Isuzu Trooper Owners Club UK™

dab · Posted: Tue May 05, 2009 14:43 Post subject: SUBARU BATTERY DRAIN

DAB.
My 3 year old Legacy Estate's battery drops voltage after about 7/10 days non use..... down to around 8 volts; result is a non starter. It has 2 alarms fitted, 1 factory and a Sigma. I can use one or both. Have tried each system on its own.... same result. Intend to get battery checked, but if ok, any advice on checking level and source of current draw would be welcome. Ideally would need to test with car alarmed, in case it's one of the security systems.
Thanks.

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Hard1 · Posted: Tue May 05, 2009 15:59 Post subject:

Insert a 3/5watt bulb between one of the battery leads and it's post, any more than a faint glow is not good, but does depend on alarm type tracker etc. Otherwise, using a multimeter set to amps/milliamps, remove the earth wire from it's battery post and just put one probe on the earth post and the other on the earth wire.

Alarms can be a big source of battery drain especially if you have motion detectors etc...
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dab · Posted: Tue May 05, 2009 16:31 Post subject:

dab · Posted: Tue May 05, 2009 19:24 Post subject:

Red Robbo · Posted: Tue May 05, 2009 19:44 Post subject:

I think there should be 2 internal fuses for the current options,depending on the meter.....Always try the highest rating first and work down.. Wink

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Hard1 · Posted: Tue May 05, 2009 19:47 Post subject:

Not necessarily but the needle will fly over rather sharpish! Set it on your lowest DC setting. If there's a drain the needle will flicker. Obviously the alarm would go off as it thinks it's being tampered with, so disable the alarm. Just hold one probe on the battery terminal and one on the negative cable simultaneously (with the neg cable completely disconnected from the battery). I hope you know your radio security code though!
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Gribble · Posted: Tue May 05, 2009 20:05 Post subject:

I had similar thing on my evo 8 and it was the battery giving up just as the warranty ran out ,is yours one of those big motorbike size ones with the smaller terminals ?

Best advice was to put a varta silver on and that stays up 4 weeks + if not used as the orginal fitments are the minimum spec.

I dont think you will measure anything from chassis to the minus post since its not in line with the load ? ave to try it ! Depending on how good the meter is and if it has auto ranging measure the battery volts to two decimal places then wait 24 hours and do it again from that you can work out the rate of drop .
Probably if you have a drop test done on the battery it will come up below spec to .
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dab · Posted: Tue May 05, 2009 21:20 Post subject:

Gribble · Posted: Tue May 05, 2009 21:52 Post subject:

If you know the ratings of the items I'm sure Chief Engineer (robbo ) can do a quick calc for you Wink

I think all stuff sold in the EU has to have its watts or amps on it to get the CE mark so some internet time might give you figures.
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Red Robbo · Posted: Tue May 05, 2009 22:06 Post subject:

Interesting thought,you want to measure current drain,easy isolate batt between meter and terminal,but two batteries in II,trickier one......
Suggest set meter to max range between batt 1 + and lead ..dissconect. lead....disconnect batt2 +.........alarm may still go off down to the high internal resistance of the meter,in which case "GRIBBLE"... Laughing

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dab · Posted: Wed May 06, 2009 10:19 Post subject:

Red Robbo · Posted: Wed May 06, 2009 15:06 Post subject:

Measure Batt voltage after an hour at least after stopping engine,measure voltage drop over a least 10 hrs.....

Current drain(mA)=(Voltage drop/2.63)*((Batt rating(Ah)*1000)/time(hrs)).

Should give a reasonable esimate...eg current drain 80 Ma,gives voltage drop of .11 V,on 80 Ah batt over 40 hrs.....
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dab · Posted: Wed May 06, 2009 15:41 Post subject:

Red Robbo · Posted: Wed May 06, 2009 16:19 Post subject:

Yep but cos its knacked your current drain will be much higher thus draining the batt akin site quicker... Laughing

So not a relextion of idle current drain due to alarm etc...
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eithan h · Posted: Wed May 06, 2009 21:11 Post subject:

the panasonics that subaru use are useless they now use varta ones when you change them under warranty, i've had to change them on brand new cars because they didn't pass the test on the pdi.

to test the draw you do as above just put the meter on amps and disconnect the negative lead put one probe on the battery negative terminal and one on the negative lead, make sure all doors are shut and ignition is off it may chirp at you but it shouldn't go off