Classic cars forum & vehicle restoration.

[FAB Cruiser]

Hi Guys,

I bought a pair of 6V batteries for my MGB a year ago. The were supplied charged.

The car has been stored and I finally got round to starting it recently. It started with the help of a battery pack (e.g. a Maplin 12V lead acid pack). The batteries won't hold a charge which is why I needed the extra help of the jump start pack.

So the 6V batteries appear to be duff because I didn't use them for 12 months. Is this expected? They were left unconnected until I tried to get the car going. I feels like I wasted £80 on them.

Thanks
David

[Keith D]

David,

Car batteries should always be kept fully charged especially when not being used. They need fully charging at least once a month. I hate to say this, but your batteries are very probably dead.

Keith D

[FAB Cruiser]

Keith,

I believe the are dead. I thought they'd be OK charged and unconnected because they sit on shelves in the parts shops for ages.

Is it possble to refil them with Acid as I know they used to be shipped with the acid in bottle.

Thanks
David

[Keith D]

David,
I don't know how batteries are sold in the UK, but in Australia the suppliers have a nasty habit of filling the batteries with acid when you buy them. They may have been sitting on their shelves for years empty. Their shelf life this way is almost indefinite, but once the acid goes in, then chemical action starts and they start aging. Whenever possible, I always get them dry with a bottle of the acid supplied; I like to add the liquid myself then I know when they start aging! Suppliers tell me that they have to add the acid at purchase to date the warranty.

I don't think that changing the acid will help, but perhaps others on the forum have more knowledge than me on this subject.

Keith D

[47Jag]

David,

Batteries on the shelf have been fully charged and then the acid is drained. In this dry state they will last indefinitely. Acid of around 1.300 S.G. is then added to re-activate them. When a battery discharges the acid is absorbed into the plates this why they are tested using a hydrometer. A discharged battey will read about 1.100 S.G. However if a battery is left unattended (I.E. the electolyte level drops) a condition known as sulphation takes place which is a hard-ish coating on the plates. This prevents the chemical action taking place during charging to expel the acid from the plates. Your problem may be that only one of your batteries has died and you should put them through a charge cycle and then have them load tested. One way of telling which cell is dead without tools is to remove the filler tops and try and start. The dead cell will usually 'gas' (bubble) and give off a smell like chlorine. Don't be tempted to add fresh acid to a discharged battery.

Art

[FAB Cruiser]

I've charged them individually with a 6V charger. They take the charge and get up to about 6.2V on my multimeter. The Hydrometer shows them as 'full', but only just. However, the charge drops away pretty quickly when I put them in the car and they won't turn the starter (the solenoid makes a chattering sound).

I may try charging at 12V with them in series just to see if that makes any difference but i think I've blown it.

Thanks
David

[ukdave2002]

I'd echo 47jags comments and the other advise about not storing batteries with acid in an uncharged state, that said a year is still quite a short time to put pay to a battery, which suggests that they may have sat on the suppliers shelf with acid in for some time? most batteries these days have a minimum of 2 year warranty any chance you can return them?

The voltage also seems low straight after charging, just check it when they are on the charger it should be over 7V, you maybe have a problem with the charger if its not.

I have brought batteries back to life by charging them slowley (trickle charge) they a heavy discharge repeat this a number of times... worth a try.

Dave

[Nic Jarman]

A strange thing I have found with lead acid batteries is that if they are stored on a concrete floor they don't last very long - just a few months. If they are put on a pallet they last much longer.

[FAB Cruiser]

Guess where I stored them ((