Knackered battery

rich28uk · Jul 23, 2023

Hi guys, not strictly Land Rover but the guy in question used to have them, anyway neighbor of mine, old guy who still tries so do his own stuff asked me to jump his car, it’s not been used in a good while, got it going he went out came back, hour later battery was flat again, he said he took it a good 20 miles so should have got enough charge in it, anyway started great with jump start, I put my volt meter on, 14.2 running, soon as it’s turned off 11.6, few mins later 10.2v my theory is battery has failed internally, doesn’t look really old but hidden in a box they don’t get as filthy as they used to. Anyone agree that battery is knackered? Car runs perfect when started, he said about parasitic drain, my reply was it’s one hell of a drain to flatten a battery in 10 mins, I said it’s just had it and not holding charge do to lack of use.

Nodge68 · Jul 23, 2023

If the battery has been flat for any length of time, then it's scrap value only. Lead acid batteries don't tolerate being flat, even new batteries are destroyed if left to go flat.

Keith_L · Jul 23, 2023

Sounds knackered to me. Letting them go flat through lack of use doesn't do them any good.

rich28uk · Jul 23, 2023

Just as I thought then, being old he said “battery isn’t that old” but his 2 years could be 5 or 10, just the way it behaves, jumps fine drives great, no charge lights on dash etc but park up, engine off, within ten mins it’s flat again, I know some cars have drain on them but never known a drain to flatten a battery in ten mins, to me it’s taking power just not storing it.
Another thing he mentioned is he only does about 1000 miles a year, isn’t much when decided out over the year, most of it id guess is the run from Manchester to Whitby where his daughter lives, other then that’s it’s just stop start round town.

Alpinewoodsman · Jul 23, 2023

Sounds knackered to me.

I'd pull it out, charge it, and then stick a voltmeter on it occasionally. If the voltage keeps dropping fast with no possible load on it, it is scrap...

rich28uk · Jul 23, 2023

I did ask him if he had a charger to put on a slow charge to try and fix it but he doesn’t and neither do I so looks like replacement.
I seem to recall a mate of mine years ago having a similar issue, he took his battery to a auto electrics place who charged 50p to charge it then phoned him and said something about a knackered cell, saying along the lines of it will run and take power just not store it.

AllanWorms · Jul 23, 2023

Sounds like a dead cell. 12.6V (fully charged) times 5/6 (5 live and 1 dead cells) gives about 10.5V...

It should hold at least 12.5V after having a rest after a proper charge, with a decent charger. (not running in the car). 12.4V is about 75% charged.

Lead acids like to be fully charged all the time. As the voltage drops, they are damaged faster, so sitting flat for weeks probably finished it off.

If he doesn't use it often, a baby CTEK or similar smart charger is probably a good thing for him. You can fit a quick release in the bumper or something, so it's easy to connect and it shouldn't need much top up, maybe weekly.

rich28uk · Jul 23, 2023

AllanWorms said:
Sounds like a dead cell. 12.6V (fully charged) times 5/6 (5 live and 1 dead cells) gives about 10.5V...

It should hold at least 12.5V after having a rest after a proper charge, with a decent charger. (not running in the car). 12.4V is about 75% charged.

Lead acids like to be fully charged all the time. As the voltage drops, they are damaged faster, so sitting flat for weeks probably finished it off.

If he doesn't use it often, a baby CTEK or similar smart charger is probably a good thing for him. You can fit a quick release in the bumper or something, so it's easy to connect and it shouldn't need much top up, maybe weekly.

Will mention ctek charger, didn’t think of them, see what he says, depending on how long he keeps driving 1 new battery may see him through, he did seem a bit worried about it, I said if it’s the battery that’s knackered it should keep behaving as it is, starts with jump then runs all day then dies after turning engine off.

