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Battery question and paralleling

Started by j.Au, November 10, 2021, 04:08:01 PM

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Hi all, I'm trying to install a Bolton battery parallel unit onto my RR+.  I'll be using a 3rd party battery along with the stock one.  Both are 48v, however when I take a multimeter to both batteries, the 3rd party one reads a voltage of ~ 54.6 while the stock Rad battery is reading ~ 53.8.

My questions are:
Is my stock battery damaged in some way or is this the normal peak charge?  If it is damaged, is it still considered a 48v battery?  I've read on some forums that this peak charge on a 48v battery can be indicative of an unbalanced battery, or at least something amiss with a row of cells. 

The Bolton parallel unit is supposed to be able to take two batteries of the same voltage and run them fine if the charges don't match by only drawing from the higher charged battery until they do match.  However, it has to be the same voltages.  That said, I don't want to risk running both batteries until I have determined that the stock Rad battery is operating normally.

Thank you!


I don't think there is anything wrong with the batteries.  I have two rad mission batteries and one will cut off at 53.8v and the other always cuts off and 54.1 volts.  I think its more of an issue with the BMI circuit if anything and who knows Rad may have them made that way so they don't over stress the batteries on every charge which in the long run will probably make the batteries last longer.  Just my 2 cents.


Final battery voltage is determined by the charger float voltage. The float voltage is nominally 54.6V. Keep in mind that most multimeters are accurate to only 1% and plus or minus 1-3 least significant digits. My Rad battery BMS has protection diodes in the charge circuit to prevent current from flowing from battery to charger. These diodes and other components reduce the float voltage a bit, so the batteries will charge to slightly below the float voltage. Earlier batteries may be different.

Your battery is fine.

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