Battery? Or something else?

Hi Guys, I've pretty much always got my car plugged into an optimiser in the garage, however, on occasion I will forget, if I forget I'll be lucky if the battery will sluggishly turn over the car in say a week of standing. Now the optimiser always picks up that the battery needs a bit of charge put back in it, even after a cruise or using the car all day, I guess this is fairly normal if I start and stop a few times. I've been through two optimisers in the past couple of years though, but both always say that the current battery is in excellent health. When I first got the car I changed the battery as it seemed to turn over a little too slow for my liking, popped over to the local battery shop and he gave me the 'recomended' battery for my car, it was pretty much the same as I had, about 70+ah and 650-700 cca at a guess (was a couple of years ago). I fitted it, and no better, I still wasn't happy it was turning over as fast as it should. I insisted on a larger battery but he said that the one I was given was the one for my car, so I got a refund and fitted the old one and carried on. I've always noticed though that the car will start perfect first time with lots of enthusiasm (and it should being plugged in and fully charged) and when taking it round the corner, accross town or into work on a run, when I leave the car and come back it turns over a little too slugishly for my liking. Most videos I've ever seen and people I have spoken to say it turns over fine, and what with it not letting me down and running the car fine (and the optimisers saying the battery is fine) I've left as is, it always starts, but the slower turnover annoys me and it's starting to bug me more now. Example I fired the car up last Friday, it started ok (taking it off of the optimiser again). I drove 34 miles, parked up and left the car for about 4 hours, I popped back started her up, she was ok but a bit slower turning over than the morning, I drove probably 4 miles, parked up and left for another 4 hours, when returning the start was more sluggish this time, she never fails to fire after a few turns, and does charge on a run, but the engine just to me seems to turn slower with each time I stop and start the car. Example, my car normally turns over very similar to the first vid I found on youtube when searching for 996 start up: http://www.youtube.com/watch?v=sd_5As_bS24 My other cars have always turned over very quickly, the porsche just seems to have a sluggish lethargic sounding turn over to me after starting a few times after coming off of the optimiser. It's bugging me now like I mentioned, I'm sure it should turn over quicker? Not that I do use it for lots of short trips but, if I used it as my wife does one of our other cars to stop and start around town every day running around after my daughter and working I've got a feeling that within a few days it would probably be really ran down. So should I try a new battery again? or check terminals on the starter perhaps? The fact it turns over faster as soon as I first take it out off of the optimiser leads me to believe that connections should be spot on and the battery is just loosing charge quicker than it should. It's never flat though unless I just leave the car standing and forget to plug her in. Also the alternator is fine - it's always given out a healthy 14.5 or more volts. The current battery is a VARTA, it is a 74ah and 680cca, but I'm told this is acceptable for my car, even though I could get upto an 85ah and 800cca. The battery is 4 years old now, although the performance has always seemed the same? Opinions / thoughts? Cheers

The one in the YouTube video doesn't sound too bad to me. If yours is more sluggish, I would check the earth strap on the engine (they corrode) and the battery terminals are tight. Getting to the starter motor is a bit of a pain, so I would check that last.

Thanks, I'll check the earth, the fact that the turnover speed diminishes the more times I start though is making me think it is something perhaps with the battery and the optimiser is lying. Should 74ah and 680cca's provide enough juice to give a healthy start time after time? Cheers,

Steve, Do you have anything to load /drop test with? I recon like Richard said check for good Earth contact. And without starting a war! [8|] what maintainer are you using?. If its an Optimate I have loads of them at work and find them rubbish compared to the Ctek I have at home.

74ah should be fine. I had a Bosch one of the same size on my Turbo. I know it should be 80, but I had it "in stock" when the original died.

