Electrical problem

[Phil W]

Some one please help!

I've just replaced the clutch master cylinder seals on m7 '74 2 + S 130/5 and have now got an electrical problem that has me puzzled. The battery will not hold its charge even though its less than a year old - a new alternator was fitted at the same time and the car has done less than 1000 miles since then.

If I charge the battery the car starts first time. The voltmeter shows the battery is on charge and showing 13 volts. When I stop and try to restart the battery is dead.

I've checked the obvious things such as battery terminals, battery negative terminal to earth (in boot - a common problem and I always unbolt this and clean the connection every spring!), alternator connections and starter motor connections but can't seem to cure it.

Anyone got any ideas?

[garyeanderson]

I would try another known good battery for a start.
Is 13v with the car running? If so sounds a bit low, should be 13.5v to nearly 14v with the engine running.

Gary

[Phil W]

Gary - its probably nearer 13.5 at idle.
I'll swop the battery out at the weekend and give it a try.
Actually thinking about it logically it must be the battery - I disconnect the negative terminal when the car not in use and it still doesn't hold its charge.

[smokey73]

On occasion a battery will develop a "dead cell," (even a brand new battery). When this happens the dead cell becomes an internal load and the other cells aren't happy and try to charge the dead cell, which results in a dead battery over time. Normally when this happens what you will see when you put the battery on a charger is that the charging current will be high and remain high during the charge (not go down like it should)

I have had this on a nearly new battery - the only solution is a new battery. You should be able to take it back to where you got the original battery and get a replacement. (They should be able to test it too and confirm a bad cell)

Hope you get it fixed - not very stylish to be pushing your beautiful Lotus by yourself and jumping in to pop in in gear. Doesn't impress the wife or girlfriend much! Been there - done that - have the tee-shirt!

Dan

[RotoFlexible]

This failure has the same characteristics I experienced when the ground wire for my alternator went bad - except that the battery would not discharge itself when disconnected. If that is really happening, the battery must be bad.

[oldokie]

It's possible to do a simple 'load test' with a multimeter, read the voltage across the battery, hit the starter and read again. My 'rule of thumb' is more than a 10% drop indicates a battery problem. Hope this helps!