Battery so dead - charger won't charge it

Psycho Sonny · 9 Feb 2019 at 12:48

So I need to dupe the charger into thinking the battery has some charge in it so it will start charging it.

This is on a weekend only car which I drive 1K miles a year i normally charge the battery every 2 months but it's been a bad winter and not done it in like 3 months and it's gone.

So i have the inside of a torch with 4 aa batteries hooked up to it. i don't have jump leads. i need to make a connection to the battery using the batteries so the charger then starts charging the battery as it will see some voltage there.

what would be the best wire to do a hack job with? ethernet? usb? hack off both ends cut in 2 then connect to either side of 4 aa batteries using the inside of a torch connection then connect to battery whilst charger is attached to battery.

best cable to use? speaker cable? i have some good copper speaker cable in attic.

Jasoncmor · 9 Feb 2019 at 13:02

Can you jump start it?
When I had my old car sat for a long time, the battery was completly flat and wouldn't charge, like yours.
I jumped it, left it running for half an hour then connected the charger after and it charged fine.

Just seen you don't have any jump cables, could you buy or borrow some? Or even get one of those jump packs?

Zefan · 9 Feb 2019 at 13:11

Even Cat5e should be fine, it carries 48v for PoE and is probably the cheapest thing you've got lying around unless you have any old USB cables you're never going to use again. Either that or find an old, cheap charger that doesn't have any sensing features.

andy_mk3 · 9 Feb 2019 at 13:27

USB cable would be fine. I've had to do similar with my ctek charger on a dead battery, but I just used jump leads off another battery. Although be warned it's likely to reduced the capacity and life of the battery being completely discharged.

Psycho Sonny · 9 Feb 2019 at 13:59

Jasoncmor said:
Can you jump start it?
When I had my old car sat for a long time, the battery was completly flat and wouldn't charge, like yours.
I jumped it, left it running for half an hour then connected the charger after and it charged fine.

Just seen you don't have any jump cables, could you buy or borrow some? Or even get one of those jump packs?

the other car is a hybrid - they say you shouldn't connect jump leads to these as it will risk killing it. lexus hybrid.

the battery is showing 1.5v on test mode. i need to dupe the charger into thinking it has 6v

Werewolf · 9 Feb 2019 at 14:47

My neighbour has/had this issue on a regular basis with his sprty/rally type car, apparently there was a known issue with the electronics on it that meant after a couple of months it would drain the battery too low for a modern smart charger.

He usually pops round to borrow our ancient (as in probably 30 year old at least) backup charger which is an old style "charge it till the voltage reaches X" type, which doesn't care about how low the battery is to begin with (IIRC my dad had it before we got our first corsa back in about 94).

As others have said, chances are any reasonably good cable should be good for a bit of a charge from low voltage/current batteries, if you've got any old PC PSU kettle leads chop the ends off and they'd probably be ok but I would suggest doing it outside/on bare concrete in case anything goes wrong

(I've managed to burn myself on a shorting 1.5v battery in the past, and have a hot wire cutter in the garage that runs off 2x D, so 3v).

Psycho Sonny · 9 Feb 2019 at 15:12

Werewolf said:
My neighbour has/had this issue on a regular basis with his sprty/rally type car, apparently there was a known issue with the electronics on it that meant after a couple of months it would drain the battery too low for a modern smart charger.

He usually pops round to borrow our ancient (as in probably 30 year old at least) backup charger which is an old style "charge it till the voltage reaches X" type, which doesn't care about how low the battery is to begin with (IIRC my dad had it before we got our first corsa back in about 94).

As others have said, chances are any reasonably good cable should be good for a bit of a charge from low voltage/current batteries, if you've got any old PC PSU kettle leads chop the ends off and they'd probably be ok but I would suggest doing it outside/on bare concrete in case anything goes wrong (I've managed to burn myself on a shorting 1.5v battery in the past, and have a hot wire cutter in the garage that runs off 2x D, so 3v).

can you still get one of these old skool chargers? amazon?

Werewolf · 9 Feb 2019 at 15:19

I suspect so, but I'm not 100% sure how you'd narrow the search down other than discounting any smart chargers as the starting point.

sigma · 9 Feb 2019 at 15:58

Why not buy some jump leads?

