Building a BMS balancing protection voltage / current monitor

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Building a BMS balancing protection voltage / current monitor

Does anyone on this forum have any idea how this could be done

I have a IMAX b6 version 2 battery tester charger which works okay but has limitations on how much information you can get out of

I would like to use the battery voltage monitoring it does on each cell only and not use the charger balancing functions on this device

But one issue this charger has is that the voltage that is reporting for each cell is a little off for just charging one battery cell is not a big issue however using it to charge 6 battery cells now it becomes an issue because each battery cell is not is not going to be fully charged or it might not be letting you know if you are having an issue with an individual battery cell if the battery voltage monitoring coming from an individual cell is way off like 1/2 a volt could be a big issue

Soldering Slave

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Last seen: 4 hours 46 min ago
Joined: 05/10/2017 - 09:13
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Location: huntspatch, alabama

It depends upon how good you want to be.

There are ICs made to perform all the BMS functions for series of cells such as used in packs. Usually the balancing is done by “bleeding”, just burning off 10 to 100 mA of a higher voltage cell thru a resistor. They can read and report voltage, temperature, current, etc. Also there are small ics, e.g. DW01, that control the BMS functions for single cells.

i don’t know anything about your charger but would guess that it is just charging all or half of the cells as in parallel, so the same voltage is applied to all regardless of any difference between cells. A half volt is a Huge difference that would take a long time and be hard to correct with a bleed balancer.

if you want accurate voltage and current measurements, then that is a function of using high quality components with tight tolerances in your signal conditioning and sensor circuits, with compensation for error sources such as temperature changes, and adjustment features for calibration. Not trivial and not cheap to do, which is opposite the goals of mass-production.

From your title and post it is somewhat confusing about what it is you really want—If you just want to accurately measure voltage then get a good voltmeter, i.e. likely to be expensive.

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drivin' around on fossil fuel,
until i saw what i was doin',
was drivin' down the road to ruin. --JT