Hello guys,

I own a 2004 Mini Cooper S w/ 66k mile, and up until recently have had no issues.

Recently, I had to replace the battery as it was dead. I replaced it, hooked everything up (ensured I had the exhaust vent correctly in place.) Today I noticed that the battery is really hot; I mean REALLY HOT. There are burn marks on the piece of the trunk that rests on it, which I assume is very very bad. Also the battery cable seems to be slightly melted.

I took a volt meter to it and while the vehicle was idling, noticed that 16.6 volts were getting sent to it. That to me seems very high. Is it possible that the alternator is over charging the battery, causing the melting/burning/overheating?

If not, any recommendations on where to look/what to do?

If this isn't the right place for this topic, my apologies.

 

That sounds like exactly what is happening. Check all your conections also. Don't drive it anymore until you can check it out and make sure, so that you don't fry things. You might want to check the voltage regulator also. You may need to remove the alternator and have it checked out on a machine. Most auto parts stores can do this for you.

 

Here is some instructions to help you remove it if need be.

1. Remove front bumper cover 2. Remove Front bumper carrier 3. pull 4 clips out of RH Rad. core support to fender liner. 4. Disconnect horn wire on RH side.
5. Detach upper radiator hose from elbow.

6. pull Rad. core support out to gain access. 7. Disconnect battery

8. Remove alt belt, using 3/8ths ratchet in tensioner(you need the special tool if you have an "S" 9. Remove alternator

 

I don't know what connections to check other then the battery cables. If there is a short/cross somewhere else in the electrical system, that wouldn't case 16+ volts to be sent to it while idle right?

16+ is high, correct? What is normal acceptable idle range?

Is the voltage regulator easy to check?

 

My scangage says that the charge voltage is 14.2 +/- a little. That should be pretty standard for any battery. I don't know about the Gen I but on my Gen II the charge voltage seems to be controlled by the computer...maybe not, I don't know for sure. Anyone got a Chiltons?

Also, I changed the battery on my Gen I Cooper, no problems. But I got an exact replacement from NAPA.

 

Way too high. Yes, a good alternator on a good battery should deliver between 14 and 14.5 volts with the engine running. 16 is showing way to high and you are risking a fire or the battery exploding.

 

I will defiantly not drive until I get this taken care of. Braminator, you mentioned the voltage regulator; how would one go abouts checking this?

 

Get someone to sit in the car and increase the revs say around 2000-2500rpms (this speeds up the alternator to produce more voltage).


Use the voltmeter in the same way as before by touching the positive and negative battery terminals using the respective sensors from the voltmeter.


Read the voltage output. If it says 13 to 15 volts, the voltage regulator is operating correctly. If it's higher than 15, or lower than 13, get it checked out in a garage

 

Before I forget, thank you for your help.

What I don't understand though, is how is your description of testing the voltage regulator different then how I tested the charge coming from the alternator (using the voltmeter on the battery terminals while idle?)

 

Alright, did the test again. Idling, 16.6, and while rev'd it was 16.65. Would you say it's the alternator, or did I test incorrectly?

Also, while off, the battery is at 14.5...which seems higher then it should as well (prob since high charge from alternator.)

 

By increasing the revs this speeds up the alternator to produce more voltage.
This also sounds like you could have a bad battery. I would take the battery out and have it check at an AutoParts store like Adance Auto where they have a machine that can check it under load off the car. It could also tell them if it has a bad cell.

 

On any car with an alternator you have a voltage regulator. And this voltage regulator is responsible for keeping the voltage on the vehicle from exceeding a limit. Usually this limit is thirteen point eight to fourteen point two volts. Which is enough voltage to allow for proper battery charging but not enough to burn out light bulbs or damage delicate computer circuits. The best way to test a voltage regulator is with a multi meter and what you do is you put your multi meter clamps directly on the battery terminals. Positive red to positive and black to negative and you set it to voltage. And with the car off you should have a little over twelve volts that's a healthy battery. Once you are hooked up you want to start the vehicle and what you'll see is that at idle the voltage will increase. This means that the alternator is charging the battery. Making about thirteen point eight, thirteen point nine volts. And so at this point what you want to do is you want to slowly start increasing the speed of the engine and once you hit between fifteen hundred and two thousand rpm the voltage would reach a point where it no longer increases. What you should notice is that it's maxing out right around thirteen point nine eight, nine seven or so which is well within that thirteen point eight to fourteen point two, so the voltage regulator is working fine. If the voltage keeps climbing with the rpm up in the fifteen plus volt range then the voltage regulator is not doing it's job and it needs to be replaced. If the voltage is too low then the alternator is not charging properly and it needs to be rebuild or replaced. And lastly, if the voltage with the vehicle off is below twelve volts then the battery is most likely in need of being replaced.

 

Before moving on, make sure your voltmeter is reading accurately. Double check it w/ another meter or same meter on another car. I'm not sure we have a regulator in. Everything seems to be controlled by the computer. Miss old school simplicity!

 

most people would kill for a 16v electrical system lol well bassheads like i would... looks like you have a bad voltage regulator. Are any of the electronics in the car acting erratic?

 

Braminator,

After testing, it appears the alternator is giving extra volts to the battery (I disconnected the negative terminal from the battery and used the voltmeter on the neg/pos cable) and 16.6 volts was gettting pumped through.

Based on your steps above, I could, with a lot of work, replace myself. A mechanic said it would be 670 or so for the part + 300 in labor. That seems quite expensive for the part; do you have any aftermarket recommendations?

 

I would highly recommend http://www.pelicanparts.com/catalog/...ELchrg_pg1.htm

Their customer service is amazing and they stand behind their parts.

 

Here are some more step by step instructions with pictures
http://www.pelicanparts.com/techarti...eplacement.htm

 

Do you think there is anything else I can do to ensure it is the alternator prior to buying this?

 

I would advise you take it off and bring it to Advance Auto or someone like them to bench test it. Remember to take your time when working on your MINI.

 

...and that has to be fully removed for them to test...if I take it out, that better be the problem.

 

Drive the MINI to them as they can test it on the car and check the battery and starter at the same time.

 

What would the difference be?

http://www.partsgeek.com/catalog/200...ml?brand=denso

vs the top one

http://www.pelicanparts.com/catalog/...ELchrg_pg1.htm

I found the original part # is 12317515030, so would the second one be OEM where as the first one is aftermarket?

 

I am sure you have an Advance Auto around. Get this http://shop.advanceautoparts.com/web...920%7CL2*14999

 

Bring yours with you so there is no core charge and they can test it before you buy theirs.

 

I don't have an advanced auto around, so I can order online.

Is this one any less reliable then the $300 OEM one from Denso? If it is, then I guess I can justify paying $300 more, but if there isn't a difference, then I would rather not.