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MG MGB Technical - Dead Batteries

Purchased two 6 volt batteries about two years ago and have driven the car intermittently and would usually have to give them a charge to get the car going.
Did my usual charge to start driving again and the batteries will not hold a charge and are completely dead.
Is this normal for batteries to go dead so soon?
gerry masterman

If they are not isolated via a shutoff switch, and if you have a clock (or modern radio with station presets) in your MGB, yes. I have found that the only to keep the batterries alive without a trickle charger is to use a shutoff switch.

Ira
Ira Spector (PA)

Whilst a clock or radio 'keep alive' circuit take very little current it's true they will discharge a battery over time. An alarm will probably be much worse, flattening them in a couple of weeks. With none of these my roadster will go a couple of months and still crank at very nearly the same speed as having been used the day before. The V8 having an alarm I had to resort to a battery disconnect switch as I was fed up replacing them every year or two.

You may have a drain, and the way to check for that is to remove the battery ground strap and connect an analogue voltmeter on its 12v scale in its place. A dynamo-equipped car should show no voltage at all. An alternator equipped should show a few volts, this is the reverse leakage of the alternator diodes and can be ignored, you can unplug the alt to check. 12v registered shows a significant drain. First unplug the alt to check for bad diodes, then remove the purple fuse in the fusebox and the in-line for the hazards if fitted. If the drain is still there you will have to start removing browns from the ignition switch, main lighting switch, starter and ignition (if fitted) relays and finally the solenoid to track it down.
Paul Hunt

I had a problem with my infrequently driven B and the best solution I have found so far is a battery tender. Whenever the battery goes down to 85% charge it charges it back up. I just plug it in when I know I won't be driving for a while and the car is always ready to go. They are avaliliable in 12 and 6 volt versions. Several of my friends have tried them also and are very happy with the results. Go to http://www.chaparral-racing.com and search on Battery tender.
Ed Emery

This thread was discussed between 20/05/2004 and 21/05/2004

MG MGB Technical index

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