battery or alternator: Please help - 986 Forum - The Community for Porsche Boxster & Cayman Owners

mptoledo · 03-08-2010, 02:14 PM

I have searched and read all the results on the subject. I just need a little more input.

Went to start my car after the winter sit. Got a new battery as my 7 year old one wouldn't start the car. It is 50ish outdoors. I installed the brand new batter from wallyworld. It is their best gold series. Had some trouble starting it and got an arc when connecting the cables.

2001 boxster "s" 62k miles. Ran perfect before winter.
1.) Battery light stays on
2.) stereo won't turn on(aftermarket jvc).
3.) oil check thing doesn't work, it just blinks
4.) Car stops the second you take off the negative terminal.
5.) Checked all fuses and replaced abs/asr/psm control unit as it had blown

I ran the car around the block for a couple miles gently but spirited once it warmed up. Every thing seemed as usual and no other issues, except the above.

I think I blew my alternator out but is there another way to check or does someone else have an idea?

JFP in PA · 03-08-2010, 02:39 PM

Quote:

Originally Posted by mptoledo

I have searched and read all the results on the subject. I just need a little more input.

Went to start my car after the winter sit. Got a new battery as my 7 year old one wouldn't start the car. It is 50ish outdoors. I installed the brand new batter from wallyworld. It is their best gold series. Had some trouble starting it and got an arc when connecting the cables.

2001 boxster "s" 62k miles. Ran perfect before winter.
1.) Battery light stays on
2.) stereo won't turn on(aftermarket jvc).
3.) oil check thing doesn't work, it just blinks
4.) Car stops the second you take off the negative terminal.
5.) Checked all fuses and replaced abs/asr/psm control unit as it had blown

I ran the car around the block for a couple miles gently but spirited once it warmed up. Every thing seemed as usual and no other issues, except the above.

I think I blew my alternator out but is there another way to check or does someone else have an idea?

Get a multi meter, check the battery voltage with the car off; should be 12.5 V or so. Start the car, check it again; should be ~14.5V. If it passes both these test, your battery and alternator are fine, you have shorted out something else. If it fails either test (low car off voltage can be a battery issue, less than ~14.5V running and your alternator is bad), you need to fix these issues before determining what else is wrong..............

Steve Tinker · 03-08-2010, 03:02 PM

As an addition to JFP's advice, if you disconnected the battery with the engine running as per your item#

4.) Car stops the second you take off the negative terminal.

there's a good chance that you have blown the diodes in the alternator......

mptoledo · 03-08-2010, 03:03 PM

Thanks for the reply. Since I just got the battery today, I am pretty much ruling that out. I am just going to take the alternator to Oreily's tomorrow. It is the original and I am pretty sure I fried it.

mptoledo · 03-08-2010, 03:08 PM

Funny you should mention that. I read that in one of my searches after I had already done it. Live and learn. I guess 9 years on an alternator, I got my moneys worth.

Why would my oil check guage not work? that is what I can't figure out. It just blinks and doesn't do anything else

ARModen · 03-08-2010, 03:31 PM

The battery light is really an alternator light, which generally indicates that there is something wrong with the alternator or the voltage rectifier/regulator on the output. The ones I've taken apart sense voltage at the diodes, so the light coming on indicates the alternator is no longer rotating, or the diodes have burnt out. So it could be a pulley issue, but you get a lot more lights if you throw the belt.

Most of the electronics in the car will run down to 5-8VDC. Below 8VDC you start losing sufficient potential to generate an arc at the plugs and run some larger loads effectively. If you're alternator isn't working then you have 12.5VDC from post to post on a fully charged battery. Battery voltage drops as load increases and the battery discharges so 10-11VDC is reasonable while driving. Any sort of grounds or dirty connections or large loads (headlights) can drop portions of the electrical system another 2-4VDC. This is fine if you're starting at 14.5VDC but enough if you're at 11VDC, which is probably what you're seeing. 5VDC is probably enough to still run the instrument cluster, but not enough to run the oil level sensor. My old 944 had dirty battery terminals that were dropping ~6VDC. They were hot from dropping that much power.

Bottom line, fixing or replacing the alternator and then driving the car around a bit will probably fix your problem.

mptoledo · 03-08-2010, 04:29 PM

No new noises or anything pully related. I pay close attention to sounds in my car after the "ims" scare of 2009 on here.

I think when I arcd my battery installing it, I zapped the alternator. I new I did a bad thing when I saw a fews blown and my rear spoiler had gone to the up position.

I am just thinking of taking the alt in tomorrow, but I will decide that after I attempt to take it off. What I have read it isn't that muchof a big deal. Cant' be as hard as when I replace my alt on my girlfriends Taurus. Some genius really screwed the pooch when they desinged that engine.

Lil bastard · 03-08-2010, 05:40 PM

I suspect you've had a bad alternator all along which is why the other battery failed to start the car. The arc is surprising unless you connected the negative (-) cable first then the positive(+), or with the key in the ignition - big NO-NO that.

When connecting the new battery, you likely blew another set of diodes (3 prs. total).

