Re: Ping Mrcheerful

Mrcheerful laid this down on his screen :
Is the replacement battery you have fitted a good quality new one of the correct type for the vehicle? and is it giving the same problems? (you haven't actually said)

The old one was a 60aH 600cca Varta and its spec. was as per manufacturer and about two years old. It charges up fine off the car, and holds its voltage was over 13v off charge for 24 hours.

The replacement is a new Bosch 72aH 680cca fitted yesterday morning. The extra capacity was recommended by other owners due to the mass of equipment fitted on the car. Obviously I have not had it long enough to find out if it suddenly goes flat yet.


The drains you mention could not flatten a good correctly charged battery overnight, so if we assume that the drains are being measured correctly then that leaves battery and/or charging.

Agreed, but at this stage I think the drain is only happening sometimes. I fancy something is not going to low power mode just once in a while.

Battery is best checked by substitution with a new one (I have only ever come across a couple of faulty new batteries (cheap makes) in many hundreds and never had a faulty top brand battery at all (bosch or similar)

Did that yesterday.

Charging is best checked by results during and after use. 13.8 is absolute lower end of charging, 14 - 15 is far more normal.

I have always considered 13.8 to be spot on, but perhaps I am wrong there. What is puzzling is the fact that it can go for days/weeks/months without any problems, then it will suddenly have a completely flat battery. Flat as in not enough charge left to even pull the starter solenoid in and this can happen overnight. It never has any middle ground of just barely cranking it over enough to start it, it really is all or nothing.

All the driver can leave on accidently is the parking lights, which would be noticeable in the dark garage, or the interior lights/glove box/boot light etc.. The latter all go off via a battery saver relay after leaving the car undisturbed for 20 minutes and I have checked this works correctly.

Even if 13.8 is not giving it a full charge, it doesn't explain the suddenly completely flat battery.

Normal is for it crank over quickly and start/run at the first pull. It is not the starter, the battery really is flat as confirmed by the dash doing an instrument reset and the lights also being dead.

[EDIT] I have just been out to check the connection of the main feed from the alternator. The nut wasn't loose on the terminal, but it wasn't what I would call tight either. I took the lug off, cleaned it up and refitted it - which has gained me an extra 0.2v.

It now hovers around the 14.06v mark on a full load at a little over tick over. Its a 100amp output BTW.

As I originally asked - how would an auto electrician go about tracking down a discharge which just happened sometimes? Is there an instrument able to pass cranking amps, but still able to measure down to a few milliamps?

Thanks for the help!

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk


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