
| |
| |
==== Battle Born ==== | |
| |
With cold cutoff. BB also has [[https://battlebornbatteries.com/product-category/lifepo4-batteries/heated-battery-kits/|a line of heated LFP]]. | |
| |
[[https://www.youtube.com/watch?v=G5E30u-66VI|Will Prowse teardown video]]. Absorption 14.4v for 20 minutes, Float 13.6v. Recommended charge rate C/2.((https://battlebornbatteries.com/faq/#tab-charging-and-discharging)) | |
| |
* [[https://amzn.to/3AL6Vn0|100Ah 12v]] | |
* [[https://amzn.to/3uaRlyw|50Ah 12v]] | |
| |
| |
==== Victron ==== | |
| |
These batteries have cold cutoff. The batteries themselves do not have bluetooth, but are intended to be connected to other Victron gear that can talk to the batteries. Victron's value proposition is increased inter-device communication when installing a Victron ecosystem. | |
| |
[[https://diysolarforum.com/threads/inside-a-victron-lifepo4-battery.2265/|teardown pics and discussion]] | |
| |
Charge 14.2v @ C/2, Float 13.6v.((printed on case of [[https://amzn.to/3kQhjV3|100Ah]])) | |
| |
* [[https://amzn.to/3kQhjV3|100Ah 12v]] | |
* [[https://amzn.to/3CY6vKL|200Ah 12v]] | |
| |
| |
| |
==== SOK ==== | |
| |
SOK models are popular with tinkerers because the case and internals are easy to disassemble for service, inspection, and troubleshooting.((may void warranty)) | |
| |
With cold cutoff. [[https://www.youtube.com/watch?v=SU86EJXcTMM|Will Prowse teardown video]] | |
| |
Charge 14.6v, max 50A, 20A recommended.((https://www.sokbattery.com/products/12v-206ah-lifepo4-lithium-iron-phosphate-battery-pack, apparently same BMS for both batteries)),((https://diysolarforum.com/threads/sok-lifepo4-specs-100ah-vs-206ah.24921/)) | |
| |
| |
* [[https://amzn.to/3ugrQMo|100Ah 12v]] | |
* [[https://amzn.to/3udOQLK|206Ah 12v]] | |
| |
[[http://support.sokbattery.com/how-to-wake-up-a-sleeping-battery/|wake-up procedure]] | |
==== Rebel Batteries ==== | |
| |
[[http://www.rebelbatteries.com/?afmc=2z|Rebel Batteries]] - with cold cutoff and bluetooth ([[https://www.youtube.com/watch?v=MIiaV8-PvIc|BT demo]]). [[https://www.youtube.com/watch?v=O_snt4qD_8U|Will Prowse teardown video]] | |
| |
RB says "just make sure [the charger] has a Lithium charging profile".((https://rebelbatteries.com/knowledge-base/charging/what-type-of-charger-do-i-need/)) The [[https://amzn.to/3EVit9I|shore power charger they recommend]] charges at 14.3-14.4v @ 20A. The BMS has a max charging rate of 100A. | |
| |
* [[https://amzn.to/2ZptY8Y|100ah 12v]] - BMS appears to be JBD SP04S028 | |
* [[https://amzn.to/3AQIHb6|50Ah 12v]] | |
| |
| |
==== Weize ==== | |
| |
Cold cutoff. [[https://www.youtube.com/watch?v=-c6A1THDaeU|Will Prowse teardown video]] | |
| |
* 100Ah 12v (not currently [[https://amzn.to/3H81EcO|listed on Amazon]]) | |
| |
| |
| |
==== Ampere Time ==== | |
| |
Now known as LiTime. | |
| |
No cold cutoff. [[https://www.youtube.com/watch?v=FQUhjDkQY5Q|Will Prowse teardown video]] | |
| |
* [[https://amzn.to/3AMiR7M|200Ah 12v]] | |
* [[https://amzn.to/39Hd08a|100Ah 12v]] | |
* [[https://amzn.to/3o7xU8P|50Ah 12v]] | |
| |
AT [[http://amperetime.com/Public/editor/attached/file/20210624/20210624144356_64421.pdf|recommends]] charging at 14.4v((+/- 0.4v)) at 20A. | |
| |
| |
==== PowerUrus ==== | |
| |
Budget PowerUrus line by RoyPow | |
| |
[[https://www.youtube.com/watch?v=2KeQZrsnz-4|Will Prowse teardown]], low temp cutoff confirmed. Bluetooth. | |
==== Renogy ==== | |
| |
Renogy's original "Smart Lithium" line has no cold cutoff. They are releasing a [[https://www.renogy.com/12v-100ah-lithium-iron-phosphate-battery-w-bluetooth/|new line of temp-protected, bluetooth enabled batteries]]. | |
| |
| |
Charge 14.4v @ max C/2.((https://store-fhnch.mybigcommerce.com/content/RBT100LFP12-BT/RBT100LFP12-BT%20manualV1.1.pdf)) | |
| |
* [[https://amzn.to/2Zg3CH1|170Ah 12v]] original | |
