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post #3 of (permalink) Old 16th August 2006
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Originally Posted by jpfrost
He said that with all the lights that come on with the the doors open it could well drain the battery in about an hour. Does this sound right??
Yeah. I've killed batteries like that before - you'd be surprised at how much current those interior lights can draw. The best way to stop this is to pull the fuse, but you only ever remember this after you do it

Originally Posted by jpfrost
Anyway, in the past week my battery has flattened three times without leaving my doors open for any length of time. i have also driven over 1000 miles in that time so it's not as though the battery has not had enough time to re-charge. Does this sound like a dodgy battery? Should I be able to get this sorted on warranty?
Car batteries don't like being "deep cycled" - i.e. flattened and then recharged. You get into a situation where the plates inside the battery cells can get warped, and are unable to sustain the current needed to crank the engine. You'll still find the battery reads 12v or thereabouts, but as soon as you try and fire up the engine, it just fails.

You can take your car to a HiQ and ask them to do a "drop test" on the battery which will tell you if it's alive or not - my guess is that it might be a bit screwed though...and sadly, Renault class the battery as a wear-and-tear item, so it's not a warranty item.

Now - if you take your car to Renault, they'll tell you that the battery must be a renault part in order to preserve your warranty, and then try and charge you over 100 for one. DO NOT AGREE TO THIS!. This is working under the common myth that in order to preserve a warranty, you must use manufacturer parts, and this is a myth that Main Stealers are very happy to perpetuate.

If you are worried, get yourself a multimeter from Maplins and measure your battery. With everything off, you should see the voltage is between 12.0 and 12.5v. That's called the "float voltage". Anything below that and the battery is screwed. When you crank the engine you'll see it drop, but it shouldn't go much below 11.0v. When the engine catches, you should see the voltage jump to anything between 14.0 and 14.5v. If you see anything less than that, then it's your alternator which is not charging correctly, and you should go back to Renault ASAP, as this is a warranty part. If the alt is damaged, it's a good idea to replace the battery at the same time - as I said before, a regular car battery is fairly intolerant to deep-cycle usage, and will be unable to hold as much charge as it would do normally.

Hope that helps.

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