| Electronics > Projects, Designs, and Technical Stuff |
| Struggling to find a simple BMS Solution |
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| Boscoe:
Hi all, I wonder if someone could help me. I'm looking for a simple, low cost BMS solution for two series li ion cells. All I want is over voltage, over current and under voltage protection. When there's a fault, the MOSFETs get switched off. TI don't seem to do over current and if they do the IC is horrendously complex for what I need. I've looked through Digikey and the usual suspects but nothing. I'm currently looking at designing something discrete which I really don't want to do for something safety critical. Thanks Boscoe |
| TimNJ:
Will this be installed mass-produced equipment? Or just personal? If it's mass produced, I'd highly recommend using an industry trusted lithium-ion protection IC. At least here in the US, people are getting sued left and right for improper lithium-ion deployment...regardless of which party is actually at fault. Voltage sensing I feel is easy to do correctly with discretes, but over-current (over-discharge), maybe a little more challenging to prove you have a robust solution. Typically those use a timers and delays to check for recovery conditions, etc. |
| nctnico:
--- Quote from: Boscoe on June 08, 2020, 08:57:00 am ---Hi all, I wonder if someone could help me. I'm looking for a simple, low cost BMS solution for two series li ion cells. All I want is over voltage, over current and under voltage protection. When there's a fault, the MOSFETs get switched off. TI don't seem to do over current and if they do the IC is horrendously complex for what I need. I've looked through Digikey and the usual suspects but nothing. I'm currently looking at designing something discrete which I really don't want to do for something safety critical. --- End quote --- How about using a readily made Li-ion battery pack? That is a much better solution; but make sure it has the right certifications. |
| Boscoe:
Thank you for the replies and yes it's going to be implemented in a mass produced product. My other problem is that I can't use a dual MOSFET switch was the body diode drop is far too high at the currents it will be used at (~15A), I see drops of up to 1V in typical devices whereas I need something like 10mV! We have been looking into custom packs but our manufacturer does not provide BMS solutions. Currently I'm using a voltage monitor and a current trip sensor (INA300) to form HW interlocks with the rest of the circuitry. It seems solid to me but I've got a nagging feeling I'm doing something stupid. The interlocks will cut the charging source and any loads reducing the consumption on the battery to uAs from the MCU and glue. |
| bin_liu:
It is best to provide detailed electrical parameters, such as the most important operating current. Generally, small current (such as 1A、2A) can use S-8232 of SII. https://www.ablic.com/cn/doc/datasheet/battery_protection/S8252_C.pdf |
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