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Oops!! 24v to 12v converter fire

Jasondrumguy

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recently I needed more amp hours in my van. I had three of the 12v valence batteries. My system has the 12v 3000 watt pure sign inverter, 4 100w solar panels, a 50am Renogy DC to DC with MPPT. This system worked fine but I run the inverter 100% for a small energy efficient AC fridge, and my sleep machine would drain batteries half way through the night. So I got 8 of the 100amp hour life PO4 lithium cells in series is 24v. My system is 12v so I got a 24v to 12v and put it on right after the wireless Bluetooth BMS. Well things seemed okay, i noticed my 3000a inverter acting like know power when over 50% in battery. Any batteries got to 100% and eventually the 24 to 12 started a fire. Any suggestions on what to do to avoid another fire appreciated. Thanks
 
Go back to a 12v battery bank. You would need a very large 24v-12v converter, or many of them, to allow a 12v inverter to run off of a 24v bank of batteries.
 
The 24V inline fuse on my 18AH battery 800W APC SUA1000XL is rated 100A. They can draw a serious amount of power.

For a test I added a 24V 35AH pair fused at 25A (the largest I had readily available) and attempted to start my full-sized fridge. The 35AH pair got the compressor started just as the fuse blew, and it continued running on the 18AH pair.
 

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Go back to a 12v battery bank. You would need a very large 24v-12v converter, or many of them, to allow a 12v inverter to run off of a 24v bank of batteries.
Would I need two new 12 volt BMS’s? I was think splitting the bank in have and parallel the two twelve banks. I just wasn’t sure about the BMS
 
Would I need two new 12 volt BMS’s? I was think splitting the bank in have and parallel the two twelve banks. I just wasn’t sure about the BMS

A BMS on each 4s battery is required if you go with the more common BMS type. There are some BMS that can span batteries but I have no experience with that type of BMS.
 
Yeah isn’t the path of least resistance in a functioning (otherwise) 24v system to just get a 24v inverter? Craigslist the 12v inverter or use the three old valences as a dedicated 12v system with the inverter and charge b2b from the 24v pack.
 
Here's where you went wrong: You have a 12V 3,000W inverter that requires 250A at full load. Your converter, depending on which one you bought, will supply 120W to 480W at 12V. That's anywhere from 10A to 40A. So you were trying to push up to 250A thru a converter that was only capable of handling 10-40A. Big oops! LOL

As suggested above, get a 24V inverter or stick with a 12V battery. Double check your cable sizing while you're at it to make sure it's sufficient for the 12V amperage your inverter requires. The size will vary, depending on the length of the run.
 
so you are going 12v alternator to 24 v back to 12v then to 120v ac???
doesn't this sound much simpler 12v to 120v ac...
 
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