This is a replacement transformer for 36 volt, 25 amp Lester models # 7850, 9655.
A battery charger transformer is used to "transform" the power supply from the wall, which is AC into a useable DC output to the batteries.
This transformer can be found on the following golf cart chargers:
Club Car, Factory Part # 1012094
Taylor Dunn, Factory Part # 79-644-27
Check out some additional troubleshooting information on Chargers.