Also, did you charge the battery prior to installing it? FYI, batteries straight from the store are not at 100% charge due to shelf life. It's always best to charge the battery independently first and not rely on the alternator - they are not intended or really designed to fully charge a battery. Their function and design is to run the car and it's accessories while topping off the charge of the battery dissapated by the start-up.

If your alternator were newer, I recommend just swapping the diode pac - available sparately. But since it's 9 yrs. old, I'd opt for replacement so you have fresh bearings, brushes and windings, it's the best way to go.

BTW, a battery in top consition should show no less than 12.8 volts and more like 13.0-13.2VDC. And for the Bosch alternator, the output spec is 13.5-14.5VDC.

Cheers!

Paul · 03-08-2010, 08:17 PM

The battery idiot light will glow when the battery is almost dead even if the alternator is OK. My 01 did this on Saturday after sitting for 6 weeks as soon as I put the key in the ignition and before I turned it.

vipola · 03-09-2010, 07:28 AM

Quote:

Originally Posted by mptoledo

4.) Car stops the second you take off the negative terminal.

I would NOT do that, even if it was a good test a while ago, with today's fancy electronic, you don't want to unplug the battery on a modern car/motorcycle while it run. The battery help to keep the voltage stable and prevent it to spike.. it's not intent to run without a battery.

Quote:

Originally Posted by ARModen

The battery light is really an alternator light, which generally indicates that there is something wrong with the alternator or the voltage rectifier/regulator on the output.

I learned this one the hard way, been a motorcycle guy for ever, when I saw the battery warning light up I tought it was a low voltage indicator and I went for a ride to 'recharge' the battery.. and got stuck when the battery died in the middle of nowhere 15 min later LOL..

mptoledo · 03-09-2010, 02:25 PM

UPDATE:

Ok, i got checked the battery with a meter 12.5 turned the car and on and it was at 11.9, turned the lights on and it started dropping to about 11.7. Took the alternator out(20 minutes). had it tested and the test machine immediately showed an error. Ordered a remanned bosch $208. I will have it in about 2 days and will update you on the results.

Side note: I would not test the alternator by taking off the neg battery cable. I have heard from too many people that this is a no no!!

JFP in PA · 03-09-2010, 03:22 PM

Quote:

Originally Posted by mptoledo

UPDATE:

Ok, i got checked the battery with a meter 12.5 turned the car and on and it was at 11.9, turned the lights on and it started dropping to about 11.7. Took the alternator out(20 minutes). had it tested and the test machine immediately showed an error. Ordered a remanned bosch $208. I will have it in about 2 days and will update you on the results.

Side note: I would not test the alternator by taking off the neg battery cable. I have heard from too many people that this is a no no!!

"Just like advertised"............for future reference, you can use a volt meter to get a "go/no-go" reading on the alternator; if you really want to be able to fully evaluate the entire charging system, consider getting a load tester. Besides being the best way to test the battery, it can also test the alternator output under light and heavy loads, putting the diodes and regulator thru their paces as well. Cost about $50-60 bucks, works on any 6 or 12 V system........and won't kill anything in the process................

vipola · 03-10-2010, 06:30 AM

Quote:

Originally Posted by JFP in PA

"Just like advertised"............for future reference, you can use a volt meter to get a "go/no-go" reading on the alternator; if you really want to be able to fully evaluate the entire charging system, consider getting a load tester. Besides being the best way to test the battery, it can also test the alternator output under light and heavy loads, putting the diodes and regulator thru their paces as well. Cost about $50-60 bucks, works on any 6 or 12 V system........and won't kill anything in the process................

Ehh.. battery tester need to match the amp of the battery.. if you test a 600amp battery with a 50amp tester, you 'may' not have a valuable result :P From my experience, those 50$ tester are best suit for small motorcycle battery :P

JFP in PA · 03-10-2010, 07:10 AM

Quote:

Originally Posted by vipola

Ehh.. battery tester need to match the amp of the battery.. if you test a 600amp battery with a 50amp tester, you 'may' not have a valuable result :P From my experience, those 50$ tester are best suit for small motorcycle battery :P

The one in the picture will handle 130Amps..................well beyond what most car batteries are capable of producing.............

vipola · 03-10-2010, 07:28 AM

Quote:

Originally Posted by JFP in PA

The one in the picture will handle 130Amps..................well beyond what most car batteries are capable of producing.............

I may be wrong, but the cheapest car battery at Canadian Tire is rated 750 amp..

JFP in PA · 03-10-2010, 07:55 AM

Quote:

Originally Posted by vipola

I may be wrong, but the cheapest car battery at Canadian Tire is rated 750 amp..

You are misinterpreting the battery ratings; the amperage capacity is a rating of the amps the unit can deliver over a period of time (total capacity), not its actual momentary amp delivery. Most of the batteries that came with the Boxsters are rated at 600-800 CCA, but actually can only deliver 50-80 amps in 10 seconds……. If it could deliver 600 amps instantaneously, your battery cables and starter would not survive…………

vipola · 03-10-2010, 08:18 AM

Cold cranking amperes (CCA) is the amount of current a battery can provide at 0 °F (−18 °C). The rating is defined as the current a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery). It is a more demanding test than those at higher temperatures.