* [[https://amzn.to/3BcC16i|100Ah 12v]] original | |
* [[https://amzn.to/3D37fOP|50Ah 12v]] original | |
| |
Initial activation may require a quick press-and-release of the button rather than longpress.((https://diysolarforum.com/threads/cant-get-bms-to-wake-renogy-100ah-battery-to-wake-up-from-shelf-mode.22628/post-296912)) | |
==== Relion ==== | |
| |
Unheated versions appear to lack cold cutoff. No bluetooth. | |
| |
Charge 14v - 14.6v, 1C up to 100A max. Float 13.3v - 13.8v.((https://ceb8596f236225acd007-8e95328c173a04ed694af83ee4e24c15.ssl.cf5.rackcdn.com/docs/product/Relion_Charging_Instructions_072020_200720_144445.pdf)) | |
| |
| |
* [[https://amzn.to/3mnQDKX|35Ah 12v]] | |
* [[https://amzn.to/3F1AVxx|75aAh 12v]] | |
* [[https://amzn.to/3CY3bzh|100Ah 12v]] heated | |
* [[https://amzn.to/3CZ4dep|300Ah 12v]] heated | |
==== Kilovault ==== | |
| |
[[https://www.altestore.com/store/deep-cycle-batteries/lithium-batteries/kilovault-lithium-solar-battery-p41011/?afmc=1q#KLV1800HLXV3|Kilovault HLX series]], internally heated. Recommended by [[https://marinehowto.com/lifepo4-batteries-on-boats/|Marine How-To]]. | |
| |
| |
==== Lithionics ==== | |
| |
| |
| |
* Lithioncs GV125, also recommended by [[https://marinehowto.com/lifepo4-batteries-on-boats/|Marine How-To]]. | |
| |
| |
| |
==== Chins ==== | |
| |
Base models with no cutoff or bluetooth and "Smart" models with 5A internal heating and bluetooth ([[https://youtu.be/Ce2ZQMvXV9I?t=196|BT demo]]). | |
| |
[[https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwix4OXatp_zAhUKg_0HHbTICgQQwqsBegQIBBAB&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DxBonGQe363g&usg=AOvVaw2E-qpZ7ETMtLihxb7teHTP|Will Prowse teardown video]] of base model; he notes they are similar inside to Ampere Time. | |
| |
Absorption 14.2-14.6v, C/5 charging recommended, C/1 max.((description and chart on https://amzn.to/3ueMs7F)) Heating element on supported models appears to [[https://amzn.to/3m2g2JK|turn on near freezing then turn off at 50F]]. | |
| |
An after-sale email from Chins to an Amazon buyer((forwarded by personal correspondence to secessus)) said: | |
| |
>Charging Limit Voltage: 14.2V | |
>Over Voltage Disconnect Voltage: 14.6V | |
>Over Voltage Reconnect Voltage: 13.8V | |
>Float Charging Voltage: 13.8V | |
>Low Voltage Disconnect Voltage: 11.6V | |
>Low Voltage Reconnect Voltage: 12.4V | |
>Under Voltage Warning Voltage: 12.8V | |
| |
| |
| |
* [[https://amzn.to/39EQkp5|300Ah heated]] | |
* [[https://amzn.to/3uf6hM1|200Ah heated]] | |
* [[https://amzn.to/3ueMs7F|100Ah heated]] (Will's [[https://www.youtube.com/watch?v=pKFh7eXeY-s|YT teardown]]) | |
* [[https://amzn.to/3EWVR8H|300Ah]] | |
* [[https://amzn.to/2WfQFeC|200Ah]] | |
* [[https://amzn.to/2ZC7v8X|100Ah]] | |
* [[https://amzn.to/2XVCc7W|50Ah]] | |
| |
There have been [[https://diysolarforum.com/threads/chins-200ah-lifepo4-battery-test-review.17997/#post-209062|reports]] that the BMS does not disconnect the battery at low voltages. External [[electrical:12v:lvd|LVD]] is always advisable. | To make an informed decision: |
| |
According to Amazon answers((bao peng on https://www.amazon.com/CHINS-LiFePO4-Battery-2000-5000-Off-Grid/dp/B08N53GF81)) reset due to LVD is done by applying enough voltage to raise to 11v: "when the battery voltage reaches about 11V, the battery's BMS will be activated." | - read and understand the specs <- srsly |
==== batteries with troubling reports ==== | - search Youtube for teardown videos |
| - search [[https://diysolarforum.com|Will's DIY Solar Forum]] to see what informed users are saying |
| |
* [[https://amzn.to/3m5vO6E|Shunbin 24v/400Ah]] - [[https://diysolarforum.com/threads/shunbin-battery-packs- | |
12v-24v-100ah-and-up-a-complete-rip-off-avoid.1304/|see this thread]] | |
| |
| |