Porsche Enthusiasts Club Forum

Having just bought a new battery (over the odds at Kwik-fit ) I'm concerned that I may now need a new alternator according to the "technician". The battery in my car was 72AH and they replaced it with a "recommended" 59AH - my manual says either 50 or 63 - but what the heck do I know about batteries! (I was told that a 72AH battery would be overloading the electrical circuits...???) With only a 9v charge in the old battery my car wouldn't even turn over and needed to be jumped by a great big Volvo in order to get it to a local battery place. I noticed that when booting the voltage was sitting just under 14v, but when jumper cables disconnected the voltage dropped to 12v on the dash with my car running. I don't use my car everyday so I'm concerned that I'm going to kill another battery come the end of winter or sooner.

I obviously need to run some tests now to try determine for myself if my alternator is doing it's job properly - can I get a reading off the alternator itself?

There seems to be some confusion over whether my 2.5 NA needs a 115A or 90A Bosch alternator. Which one is the correct one? - there's quite a difference in price!

I've read the various posts on battery problems & voltage, so I'm off to buy a multimeter of my own to take readings across the battery. Unless I'm mistaken I'm after ±13.8v with the car running - is that correct?

thanks!

Yes, you are looking at around 14v, normally 14.2 with the engine on fast tickover (2000rpm) and 12-13v when off.

Most battery manufcturers recommend 70+amp/hr for the 944 indeed I replaced the one in my S2 with a Bosch Silver which I think was a 90+ or 100A/Hr and the car has no problem charging this running at 12-13V on tick over and around 13.5-14V at 2000rpm and can easily turn the engine over even when freezing cold and not having been started for a week which is why I went for such a high capacity battery.

David, so there's no reason why I shouldn't have been given a 72AH again?
That malarky about overloading the the electrical circuits is pure nonsense.

If the 73Ah fits go with that. Electrical circuits will draw the current they need only.

Rich

The Bosch silver batteries are 78a/h and are fine. 59 may be a little feeble in the winter if everything else is a little worn too.
Certainly the combination of a new alternator and a 78a/h battery goes like mad!

Yes I originally had the Bosch Silver 100A/hr in my 924S but I had to buythe older style although brand new as this was not as tall as the later style and it would fit under the bonnet. However when I got my S2 it had a new Halfords 78A/hr battery in and I swopped this for the Bosch one as the battery in the S2 is in the boot wheel well and has no problems with space and I reckoned the bigger battery would be better for the bigger engine which it seems to be. The 78A/hr Halfords one worked fine in the 924S before I sold it and both cars turn over nice and quickly.

So in answer to the question was the story from the battery supplier cock and bull probably "yes". I would go back and get it changed or a refund and fit the bigest capacity battery you can physically fit but remember to check the bonnet closes (gently before slamming it shut) if the battery is under the bonnet.

Well David I took your advice and returned the battery to Kwik-Fit - I actually told the guy that I'd be happy if he just gave me a match to what I had - he said he won't give me what wasn't recommended by his book and made no apology for trying to pull the wool over my eyes. So I took the £90 refund - better result in my book. Lesson learned: avoid Kwik-fit.

I called around a couple places, and visited Halfords who had both own brand and Bosch 77AH for £99 - £109. But I went with a deal from a local motor factors who had a 72AH 670A battery for £54! Bargain.

I'll test the readings tomorrow with my newly acquired Multimeter from MachineMart.

Now for the alternator - there's a chap who rebuilds them in a nearby village who my local friendly garage has referred me to. That seems a better option than spending £245+vat plus £115 surcharge! More on that later.

If you think the alternator is not working then you could try Design911 http://www.design911.co.uk/fu/pt259_271 ... lternator/

They do a replacement unit for £159 or £175 depending on which type you want, but I would suspect most electrical auto engineers could refurbish the one you have for much less than that, I believe it is only a Bosch or Lucas alternator after all.

It is a Bosch alternator & will charge all sizes of battery than can be fitted to a 944 anyway.
Don't believe the dash voltmeter cos it lies. Put a decent DVM on the battery itself. With engine running you are looking at 13.75volts or more, any less then you probably have an alternator that is US.

Must be catching. Mine failed to start this morning. Too many short runs with lights & heater on. Took the battery off & it's on charge & warming up in the kitchen. Hope the thing isn't goosed as it's too late to get another before Christmas. Apparently the suppliers are now sold out! The trains have been useless this week so I ended up driving the too short distance to work. This is not popular with Mrs JJ.

The bad news is it's goosed. Not charging at all. How do I tell the wife that the Porsche is broken again!

JJ Eurocarparts is your friend - i got a Bosch silver S4 for about £70.

Do they deliver? It's a long way & I don't finish until 5 on Christmas eve.

Ok Battery now charging at under 1amp. It's only a trickle charger but was putting 3.5 in when first put on. Voltmeter reads 13.3 charger off. 14.6 with it on. Maybe it's ok. Condition indicator on the top of the battery says it's had it!!

I don't think ECP deliver batteries tbh.

Like Rav, I also have a Bosch Battery of a similar type (a Silver top mind you) in 096 size (so just over 70Ah) fitted in my car by the previous owner.