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MG MGA - Battery woes

Last week I tried to start my MGA after a couple of months "rest". I found the batteries totally flat. After about two days charging (and the batteries were apparently still taking 2A), I managed to get enough juice in to start the car.

The car is positive earth with original type twin 6V batteries.

When I took the battery cover off, there was a large collection of whitish-green powder around the positive terminal of the negative battery i.e. on the positive terminal between the two batteries. Initially I removed all of this.

The electrolyte level was down in all the cells - so I topped up with de-min water. About 100 ml into each.

After the first overnight charge, there was still no power in the batteries although the charger had started off at 1A which reduced to 0A. I cleaned up all the terminals and charged the batteries disconnected from the car. Again this rapidly decreased from 1A to 0A, and had no charge in the battery.

I tested the electrolyte SG and it was off the scale in the discharged side.

I tried a different charger that put 2.5A overnight and was still charging in the morning at 2A. The SG was now 1.120 - about half charge.

What causes the powder accumulation around the terminal?

What causes the loss of electrolyte?

These batteries seem to be taking a lot of current for very little return. Are they just knackered?

If I replace them, I would prefer to put a modern 12V battery on one side without modifying the cradles - are there any batteries that fit the bill available in the UK? I seem to remember that Steve has such a setup.

thanks

dan
Dan Smithers

take them out of the car and the connecting lead, or use some jumper leads and charge them that way.
maybe you have a leak.
Once there fully charged take them to halfords and get them to load test them.
Should be free. then you will know for sure.

Next tip, convert to 12v they have so much more amps I seem to remember 280 even from the smallest one's.

Cheers <MARK>
Mark Hester

Dan

I hope I am not insulting your intelligence by asking if you charged the 2 batteries together at 12 volts and not 6 volts? Also, did you put the charger cables on the correct terminals: Red (+ve) to earth and the black (-ve) to the negative terminal of the battery that runs the cable to the starter motor solenoid

Steve
Steve Gyles

The white powder is probably mainly lead sulphate. Be careful removing it as it is toxic and corrosive especially in the eyes. It is caused by sulphuric acid gassing from the cells and reacting with the lead terminals.

The electrolyte goes down because it boils off through charging especially if the rate is a bit high or by straightforward evaporation (slowly).

It sounds like one or more of your cells have gone high resistance. With this the battery will charge as low currents pass OK but trying to pull a starting current will drop the voltage to something fairly useless. This can happen very quickly. A couple of years ago I took my car out, left it in a car park and two hours later it would not start, one cell had failed and it was time to get out the starting handle. To test, if your batteries have exposed links between cells, turn on the headlights and measure the voltage of each individual cell, the current draw should find the faulty cell.

Change to a 12 volt battery, its easy to find one that fits. Modern batteries are "maintenance free" and with the hidden away location on the A this is a most useful feature.

Malcolm
Malcolm Asquith

I charged the two batteries together at 12V +ve to +ve and -ve to -ve with the linking cable in the middle.

The car is now starting and running fine.

All the cells seemed to have about the same SG.

I'll check the cell voltages though.

dan
Dan Smithers

Hi Dan, I have a 12 volt battery in my MGA - it was fitted by a previous owner about 5 years ago and I believe it was designed to fit a motor bike - might be an idea to visit the m/c dealers. Being smaller than the usual 12 volt car batteries it fits the original battery cradle perfectly . You need to put petroleum jelly( Vaseline) around the terminals before putting the battery leads back on - this stops the acid fumes attacking the lead terminals and causing the sulphate forming - which reduces the flow of current and also "eats" the clamps away. Cheers Cam
C Cunningham

Dan,
if you have a FIAT dealer nearby check if they have a 12V Battery #71730452 which fits perfect in the original battery frame. Sorry forgot which type of FIAT car it is from.
Siggi
Siggi

Corrosion!
All batteries corrode.
Really!

You can clean it off carefully without getting anything into the cells with plain old BAKING SODA.
And hot water. Be sure to clean the insides of the battery cable clamp as wel. I mean polished.
And try to obtain some felt washers for battery terminals. It will slow that down or even stop it.
but I must emphasize, do not get this into the cells, as it will destroy the battery.

And to fully charge a battery takes between 8 and 12 hours. Oh sure, it will start after 10 minutes of charging, but not enough.
Safety Fast
Dwight
Dwight

This thread was discussed between 03/01/2006 and 07/01/2006

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