Morris Minor Owners Club

When I try and start my car the battery is flat, I've not been leaving the lights on etc and it is charged when I turn it off. To get it started I have to charge it for 20 mins then try again and it starts no problems, but then I leave it off for a while and the next time I try and start it it is flat again. I am using a dynamo and the car is a 1962 two door saloon.
Any ideas as charging every morning will not be pratical!

Thanks

Either your battery is not capable of holding a charge any more
or there is a fault in your charging circuit, or there is something
draining the battery when the car is parked up. To prove the battery
you should fully charge it and then have an auto electrical shop
give it a 'discharge test'. Without a meter it is difficult to prove
that the dynamo is charging but you could turn on the headlights
with the engine running and just see that the brightness increases
when you rev up, a bit rough and ready but helpful. You can check
for a 'drain on the battery' by disconnecting the unearthed battery
terminal from the battery and,with the car shut down and the doors
shut (so that the courtesy lights are off) gently touch the battery
connector to the battery terminal from which you disconnected it.
If there is a drain then you will see a spark! DO NOT DO THIS
UNLESS THE CAR HAS NOT BEEN RUN FOR A GOOD FEW HOURS
because the battery could be gassing after a recent charge.
obviously an auto electrician would have the test meters to do
all of these checks quickly and safely.

Hello Idral,
a twenty minute charge with a basic charger just refreshes the battery, it talkes several hours to get even a partially discharged battery to full charge. If your ignition light extinguishes readily there is not much wrong with your charging system.
As Willie suggests, check for any drain while the car stands , but with batteries relatively cheap I would not mess about with an old one.

Alec

Another option to test if the battery is not maintaining charge is to leave it disconnected for a while. If its still charged after the sort of time it would normaly be flat, I would start looking for something thats discharging it. (Interor lights, radio, alarm...)

With everything switched off, connect an ammeter in-line with the battery connection and see what current (if any) is drawn. A cheap multimeter with amps on it will do this as the current should be virtually zero with everything off.

If you do the above, set the meter on the highest setting first, and work your way down. (That reminds me I need a new fuse for my meter....)

(That reminds me I need a new fuse for my meter....)

Im glad we have a proper Auto Electrictian on here

just call me sparkie