auxiliary 12v loads on a 24v system

c3auto

New Member
Hi y'all

My main solar system in my sprinter van will be a 24v system. From there it will feed into my AC system through a big inverter.
However I have a few small loads that run off on 12v.

The 24v system is 2x banks of 320A lifepo4 cells in 8S with a JBD BMS.
But the piggy back system will run just off of 1 bank.

Am I able to run a small 12v load off these batteries?

My idea is that I would be making effectively a 4S 12v system by putting the positive of the first cell and the negative of the 4th cell.


The 12v load is 4A (for a linear actuator bed lift) 2-4x a day for a few minutes each time.
The other 12v load will be for LED strip lighting. I'm not yet sure how many A but I can't imagine it being over 5A.
I'll fuse them appropiately of course.

The proper way would be to get a 10A or so 24v to 12v DC to DC transformer but wondering if I could get away with it for such low loads.

I've been also thinking of wiring a 12v jump start circuit from my 24v system through an anderson plug.
Would the BMS go crazy over it, or would it not sense it (just the voltage/current drop over the first 4 cells) as I'm using the battery positive and negative and not connecting to the BMS.
My starter is 1.7kw so would be less than 0.5C for a few seconds. I was thinking of using a 200A fuse for this 12v jump start plug.

Thank y'all
 

NVS

Solar Enthusiast
Spend the money on the 24v to 12v converter. Otherwise you will unbalance your man 24v battery. That's the right way. To do it and put 30 to 60amp converter in. There is a lot to run off of 12v.
 

eXodus

Solar Addict
t
Would the BMS go crazy over it, or would it not sense it (just the voltage/current drop over the first 4 cells) as I'm using the battery positive and negative and not connecting to the BMS.
The BMS would not like that. And 5A is no small load - the BMS is build to balance a few milliamps. You probably burn it out rather quickly.

You got a Sprinter - you got a 12V lead battery? Why not use that one? Get a 24V to 12V charger 1-2A should be plenty since it will be connected 24/7. Those things are like $10-15. Just set it to float voltage 13.2V for the lead.

Or if you are as cheap as I'm, I got 120V to 12V charger. 24V - Inverter 120V - 12V :p very inefficient but only used for a few amps a day so it doesn't matter.
 
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