It has to be able to charge dead batteries -- many of them will look for battery voltage to be in a certain range (like above 45 volts) before it starts charging, so that won't work. And, it has to not hit them with too high of voltage when the battery voltage is super low, which can cause the BMS to do a high voltage shutdown even though the battery cells are super low. The ones that present 58 volts to a zero volt battery can cause this issue, even though they would normally be able to start a 0 volt lead acid battery. If it's 35 volts now, or if you are bypassing the BMS to charge it, that might work, but if it's zero voltage because the BMS has turned off the discharge fet, the charger can't see the battery to begin charging, and the BMS sees way too high of voltage on the terminals, so won't turn on the charging fet because it doesn't know why the terminals are so high and what the current will be if it turns on.
I've honestly had better luck with a DC power supply that you can adjust the max current and max voltage on. Set it to 52 volts to start, and it will current limit while charging it up from 35 volts to a normal range. -- Zeke Yewdall PV Engineer NABCEP #031508-89 [email protected] 303-523-3592
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