Terminal_Boy · 9 Feb 2019 at 16:02

Get a dirt cheap trickle charger.

andy_mk3 · 9 Feb 2019 at 16:25

Another option, use a 6-12v transformer you might have spare? An old network switch or old torch charger or something perhaps. Cut the plug off it, make sure you know the polarity is correct and hook up to the battery.

Psycho Sonny · 9 Feb 2019 at 17:13

Terminal_Boy said:
Get a dirt cheap trickle charger.

i will do for future recommend any?

sigma said:
Why not buy some jump leads?

they are on way from amazon.

i've managed to find a solution though just used an old cat5e cable and batter to mimic some charge on battery. so got it charging

itchy · 9 Feb 2019 at 22:03

Battery dead or alternator gone. If a push start does not get the car going it could be something else.

Do what I used to in my mini metro open door run with it and jump in and start it, then rev the balls out of it on the street corner.

Also if you only doing 1k a year that's only 2.7 miles a day you don't need a car. I walk that far everyday.

Usel · 9 Feb 2019 at 22:13

Have you got an old PC psu? That should jump start the charger.

Psycho Sonny · 9 Feb 2019 at 22:56

itchy said:
Battery dead or alternator gone. If a push start does not get the car going it could be something else.

Do what I used to in my mini metro open door run with it and jump in and start it, then rev the balls out of it on the street corner.

Also if you only doing 1k a year that's only 2.7 miles a day you don't need a car. I walk that far everyday.

Battery dead.

It's a weekend car. It's also an automatic so good luck push starting it.

It gets used maybe 5-20 times a year mainly summer because it's a convertible.

My long term solution is to just remove the battery from now on and leave it on trickle charge. I'll probably get rid of the car in a year or two.

bainbridge · 10 Feb 2019 at 08:23

Using an old psu sounds like a good idea.

Glad I hung on to my old analogue charger, it's not fussy.

Haze · 10 Feb 2019 at 08:40

Isint there Motors section on this forum? or is it just my imagination?

agw_01 · 10 Feb 2019 at 09:04

Psycho Sonny said:
the other car is a hybrid - they say you shouldn't connect jump leads to these as it will risk killing it. lexus hybrid.

Are you charging the battery while it's connected to the car? If you're concerned about it being damaged by jump starting, you could just switch off the running car while you jump start the hybrid. That way, the hybrid will only absorb what it needs rather than being supplied with lots of amps from the other car's alternator.

itchy said:
Do what I used to in my mini metro open door run with it and jump in and start it, then rev the balls out of it on the street corner.

I've been guilty of it myself in the past, but it always makes me laugh when you see people trying to jump start a car and they're revving the absolute knackers off it. I don't think they realise that power is being supplied from the battery and not the alternator and you shouldn't even need to lift the revs above idle to get the other car going, providing your jump leads aren't a total POS that is.

Psycho Sonny · 10 Feb 2019 at 11:34

agw_01 said:
Are you charging the battery while it's connected to the car? If you're concerned about it being damaged by jump starting, you could just switch off the running car while you jump start the hybrid. That way, the hybrid will only absorb what it needs rather than being supplied with lots of amps from the other car's alternator.

I've been guilty of it myself in the past, but it always makes me laugh when you see people trying to jump start a car and they're revving the absolute knackers off it. I don't think they realise that power is being supplied from the battery and not the alternator and you shouldn't even need to lift the revs above idle to get the other car going, providing your jump leads aren't a total POS that is.

the car i need charged isn't a hybrid but the other is. i know it says the hybrid shouldn't be jump started but i'm worried something might get knackered if i try to draw power from it. it's a much newer car (under warranty) and i'd rather not mess about with it having read people killing them by jump starting them.

i was charging the battery whilst connected to the car however i have now taken the battery out and tried recondition mode and it failed but it got it up to 20%. i'm now going to try normal charging and see what happens over the course of today.

https://www.eurocarparts.com/ecp/p/...ttery/096-car-batteries/?444770968&0&cc5_1004

it's this battery and carries a 5 year guarantee and i bought it in 2016 so i have contacted ECP for a replacement. i will from now on charge the battery every weekend or try and use the car more when i get the new battery.

hominid · 10 Feb 2019 at 21:00

You could try a battery desulfator, they don't always work but I've seen them work well and extend the life of some batteries for years.