I often get asked to repair mobility scooters, most of the electrical faults are due to poor corroded contacts or broken wires, poor batteries or chargers that are dead but easily repaired. When I've repaired a charger it's ok to test IF I have the scooter and battery pack, often this is not the case. I am trying to find a circuit that will simulate a battery charging and discharging, ok I could use a real battery, but these scooters run on 12 or 24v SLA. has anyone any suggestions? As my forte is repairing power supplies, electronic loads, PSU's etc are available.