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Calculating usable battery capacity...help

Roqm

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Jun 17, 2020
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Hello all i am looking for some help, i have some battery modules and i would like to know how do i go about calculating the usable capacity (power my inverter can actually use) the inverters range is 40-60v the modules are 3.7v nominal 14s 50ah @2hour rating. The module's capacity i can work out and will test for accuracy once tester arrives but i would like to have the usable capacity as well. Thanks in advance for any help.
 
First, these are NMC cells. The electrolyte is toxic and flammable. Use of a BMS is MANDATORY. You should completely understand the risks involved and become your own expert.

Typical 3.5-4.05V/cell should be AROUND 20-80% SoC.
 
I have done research including trying to get info directly from the manufacturer( no luck)
Safety wise i have sorced the bms that will be used already, i have familiarized myself with the specifications i could find and sourced equipment to do some basic test (actual capacity checking soh) my issue is wanting to know how to go about calculating the usable capacity specificaly in the voltage range of my inverter so i know what i have at my disposal to actually use.
 
Simple:

40V/14S = 2.86V/cell - avoid the shit out of this. Will shorten life.
60V/14S = 4.29V/cell - SERIOUSLY avoid the shit out of this. Will shorten life and presents substantial fire risk.

Your operating range is below 0% and above 100%. In other words, if you use the entire available inverter voltage range, you will dramatically reduce the life of your cells AND run a risk of fire/explosion every time you charge to 60V.

You need TO LIMIT your range from 14S*3.5V = 49V to 14S*4.05V = 56.7V if you wish to maximize cell life and minimize fire risk.

Lastly, each CELL in the battery module should be fused. If a single cell in a parallel group fails, all parallel cells will dump their current into it, and you'll likely get thermal runaway/fire with an entire parallel group of cells destroyed.
 
Thank you, the intention is to keep the modules as they are 14s and parallel all the modules and yes each modules connection will be fused with a dc breaker .
 
No. each CELL in parallel with other cells need to be fused.
I understand and was explaining a added layer i am using also it will help with being able to take a module offline if i needed
 
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