Spare parts
Batteries & Starting Systems
Batteries, starters, charging alternators and trickle chargers: the starting system is the only part of a generator whose failure renders the whole machine useless.
Symptoms
- Will not crank at all
- Cranks slowly then gives up
- Battery flat every time the set is needed
- ATS does not start the set during an outage
- Battery replaced recently and flat again
The component that makes everything else irrelevant
A generator can be mechanically perfect, correctly sized, beautifully installed and fully serviced, and still be useless if the battery cannot turn the engine over. It is the only part of the machine with that property.
It is also the part nobody inspects, because it lives inside the canopy and gives no sign of its condition until the moment it is needed.
Why standby batteries die
A battery that is never cycled self-discharges. If the trickle charger has failed, and charger failure is silent, the battery spends months slowly going flat and is then asked to crank a cold diesel engine. It cannot, and the discharge cycle damages it, so the replacement starts its life in a circuit that will kill it too.
This is why we measure charging voltage at every service rather than only testing the battery. A battery that fails again a few weeks after replacement is telling you the charger is the fault.
The false ATS fault
A very large share of “the transfer switch did not work” calls are a starting-system problem. The ATS sensed the outage and asked for a start; the engine did not crank.
The other frequent cause is a controller left in OFF or MANUAL after a service visit. Both look identical to the building owner: the power went off and the generator did nothing.
What we check
Battery condition and terminals, charging voltage from the charger and from the engine’s charging alternator, starter motor current draw, control fuses, and the controller mode. It is a short list and it resolves most no-start calls.
FAQ
▸Why is my generator battery always flat?
Either the charger is not working, or the set is not being run. A standby battery self-discharges and needs either a working trickle charger on mains or a regular exercise run. A battery that is flat again weeks after replacement points at the charging circuit, not the battery.
▸My ATS did not start the generator. Is the ATS faulty?
Usually not. The commonest causes are a battery that cannot crank and a controller left in OFF or MANUAL after a service. Both present to the owner as a dead generator or a failed transfer switch.
▸How long should a generator battery last?
Three to five years with a functioning charger. Considerably less if it is repeatedly deep-discharged by being left to self-discharge and then jump-started.