Deka 8G31 batteries were drained, what's the procedure to try to get them charged

I was just informed by a freind that our GEM (many miles away) was left unpluged for weeks or months and that now pluging in the charger does nothing.
Zivan was upgraded, Deka gel batteries were new in 5/11 and everything was working fantastic until now.
I remember but searched and could not find a specific one at a time battery recharging procedure that needs to followed but if anyone knows or can direct me to that process I would appreciate it!
Thanks & Happy new Year!

Very good, appreciate it Marlon for getting this info over quickly!


Be sure to confirm the voltage of your batteries before charging them individually. Most GEMs use six 12 volt batteries to achieve 72 volts. Some later years use nine 8 volt batteries to achieve 72 volts. A 12 volt charger will overcharge an 8 volt battery. Instead, use a 6 volt charger on these. There are rare and expensive 8 volt chargers available, but you do not need one.


Thanks everyone for the help, I was fowarding this info 2500 miles away and they eventually got it solved. The Zivan repair facility in Sacramento said that the system needs to have a minimum of about 55V or 56V in order for the charger to then step in and finish the job. Also someone mentioned that it’s a good idea for each of the 6 to have a similar level of charge. So the safe recommendation of getting each battery to 10V (60V overall) worked great.