Battery Woes

[Ian Abel]

Hi All
My battery is currently on charge via C-tek charger (will check with volt meter later) but one question I have before I renew the battery:
My car will start up straight away via jump leads but even tho I have had the battery on charger for 12 hours plus when I turn the ignition I get nothing, not even turning over. Can you charge (?) a battery but the battery is so dead it won't hold any charge or am I looking at something else?

Many thanks one and all


ps- battery is over 5 years old so guess I'm overdue maybe!!!

[sparkythecat]

The first thing I would do is check the ctek charger. I've just binned one that had expired.
If you google ctek charger problems, you'll see that they are not as reliable as the hefty price tag might suggest.

[Ian Abel]

Hear what you're saying. Have used it on my other car and it worked ok on that so guess it must be ok.

[QBee]

Your local car spares independent will test the existing battery for free with a tester that tells you if it is ducked despite apparently having been charged

[Discopotatoes]

I don't try charging a flat battery with a battery conditioner any more, I've found a number of times i haven't been able to get it to charge properly.
proper battery charger then if left for long periods bang it on the conditioner.
thats not to say your battery isn't goosed

[QBee]

On that subject, if a battery is really flat, you may need to fool the charger into understanding that there is a battery to be charged. Chargers these days are intelligent....bit like MPs and voice recognition phone answering systems.

You do this by connecting a second, good battery to the charger as well, then as soon as the charger has spotted your flat battery and started charging it, you remove the good battery without disconnecting the charger from the one you want to charge.

So charger onto flat battery, jump leads to connect Good battery to both.....then disconnect Good battery at the good battery end of the jump leads to avoid disturbing the connections at the charger.

[ianwayne]

Check the voltage of the battery with a multimeter while it is still charging. It should be well over 13V. The wiki entry for car batteries used to be very good regarding capacity and charging but has changed recently to actually be LESS informative IMHO.

After disconnecting the battery from charge, the open cct voltage should settle at about 12.6 - 12.7V (depending on the temperature) for a fully charged battery. Check it again every few hours and if it is dropping, the battery has had it. I realise this means leaving it off the car for quite some time but connecting it up again may be causing the discharge. N.B. A car battery needs to drop to about 11.7V to be considered totally flat. I've had a car turn over with a car battery only reading 11.9V.

I've done this with car batteries over the years just using a basic trickle charger. It is sometimes just not worth it, considering the importance and low relative cost of a new battery, but establishing if the battery is good may eliminate other possible faults.

After periods of non-use, I've had to charge the battery on my Chimaera but these cars are not complicated electrics wise, I don't even disconnect it. Nothing fries. The ECU is out of cct with the immobiliser activated. (I do monitor it by the way, don't go out shopping and leave an extension lead and charger connected in the footwell!)

Edited by ianwayne on Monday 6th February 23:00

[N7GTX]

Once a battery has become this flat then it has had it. No amount of charging will get it back to good condition.
The recovery rate is for me the best way to determine the state of a battery and is easy to do. Once you have charged the battery up to at least 12.6v i.e. 6 cells x 2.1v each, leave it for just 5 minutes. If it has dropped then as said above the battery has had it.
Or, once charged to 12.6v, switch your lights on and watch the voltmeter drop to around 12v. Switch the lights off. With the voltmeter still connected, watch the readings. A good battery will recover at roughly 0.1v every 3 or 4 seconds all the way back up to 12.6v. If it stays at 12v or does not recover then replace it.

[Ian Abel]

Had a problem with my xj8. That dropped to 1.7(!!!) but charged it back up to 12.3 and everything was good but as I had problems in the past with the battery draining I checked it over the next couple of days with a volt meter and the readings were 11.9 ish. It still started ok so assumed it was a one off. Should it be 12 plus then? It is about 9 months old and is the recommended battery for the car. I appreciate the xj8 has loads of electrical stuff on it whereas the TVR doesn't.
To be honest I seem to be fighting a constant battle with car batteries

Edited by Ian Abel on Tuesday 7th February 20:30

[Paulprior]

The problem with the modern conditioner trickle chargers is that they don't recognise that they are connected to a battery when it is too flat, if you have an old style charger that is just on or off you could use that to put some charge into the battery first, if not if you can connect the trickle charger and the jump leads at the same time then the charger will recognise the battery on the other end of the jump leads and switch itself on, so maybe charger and battery are ok?

[Penelope Stopit]

Paulprior said:

The problem with the modern conditioner trickle chargers is that they don't recognise that they are connected to a battery when it is too flat, if you have an old style charger that is just on or off you could use that to put some charge into the battery first, if not if you can connect the trickle charger and the jump leads at the same time then the charger will recognise the battery on the other end of the jump leads and switch itself on, so maybe charger and battery are ok?

This, it works