battery fault - diagnosis?

[EchiDna]

Hi all,
I've got a battery in a non-LR which had a strange (to me) fault...

the battery still reads 12volts across the terminals, but will not turn over the car at all, so i replaced it...

I can still use the battery though for lesser tasks - seems like it lost a lot of it's current capacity.

The alternator (since replacing the battery) puts out 14.7volts when running, so no problem there....

any ideas?
is this common?

[fossil]

You might like to have a look at this link, according to them to get a accurate reading of a batteries state of charge is a bit more complicated than just putting a meter on it. It's too techo for me but might explain your problem.

http://www.batterystuff.com/tutorial_battery.html#6

Hope it helps

Iain

[Blknight.aus]

check your readings with a load on, turn the low beams on and then have someone hold the "overtaking flasher" on for about 10 seconds before you take the reading, have them hold it while you take the reading...

its not as good as a proper toaster test but does give you an indication

anything less than about a steady 11v is bad and with just the lights for that long Id want to see at least 11.8v.

[JDNSW]

Just to hijack the thread!

Before Easter I was servicing the 110. I decided I needed some music so switched on the ignition and radio; silence. Further investigation showed no warning lights either. Oh well, must have left something on. Put charger on - charger cycles on and off (does this on a dead flat battery). Half an hour later, checked voltage. Still cycling, 2.0 volts while charging, zero when not. Short in wiring? Disconnect battery. Leave for an hour on charge. Still cycling, 2.6v when charging, zero as soon as the charger switches off.

At that stage gave up on that battery and went and got a new one - it had served for over four years, so probably owed me very little.

But the question remains - the battery appears to have a low resistance short in all cells. What mechanism could cause all cells to fail in that manner, after being quite capable of starting the Isuzu 24 hours earlier?

John

[LandyAndy]

Hi JD
Sulphide deposits build up on the plates creating an internal short,Inox battery treatment is suposed to be good on the old non sealed batteries to help prevent it.I used to use it on all batteries but only get good quality sealed batteries these days,they last heaps longer.
Andrew

[JohnE]

Ah Crook batteries, nothing worst, since I have let the rego run out in the batmobile the battery has been playing up, ie won't hold good charge, has anyone ever used that innox stuff and is it any good.


john

[DEFENDERZOOK]

Ah Crook batteries, nothing worst, since I have let the rego run out in the batmobile the battery has been playing up, ie won't hold good charge, has anyone ever used that innox stuff and is it any good.


john



i would skip the inox and simply connect a cheap $20 charger and connect it to a timer.......

[Blknight.aus]

what can cause it is sort of like a cascade failure...

once cell goes dead short and becomes in essence a resistor...

through the residual electrics that are left on (to complete the circut) it burns more power and eats the volts out of the other cells.

as they try to keep up their discharge rate they to die and become short circut or pretty close to.

because of the dead cell creating lots of resistance the remaining cells dont get enough juice to maintain more than a surface charge which is promptly lost through the dead cell.

Other times the plates get enough contamination on them that they short out interally across the top of the plates near their output connections.

when this happens the battery essentially becomes a very big chunk of conductor and the voltage your measuring is simply the chargers output voltage across what is pretty close to a dead short..

[JohnE]

Answers for a similar problem,
dave that all makes sense, but for me, I'll give the Innox a go, its cheap enough at supercheeeeeep, just so i can say if its any good or not.


john

[EchiDna]

check your readings with a load on, turn the low beams on and then have someone hold the "overtaking flasher" on for about 10 seconds before you take the reading, have them hold it while you take the reading...

its not as good as a proper toaster test but does give you an indication

anything less than about a steady 11v is bad and with just the lights for that long Id want to see at least 11.8v.

just not possible I'm afraid... there is nothing like enough ooomph in the battery to even turn over the car, so no way to apply a real world load - yet it still reads 12.1 volts (3 days later). Intriguing no?

[Lionel]

Hi all,
I've got a battery in a non-LR which had a strange (to me) fault...

the battery still reads 12volts across the terminals, but will not turn over the car at all, so i replaced it...

I can still use the battery though for lesser tasks - seems like it lost a lot of it's current capacity.

The alternator (since replacing the battery) puts out 14.7volts when running, so no problem there....

any ideas?
is this common?

The problem here is failure of one of the internal cell connectors, causing the internal resistance of the battery to become way too high.

You will still measure 12V with a meter, which draws very little current, but when you put a proper load (eg. starter) across it, the battery cannot pass enough current.

Also, the connector problem will not allow the battery to be charged correctly.

Cheers,

Lionel