If you want to eliminate the battery, go to your local thrift stores or freecycle.org lists or craigslist, and find really cheap or free celphone AC adapter chargers. I
Since your main pack is 72V (or 36V) according to your signature, then it will run most of the ones I've tried so far. I've found that virtually all of the little 115V AC input / 4V to 6V DC output celphone chargers I have laying around here will turn on and run at their regulated levels at 48-50V DC, and most of them will go down to 34V. Some will go down as low as 23-24V before they either just turn off or regulation becomes problematic.
They draw more current at lower input voltages to get the same regulated output voltage/current, but they still work.
For the ones that are above the safe input levels of your LED power boards, just put a high-current diode or two in series to drop it a bit. If you have an old computer power supply laying around, there are probably several bare diodes in there with largish black plastic bodies; usually on the AC input end. Paralleling at least a couple of them would almost certainly work even without knowing their specs.
If you have any old CRT TVs or monitors around that don't work, there's a good chance the heatsinked high-voltage/high-current diode(s) near the big transformer in the (usually left) rear corner will work for this, too. Just remove the whole heatsink and diode from the board and use it as-is.
EDIT (ADDED): FWIW, I've tried working with SMT parts that appear to have enough leg to deal with, and even with my tiny tip for the iron, and even some other things I've come up with like clamping a needle into the iron instead, still don't let my shaky hands solder well enough to them without damaging things, especially without a PCB to just connect traces to. "Dead bug" style with SMT is very hard....
