Quote:
Originally Posted by Sudsy
I have not researched them beyond the cost. That was a show stopper for me that uses the coach maybe 10 times a year. i would almost bet that they have some kind of charger built into the pack.
Sudsy
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The drop-in replacement LiFePO4 have built-in BMS (Battery Management Systems) that keep the cells balanced, enforce the charge and discharge current limits, have buck/boost voltage converters for charging (although they're usually limited to only a small buck/boost level), and shut down the pack if they detect an error condition such as overheating. The better ones will also not allow the pack to charge if the cells are below a certain temperature as that will damage the cells - the other features above are common, but low temperature detection is not - Battle Born batteries have it, available on Amazon.
The fancy BMS system itself (you can buy them separately) cost several hundred dollars and building your own pack by buying the cells and BMS with all those features doesn't save much. The end result is very expensive, but has very good cycle life and safety.
One thing to keep in mind: Cycle life != discharge life.
A 100 amp hour LiFePO4 can supply 100 amps for an hour before going dead, same as a 100 amp hour lead-acid. (Caveat: It doesn't shorten the cycle life of the LiFePO4 to discharge it to 90%, while the lead acid should only be discharged to 50% to maintain good cycle life, so usable capacity is higher if you limit things in that way. Also the Lithium pack will maintain a mostly-constant voltage for most of that discharge cycle.)
If you buy a Lithium battery charger (readily available - google is your friend), you can use a slightly less fancy (and costly) BMS, although you still need one to keep the cells balanced and automatically shut off the pack if it goes over temperature, and then not charge below freezing. Lithium battery packs ABSOLUTELY MUST have cell balancing for both safety and good cycle life.
FWIW - I have 300Ah of lead acid AGM in the trailer, and twice that in Lithium packs that I've been using safely for years in another application that requires high cycle life. Just can't justify the expense for the trailer. (I wouldn't even need a different charger - my solar charge controller has settings appropriate for LiFePO4 built in.) The prices have been slowly going down, but aren't low enough yet.