Author Topic: MOT fail - car battery died - new battery?  (Read 1071 times)

Offline AdzCM

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MOT fail - car battery died - new battery?
« on: July 18, 2014, 10:04:18 pm »
Car failed MOT because the guy sat with the engine off while he tested the headlights etc. I also have 4 gauges that light up with the ignition lights on.

With the car started and multimeter on - I get about 13.2 - 13.5V

Does this mean the battery is at fault or the alternator, or are these batterys just crap that they drain very quickly???

That battery has sat since October, and the car started first time [after I rebuilt it] in June without having to charge it. And it had started every day since then ok until MOT time, and it dies quite quickly when engine if off and lights are on.

I tested it when I came home - battery was reading 12.8V - turned on headlights with radiator fan and heater fan - the voltage dropped relatively quickly - went to start it with about 12.2V and it tried, clicked and reset the clocks....batterys dead

Do I need a new battery would you say? or possibly a heavier duty battery? Sorry about the serious description but its what happened haha.

Offline C0UP3

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Re: MOT fail - car battery died - new battery?
« Reply #1 on: July 19, 2014, 12:19:53 pm »
Euro car parts have sale on atm so worth getting a new batt anyway. I have a Bosch silver I think. Voltage when running should be 14v with no lights or anything on just the engine running. Low voltages from alternator can also make the car run slightly bad

Offline AdzCM

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Re: MOT fail - car battery died - new battery?
« Reply #2 on: July 19, 2014, 01:29:25 pm »
You just reminded me. My polo originally had a Bosch silver which was pretty much done, but was better than the one I replaced it with. The one I have is a low budget piece of crap really... I'm going to get a Bosch S5 then. Might get my alternator reconditioned too.

Cheers man!

Offline Ben.lopo

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Re: MOT fail - car battery died - new battery?
« Reply #3 on: July 19, 2014, 05:00:48 pm »
If it's been sitting and not driven about then the battery won't charge properly if you got over 13v that's really good after a good run about that should be fine