Awakening a dead battery
Discussion
surveyor said:
The battery is relatively new, but no charger want's to know it after the car has been parked for a month. A new battery is 10% of it's value.
Any magic ideas before I splurge?
Over the years of having this exact problem I've had the best success using a ctek or similar battery conditioner. I've always assumed that it works because it's not trying to force the charge in to the same degree as a proper charger. Any magic ideas before I splurge?
I suspect much depends on whether it has been 100% flat for a while or whether there is just a fraction of charge left in it?
Edited by DonkeyApple on Monday 23 September 14:10
I have a NOCO Genius on two of my cars, they're quite good at telling you if a battery is faulty/damaged/deceased or just flat. On one car I left the lights on for a week and the NOCO was able to recharge it.
Is your charger a smart charger with these functions of just a cheap halfords type charger? I believe the latter struggles with flat batteries whereas the former will charge it?
Is your charger a smart charger with these functions of just a cheap halfords type charger? I believe the latter struggles with flat batteries whereas the former will charge it?
New chargers don't like a flat battery so nothing happens when you connect them. I've had the problem and I got jump leads from another car/battery and then the charger started to charge. Then disconnect the jump leads and the charger will carry on charging. Most new chargers will go into trickle or maintenance charge once the battery is full
DonkeyApple said:
surveyor said:
The battery is relatively new, but no charger want's to know it after the car has been parked for a month. A new battery is 10% of it's value.
Any magic ideas before I splurge?
Over the years of having this exact problem I've had the best success using a ctek or similar battery conditioner. I've always assumed that it works because it's not trying to force the charge in to the same degree as a proper charger. Any magic ideas before I splurge?
I suspect much depends on whether it has been 100% flat for a while or whether there is just a fraction of charge left in it?
Edited by DonkeyApple on Monday 23 September 14:10
In your case, I'd jump start the car and leave the engine running for half an hour or so, then switch off and see if it restarts.
I've only had a CTEK fail once, and that was on our MX-5's battery which wouldn't restart the car after running it for 30-40 mins. The car had been sitting for over 2 years before we bought it. Even after several hours on the CTEK, the battery couldn't be brought up to the 12.6v necessary for the charger to move on to the main charging routine. We simply got a red light, and it wouldn't go any further.
I've had it recover a few "dead" batteries previously. They're good things to have, and can be left permanently connected on a car that isn't used regularly.
I've only had a CTEK fail once, and that was on our MX-5's battery which wouldn't restart the car after running it for 30-40 mins. The car had been sitting for over 2 years before we bought it. Even after several hours on the CTEK, the battery couldn't be brought up to the 12.6v necessary for the charger to move on to the main charging routine. We simply got a red light, and it wouldn't go any further.
I've had it recover a few "dead" batteries previously. They're good things to have, and can be left permanently connected on a car that isn't used regularly.
Limpet said:
They're good things to have, and can be left permanently connected on a car that isn't used regularly.
So long as the car's not on the street. 
One of the little annoyances of modern cars is that when I was you her I'd just lift the battery out of my car when I knew I'd not be using it for a while. This also helped ensure the car was still where you left it when you did eventually need it again.
See if you can find a punchy jump-starter where you can bypass the cut-out limits - that was my problem when a battery went properly-flat - the jump-starter's cut-out wasn't letting it register.
Once it's started, then the usual rules apply - run it for a bit to get some charge in, then put it on a CTEK or similar and see if it recovers properly.
Once it's started, then the usual rules apply - run it for a bit to get some charge in, then put it on a CTEK or similar and see if it recovers properly.
leyorkie said:
New chargers don't like a flat battery so nothing happens when you connect them. I've had the problem and I got jump leads from another car/battery and then the charger started to charge. Then disconnect the jump leads and the charger will carry on charging. Most new chargers will go into trickle or maintenance charge once the battery is full
This worked for me, or else use an analog old skool charger with nothing but an (analog) ammeter on the display. Those will even attempt to charge the household pets.Lotobear said:
Was going to post the same, but whereas my Ctek would not recover it my £14.99 Aldi version did recover a fully discharged battery!
I have had success with an Aldi/Lidl special too. Had to leave it for a couple of days but it revived an absolutely flat battery. I think I may have had to connect a very old school jump starter to get it to recognise the battery first too IIRC.Haltamer said:
Connect another decent battery with jump leads and leave it for a few hours; Should get enough juice to be recognised by a charger - Then just charge up both batteries.
This with bells on. Has worked numerous times for me - the trickle charge provided by the conditioner when it sees a "good" battery massages the knackered one back into life.996TT02 said:
This worked for me, or else use an analog old skool charger with nothing but an (analog) ammeter on the display. Those will even attempt to charge the household pets.
This is exactly what I have got (without the pets). I have used it a few time when the CTEK said "nah, too low".Yeah its on 0v then you need some what to jump start the charge for most smart chargers.
Either a smart charger with a 'from zero' option., or another battery, dumb charger, bump the car, etc.
If its not been flat long, or your selling the car, it might do what you need.
But generally its its been a few months its a pretty solid way to kill a lead acid battery.
Often scrapyards will sell you, or even swap you, you knackered battery for one of the better ones in their pile.
Either a smart charger with a 'from zero' option., or another battery, dumb charger, bump the car, etc.
If its not been flat long, or your selling the car, it might do what you need.
But generally its its been a few months its a pretty solid way to kill a lead acid battery.
Often scrapyards will sell you, or even swap you, you knackered battery for one of the better ones in their pile.
mario328 said:
This week, Lidl are doing their £14.99 CTEK clone, I've had the Aldi version for some time and it works well on car batteries that have gone flat.
See: https://www.lidl.co.uk/p/ultimate-speed-car-motorc...
Cant fault that for price. I might not trust leaving it on my pride and joy 24/7/365 but for the odd charge on a runabout motor, happy days.See: https://www.lidl.co.uk/p/ultimate-speed-car-motorc...
I have a 5A CTEK and a 5A Noco and they are both good kit, but not cheap these days.
dhutch said:
mario328 said:
This week, Lidl are doing their £14.99 CTEK clone, I've had the Aldi version for some time and it works well on car batteries that have gone flat.
See: https://www.lidl.co.uk/p/ultimate-speed-car-motorc...
Cant fault that for price. I might not trust leaving it on my pride and joy 24/7/365 but for the odd charge on a runabout motor, happy days.See: https://www.lidl.co.uk/p/ultimate-speed-car-motorc...
I have a 5A CTEK and a 5A Noco and they are both good kit, but not cheap these days.
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