Thread: Battery recharging problem

You need to take the specific gravity of the acid with a hydrometer.What is the specific gravity reading on all six cells? Starting at the positive end.

An SG of 1.160 @ 20C is fully discharged and an SG of 1.260 @ 20C is about fully charged. ie about 100 point of gravity between them.

A temperature correction table is available if required.

Do you know if there is any current going into the battery?

Most chargers have either a needle or some LEDs to indicate when they are charging and some indication of how much current. With most chargers they let off a bit of noise as the transformer vibrates under heavy load. If it is making a noise, a growl as opposed to a feable hum then it is mostlikely charging at maximum current.

I think that even a cheap charger at 4 amps should start to reduce the amount of current going into a charging battery after 10-12 hours. If the current hasn't started to drop by tomorrow unless it is a huge battery I think you can kiss you battery good bye.

How long have you had the battery for?

Hi B29, need a bit more info before being able to help you.

What type of battery is it.

By dead flat, what voltage reading were you getting before trying to charge it up.

What type of battery charge are you using.

Many multi stage battery chargers will NOT try to charge a battery that is below a given voltage, so the problem may be the charger and not the battery and this is not to say that you can recharge the battery, it just may mean you need a different approach.

I’m assuming it’s your cranking battery and if so, if you can get a jump start, try driving for a while and see if this brings the battery voltage up enough for the battery charger to get a reading that it is high enough for it to start charging.

you might need to give the battery a blast to get it to start charging zap 20 odd volts onto it the correct way for a couple of seconds and then put the charger on.

this of course assumes that the acid is still close enough to acid to actually allow the chemical reactions to take place.

Thanks for all the advice everyone. I'll have to go and check the specifics.

Originally Posted by Blknight.aus

you might need to give the battery a blast to get it to start charging zap 20 odd volts onto it the correct way for a couple of seconds and then put the charger on.

this of course assumes that the acid is still close enough to acid to actually allow the chemical reactions to take place.

That is exactly what my neighbour reckons, would two other batteries in series do it?

How would you do it?

Originally Posted by B92 8NW

Thanks for all the advice everyone. I'll have to go and check the specifics.



That is exactly what my neighbour reckons, would two other batteries in series do it?

How would you do it?

Just like you suggest, unless you have a big powersupply that you can dial up a voltage and set the current limit to max.

I would only leave it on for a second or three.

(I have done this with older NiCad batteries to burn the crystals, did not know it was done on lead acid as well)

yep 2 batteries in series with some 6mm wire Id use about 10m of it firstly because of the possable hydrogen issue and partly becuase of the current limiting it will give, wear gloves goggles/aprons while you do it or have someone you dont like do it for you. dont forget to crack open but not remove the vent caps.


hook your 2 good batteries in series and then zap the dead battery,(5-20 seconds is usualy as far as I go hook the charger onto it and see what happens (use your multi meter) if it starts to take a charge leave well enough alone, if it doesnt zap it again.

if that doesnt work you can try hooking a battery in parallel and the charging both batteries at the same time.

I think the logic behind how it works is once the acid gets down to a certain level something changes on the plates so trying to reverse the reaction by charging doesnt work. I think of it as like a coating that stops the acid from getting to the lead. Blasting the battery with higher voltages causes the coating to crack up acid meets lead and the battery can be charged.

the last trick thats in the book is to top off the electrolyte with a little acid instead of distilled water.

[QUOTE=drivesafe;922118]

"Many multi stage battery chargers will NOT try to charge a battery that is below a given voltage,"



Is this the case with the Ctek chargers as well Drivesafe?