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Need help understanding BMS amp possible bottlenecks

johncolson

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Dec 24, 2021
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What kind of bottleneck does a 200a BMS on each battery create when you have 2 300AH batteries connected in parallel. 12V System.
I need to keep the wife comfy, she does not like the heat, or she might quit RVing with me so I need to design a system that could possible run 2 15000btu ac units at night for around 3 total hours of run time. We hope to boondock most of the time. I will be using a generator during the day to charge the batteries and run the RV. Eventually I will be adding Solar Panels. I believe I may need a 5000 watt inverter/charger for future upgrades or additional batteries if necessary. I know I will have to install a softstart on each ac unit. I thought I had all this figured out until I read an article showing how running a microwave takes about 95 amps to run and will almost trip a 100a BMS. I do not know if this article is correct or not. If I have 2 batteries in parallel each with 200a BMS do they share the amp volume so that if a 200a pull came through it would be treated as a 100a pull by each battery. Thanks for your help.
 
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Amps are not the meaningful unless we know the system voltage.

200 amps at 12.8 volts nominal = 2560 watts
200 amps at 25.6 volts nominal = 5120 watts
200 amps at 51.2 volts nominal = 10240 watts

200 amps is a lot of current regardless of voltage but in order to get work done you need to combine those amps with voltage.

If the BMS is procured via Ebay, Ali-express or similar the continuous amp rating should be taken with a grain of salt.
Different vendors stretch the truth to varying degrees.
 
Sorry about that. My system will be 12V.
A 5000 watt inverter is beyond impractical at 12 volts.
5000 ac watts / .85 conversion factor / 12 volts low cutoff = 490.196078431 service amps
490.196078431 service amps / .8 fuse headroom = 612.745098039 fault amps
 
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