Shmurzik

Hello everybody,

Before going a on a business trip few weeks ago I discovered that the 928 isn’t starting – the night before cranking was somewhat labored and now it’s wasn’t turning at all. I have a replacement starter but prior to installing it I would like to eliminate battery as a suspect. So, I have the following questions for those willing to share their expertise:

1. Should I use a booster battery and if yes – through the terminal connections under the hood or by connecting directly to my car’s battery? I understand there is a considerable amount of debate on the subject…
2. If a booster battery is a no go – should I just go and buy a new battery? And if yes – what brand/type.

Many thanks!

jim morehouse

Before you replace the starter, I'd try cleaning your battery and ground connections first. Not only those at the battery itself, but the ground behind the tool cover, the engine grounds, the connections at the
battery terminal/jump terminal under the hood. You can connect the boost battery (if it's one of those self contained units...not a boost /charger that plugs into your AC outlet...I wouldn't use that) at the underhood connection to start, then get a voltmeter and measure the voltage..should be around 14v if you're charging system is working properly. I've used the underhood terminal to jumpstart from another car without any issues but wouldn't trust the voltage being putout by one of boost/start AC boxes.

There are a number of threads on measuring your OFF current drain (to see if that's what is drawing your battery down) and Wally's Electrical Maintenance check list on cleaning grounds/connections. I'd eliminate connections/charging/ defective battery as causes before doing the starter unless you have a reason to believe it's gone. I put a battery disconnect switch in mine last year when I couldn't locate the source of my drain and it works great...car can sit a month or two and still fires right up....hmmm, roads are dry here in PA, might be time for a ride.

Jim

Mark

This is one of the indications of:
1 - The points that Jim made in his post
and
2 - A battery going!

I would NEVER use a booster! It is just too easy to fry the sharks delicate/complicated electronics. I, and many others here - just use a trickle charger. Even at a couple of amps, it should fully charge a battery overnight.

Most ANY auto parts store will test your battery for free!

deliriousga

I use a 6amp charger, but never in the car. The battery must come out before charging.

I carry a jumpstart pack with me just in case I'm out somewhere and have a problem, but will not allow the 928 to be jumpstarted by another car. The jumpstart pack I use is small enough to fit in the spare tire well and has an on/off switch. The switch prevents the surges caused by direct battery connection with a live battery. The surges cause the electrical problems with all of the modern cars that have computers. Since you connect the jumpstart pack before the electricity is turned on, there is no arching electricity and no surge.

For the battery, I recently put an Everstart (Walmart) battery in and it works great. They are made by Exide (my personal favorite battery company) and the one I got was about $50. The only things you have to do are make sure you have the right amount of minimum cold cranking amps and the new battery needs to have the same size base and height of your old battery to fit in the compartment. Take your old one with you for comparison and everything will work out great.

Imo000

I’ve charged my 928 at the terminal under the hood many times. I never boosted it from there only charged it. After all, that’s what that terminal post is there for. I did the same thing in my old ’83 and never had any problems.

hacker-pschorr

I do not see what the difference is between using a 2nd stand alone battery and a jumper pack dedicated to jump starting a car. The issue with jump starting a 928 (or any other car) using a doner car (usually running) is any possible surges from the other vehicle. Just hooking up a 2nd battery without the 2nd car should not cause any harm. No different than installing a new battery.

My 1.5amp Interstate Battery Saver takes a few days to bring a dead battery up to "full charge". Only takes about 8 hours to take a dead battery to enough juice to start my Audi (just went through this drill last week).

Everyone should carry a jumper pack in their cary. Find one that fits behind the drivers seat. This way you never have to worry about frying your 928 in case the battery goes dead. $50 - $100 is a very cheap insurance policy that your car will start.

Mark

My bad, Hack...I read "battery booster" instead of "booster Battery"...was thinking of a high amp battery charger/starter - in the "starting mode" they can throw 75-100 amps to the car...MORE then enough to fry some 'puters! (I think there are more then a couple of documented cases of that.).

Yep - I carry and have used one of the booster battery packs. But - as you have probably experienced - if your car's battery is almost dead, even a 'spare' full size battery has trouble getting her to turn over (much of the 'juice' is absorbed by the cars battery in an attempt to rejuvinate itself!)

hacker-pschorr

Reason why I keep a cutoff switch on my battery so if I need to jump it, I can disconnect the battery pretty easy, sending the jumped power 100% to the car vs the dead battery.

