Beware the curse of the duff battery

Harry · Post by **Harry** » Thu Dec 13, 2007 10:21 pm

As many of the North West crew know I've managed to need a jump start at the end of nearly every bongo meet this year.

Got the battery tested and it was ok when I got a new alternator a few weeks ago.....no probs until this evening

Pitch black...down a lane doing a delivery...full beam on, aircon on full blow, radio on, tailgate courtesy light on ...ENGINE OFF.

Customer took a long time answering door then an age paying for her birdseed so twelve minutes later I returned to the van and guess what....another flat battery.

Yes folks...TWELVE MINUTES.

My own garage just around the corner came out and jump started the van (gratis

) and I then drove 25 miles to my nearest Halfrauds intent on not stopping the engine until I'd got a new battery sorted.

Halfords fitter checked the battery....now fully charged and ok. Said it didn't need replacing....did I really need a 50 mile round trip?

Any recommendations folks? (apart from remembering to turn the electrics off when I leave the van).

francophile1947 · Post by **francophile1947** » Thu Dec 13, 2007 10:41 pm

Surely, if it last only 12 minutes, it has to be a faulty battery, despite what the tests show

NeilT · Post by **NeilT** » Thu Dec 13, 2007 10:58 pm

I am no techie.. but is the alternator kicking out the right voltage?

madmile · Post by **madmile** » Thu Dec 13, 2007 11:07 pm

No expert on batteries, but surely main beam, air con and full blowers is enough to temporarily kill most batteries. - If you cant be bothered to turn all them off, why bother turning the engine off - it will save you a lot of hassle

haydn callow · Post by **haydn callow** » Thu Dec 13, 2007 11:29 pm

Thats a hell of a drain on your battery. Not surprised it was flat.

roosteruk · Post by **roosteruk** » Thu Dec 13, 2007 11:30 pm

get a run lock fitted h, then if someone does try and drive off, it cuts out.
You could keep a spare door key and leave th ignition running and still lock the door?

moonshine · Post by **moonshine** » Thu Dec 13, 2007 11:38 pm

I have known a duff battery to charge up very quickly, hold a full charge for a short while, then die just as quickly as it charged up. The only way to really test a battery is to do a heavy discharge test. Did Halfords do a proper test, by putting a heavy load across the battery for at least 20 seconds, or did they just test it with a voltmeter or hydrometer?

If you put a knackered battery on a vehicle and drive it for 5 miles, or charge the same battery from a home charger for a few hours, you can put a voltmeter on it and it will show a healthy voltage. Stand the battery on the floor for a few hours and test it again with the voltmeter, and it will be flat.

dandywarhol · Post by **dandywarhol** » Fri Dec 14, 2007 12:47 am

The only way to properly test a battery is with a hydrometer - that way you will instantly see if a cell is duff.

moonshine · Post by **moonshine** » Fri Dec 14, 2007 8:24 am

If a cell is duff, a hydrometer will certainly show it, but often it's not that one cell is duff, but the whole battery is sulphated and thus suffering from greatly reduced capacity. It will charge ok, and hold a charge for a little while, but will fade very quickly especially on load. A hydrometer will not always show this up unless the battery has been standing a while before it is tested.

scanner · Post by **scanner** » Fri Dec 14, 2007 10:59 am

I've got a discharge tester but it's too far away to be of any use to Harry.

It is the ONLY way to test a battery as the change in voltage under test indicates exactly what (if any) the fault is.

helen&tony · Post by **helen&tony** » Fri Dec 14, 2007 11:24 am

Hi Harry
I had the same problem as you ....about 25 years ago!! I replaced the alternator, as one night , on my way home, the lights would dim, and I had to keep stopping and turn the lights off for a while....replaced the alternator....no probs.....this was after having the electrics "tested"....after a while, the battery totally failed. I called another electrician out, and he said that it was most likely the battery all along, as the car was only a few years old, and that if you test a charging system with a duff battery in situ, then you can find the readings may indicate a duff alternator if you don't know what you're doing....it makes me wonder how many folks get caught in this way by an incompetent auto electrician
Helen

bigdaddycain · Post by **bigdaddycain** » Fri Dec 14, 2007 2:16 pm

It may be worthwile to replace the battery anyway harry,despite the halfrauds test results,simply from a peace of mind point of view...

All that electrical draw,in this temperature,is a fair old drai on any battery without the engine running though mate...