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MG MGF Technical - charging a nearly empty MGF battery ?

sorry, may be a stupid question, but my MGF suffers recently (i.e.) under the problem, that the battery got empty after 14 days holidays.
I know, we talked about it and the reasons several times, but the archiv does not contain messages of the last few weeks.

- mine is 3.5 years old, so probabbly time to get a new one.
- battery voltage was 11.8 V when I found the starter 'not working'.

- I released in the meantime the 'ground-pole' and charge the battery with a small standard battery charger. At staart of charging the battery pulled app. 4 Amps.

So far so good. I recently did not check for any MGF failure, but I know that all lamps and other parts like radio etc. where switched off. So, may be my car has the MEMS-Main-Relay Syndrom, as described by Carl already. (The Main Relay may be not switched off by MEMS).

Anyway, its boring to key in the security code.. ;-)

So, the question is:
Can the battery be charged with a battery charger without releasing the cars connection poles ? Or can something be damadged at the MGFs electricals if the groundpole is not released while the charging process??


I may answer myself, after having asked my dealer.
He said.
No, remove the ground-cable before charging.

You can charge any car battery with it still connected with any half decent modern charger without risk of damage. The main area for concern with re-charging lead acid batteries is with the formation of gases producced in charging and the potential for explosion which may result if a spark ignites them.

Sensitive electronic components may also be damaged if the battery charger is faulty and applies a half rectified current to the the electronic components, but a reasonably health battery will absorb the effects of this. The greatest danger is with a faulty charger and a completly flat battery, where if left connected there is a posibility of damage to electronic components, but as long as there is a reasonable voltage (interior lights come on to a reasonable level) you should be safe charging the battery on the vehicle in a well ventilated area.

Connect the charger before swithing on the mains and switch off the mains before disconnecting the charger to avoid creating a spark near the battery.

If like me you cannot open the bonnet on your MGf you can sucessully tricle charge your battery through the boot light wiring, and I've had no problems (not recommmended though, an opening bonnet would be nice but Rover deem this an optional extra!).

many thanks for your comment. I cannot really understand everything (my language problem), but it sounds true (confidence).

So, I own a hopefully good charger.
4 Amps Type with Amp-Meter from BOSCH. It has an 'overload security' button.
I think its inner regulated in any way, because the Amp-meter 'swings' alittle when I start charging.

To prevent from explosions. I think removal of the 6 Cell-caps must be too and fresh air in the garage anyway.

Thanks, so, I'll try that instruction the next time when the power is to low but not when a battery is completely empty. And I'll power on the charger after having connected the cables to prevent against sparks and EMF.

Somebody else who can approve this ? :)



Hups, I just recall (Alzheimer) that I uploaded a charger picture with disconnected ground pole this afternoon.

Apologies if this has been discussed before but I couldn't find it in the archive.....

After a period of not been used, the F battery was completely lights..nothing!

I managed to jump-start it from my wife's car and went for a drive.
After about 6 miles, I was in lane 2 of the A1M and flashed my headlights to thank a Merc who'd moved out to let me overtake a lorry.
When I flashed the lights, the engine and all electrics died...
Couldn't restart the engine...
Couldn't indicate...
No hazard lights...
Couldn't drop the windows to give handsignals ( whatever they are!)..
Luckily the lorry realised what had happened and undertook me so I could pull onto the hard-shoulder.

Once I stopped, the battery was flat as a F&*^ ( aka pancake).
After quick phone call home, we managed to jump the F again.

Quick thoughts:-
Alternator must have been charging as 'Alternator' lamp was off.
Alternator belt seems OK
Why would flashing the h/lights cause engine to cut-out?... volt drop?
Should I not bother jump-starting but always mains charge?

Rgds, Tony
Tony Burke

Hi Tony,
sounds like You were running "Lucas Memorial " as we have once a year over here = Autum evening pathfinding , no lights allowed! :)

To be more serious, have a competent garage chech the battery under load. Possible an open cell.
This gives totally flat battery, jumpstart makes generator deliver enough current to keep car alive - but when everything gets a bit too much for the generator without battery as reservoir voltage drops below limit and You get no charging at all ! Headlight flashing was probably the straw...

Regards, Carl.

Trickle-charging the battery is just tackling the symptoms, not the problem. A typical car battery is designed for high starting current and is never meant to be discharged below about 70%. A recharged flat battery will never be as good again and is more likely to cause future problems even with a charger connected (and what happens when you park somewhere and don't connect the charger?)

I think that you should bite the bullet and get a new battery. There are some good bargain deals around but I advise going for a reputable make and if possible get a higher rated battery than the one fitted (70Ah I seem to remember).

My battery also went after 3 years, after one heavy discharge (left internal lights on over long weekend) I don't think the Rover fitted standard item is that good.

9408 SD 76

>I think that you should bite the bullet and get a new battery.

Surely, mine is 3.5 years old. But recently I unfortunately need none (broken hydragas):(

fitting low price aftermarket batteries are listed on:
The cheapest one for the MGF I found is app 38 GBP incl. VAT. But I'll go for a common brand one, like Bosch or Varta (for germans)

(NoName 55Ah runde Kontakte
(+) Anschluß vorn-rechts
B/L/H 170x240x175 (+30)mm)

sad Dieter

This thread was discussed between 05/01/2000 and 06/01/2000

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