Does a Generator Charge Its Own Battery While Running?
Yes, an electric-start generator charges its own battery while it runs. But a short run won't refill a flat one, the 12V socket isn't for it, and it still goes flat in storage. Here's why.
Electric-Start Generator Batteries
Charging While the Generator Runs
An electric-start generator carries a small 12V battery to spin the starter motor. Westinghouse fits one to its iGen4500s, iGen4500AS and 8500E models, according to its FAQ.
Its WHXC instruction manual describes that battery as sealed for life, needing no regular maintenance, and automatically charged whenever the generator is running. The iGen4500AS manual says the same thing.
Not every maker works that way. US maker Generac says only some of its portable models charge their own battery, and those do it while running with a load applied. Check your manual before you count on it.
Why a Short Run Won't Recharge It
Starting the engine takes a bite out of the battery. Australian retailer Generator Store explains that the generator then has to run for a while just to replace the charge used to start it.
Whether a run keeps the battery topped up depends on how often and how long you run it, the charge it started with, the temperature and the battery's age. Their advice is to plan on an external charger unless you run the generator regularly.
Lithium Batteries With Plug-In Chargers
The Westinghouse iGen3750S does it differently. Its spec sheet lists a lithium-ion starting battery, and it comes with a plug-in mains charger that connects to an inlet on the control panel.
Westinghouse's iGen3750s manual says to run the generator at least once a month for 30 minutes to recharge the battery. If you can't, fully recharge it after no more than three months sitting idle.
Recoil Starters and Flat Batteries
Generators With No Battery
Plenty of generators skip the battery altogether. Our Champion 2.5kVA listing shows no battery fitted, and the Briggs & Stratton P3500, Westinghouse iGen2250 and Hyundai HY2000Si are all recoil start. There's nothing to charge and nothing to go flat.
Pull-Starting an Electric-Start Model
Most electric-start units keep a pull cord for the day the battery dies. Westinghouse's troubleshooting advice for a flat battery is to start the engine manually if possible, then recharge or replace the battery.
Don't take the cord for granted, though. Hyundai's HY3200SEi owner's manual (the UK edition) warns that if the battery is flat, the generator can't be started by any starting mode. Check your own manual before a blackout, not during one.
12V DC Outlets and Battery Charging
Charging an External 12V Battery
Lots of generators have a 12V DC socket. The Westinghouse iGen2250's is rated at 8A and 100W, and the Briggs & Stratton P2500 has a 5A outlet and comes with a 12V DC charging cable.
Westinghouse lists two ways to charge a separate 12V battery: straight from that DC socket, or with a mains battery charger plugged into a 240V outlet. It calls the direct method not recommended and for emergencies only, because the DC output is unregulated and may damage the battery by overcharging.
Hyundai's manual says its DC receptacle is for charging a 12V battery only, with the economy switch turned off.
Never on the Generator's Own Battery
This is the part that trips people up. The same Westinghouse manual says never to use either method to charge the generator's own 12V battery.
That battery charges from the engine while it runs. When it's flat, Westinghouse has you stop the generator, let it cool, take the battery out and charge it on the bench with a mains charger.
Using a Mains Charger Instead
For a caravan or camper battery, a proper charger plugged into the generator's 240V outlet is the method Westinghouse doesn't flag as emergency-only. For batteries left on charge, it recommends a smart, microprocessor-controlled charger, and warns that a fixed-current trickle charger will overcharge and damage the battery.
Charging batteries through a generator also wastes a fair bit of fuel, which our generator fuel consumption guide works through.
Flat Batteries in Storage
Self-Discharge Between Uses
A battery that charged perfectly on the last run still goes flat in the shed. Westinghouse says its generator batteries self-discharge slowly when not in use, and after some time may not hold enough charge to start the engine.
Auto-start models drain a little faster. Westinghouse notes the WHXC8500E-AS II uses a small amount of power in standby for its auto-start indicator light, less than 1 watt.
Monthly Runs and Maintenance Chargers
Westinghouse's routine is simple. Run the generator at least once a month for 30 minutes at no less than a third of full load, which looks after the fuel as well. If it's stored for one to three months, recharge an electric-start battery at intervals of no more than three months.
For a generator you rely on in blackouts, Westinghouse suggests keeping a maintenance charger connected. Use a smart charger, it says, not a fixed-current trickle charger or a solar panel without a proper regulator, because those will overcharge the battery.
Generator Store's check takes a minute. Measure the battery with a digital voltmeter every three months, and charge it if it reads 12.4 volts or less.
So does a generator charge its own battery? Yes, while it's running, if it's electric start. It won't keep that battery healthy through months in the shed, so give it a monthly run or a smart charger.
Choosing between electric start and recoil for blackouts? The generator finder sorts it by what you'll run. Or call 03 7056 6732, or SMS 0476 330 590.
