Jim, unfortunately the new battery will have a pretty short life. I suggest you always charge the cart in a well ventilated area with the seat up, and check the fluids in that battery before each charge.
Tim, I understand your caution. I've been very concerned with the charging cycle, much more than the discharge side for sure. The last time I discharged, I drove the cart until it stalled. All batteries were above 11 vdc except for one. It was 10.6 volts. The Everlast Maxx was still up at 11.5 volts. When I start the charger, it slowly ramps up to full charge current. It shows a normal charge cycle until 90% charge level is attained. At that point, the charging voltage on the three original batteries is up around 13.8 volts. The Everlast Maxx shows about 14.5 volts. That tells me it is charging up quicker and dropping more voltage at that point. As full charge is achieved, two of the original batteries go to 14.4 and one at 14.0 (the weakest older battery). The Everlast is peaking out between 15.3 to 15.5 volts. So, the total charging voltage from the charger is around 58.5 volts. The actual target for full charge is probably 60 volts, but my charger seems to cut off before it achieves that much.
The reason I am not alarmed is that my regular 12 volt charger charges up above 15.5 volts on a slow charge and just maintains 5 to 10 amps for as long as you leave it attached. The golf cart charger senses full charge and shuts off below 60 volts or after 8-10 hours when charging from full discharge. For that reason, I don't think this is a high charge rate for any of the batteries. It's true that the Everlast is reaching full voltage before the other batteries, but it also is limiting total charging current. All of this is within specs of a normal battery charger. I have checked the electrolyte and don't see any boiling away.
If I didn't feel so confident that this is a workable arrangement, I'd go get four of the Everlast MaxX batteries and install them. Because the parameters are similar to my stand-along 12 volt charger, I am willing to give this a try. My brother's charging area is in his yard, parked beside his house at an outside outlet. I prefer he leaves his seat down because the seat bottom is a plastic material that is non-corrosive. If there were an explosion, I think that seat would deflect most of the acid and keep it contained.
I am hearing everything you are saying and I know how dangerous batteries can be. My brother will probably only charge this cart every three or four weeks and I'll be checking it regularly over the next 6 months. Every time I visit, I'll carry my battery filter jug and a gallon of distilled water. The voltmeters I installed will give me good instant feedback anytime I need a quick check.
