# Arduino BMS



## arklan (Dec 10, 2012)

i looked in this back when i got my car, but arduinos have common ground so its not really possible. even with transistors coz they have common grounds aswell. youd need to isolate each battery from the arduino and then it wont be able to sense anything, youd need something that can send the voltage over an isolated connection, i dunno how to do that :/


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## Moltenmetal (Mar 20, 2014)

Whatever you use needs to be either isolated and powered from each cell or it needs to have high voltage true differential inputs. It also needs very high RFI/EMI immunity and to be robust under automotive conditions. For the cost of it, buying a ready made BMS is probably your best bet. 

If you want cheap and don't mind a little cell imbalance caused by the device (not a big issue if your cells are of a decent capacity and don't leave the batteries for long periods without charging), and you don't mind trusting the health of your pack to a very cheap device, you can use two CellLog8s to log and alarm on low or high cell voltages. $30 each, so you can't beat the price- and way better than going without a BMS in my opinion. Note that this arrangement won't give you shunt charging capability so you'll have to balance your cells yourself, but since most people feel that cells don't drift much under normal circumstances (some feel this so strongly that they'll use LFP cells without a BMS), you're really not at much risk. Not using shunt charging isn't a big deal as long as you terminate charging when your lowest capacity cell reaches the high voltage cutoff and you choose a reasonably conservative high voltage cutoff setting, again assuming that you aren't charging at a high rate relative to your cells' C rating. The CellLog can be configured to alarm on high or low cell voltage or high cell differential voltage as well.


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## remy_martian (Feb 4, 2019)

^ Can you translate that from Canadian, 'bot?


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