Jump starting/charging a 24v battery?

nyyankees588 · 04-06-2022, 05:32 PM

Odd question, figured I'd ask here before admitting defeat to see if brighter minds have better ideas than me.

I need to charge a 24v lithium battery. It's basically dead (voltage-wise) - sitting at 9v. I'm helping the owner get their small solar + storage setup back up and running and because the battery is at such low voltage, the solar charge controller will not kick back on. I don't have a 24v charger and I can't find anybody that has one to pay to use (boat shops, auto parts stores, battery stores). I could have the owner buy a 24v charger, but it'd be a bummer to spend $100-$200 to charge a battery once (and likely never need it again).

Any suggestions? I'm in Santa Cruz, CA.

Lilnuts2 · 04-06-2022, 05:55 PM

truck stops with a shop can charge it for you

Twoxentrix · 04-06-2022, 05:56 PM

This forum Thread has some interesting conversation about the same thing, may prove helpful:
https://www.rvforum.net/threads/jump...attery.116974/

nyyankees588 · 04-07-2022, 07:42 PM

Thanks! Yeah, truck/diesel shops were going to be my next check. With trucks that run on 24v systems, I'd imagine they have them.

The lithium aspect is another uncertainty... we'll see. May end up just buying an amazon one with programable charge settings to charge it more safely.

carringb · 04-07-2022, 09:09 PM

Beware that if the battery is actually deep-cycled (meaning improper BMS or no BMS or stored a very long time at minimum voltage), trying to recharge it, especially unregulated, can lead to thermal runaway.

moorefc · 04-15-2022, 08:44 AM

If you haven't, start with a 12v charger which will at least boost the charge....You can tie two similar old school (10a?) automobile chargers together in series to help bring it up, but monitor that process.....Also programmable power supplies (trickle), computer power supplies in series, etc...
As mentioned earlier you probably want a slower charge to avoid internal hot spot generation...

nyyankees588 · 04-15-2022, 01:01 PM

Yeah, I considered two 12v chargers in series to get 24v, but decided against that as it would be a bit sketchy, even with 2x of the exact same chargers. Ended up ordering at the cheapest.

I ended up buying the cheapest programmable 24v battery charger on amazon (~$70) and we'll see where that gets us. The lifepo4 battery isn't name brand and my guess is that it has no (or a pretty bad) BMS, since it's sitting at 9v.