Flat battery again

[mikal83]

Drove the car for 3 days solid, no probs. Get home, wash it, put it away, 2 days later flat battery.
Charged it up, it drew 2 amps for 2 hrs and it all started fine. Battery shows 12.5 volts and 13.5 at tickover.....is my alternator tits up?
Heath book, page 112, says a healty battery should have 12.7 volts and the alt should chuck out above 13v @ 2000 rpm............help

[WazzaL]

If you've been running it for 3 days without an issue, surely that means your alternator is working.

If it is discharging quickly, then either a constant drain on the battery, or the battery itself is at fault..

I had a relay stuck on my Chimera (was obvious as it was a fan that would not shut off - but the principle stands) and have heard that the boot light could be remaining on.

Also had a battery issue if left unattended for more than a week or so. Put it on a Ctek charger with a reconditioning feature (I'm sure an accumate version will do the job as well) and not had the issue since.


Wish you luck.

[mikal83]

cheers mate.
I'm pretty sure that there was nothing on when I put it away on Sat morning after a wash etc, but was flat on Sunday. The previous owner also let the battery go flat as he didnt use the car for over 6 months when working in the far flung....Checked the output on the alternator on tickover and it was chucking out 13.5 volts. The heath book says it should be "over" 13.1 volts. My tiddly civic chucks out 14.4 volts at tickover! I do have another battery.....from a tractor...that I'll charge and slot it in and see whats what. BUT I'm leaning towards a duff battery!

[nawarne]

I'd agree with a duff battery.

They don't like to be left completely flat, particularly for a long period. As you say, alternator seems to be kicking out a healthy'ish voltage. Any slight reduction might be due to a battery cell(s) gone down.

I recently bought from www.tayna.co.uk. Very reasonable, they know what they're talking about and good service.
Nick

[mikal83]

have "borrowed" a newerish battery from my bro-in-law out of a tractor. Shows 12.8volts and is charging at 2 1/2 amps....so str8 away its got more juice than the old one.....will leave it to fully charge over a day or tow and then take some readings.

cheers

[mikal83]

Update. Charged the battery overnight and it had a healthy 13.5 volts at the posts. At 2000 rpm, I read 13.5 volts ????? Was hoping for 14 ish volts from the alternator. It dropped to 13.3 volts with all the lights on at 2000 rpm. Thoughts?

[wild rover]

I would say that the voltage output is ok. From your explanation it says you had a faulty cell in the battery just about to show itself. It would be best to check the earth leads from the battery to the engine ensure that they are perfectly clean and tight. Could use a jump lead as an additional to see if it makes any difference.Best of luck only time will tell TVR s we still luv em.

[K4TRV]

mikal83 said:

Update. Charged the battery overnight and it had a healthy 13.5 volts at the posts. At 2000 rpm, I read 13.5 volts ????? Was hoping for 14 ish volts from the alternator. It dropped to 13.3 volts with all the lights on at 2000 rpm. Thoughts?

I'm sure if you check the voltage of the "old" battery, it will drop away from 12.5v very quickly. Unfortunately, modern batteries when discharged/flattened rarely recover - one cell gives up and you end up with 10.5 to 11.5v after a few days off charge. When charging they give all the indications of looking "good".

Alternator will only give you 14v+ if the battery "needs" it!! Running at 13.5 to 13.9v is the normal range - even with lights on - shows you have a healtly battery - yet another good indication?

[mikal83]

Cheers mate. Have bought an optimate charger thingy and put two fly leads on the batt posts. Showing yella at the mo and will monitor the situation.....am going down the ....I had a duff cell in the battery.......route?!