My 91 Caddy with side posts is a royal bitch to not only attach jumper cables, but remove the negative terminal. Leave it up to GM to fix something that has never been broken for the rest of the automotive world.

Imo000

My charger has the option for the “starting mode” but it's only 50 amps and it takes a good 10 min to bring the battery to crank the engine over. I did this a few times but try to avoid it as much as possible. After hooking up the charger I start off at 2amp then switch to 10 amp and then to 50 amp. I never went straight to 50 amps. This seems to work fine for my ’85. I do all my charging at the front post.

The booster pack is a good idea. However my only concern is that they are pretty heavy and in case of an collision they can become airborne and hurt someone in the car.

Alan

I would not use the engine compartment +ve post to start the car - go straight to the battery posts. The wiring from the battery +ve is 35mm^2 wire direct to the starter. From the engine compartment post to the starter its 16mm^2. So reduce your voltage drop by using the battery direct.

I have a battery maintainer permenently in the car - works great - if I ever detect weakened starting it gets plugged in... I also have battery ground cutoff switch and a permanently powered outlet in the back of the car that is connected on the "off" side of the ground switch so I can use this as a battery charger port when the car is off. I like this a lot. For 2A or 6A charging it works great, although I usually use the battery maintainer instead.

A 6A battery charger should never cause any issues with frying things on your car - as long as the battery is in fact healthy.

However usually when you need to charge the battery you don't really know that its healthy since its just done something unexpected...

If a battery develops a high internal resistance it can have a much higher voltage requirement to charge @ 6A - On cheap battery chargers this can give you very high charging voltages - maybe above 20V - really not good.

Best bet is to disconnect the battery before charging - or use a battery maintainer (can take a long time) or use a low (2A) mode initially and monitor the battery voltage before switching to Med (6A or more....)

Incidentally if you do boost with another battery - if you later remove the booster battery when the car is running... be careful... if your original battery is really Kaput your voltage regulation may then be really bad - (just like disconnecting the battery) monitor the alternator/battery voltage - if it suddenly increases a lot when you remove the booster battery you may have a problem (it will go up a little due to reduced charge loading) If it goes above 14.5V at idle you likely have a major battery problem and I would stop the car and have the battery tested.

I think its always better to charge the battery disconnected and then see if it can start the car. If it can start the car it should also be fine to stabilize the voltage.

Best way to charge the battery -> drive the car on a nice long one...

Alan

SharkSkin

If your battery has been dead for weeks -- regardless of the reason -- it's probably dead forever. At the very least it will be marginal then die at a bad moment. Batteries do not respond well to being discharged for any length of time.

cfc928gt

Along these same lines don't use your alternator to charge a weak battery. It takes too much out of them and will lead to premature failure of the alternator. I use a 6 amp charger on the battery a lot in the winter when it may sit for weeks between me driving it. I use the front post to connect to and as others have said I've had no problems.

Imo000

Once the battery is totally drained, all it takes is 3 days for a battery to become unchangeable. Cold weather really accelerates the draining of a battery. On average a battery will loose 1%/day, so after 3 months even a fully charged battery will become empty.

Shmurzik

Dave,

That's exactly the question. The battery could be alright. As I wrote earlier first I noticed somewhat labored cranking and the next day I could here the solenoids clicking but the starter was not turning. Meanwhile all the cabin/dash lights came on and so did the AC. So the battery did have a rather significant amount of charge. I did not have time to attempt to fix the issue then, so on the advice from the prince among men (some dare to call him Bill Ball) I disconnected the ground wire in the trunk and went on my way. Now I am trying to figure out what I need to do prior to biting the bullet and doing the starter (the car is sitting in my carport in Bulingame and I anticipate it being somewhat of a pain).

I got some ideas from the responses to my questions and will most likely go and get a replacement battery just in case (current is at least 3 years and 20K miles old).

And once again - I would like to thank you and all those who took time to respond.

Bill Ball

Shmurz:

I can bring my charger over and we can let it sit for a few hours and see what happens, BUT if the battery was dead before you left, then it is probably sulfated and unable to accept a charge. It would be most expedient to go down to Autozone and get one of their Duralast batteries. I've had mine for more than 3 years. Relatively cheap ($60?) and a good battery.

Edit after post - I see you D/C'd the battery ground prior to the trip, as I advised. The battery still loses some charge just from sitting, but I would have expected it to still be able to accept a charge unless it had been a real long time. However, that assumes the battery was OK before. Since it is 3 years old, that is an open question. Easiest to go get a new one and have no worries about that.

We can look at the starter on Sunday, if you want.