How can I charge a dead car battery at home?
Updated 25 Mar 2021
Most car batteries can go for at least five years without needing to be replaced or recharged.
But even the best car batteries will run out of power eventually — or lose their charge prematurely when you leave your lights on too long.
But recharging one can require little in terms of tools or mechanical experience, even if it is just to get the vehicles started to get it to a garage.
Remember, batteries are based around a chemical reaction involving an acid – so treat them with respect.
Always work in a well-ventilated area, never lean over a battery when working on them, including when inspecting levels in the cells, and it’s a great idea to wear eye protection too.
If you get acid on yourself, rinse the area with running cool water for 20 minutes or more and seek medical attention.
Vehicles started with these methods should not be turned off if a new battery is needed - or you’ll have to start the process again!
Jump starting a car with a dead battery is probably the most common method and isn’t hard to do if you’ve got all you need - namely jumper cables and, most commonly, a second vehicle, although it can also be achieved with a second battery or a battery booster.
While it isn’t a complex operation, it must be done correctly to ensure you and your vehicles’ safety.
A home battery charger can also be the answer. Ensure you have the right charger for your vehicle’s battery type and always follow the manual to the letter.
But there are a few other ways you can possibly revive a dead battery, but bear in mind they won’t always work and care should always be taken.
And there are some that may indeed work but seem dodgy to us, including rigging up a laptop charger to do it. We’ll leave that one out . . .
- Distilled water: If the electrolyte level in the battery is low, adding distilled water might be enough to fully submerge the plates and enable a bit more reaction area. This may be enough to give the engine’s starter motor a few more turns and get you moving.
- Epsom salt: AKA magnesium sulphate, or MgSO4, can be found in grocery stores, home gardening centres and pharmacies. Adding a stronger acid to the electrolyte mix, such as Epsom salt, might be enough to tip the chemical balance, delivering enough charge to start the engine. Dissolve 1 part MgSO4 with 3 parts warm water, then add to each cell until the plates are covered by 6.5mm to 13mm.
- Aspirin: OK, so this is really for desperate circumstances - like you are literally in the middle of nowhere . . . and have a couple bottles of water and aspirin. Believe it or not, Aspirin (acetylsalicylic acid or C9H8O4) can be used to chemically alter the electrolyte mix. Crush and dissolve 12 Aspirin tablets, 325-mg or 500-mg, in about 175ml of warm water and add equal amounts to each cell. Add additional water to make sure the plates are covered and see if you can’t get your inner MacGyver on!
Tried everything and still no luck?
You may need an new battery.
Lucky you can use AutoGuru to get quick quotes from battery specialists near you!
Lindsay Saunders has been writing, editing and producing words and photos for more than three decades, starting back when he drove a 1971 VW Type 3 fastback.
Now he’s got a Hyundai I30 diesel, a 1999 LWB Hi-Ace (camper project) and wishes his wife’s EJ Holden station wagon was actually his.