Reversed polarity

[StephenRae]

I have an old (1995) Red Top slave battery which I cart around but rarely use.

Thinking I should charge it, I first checked the voltage... 12.3v and noticed that the minus showed on my meter, indicating that positive was now negative! The trickle charger seems to work if attached the wrong way.

Does this happen often, will it reverse itself, can I safely use it by simply connecting the jumper plug the wrong way round?

[GORDON STREETER]

It is possible to charge a battery the wrong way round. The best thing to do is completely discharge it by connecting it to a headlamp bulb/heater motor etc and recharge it with a maintenance charger. This used to happen in the motor trade years ago and isn't uncommon.

[StephenRae]

Thanks Gordon......I have a distant memory that Varley batteries don't like being completely discharged....if this is the case would I be better using it as it is. As it is only a slave battery it doesn't matter where the terminals are.

I've never heard of this happening, I wonder why?

[GORDON STREETER]

It wouldn't have just happened its been charged the wrong way round !.
I trust that your testing device is working OK ?

[JimW]

Sorry but, you're . That is an ex-battery, a very Norwegian blue of a battery.

Even if you get it to accept the correct polarity again, the construction of the plates and probably the electrolyte arrangement has been ruined. It will have no capacity.

Bin it and contribute to the economic resurgence by buying a new one.

Jim

[THR]

yea, can you afford an 13 yr old battery to ruin your race weekend!!

[GORDON STREETER]

While we are on the this thread about varley type batteries I found out years ago that the telephone exchange in our village in the UK used them for a back up if they had a mains power failure. They used to change them frequently and bin the old ones . They kept my race cars going for years !

[StephenRae]

Originally Posted by GORDON STREETER

It wouldn't have just happened its been charged the wrong way round !.
I trust that your testing device is working OK ?

Both of my voltmeters are the best Aldi can supply and they agree with eachother.
Now I think about it I the last time the battery was used was in a vain attempt to start my transporter.... I must have connected it the wrong way round!
On the plus side I've trickle charged it (the wrong way round) for 24hours and it is now showing over 13 volts.
On the minus side JimW may be correct and it is an ex battery, but as I am not much of a spender I think I'll put it on a road car and see how long it lasts!
Back on the plus side the battery on my race car is 18 years old and is good enough for me to never need a slave battery....but I'm tempting fate now.