I'd like to wire 2 ebike battery packs (24v 10ah, two 12v sla in each pack, wired in series) in parallel, but I don't want to open the packs, id just like to splice the external wires and connect the + and the - together. Will this work properly? I only care about motor discharging, since I will charge them separately.any concerns? Thank you.

It should double your runtime, if charging separately, see no problems.

Thank you!