2002 Battery Charging Issue - LotusTalk - The Lotus Cars Community

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post #1 of 10 (permalink) Old 10-25-2012, 10:41 PM Thread Starter
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2002 Battery Charging Issue

A few months ago, I replaced the battery but hadn't tightened the posts adequately. After a day of driving, the battery died, naturally. It happened close enough to home and a couple of boosts later, it was in my garage and back on to a battery maintainer. I charged it for a few days and all seemed fine on the next drive, though it was only about a 10 mile drive. The car sat on a maintainer for the next 5 weeks. I drove it for a day this past week and, again, the battery died, preceeding by an erratic tach and speedo and the ABS light coming on, just like the first time it left me stranded.

It's now at the dealer and they're a bit stumped though suspect the ECU/ECM. The alternator is apparently spitting out the correct charge. JAE suggested a 140 amp alternator and was puzzled by why the ECU/ECM might be suspected.

Has anyone had a charging issue that was not due to the alternator?

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post #2 of 10 (permalink) Old 10-26-2012, 12:39 AM
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If the alternator runs without being connected to the battery, it will be damaged.(however you stated it was OK).
It simply may be a bad battery. Frequently, if a battery is discharged, it will not recover.
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post #3 of 10 (permalink) Old 10-26-2012, 06:13 AM
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I have found that maintainers do a great job of keeping a charged battery charged.
With that being said, I have also found that they wont bring a battery thats in need of a charge up to full.

A battery charger,rather then a maintainer is needed to bring that battery to full again. After all, a maintainer does exactly what it says it does.

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post #4 of 10 (permalink) Old 10-26-2012, 06:15 AM
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It's the alternator. Because the battery was drained completely it may also be bad now. Load test the battery and see if there is any black goo dripping off the bottom of the alternator. If there is, it doesn't matter how good it tests, the alternator is bad. The ECU does not control battery charging. Low system voltage can cause all kinds of weird symptoms. Do not replace the ECU, at least not till you have a good battery and charging system.
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post #5 of 10 (permalink) Old 10-26-2012, 09:20 AM
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David is correct, you have a bad charging system. Auto alternators have internal regulators that determine output. They determine output based on load and voltage. An alternator not properly connected to the battery will be damaged. It is possible your battery was damaged by the deep discharge, but it would not be able to,start the car if it was severely damaged. The computer has no influence on this.
Depending on the car and the load you can usually drive a few miles with just the battery and no charge output.
In a normal system the battery does not provide power for ignition or accessories, but rather the alternator does. Once the alternator is charging it provides the power, the battery gets recharged and only provides a reservoir of stored energy for momentary high loads, and a sink to keep the voltage even.

All connections should be carefully checked including grounds before installing anything new. Alternators are damaged when connections are poor.

If your mechanic says the alternator is ok it is because he is reading output voltage at idle as being adequate. However you could still have a damaged output or faulty regulator. It would be a more logical move to replace the alternator, check connections, and maybe replace the battery, than to worry about the computer. Especially since your problems started right after you replaced a battery and improperly hooked it up.

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post #6 of 10 (permalink) Old 10-29-2012, 10:37 PM Thread Starter
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I appreciate everyone's feedback and it re-affirms what I thought. However, what I did learn here is the possibility and likelihood that the alternator was damaged. Indeed, the battery connections weren't tight when I hooked up the new battery. Perhaps the damage was done at that point. I managed another 50 miles or so on the recharged battery before it died again leading me to this post. Thanks for the advice.

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post #7 of 10 (permalink) Old 11-12-2012, 08:27 PM Thread Starter
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Well, to follow up, the dealer replaced the alternator with a 140amp one that I ordered from JAE and the problem persists, even draining their portable battery packs. So, the ECU has been sent out to Lotus. Could I have hurt it somehow when it originally failed and I had to boost it?
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post #8 of 10 (permalink) Old 11-13-2012, 06:02 AM
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Personally I still wouldn't think it would be the ECU. Sounds like you might have a bad connection to/from the battery (especially with those erratic gauges) or possibly a short somewhere in the car that is draining whatever battery you connect to it.

I believe the way to test for a short would be to use a meter and removal of fuses until you find the culprit.

Like this: How to Fix Electrical Shorts in a Car | eHow.com
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post #9 of 10 (permalink) Old 11-13-2012, 06:37 PM
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It is possible the new alternator is bad or it was hooked up wrong or somehow damaged. It should be tested and so should the battery. The ECU would not drain the battery. You probably have a wiring problem with the car causing the drain. I would not think the ECU is the problem here.
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post #10 of 10 (permalink) Old 11-13-2012, 07:48 PM
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FYI, there are a couple of ECU's for sale on eBay in case you are being faced with a huge ECM bill from Lotus.
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