964rh

Hi

Just put the battery (74ah) on charge using a 8 amp charger.
How long do I need to charge the battery for?

Voltage reading for the battery was 11.48v when I tested it out of the car.

Thanks

Rob

MisterRisky

I assume the objective is to get the car to start off of the battery. Based on personal experience, my guess would be 4-6 hours should give you a good start. Temp will, naturally, have an impact.

964rh

Yes, just want to start it.

What's the min. voltage req. to start it?

jimq

If thats all it down it probably should be ready to use in an hour or less. If its a trickle charger then yea a few hours. A lot of chargers shut off and have a green light when charged.

MisterRisky

Shooting for the minimum just to start is really tough. Depends a lot on the car and the temp. And voltage is a poor proxy for cranking amps, which really matters.

If you just want to crank it, get another car and jump it.

Richard Curtis

to answer your question, I've found that a minimum of 12.5 volts is required. 13 is better.

964rh

Thanks, batteries not charging above 11.68v so new battery may be in order

Jamie Summers

Rob,
Just had a similar problem - car wouldn't crank, assumed dead battery, put it on to charge but charger said it was full and went into "maintain" mode. Couldn't jump it, so called the AA, the voltage was fine, but plummeted as soon as any load was put on the starter circuit. Took off the cell caps, and sure enough, and nice sulphurous smell - it had dropped a cell. £85 and a new battery fitted by Mr AA and I was on my way. Rather sacreligiously I opted for a 70ah battery to replace the lightweight RS 36ah battery that comes as standard - it only seemed to be a couple of kilos heavier. I used to run a 74ah Bosch Silver in my old C2 which seemed to do the job nicely.

Jamie

964rh

FLT engineer drop tested the battery this afternoon (wanted to get it checked out prior to spending more money and hiding it from the boss) and it's fine.
He thinks the charger may be knackered as it's only pushing out 11.68 volts, tested his and it pushes out over 13v. So i'm hoping the borrowed charger will have me up and running tomorrow.

If not, I've got a new bosch silver on hold at my mechanics for £64+

Rob

964rh

Yep, chargers fubar'd.

Plugged the borrowed one in and it's putting out over 13v and charging nicely with a decent ampage figure.

Oh Jamie, I'd keep that quiet if I were you? what would Des say??

boxsey911

He'd be in no position to say anything now that he's selling out

Jamie Summers

Rob,
I know that Des would have me strung up for committing such a mortal sin, but it was more a question of what degree of hassle I could be bothered to put up with to get the problem sorted at the time. Porsche charge something like £300 fitted for the correct "Porsche branded" battery, and yes I'm sure I could have got a correctly sized Bosch Silver from Eurocarparts of GSF, but the AA man happened to have a 70ah which did not seem noticeably heavier, with a 3 year warranty, at an acceptable price there and then. As it stands I have no power in my garage (though being sorted soon), so can't use a battery maintainer, and even though I use the battery isolator, having a bit more capacity and cranking power is no bad thing on a car that doesn't get used much.
Also, I reckoned that with 335bhp on tap, a couple of extra kilos won't make a hell of a lot of difference to anything, and I've taken off the brake dust shields to compensate !!!

Glad you seem to have got your issue sorted !

Jamie

964rh

andrew964

In case anybody's interested Costco had the red tops on special (about £55) last time I was there