Charging a dead battery

scubascuba3 · Apr 17, 2014

My battery is dead and my charger isn't doing anything. I've read that if the battery is so dead that the charger sometimes doesn't recognise that it needs charging.

Now, I've read another forum where a guy connected a mobile phone charger to the battery to give it a small charge, then the proper charger kicked in and away you go.

My question is, I might try this,there are 4 wires in the USB cable. Black, white,green,red. Which should I connect to the positive and negative terminals of the battery? Anyone have a clue? I will quadruple check before I try.

I wasn't sure where to start this thread

scubascuba3 · Apr 17, 2014

Interestingly wiki says the following:

The standard USB A plug (left) and B plug (right)
Pin 1VCC (+5 V, red wire)
Pin 2Data− (white wire)
Pin 3Data+ (green wire)
Pin 4Ground (black wire)
USB - Wikipedia, the free encyclopedia

So does this mean I can just connect black to black and red to red and ignore the other two wires?

Blackal · Apr 17, 2014

Stick it on a normal charger (mains-fed). At least it will receive a current (up to the limit) comensurate with the potential difference between charging voltage and battery voltage.

it could need that kick in the arse.

Give it a good 8 hours and then bung it on an Optimate or similar.

Al

scubascuba3 · Apr 17, 2014

Blackal said:
Stick it on a normal charger (mains-fed). At least it will receive a current (up to the limit) comensurate with the potential difference between charging voltage and battery voltage.

it could need that kick in the arse.

Give it a good 8 hours and then bung it on an Optimate or similar.

Al

Normal charger you mean the car battery charger I have? The problem with this is it doesn't seem to be charging whether on standard or high charge. This is why someone has used a phone charger to charge it a little before using the main charger.

Blackal · Apr 17, 2014

A normal charger isn't "smart".............

If it doesn't lift your battery - your battery is probably fcuked I think.

Has your battery been subjected to sub-zero temperatures while flat?

Al

scubascuba3 · Apr 17, 2014

Possibly sub zero over the winter. But I usually leave it for a few months over winter no problem. This time I left it for 5-6 months

Blackal · Apr 17, 2014

When discharged - the electrolyte is basically water, so freezes more readily. That is fairly terminal for L/A batteries.

Al

Bendy toy · Apr 18, 2014

When the no load volts go below about 9.5v the chemical change becomes permanent - hard sulphate. If it's been dead for a while It's unlikely to be reliable even if you do get it woken up.

The Optimate has a high voltage low current boost that can kick a recently dead battery back into accepting a charge. If that's not doing anything useful you have a new battery style door stop.

You might get same effect by series connecting two 12 volt batteries across the dead one so it sees 24V for a few minutes. Then put it on trickle charge and watch how long it takes to show fully charged.

But if it's been dead for some time it won't have much useful capacity. Quickly reaching full with the correct charge current is another bad sign.

Correct charging current is not more than 10% of battery amp hour rating. Current should be reduced on older battery's to avoid accelerating their demise.

AberdeenAngus · Apr 18, 2014

If the battery is that flat, it's permanently damaged.
You may get a charge into it but its capacity is reduced.
It will let you down on a cold wet night in the middle of nowhere and no phone signal.
Do yourself a favour and replace it.

Charging a dead battery

scubascuba3

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