1988smithy · Jul 23, 2023

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I've got one of these, got a repair function that sorted my caravan battery and its been used to charge a few car batteries. Can't moan for the price, think I spent £20 couple of years ago. Doubt its a patch on a ctek but worth a look

backinblack · Jul 23, 2023

IMO a 20 mile drive is no where near enough to charge a flat battery, I think you need at least 10 miles just to replace the power from starting. I reckon maybe 12 to 24 hours on a charger if he's lucky. I had a couple of solar panels connected to the battery on the wifes Corsa for 18 months when she started working from home.

rich28uk · Jul 23, 2023

Agree there a good long run will help but if the battery has an internal fault no matter how many miles it won’t help, to me that’s what it is, internal failure, runs great after a jump then soon as engine is off power just goes, even saw the interior lights dim to off within the time I was talking to him (ten-15 mins)

backinblack · Jul 23, 2023

rich28uk said:
Agree there a good long run will help but if the battery has an internal fault no matter how many miles it won’t help, to me that’s what it is, internal failure, runs great after a jump then soon as engine is off power just goes, even saw the interior lights dim to off within the time I was talking to him (ten-15 mins)

Even a new battery needs more than a few minutes charge, IMO it needs at least 12 hours on a charger.
Without testing you're just guessing it's faulty, which it probably is.

rich28uk · Jul 23, 2023

I don’t think it could be much else, as I say once started runs fine no warning lights etc, turn off and voltage drops off so to me it’s taking power but not storing it.

Shippers · Jul 23, 2023

If you want to check for parasitic drain set your dmm to 10a plug red probe into amp socket remove negative lead attach red probe to negative cable and black probe to negative terminal it should read zero with ignition off...if it is a complicated ecu digital car there is a bit more complicated way so you dont lose data...

kermit_rr · Jul 23, 2023

That's a good way to kill a multi meter, especially if it sparks when you connect it up. Plus, a lot of modern cars will pull more than 10A when everything is 'awake'.
An amp clamp is better and you don't need to disconnect anything.
If you want to find a parasitic drain, you can measure mA across fuses as a telltail

rich28uk · Jul 23, 2023

Shippers said:
If you want to check for parasitic drain set your dmm to 10a plug red probe into amp socket remove negative lead attach red probe to negative cable and black probe to negative terminal it should read zero with ignition off...if it is a complicated ecu digital car there is a bit more complicated way so you dont lose data...

Merc C class not really that new as It only has 1 battery for everything not one for engine and one for electrics like newer ones but still enough ecus.
Even a parasitic drain would drain a battery in ten mins would it? Even if you leave lights on or radio cars normally last longer. Personally I think it’s lack of use hasn’t helped battery and it’s gone inside, dead cell or something along them lines as it would still run just not crank engine to start without jump/ boost pack.

kermit_rr · Jul 23, 2023

Yes agree but a battery that's gone totally flat like that will need a proper charge and a 'recovery' cycle (if yourcharger offers that) which will take hours

Shippers · Jul 23, 2023

kermit_rr said:
That's a good way to kill a multi meter, especially if it sparks when you connect it up. Plus, a lot of modern cars will pull more than 10A when everything is 'awake'.
An amp clamp is better and you don't need to disconnect anything.
If you want to find a parasitic drain, you can measure mA across fuses as a telltail

Thats why I said there is a more complicated way to do it for a modern car it's an easy way to do it with a cheap diy dmm...if it sparks when you touch neg to post does that show a drain?

rich28uk · Jul 23, 2023

kermit_rr said:
Yes agree but a battery that's gone totally flat like that will need a proper charge and a 'recovery' cycle (if yourcharger offers that) which will take hours

Neither me or him have a charger, I used to have one but damp got to it.

1988smithy · Jul 23, 2023

He said it was 2 years old, has he got receipt? Usually at least 3yr warranty on them..? As @kermit_rr says, a recovery cycle might work. Worth a go for the cost of one of those chargers i linked then you've got one for future

Knackered battery

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