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MG MGF Technical - How long will your battery last

Hi how long will your battery last if you don't use the car very oftern as mine only lasts about 5 days and the battery is only a year old! the car is 10 years old and i wondered if anyone else had this problem or is it because its not used very oftern


I would be surprised if your 10 year old battery is retaining a good charge.

My battery has never been very good from new and has gone completely flat on a regular basis due to lack of use - which apparently doesn't do it much good.

The car is now 5 years old and I replaced the battery recently. I intend to use a conditioning (trickle) charger when it is sitting in the garage from now on.

Sam Murray

I've just had to have a new battery fitted.

I thought I was having alternator problems as the car is not used that often these days and the battery was only 3 years old, yet it kept going flat.

As it was in for its MOT I thought would get it checked and the verdict was the battery was knackered and some of the cells had gone down, yet the car still started okay once battery was charged but only lasted 2 weeks.

I had even bought a charger and even that cut out probably due to the cells as it thought it was disconnected from the battery.

Also the garaged stated I had the wrong battery fitted which did not help things. So much for those tyre and battery firms.

Tom Randell

The battery on cars with EPAS is bigger (both in capacity and physically, I believe) to cope with the additional load. Also, there's quite a drain on the battery from the alarm - but it should last more than a few days! Have you checked the interior lights go off?

Tim Jenner

Had a similar situation as Tom - just had to replace a 3-year old battery because the old car doesn't get so much use now I have a family to cart about.

But back to the original question, assuming that the battery is in good condition, I usually find that the battery will last about a month without use. If yours is flattening within 5 days, then this to me suggests an excess current drain...

Are all the courtesey lights switching off as they should (including those in the boot and bonnet)?

Is MEMS powering down as it should? (Some units maintain power to the carcoal/scavenging system for an excessive period of time, causing a current drain)
Rob Bell

Hi Paul

My 98 Abingdon is used far too infrequently and I found that the new battery would not hold its charge for more than about 4 weeks.

I initially overcame this by occasionally using a 4 amp battery charger.

After talking to an auto electrician friend I have acquired a 0.4 amp charger which can be left on for longer periods. It has a red light indicating an under-charged battery. This changes to green when the battery is fully charged.

I use the 0.4 amp charger about once a fortnight and seem to have completely eliminated the problem.

My F was seven yesterday.
Same battery !
Same exhaust!
Same H Gasket!
Tony Harrison

A one year old battery should last at least a few weeks.
The most likely suspect is the light in the boot - the wire can break and short to earth in the hinge - causing the light to remain on after the boot is closed. Check it by closing the boot latch with a screw driver shaft or similar - if the light stays on you have found the problem.

If the car is left for longer periods, a low power trickle charger is a good idea - but make sure you pull the spade connector of the bonnet switch (or remove the bulb).


As well as checking the battery, it's worth considering whether the alternator is pushing enough current back into it. The warning circuit/light only seems to operate when there is absolutely no current, so if the output isn't enough to cope with the loads of winter driving then even a shiny new battery won't last long.
Mike Hankin

After six weeks holiday in the UK I jumped in to the F and away she went. I use the car every day so the only long break is when I take annual leave and have never over the past three years had a problem. The original battery lasted six years before it died.
Andrew Regens

There is a simple answer. equip your F with a trickle charge system. I don ot allow my F to get wet - just in case it shrinks. So during the winter I keep the battery up with a trickle feed system - simply a step down in voltaage from 240 volts into a connection permenantly wired. The system was a commercially produced unit. Cost about $NZ40
David Richards

What's a reasonable current to be drawn from the battery when your car is sitting unused. My wife's car is currently having a problem with the battery draining after a couple of days. I plan to get the multimeter out but don't know what level of current I should worry about and what's normal.

Chris Rudge

This thread was discussed between 02/03/2006 and 03/03/2006

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