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Any of you technical chaps got any thoughts as to why the battery on my brother's 850 T5 keeps running down. It's not old and seems to lose its charge even after a long run on the motorway. The obvious thing to do is to buy another but could it be something else which might damage the new battery ? All help/advice gratefully received.
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Had a similar problem on my Subaru it turned out that I hadn't kept an eye on the levels in it and a couple of cells had dried out and died. Result new battery.
However it could be that it isn't charging alternator problem however you would have a battery warning light coming on on the dashboard.
It could also be discharging through say a faulty alarm or interior light.
Get a multi meter and put it across the battery terminals, get someone to start it. The volts should drop and then rise again as the alternator charges it (Most cars with an on board computer have a voltage guage it should do the same) Then turn off the engine and see whether the read out drops on the multi meter if so quickly it could be a knackered battery if very slowly something is discharging it. Then move on to the fuse box and start removing fuses and see if you can eliminate a circuit especially an after market alarm.
Hope all that makes sense!
Good Luck
Tom
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Thanks Tom - I told my brother it wouldn't take long for someone to come up with some advice ! You can't get much quicker than this. I've given him this ite's address so he'll be able to check for himself any other posts on this subject. Ta very much.
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Had this trouble on a Saab;Boot light was staying on.
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Sound advice, before buying a new battery - even little things can drain a battery if accidentally on for a long time.
Be careful before pulling out fuses. Some may control things with computer memories, which will need resetting if disconnected. eg find out the radio code before unplugging it.
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The alternator could be failing to charge the battery even if the light is out.
Leave the car to stand for 2hrs. Check the voltage across the terminals - it should be around 12. Have someone turn the motor over whilst watching the voltage carefully - it shouldn't drop below 10. Once running at fast idle turn off all electrical accessories and check the voltage - it should be around 14.
If the voltage at the battery terminals when running is low then check the voltage at the output terminal of the alternator. If this is also low then you have an alternator fault. If it's OK then you have a wiring fault.
From your description it sounds like you have charged the battery successfully off the car but then after a run it is discharged. What happens if you charge it up, then leave it unused for a period? Does it self-discharge? Could have an internal battery problem - one faulty cell perhaps. Don't assume the battery is OK just because it's new. If the battery has been discharged below a certain level (don't know the figure) then it may no longer be able to hold charge other than for a short period.
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Thanks Cyd - even I can understand that ! Ta to the others who replied too.
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Had the same problem with an Astra that stranded me.The car had just been serviced and the garage had adjusted the alternator drive belt tension. In doing so they broke off most of the strands on the alternator earth wire. There was enough of a path not to bring up an ignition warning light but the resistance was too high to charge the battery properly. The National Breakdown man (now Green Flag) was on to it straight away! A good battery supplier will be able to do load discharge test on your brother's battery free of charge.
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