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electrical:12v:directcharginglfp [2024/03/19 22:25] frater_secessus [application] oops, R, not mR |
electrical:12v:directcharginglfp [2024/06/04 14:37] (current) frater_secessus [testing phase] |
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If the SoC was very low (near cutoff) the combiner would slightly faster, ~7.5 minutes. | If the SoC was very low (near cutoff) the combiner would slightly faster, ~7.5 minutes. | ||
- | ===== assessing your own setup for direct | + | ===== reasons NOT to attempt |
- | + | ||
- | There are good reasons //not// to attempt direct charging: | + | |
- | For example, if | ||
* you have [[electrical: | * you have [[electrical: | ||
* you have a **small or already-overloaded alternator** | * you have a **small or already-overloaded alternator** | ||
* you **already own a DC-DC** | * you **already own a DC-DC** | ||
+ | * your BMS has no low temp charging disconnect and you have no desire to work around that((to be fair, this also rules out DC-DC that lack low-temp disconnect)) | ||
* you **want predictable charging rates**, like 40A over the next hour. DC-DC will provide this((barring interference from big chassis loads, BMS protections, | * you **want predictable charging rates**, like 40A over the next hour. DC-DC will provide this((barring interference from big chassis loads, BMS protections, | ||
* you want **stable charging rates** regardless of state of charge((acceptance will taper in Absorption if present)) | * you want **stable charging rates** regardless of state of charge((acceptance will taper in Absorption if present)) | ||
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* a set of heavy jumper cables and a clamp-on monitor might help assess max current draw before buying any wiring. | * a set of heavy jumper cables and a clamp-on monitor might help assess max current draw before buying any wiring. | ||
- | If you are still interested, here is one approach to assessing your setup for direct charging | + | |
+ | |||
+ | ===== assessing your own setup for direct | ||
+ | |||
+ | [Note: | ||
+ | |||
+ | ==== assessment phase ==== | ||
- pay attention to the **chassis' | - pay attention to the **chassis' | ||
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- now make a **sanity check** about the ability of alternator, your isolator, and your Li battery to cooperate. | - now make a **sanity check** about the ability of alternator, your isolator, and your Li battery to cooperate. | ||
- ensure the **fuse** between your chassis and battery bank is sized so //you cannot draw more than the alternator and wiring can handle// | - ensure the **fuse** between your chassis and battery bank is sized so //you cannot draw more than the alternator and wiring can handle// | ||
- | - make the first test run a brief one and with the Li fairly well charged.((higher states of charge will typically lessen current demands to some degree))((if you have paralleled batteries you might want to do this step with just one in place to get a feel for the draw.)) | ||
- | - test it with a drive. | ||
- | - repeat the last two steps with the Li bank at lower and lower states of charge, down to the lowest state of charge you expect to recharge from alternator. | ||
- | - disconnect the isolator with **a switch** when you come to the desired SoC, when charge rate exceeds your preferences, | ||
+ | ==== testing phase ==== | ||
+ | |||
+ | - make the first test run a brief one and with the Li well-charged.((higher states of charge will reduce current demand)) | ||
+ | - if solar or other charging source is present, disconnect those chargers and repeat #1.((other chargers will push up apparent bank voltage, which would decrease current demanded of the alternator)) | ||
+ | - repeat steps above with the Li bank at lower and lower states of charge, down to the lowest state of charge you expect to recharge from alternator. | ||
+ | |||
+ | |||
+ | ==== caveats ==== | ||
- | **Caveats**: | ||
* Only alternator charge while driving ([[rv: | * Only alternator charge while driving ([[rv: | ||
- | * Pay attention while charging from alternator to keep from overcharging the Li or holding for long periods at high [[electrical: | + | * Pay attention while charging from alternator to keep from overcharging the Li or holding for long periods at high [[electrical: |
- | * Fuse the wiring from the chassis so the bank cannot pull more than you specify | + | * if current is excessive but you want to direct-charge, |
- | * if current is higher than you want consider adding resistance | + | |
===== the parts list ===== | ===== the parts list ===== |