If a Boxster Battery is rated 600 CCA, that's the amount of amp it can deliver for 30 sec without draining itself..

A Battery Tester put a high load on a battery for 10-30 sec, and you look how the battery recover from that load..

look like the same specs for me.. from what I understand you should test a battery with the closest possible of it rated CCA to get a valuable result..

You want to know if you kill the battery with that test, and if you do, then it show you that the battery is not able to deliver those promises CCA anymore..

Testing a 800 CCA battery with a 150 Amp tester won't give much info about the true performance of the battery..
If a battery is supposed to be able to deliver me 800 CCA, it dosn't mean much to know that it can deliver 100 CCA :P
isn't just like asking a body builder to bench press 5 lbs?

(This is all from what I understand, I'm always open to learn better

)

JFP in PA · 03-10-2010, 09:40 AM

Quote:

Originally Posted by vipola

Cold cranking amperes (CCA) is the amount of current a battery can provide at 0 °F (−18 °C). The rating is defined as the current a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery). It is a more demanding test than those at higher temperatures.

If a Boxster Battery is rated 600 CCA, that's the amount of amp it can deliver for 30 sec without draining itself..

A Battery Tester put a high load on a battery for 10-30 sec, and you look how the battery recover from that load..

look like the same specs for me.. from what I understand you should test a battery with the closest possible of it rated CCA to get a valuable result..

You want to know if you kill the battery with that test, and if you do, then it show you that the battery is not able to deliver those promises CCA anymore..

Testing a 800 CCA battery with a 150 Amp tester won't give much info about the true performance of the battery..
If a battery is supposed to be able to deliver me 800 CCA, it dosn't mean much to know that it can deliver 100 CCA :P
isn't just like asking a body builder to bench press 5 lbs?

(This is all from what I understand, I'm always open to learn better

)

OK, let’s start simple: Think of the battery’s amperage rating as you would a fuel tank’s capacity (around 18 US gallons for the 986/987). Much like the battery, the fuel system is never called upon to deliver all the fuel instantaneously, but it does have the total capacity of 18 gallons, and could do so under the correct circumstances, although that outcome would also be disastrous.

Most of the non-momentary electrical loads (lights, stereo, etc.) only draw a couple of amps each, so they really do not place much of a load on the battery, particularly while the car is running. This is why a car with a weak battery will run fine after a jump start, but be incapable of restarting on its own. A typical car, with a good battery and charging system, is running down the road with only a few amps load on the system. Placing a momentary high amperage static draw on a battery using a proper 130 amp rated load tester for 10-15 seconds (I have never seen a shop load tester capable of doing it for more than that length of time, because they do get hot; although much larger liquid cooled units are used by the battery manufacturer’s to test the battery’s) pulls the battery voltage down and shows how capable the battery is dealing with the high momentary load, much as it would when trying to spin the engine over. After 10 seconds of static load (engine not running), the tester will read out the battery voltage, with an 800 amp rated battery that is in good condition reading in the 7.2-7.8 V range. If the battery goes below that level, it is either only partially charged, or defective (in our shop, we always run a specific gravity check on a battery to make sure it is fully charged prior to load testing).

The 130 Amp load tester we use on our client’s cars has regularly identified batteries that were becoming questionable before the owner’s even knew there was a potential problem. We recently had a 911 in that periodically refused to turn over, but otherwise ran fine. Every time it refused to spin over, a quick jump got the car running, and it would then act normal for several starts, but would eventually again refuse to spin over. The dealer told the owner he needed a new alternator, battery and starter. Not wanting to spend that kind of money, he brought it to us for a second opinion. When we looked it over, the battery specific gravity said it was fully charged. But after only about 5 seconds under a 130 Amp load, the battery voltage dropped to 4 volts. We immediately suspected the battery, but jumped the car to start it, and ran a “dynamic” load test (130 Amp load testers are also capable of testing the alternator’s response to high current draws in a similar manner, but while the car is running. The load period is the same 10-15 seconds, and should cause the charging system to jump to maximum output to offset the current drain. Some of the better 130 Amp load testers also have a separate lead that attaches to the alternator’s power terminal, which allows you to see the diodes and regulator respond in real time to the brief load in separate digital display.) and saw that the alternator responded well, but again the battery voltage momentarily dropped very low. We checked the starter for current draw, and it was also in spec. As we suspected the battery, we replaced it, and the car repeated the tests without incident, and has run fine ever since.

130 Amp load testers do work, and can often find otherwise elusive problems………

ARModen · 03-10-2010, 02:17 PM

600amps over 30seconds=20amps per second. 150amp rated tester is rated for 150amps per second, well in excess of your maximum battery discharge rate. If you managed to get near 600amps per second out of your battery, you'd completely ruin a wrench and have purple spots in your vision for several hours... just trust me on this one.

Paul · 03-10-2010, 05:25 PM

So are you saying that our starter motors only need 20 amps x 7.2 volts or 144 watts of power? Since 746 watts are needed to produce 1 hp, that seems to be very low.