Car Battery showing 5V - faulty?

Posted 4th Jan 2013

Thx all. Took the battery out and it started charging. Must not have been getting a proper connection in car.

I just have to keep an eye on the car now to see if it discharges the spare battery. I guess if it does then the fault is on the car.


Car would not start so I hooked the battery charger up to it and it is showing between 5 and 6V.

Battery is less than 6 months old and no problems until now.

Am I right assuming this is the battery and not the car? Even a drain that left the battery flat should show more than that and be able to recharge - car has not been left stood for more than a few days.

So before I cart it back to the parts store and make an idiot of myself, faulty battery?

Community Updates


Charge it before making a judgement.
Not necessarily, if something on the car is draining it, it can go that low. Are you saying that it's not now accepting a charge? Have you disconnected it from the car and tried? Lead acid batteries that drain too low can be a pig to get them to accept a charge, there are chargers available that can 'deep' charge them.

5-6v sounds very low for a lead acid battery - they should never get below about 7.5v. Normally you only see levels this low when one or more of the cells have died (and shouldn't on a 6 month old battery!).

Has this been deep discharged (radio left on etc)? I would leave it on charge to see if it recovers before heading back to the shop.

Last thing: are you sure you have a volt meter on the charger? Most only have am amp meter showing what it is charging the battery at (in which case it's right)

Could be anything - Something left on, alternator not charging. Try charging the battery up and keeping it in the house and see if it looses charge. Or just take it back, they'll test it before replacing it anyway.
Even batteries showing 12v might not be enough to start the car and still can be faulty at 12v.

as its under 5 years old it will be covered under warranty
Edited by: "J4GG4" 4th Jan 2013
okay, still in the car at the moment - I am charging up a spare and then I will swap and re-test when it is out f the car.

No short journeys, I actually did 100 miles 2 days ago. If it is the car then it is a fault.

It is not charging at all - just showing about 6V and sitting there. The spare battery is charging fine - so suggests not the charger.

I am assuming the charger has a meter as it shows 12-13v on the spare battery.

Charger is supposed to have a deep charge revive mode for totally discharged batteries.

I am willing to entertain the idea that it is a fault on the car but would a totally dead nonchargeable battery be expected if it just ran flat a day or so ago?


I will likely head to get it tested at the part place when the spare battery finishes charging. Just wanted a second opinion.
Edited by: "alternate" 4th Jan 2013
If the battery is really discharged some chargers will not charge them. There is a charger than can often do the job that others cant made by CTEK. Aldi and Lidl occasionally get the same chargers at a much lower cost but they had them earlier in the year so I think you have missed that boat
Try getting a refund on a faulty battery lol

Always user error.

Try getting a refund on a faulty battery lolAlways user error.

In your case it might be. Seeing a bit of a pattern in your posting
Wasn't me, dude. Take things at face value sometimes.
You ideally need to leave the battery charging at least over night and test voltage with a volt meter in the morning. If it still hasn't charged it's either your charger not working or the battery. If it does show 12-13v then then get someone to hold the volt meter on it whilst you start the engine. If the voltage drops very low (like 5-6 volts) then the battery has issues.

If you get it charged and it discharges again any time soon it could be alternator at fault. Once you get the car started get someone to rev it to a constant 2-3000 RPM and the with the volt meter on the battery it should read around 13-15v. If it doesn't then you're alternator may be at fault. Most new batteries are covered by warranties as long as it's a fault with the battery and not an electrical fault in the car that has done it. Also make sure you didn't leave a charger or something in the 12v socket in the car as some cars (like mine) allow that socket to be used even with the ignition etc off.
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