Cheers haven't had chance yet as I've been out all day, but will check the earth tomorrow. The optimiser is an accumate 614 iirc. I used to use a oxford 360t, but it blew up after about a year. I haven't got anything to test the draw from the battery, but at a guess I would think it should be fine as all accessories are stock, and tbh, being an early 996 there is little to drain it anyway

Optimate is made by accumate its the industrial side of the company I think. Most of there chargers are 3 stage and its the Maintain stage that I have issues with.

what dies cca stand for?

Cold Cranking Amperes

Ok thanks, how long does a normal battery last as i think i still have the original in mine.

Depends very much on use, but the original Porsche (Moll) batteries tend to expire in about 4-5 years. I doubt if yours is original, as I think it would be some sort of record if it was! A good quality Bosch or Varta should last 6-7 years. If you don't use the car for long periods, a conditioner will help keep it healthy for longer, rather than letting it go flat and recharging.

ok, mines not been on an optimiser in my ownership. I do use it for my everyday run around tho so that might help the battery.

That will be charged everyday then, unless your using it for 5 mins per day.

hi easy way to check if earth cable faulty or corroded , use jump leads from eng block to chassis and see if cranking RPM increases .

Just as a yard stick for comparison, my recently purchased 911( I say recent, was it really back in April?) goes about 5 or 6 weeks without being on any kind of maintenence charger. I have only glanced under the battery cover once and I seem to remember 110 AH but be it 75/80/110, A week with slowly decaying crankspeeds seems suspect. A bad earth is a good place to start as corrosion will lead to a high resistance connection which will heat up and increase the resistance which might be why the cranking speed gets worse after a run, although a battery in poor condition, will take a high current which will lead to a phenomena called polarisation where oxygen and hydrogen bubbles collect on the plates, effectively insulating the plates from current flow. These bubbles slowly dissipate and is the reason why a battery will seem to recover after being left for a while after periods of heavy cranking. Having tried another battery I think the earth investigation is a good place to start. Actually, The 2 year old battery in my 944 was left disconnected since the beginning of April (quick release terminal) and when reconnected for the Aug bank holiday run to the Porsche Championship at Castle Combe, the car started as if I had driven it the day before. This is not so practical on a 911 of course as everything is electrical and who wants to "f4rt" about in the drivers footwell with wires to jury rig the car so you can open the luggage compartment? It is however a measure of how a good battery should perform.

When I bought my car it was 7 years old and had the original Porsche batt. I used a CTEK to keep the batt topped up, but if I was away from the CTEK the batt would be really ropey on first start up after only 4 days of no use. Anyway, I had a Bosch batt put in and the turnover speed is v quick. The new batt makes a real difference. If you find the car turning over quite well after a charge, it doesn't sound like it's a terminal. Personally I'd get a new batt if I was you.

I had a battery problem as it was not charging even after a drive. was have more problems starting when warm and the starter was making a squeel. As I was not driving my car very much i think it was draining too much so i replace it with a Borch S5 110. bigger battery with more starting power. Bought it from ebay with 5 year warranty. fitted my C4 2002 without any issues. Not had any starting problems since feb when i replaced it. Even if i leave it standing for a few days and no more squeel from the starter.

Sorry, just seen your posting - so this is a bit late... TADTS... or at least I think mine does... I've had my 996 for 5.5 years now and have replaced the battery halfway through ownership. I don't have a battery conditioner, use the car only a couple of times per week normally, and it's kept outside. I've noticed that from cold (e.g. first thing in morning) it starts up "normally" - just like the vid you linked to. However, if I have parked up for a few minutes and then gone back to start the car from warm, it cranks at a noticably slower speed. It always starts just fine and has never let me down. Replacing the battery didn't seem to improve things either. Maybe they all do that and others haven't noticed Either way, it is unlikely to be an terminal or earth strap as i can't see any reason why the resistance of an earth strap would change between the initial and subsequent starts. The only think I could think of is that, when warm, either the starter motor is not performing so well (unlikely) or that the engine is harder to turn over. I always depress the clutch during startup, btw, from my days of running really old cars in the past. Anyway, it has remained a mystery to me, but I've got so used to it, I don't think about it any more.