posted 11 months ago
No, out of my wheelhouse.
You have six batteries connected in series to make that 36v. Means in general, that the batteries 'closer to the discharge' do a little more work and those 'farther down the line' get a slightly lower proportion of the charge. If you follow the solar forums, there is a lot of talk of battery balancing, even folks building their own equipment to charge such setups to within a few hundredths of a volt.
If you want plug in wall simple, then sourcing an original type charger or repairing yours would be the way. Those chargers are fairly simple, I think. If yours has failed likely the power supply is defunct. Could be easily fixed if you live where a tech or hobbyist can be found. Throw away society has banished them.
If you have solar DC available, then DC-DC chargers are available.
If you want slightly more work, then temporarily break the string up into three pairs of 6V batteries, one cable each, and charge/recondition each pair with any 12V battery charger. Mix them up if you like balance them out.