Battery discharging

[Gerard1234]

Hi all,

After 48 hours my battery dropped from 12,7 V to 12,25 V

The red light for ignition goes on when I turn the key and goes off when the engine starts

The battery loads at 1500 rpm to 14,6 V

The only thing I changed in the car is a new radio but I connect it so that it only works when the car is on ignition

The battery was tested by a local shop that sell batteries and he told me that the battery was oke

The problem started the last weeks or so , I never noticed the problem because the engine starts in 1 sec

After reading this side someone wrote that it was perhaps the dynamo, is this a commen problem?

Anyone a idea?

[geoberni]

You've not actually said why you did this '2 day voltage test'?
What was/is the problem?

When did you take the first reading and how cold is it where you are?

It's been many decades since I studied the theory of why, but I would say a battery could easily drop 1/2 a volt from being measured straight off charge, when it's warm, to standing cold at -2C a couple of days later.

[Gerard1234]

Last week it was cold in Holland and it came to my notice that the battery was not very strong

so I measured it and it said 11.8 V

I drove with the lights and radio on the last several times and drove short distances so I thought that would be the problem
but after charging the voltage dropped after 48 hours from 12,7V to 12,25V

This morning I disconnected the battery (after a short charge ) and it is now on 12,58V (measuring after 0,5 hour)

[geoberni]

There are some electrical checks you can do on the charging system, but I suspect the cold is at least part of the problem.

See this booklet on Lucas Generator and Control Box tests.
https://mgaguru.com/mgtech/books/pdf/Lu ... _Tests.pdf

Is the battery still turning the engine at a good speed and the car starting?
If you're using the car for short journeys with the lights on, you will be struggling to replace the charge you're using to start it.

[Gerard1234]

The problem is solved

Don t laugh but my voltage meter is going crazy
This morning it said that the battery was 16,7 volt

I took another one and that one said 12,6 V
after starting with 1500 rpm it said 14,6 V so I am a happy moggie driver again.