they are a 1500mah 15a continuous cell. and probably old age and an application that dumps them in about 5 minutes.
i would replace with these.
those are my go to for tool pack rebuilds.
just rebuilt some...
i have rebuilt a bunch of bikes myself.
got a goldwing tore down right now.
getting that tank fixed is first.
as long as its shedding crud you wont keep a carb working very long.
i tear the carb down and remove any plastic.
then soak in hydro seal or berrymans carb dip.
blast it out with air...
enough energy to blast that diode=dead driver opto.
and likely other parts.
on high cost parts jobs i replace everything.
then test via dim bulb.
idea is to have enough resistance in circuit to limit current if something gets latched up .
a bulb does that and serves as an indicator.
got one of those chinese componant testers?
since you have several identical channels grab the diode from either side.
the tester will tell you if its a plain diode or a zener.
the ic behind it is likely an optocoupler and bad too.
any part on the gate of a failed fet is suspect.
and if you dont...
can you see whos cells are in these?
all the real ryobi packs i have seen had samsung or lg.
had 1 knockoff that had generic 2200mah laptop grade cells.
they must have thought that in 3p they could get away with it.
they were beat.
many cheap and nasty ups units have a timer in firmware.
its not designed to run beyond its stock battery capacity.
best ones are the old metal case apc and best power units.
i usually set up a fan that runs from the logic so it runs in inverter mode only.
metal case= probably good.