[968Syncro]

So, last night my daughter decides to take the 968 (against guidance) to pick me up at the airport. Then it wouldn't start, low battery, 30 minute walk to the "cell phone waiting lot" -- Dads gotta take care of this kind of problem!

We got a jump start, but then the tip warning light came on, and it obviously went into limp mode, so we drove in 2nd gear all the way home, some of it was hairy, I kept the RPMs to about 3,500, gave me about 45 mph max (yes in part on the freeway).

My wife reminded me that this happened to her a few weeks ago, although she couldn't be clear about the symptoms at the time. Her diagnosis was something like "it was weird".

In both cases, like today, I just started it up, ran some errands and all was fine. Turning it off obviously cleared the condition.

A few other notes:
- The owners manual says that the tip will go into 4th gear, I am not sure what that means, we were stuck in 2nd.
- Then it says to "step on the brake to switch off the automatic speed control". I didn't want to do that with a weak battery.
- Obviously I need a new battery
- Lame brain owner story: At one point in the drive home last night, while being locked in 2nd, there was a long steep downhill on the freeway, so I put it into neutral to coast for a bit, get up some speed maybe. Then at close to the bottom I shifted back into drive. Bad, bad idea. The tip really is hard locked in 2nd gear, so putting it back in drive at speed with the engine RPMs at idle created a sudden shock and shudder because of the mismatch in RPMs of the wheels and engine! Don't try this at home, there is no clutch to softly engage the two rotating masses. I might have been flash's first customer for a damper.
-When you are going too slow on the freeway, it is amazing how many people will ride up on your rear bumper thinking you need a push and stay there for a couple of miles, or flash their headlights as if you don't know you are going slow! Damn impatient SoCalers.

So. What is it about a jump start that knocks the tip electronics into limp mode? I have no idea, the battery wasn't all the way dead, interior lights were still well lit.

[img]style_emoticons/<#EMO_DIR#>/wink.gif[/img] That's it, I love my tip, but sure miss the control and predictability of a manual trans. Flash we need a downgrade kit: manual trans, distributor with points, single barrel carb with a choke knob on the dash, leather straps for the boot lid, and a spray can of ether in the trunk -- hey isn't that how we kept our MGs and Austins going?

Roland

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[coloradocab]

Limp mode is indeed 4th gear, so you were in some other mode. At least you could drive it. Folks who really get into limp mode will have the car stall on them unless they're already moving at a decent pace before it goes into that mode. Still, no fun from the sounds of it.

I suspect the jump start shorted something out in the tiptronic control unit. That's the only thing I can think of that would cause this second gear mode thing. Hopefully you can put a new battery in, and all will be fine again. If not, scan for codes.

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[flash]

yup - jump starting these cars can do all sorts of weird things - i've seen it do weird stuff like throw the airbag light, fry a computer, short an alternator, and kill an alarm (all different cars) - it does not surprise me that the tip computer freaked out

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[968Syncro]

Thanks guys, yes I too thought that some electrical pulse might cause the problem. It can't be anything permanent (like a short) since it was working fine today, the same as usual. I sure wish I knew the details on the electrical profiles, I always thought that the lowly charged battery would provide some kind of buffer, but with the cable attached to the "in car" battery cables I suppose it can be much.

Usually when I jump start I try to wait about 5 minutes for the destination battery to accumulate some power first. I think this helps to take a little time to charge the battery for local power. Couldn't do that last night since we were in such a rush.

Roland

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[rxter]

I'd be interested in hearing other's experiences with jumping the car. I don't run mine everyday and so for sure eventually I'll be in that situation of wanting to jump it - my battery must be going on 3-years and I've never had one that was reliable for more than 4. Perhaps removing the battery cables and trickle charging would be a better alternative? Or just getting a new battery?

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[968Syncro]

Joe,

I am sure that charging or trickle charging is always way better than jump starting with cables. Keeping a battery charger around the house for the last 10 years or so is really one of the best tools I have (given my interest in older cars and discomfort with car payments). My charger even has a 50 Amp "start mode" that can be used to start a car with a dead battery within about 2-3 minutes, no waiting.

And my experience with the new battery: Keep all receipts! I found the receipt for the battery, a Bosch, now 3.5 years old. Replacement cost: $22. Took the old battery back to Pep Boys, it tested bad. The warranty was 36 months free replacement, and 96 months pro-rata replacement. So I got a $56 credit on the old battery, and they currently have a $20 rebate, so my final cost was around $22 to get a brand new battery. There would be no credit at all unless the battery tests as "bad", it is not just a simple exchange policy based on time.

A well maintained quality battery should be good for at least 4-5 years, if not more, mine was an exception. Remember we are coming up to 2 years ago when my son "customized" my 968, and so it sat for months without being charged at all which seriously degrades the battery. Unless the battery is deep-cycle (marine battery), discharge of these lead-acid batteries to low levels degrades it's life, that is why some people like the trickle chargers.

Roland

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[flash]

the following is for standard lead/acid batteries:

different batteries vary widely in how long they last - the size and draw on them plays a large part in this - using a battery that is too small in capacity will cause it to have to reach down deeper, which shortens its life - always use the biggest battery you can

according to studies done, only abut 30% of batteries sold today reach the 48 month mark - 80% fail due to sulfation buildup

every time you kill the battery, you diminish its ability to recharge, roughly 5-10% each time - always recharge a dead battery as soon as possible - a battery allowed to sit at low voltage for 12 hours will begin to sulfate and shorten its life - after 24 hours there is a full 1 year loss in its life expectancy - kill a battery half a dozen times and you will be lucky to get a year out of it

i have never had a battery last more than 3 years without very measurable loss of charging potential - a new battery should charge to 12.6-12.7 volts - when a battery gets down below 12.3 volts after charging, it's about done, and could leave you stranded if the circumstances add up wrong (like out doing a bunch of stop and go xmas shopping in cold wet weather)

it is always good to hydrometer check your battery - the specific gravity will tell you a lot about the condition - when testing, fully charge the battery, measure at room temperature, and wait at least 12 hours between charge and test, because the battery will read a false high at first, and gradually go down to its true reading by that time

as a reference:
12.7V is 100% capacity (1.265 specific gravity)
12.45V is 75% capacity (1.225)
12.24V is 50% capacity (1.190)
12.06V is 25% capacity (1.155)

that being said, you can do a lot to maximize your battery's life expectancy:

make sure you cables are in good condition
make sure the terminals are clean
make sure the water is topped up on serviceable batteries (distilled water ONLY)
avoid "stop and starts" - give the battery a chance to recharge after starting

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