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2P 12v different brand lfp batteries

Geokilroy

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Aug 14, 2021
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Las Vegas, NV
I have a question: 2 12v 100ah lfp batteries in paralell. One has bluetooth. How accurate is my bluetooth going to be as far as SOC and up to the min amps in and out? Do I have to double or half the readings? What if it was in series?
I am not going to keep this setup very long because I have DIY'ed a 280ah replacement with bluetooth. It's going into my class C.
I am asking for my own education. Please advise.
 
The Bluetooth BMS for one of the batteries is only going to provide details about itself. The SOC will be for the one battery. The amps in and out will be for the one battery.

With two equal batteries in parallel the total current is split between the two batteries. So if the BMS says there have been X amps then you need to double that value to get the total for the whole battery bank. It won't be exact due to slight differences but it will be close.

You should avoid putting two different brand batteries in series but for sake of discussion, let's say you did. Two batteries in series see the same current, just half of the voltage. So the info from the Bluetooth BMS about current in and out applies to the whole battery bank.
 
I have a question: 2 12v 100ah lfp batteries in paralell. One has bluetooth. How accurate is my bluetooth going to be as far as SOC and up to the min amps in and out? Do I have to double or half the readings?

It will be exactly accurate for THAT battery. Assuming you have the two connected in a proper configuration for equal current sharing, you can mentally multiply or divide capacity/current by two as you like, but the ONE battery SoC will be relatively accurate for both.


What if it was in series?

It would correctly report bank SoC and current but not voltage.

However, ANY two 12V batteries to be placed in series must be charged to full individually and again in parallel @ 12V before being placed in series. You should also routinely monitor the two 12V to insure they are as close as possible throughout the operating range.

Confirm with manufacturers that BOTH batteries can be used in series.
 
Thanks for your replys. I have quite a few friends following my change from the orig lead acid to lfp. I like to be able to speak truth to their questions. I belong to a few "Gold Prospecting" clubs and boondock at least once a month. In the southwest, most of us started with solar then to lfp. I seem to be the "expert" because I am the first to research and try new things. I am far from "expert" but with your help I can speak correctly to others.
 
Thanks for your replys. I have quite a few friends following my change from the orig lead acid to lfp. I like to be able to speak truth to their questions. I belong to a few "Gold Prospecting" clubs and boondock at least once a month. In the southwest, most of us started with solar then to lfp. I seem to be the "expert" because I am the first to research and try new things. I am far from "expert" but with your help I can speak correctly to others.

We all have friends like that. Half the time they don't listen to what you tell them. Don't take it personally. Some people just like to ask for advise, knowing they won't use it. I have friends that would like to know more about my DIY LiFePO4 battery. Instead, I point them to off-the-shelf batteries. I'm not saying I have dumb friends. I know they don't have the same attention to detail that I do.
 
We all have friends like that. Half the time they don't listen to what you tell them. Don't take it personally. Some people just like to ask for advise, knowing they won't use it. I have friends that would like to know more about my DIY LiFePO4 battery. Instead, I point them to off-the-shelf batteries. I'm not saying I have dumb friends. I know they don't have the same attention to detail that I do.

These people are called "Askholes."
 
Feel free!

I credit my wife with that one. She had a particularly cantankerous coworker that would literally ask everybody in their group and then take no one's advice.

Daily.
 
As long as your BMS is accurate, I have two Daly 250 amp BMS and they don’t register any currant below about 3 amps. The soc is useless on these, I go by voltage for a rough idea. Voltage hits 12.5 it’s time to charge.
 
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