Flat battery - managed to bump start - what next?

bluedrop

Hi all,
I forgot to switch off the headlights while going into the gym today. The battery went flat by the time I came back about 1.5 hrs later. Luckily, the car was parked on a sloping road so I managed to start it. Drove around for about an hour after that (picked up my husband from his office 30mins away).

Have I damaged the battery?
Would the 1hr drive have charged the battery sufficiently for tomorrow? Will the cold weather drain it over night?

What should I do now? Get the battery recharged? Replace it? The car is 5yrs old (We bought it new)

bobbymotors

Try it in the morning. If it starts you'll be ok. no the battery wont be damaged.

cold weather won't drain it as such, it just has to work a bit harder thats all.

if you have a trickle charger then charge it overnight tonight if you want to.

EssexExile

Don't panic. If it starts in the morning all is well.

Gloomendoom

^^^^ As above. If it does it again, replace the battery.

System

bluedrop wrote: »

Have I damaged the battery?

What should I do now? Get the battery recharged? Replace it? The car is 5yrs old (We bought it new)

Yes you have damaged the battery. If the voltage drops below 10.5 it causes damage to the plates inside it through sulfation which is where the surface of the lead plates crystallises. If you use the car regularly you may not notice any issues but if you go out to it one day, especially after a freezing cold night, and it won't turn the car over then you know why.

Put aside £100-£150 in case you do have any issues.

Robisere

Tarambor wrote: »

Yes you have damaged the battery. If the voltage drops below 10.5 it causes damage to the plates inside it through sulfation which is where the surface of the lead plates crystallises. If you use the car regularly you may not notice any issues but if you go out to it one day, especially after a freezing cold night, and it won't turn the car over then you know why.

Put aside £100-£150 in case you do have any issues.

Correct advice!
If it starts in the morning, let it run for 5 minutes, then switch on headlights, preferably Main Beam. Stand in front of lights, get someone to sit in driver's seat and Rev slowly upwards. Lights should brighten as engine is revved. If they don't, it will be because battery is on its way out, due to alternator working to recharge it but failing because battery is Sulphated, as described above.

Jonesya

If the battery is now 5 years old then it's getting to the point at which you need to replace it, and it's a lot easier to replace it when it's convenient than when it fails on you and won't start one cold night.

Also - you say it went flat after leaving yours lights on for just 1.5 hours - that's quite quick, a typical car battery should be able to keep the lights running for quite a bit longer than that, suggesting the battery is on its way out.

I'd check your car manual for the battery details, shop around around to get some prices and get it replaced.

fred990

I've been messing around with some old (10 yrs+) abused, neglected and frequently over discharged car batteries that won't hold their charge, one down to the 10.5v level.
Bought a CTEK charger, couple of maintenance cycles later they're sitting at 13v + and now usable!
Worth the money.

oldagetraveller

"Bought a CTEK charger"
Which probably cost close on what a new battery would be.
However, you do have the device for possible future use.

System

fred990 wrote: »

Bought a CTEK charger, couple of maintenance cycles later they're sitting at 13v + and now usable!
Worth the money.

Plates are still sulphated, no charger can undo that, only replacement of the plates can. If they're at 13+ volts an hour after disconnecting the charger that would worry me. 12.6V is the normal resting voltage of a car battery and 13+ is what you'd get with the engine running so to be at over 13 volts god knows what rate that charger is charging at.

Richard53

Tarambor wrote: »

Plates are still sulphated, no charger can undo that, only replacement of the plates can. If they're at 13+ volts an hour after disconnecting the charger that would worry me. 12.6V is the normal resting voltage of a car battery and 13+ is what you'd get with the engine running so to be at over 13 volts god knows what rate that charger is charging at.

By 'a couple of maintenance cycles' I assumed he meant a couple of sessions with the charger, not the time after charging. I have an Optimate and have used that to resurrect several batteries. An intelligent charger is a good investment IMO.


OP, at 5 years old the battery is nearing the end of its useful life (average is about 7 years) so I would replace it in the next week or so before the really cold weather starts, for peace of mind. Repeated flattening will kill a battery. Doing it once won't do much damage, but it is cumulative. As has been said above, it's far easier to replace a battery at your leisure than have it let you down when you are late for work. And, if the AA/RAC have to come out and sell you a new one at the roadside, a LOT cheaper too.