This shows you the differences between two versions of the page.
Both sides previous revision Previous revision Next revision | Previous revision | ||
electrical:12v:drop-in_lifepo4 [2024/02/11 12:22] frater_secessus [myth: you can't use a combiner to charge batteries of different chemistries] |
electrical:12v:drop-in_lifepo4 [2024/05/21 22:08] (current) frater_secessus [myth: you have to charge Li to 100%] |
||
---|---|---|---|
Line 45: | Line 45: | ||
* the flat voltage curve makes gauging SoC by voltage extremely challenging, | * the flat voltage curve makes gauging SoC by voltage extremely challenging, | ||
+ | ===== sizing the bank ===== | ||
+ | Other than cost, there is little downside to having a larger LiFePO4 bank.(([[electrical: | ||
+ | |||
+ | * greater [[opinion: | ||
+ | * supporting larger discharge current - [[electrical: | ||
+ | * safely accepting larger charging currents when charging time is limited. | ||
Line 274: | Line 280: | ||
* 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: | ||
+ | * both will charge ~at [[electrical: | ||
+ | |||
+ | If we observed closely we //would// see some differences: | ||
==== 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 ==== | ||
Line 317: | Line 330: | ||
* **Equalize duration** - zero, or as low as the controller will allow. | * **Equalize duration** - zero, or as low as the controller will allow. | ||
* **Temperature compensation** - Lead needs different charging voltages at different temperatures but Li does not. Change setting to **0**mV/ | * **Temperature compensation** - Lead needs different charging voltages at different temperatures but Li does not. Change setting to **0**mV/ | ||
+ | |||
+ | Note: if you are willing to babysit, even a single-voltage power supply would work. Stop charging when the voltage hits your desired setpoint. | ||
==== myth: you shouldn' | ==== myth: you shouldn' | ||
Line 360: | Line 375: | ||
=== testing your isolator with Li === | === testing your isolator with Li === | ||
- | see [[electrical: | + | see [[electrical: |
==== but that Victron video ==== | ==== but that Victron video ==== | ||
Line 508: | Line 523: | ||
Charging is disabled for a few different reasons: | Charging is disabled for a few different reasons: | ||
- | |||
- | People who camp in cold weather may want to select a battery that has "low temperature cut-off", | ||
Note that the BMS overcurrent protection kicks in only at the limit, typically 1[[electrical: | Note that the BMS overcurrent protection kicks in only at the limit, typically 1[[electrical: | ||
+ | |||
+ | === low temperature charging cutoff === | ||
+ | |||
+ | |||
+ | People who camp in cold weather may want to select a battery that has //low temperature cutoff//, which disables charging near freezing.((Lithium is permanently damaged by charging below freezing)). | ||
+ | |||
+ | It may be possible to add low temperature cutoff to a battery whose BMS lacks that feature. | ||
+ | |||
+ | >> For belt-and-suspenders you could add a $10 12v temp controller or NO thermal switch in series [with the disabling method]. | ||
+ | |||
+ | Note that some chargers have built-in low-temp charging cutoff already. | ||
+ | |||
+ | |||
Line 570: | Line 596: | ||
Some batteries have BMS with bluetooth or other forms of connectivity. | Some batteries have BMS with bluetooth or other forms of connectivity. | ||
+ | Having visibility into the state of the BMS/cells might be useful for tech geeks, but often muddies the waters for non-technical customers. | ||