Quote:
Originally Posted by WalterM6
Here is the reason the charger has to be plugged in before the BMS will turn on again. The BMS will open the discharge switch if a individual battery cell falls below 2.5v. But it won't turn back on again until that cell recovers to 2.7v It happened to me yesterday. It confused me for a while because my lowest battery was setting above 2.5v.(2.637V) What I did to fix it was temporally reduce the recovery voltage to 2.55v and the BMS turned on w/o connecting a charger. This probably won't help with the store bought batteries because you don't have access to your BMS settings but it's worth mentioning. But it will work for DIY batteries.
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This is also a scenerio where having a solar panel on the roof (or as the roof) will correct this issue fairly quickly in daylight conditions as it will get the cell back over the 2.5v threshold in short order allowing the bms to rest in short order. I believe a balancer can help with this also if you have a weaker cell as it will transfer power from adjacent cells.
Also this may only be useful for those with single batteries or diy batteries where replacing the bms is an option but they do make BMS units with built in shunts and remote hardware amp meters in addition to the bluetooth info.
I recently bought one for the battery im building. it also allows a continuous current draw of 240amps which could be advantageous to those having to turn down their current on the controllers to prevent overdraw disconnects. these types of smart bms units often also giv you a record of what kind of current your pulling and how often which is useful.