How to charge low 8v batteries?

[FerrumCampitor]

Hello. My father brought me his golf cart to find a slow drain. The cart charger won't work because the system is too low (below 28v). The batteries are at about 4v each right now. I understand that you can use a 12/24v charger on three batteries at a time. I tried doing that but the charger I have auto-detects 12/24 and it's not seeing them as a 24v system that is too low. It only sees it as a 12v that is overcharged. So it won't charge them properly at a 24 system.

What do you do with 8v batteries to bring them up to capacity? Are there chargers you recommend?

[meimk]

An old fashioned 12 volt automotive charger (dumb charger), one battery at a time, low amperage, for 15 or 20 minutes each battery should bring them up enough for the regular cart charger to "see" them and come on.

[AdamDavis]

I agree with meimk. I've done that method quite a few times and worked every time - make sure not to over charge... Just be aware that if the batteries are completely drained - be prepared for an extremely shortened life on the batteries.

[JohnnieB]

FWIW: The max On-Charge voltage for most deep-cycle batteries is about 2.7VPC (Volts per Cell), so the max for an 8V battery (four 2V cells) is 10.8V.

Monitor the voltage on the 8V battery while charging it with a 12V charger and stop charging when the monitored voltage reaches 10.8V.

[FerrumCampitor]

Awesome thanks guys!