Harry, Congrats on the buy. 'Not a clue about later charging systems, but I found two things really helpful from Harbor Freight recently. I bought an actual 'battery tester'. I am from the era of colored balls floating in fluid from each cell to tell the viability of the battery. This item is just like you would find at any decent battery store - but for ~$20. (Item#61747)
The second one is even more trick. It's a batt. charger and conditioner. It's mostly automatic with graphics for the common charge, but the other feature will revive what-appear-to-be dead batteries. (Item#63299) I took an old marine battery I knew to be dead at least a decade and got it to come back - but it quickly loses its charge. Another, old, cheap 12v never took any charge. But, it seemed to work well and much faster than the old 'hummer' I have used for 20yrs ..on three other batteries.
(I found out about it from the praises of an electronics whizz who writes for an airplane magazine. Normally these guys are pretty snooty about 'China Designed/Made'.)
I also use those mini 'Battery Saver' gizmos ...but think they're a waste. I could have paid for half a good quality battery.