Battery

[cypruselise]

Hi thanks for you help again. Here is my next 'new to Elise basic probs ' The car battery goes flat after two or three days, even after putting in a new battery (Bosch S5 - what a pain to do, how come automotive design and consultancy engineers came up with the Elise battery lay out!) This is a problem with fibreglass cars in general but I think that I should get two or three weeks before going flat. I have checked the fuse box and the only readings I get are 12.4v on the alarm and battery management fuses which I suppose is normal. I also get 0.2v on the 50 amp lighting fuse. Is there any obvious area to check before going into the realms of an auto electrician?
Cheers to all.

[j2 lot]

Fibre glass cars are no different to any other, if the battery is charging properly and there is no drain on the battery it should last for 2-3 weeks ( with the alarm armed) without any issue.

Its either not charging or there is something drawing current when its parked up.

[Shug]

Paging Robin...

You'll need to measure the current drain when it's all off - but that's definitely not normal and you do have something draining it somewhere.

[robin]

Check your brake lights aren't staying on - common fault with the brake light switch on the pedal.

Alternator can also fail in this fashion - if you're parked up somewhere quiet you might actually hear a whine coming from the alternator (in the engine bay, behind the driver's seat).

Water in the MFRU (big relay pack near the ECU) can also do this.

What are you measuring when you measure the fuses? The voltage across the two fuse terminals or the voltage between the fuse terminal and the chassis ground? Are the fuses in the fuse box or removed?

Many of the fuses will be isolated from the battery by the ignition switches and I would expect 0v across them and 0v between either fuse terminal and chassis ground. For those that aren't isolated I would expect the battery voltage on both sides and 0v across the fuse. If you set your meter to the lowest range (usually 200mV) and place the meter across the fuse terminals then you might see a very small voltage across any fuse that has any substantial current flowing through it, assuming the fuse is actually in the fuse box, of course.

If you cannot find it that way you could try this.

Find the 10A ammeter setting on your meter (note this often requires you to move the red probe into a different terminal on the meter).
With ignition off, remove the first fuse. Insert the meter probes into the spade terminal sockets that the fuse came out of. If there is any drain on that circuit the meter will read non-zero. Replace the fuse and move on to next fuse.

Cheers,
Robin

[cypruselise]

The battery is now lasting a week without charging and started strongly. I have not yet manged to leave it for more that that. The only thing that I did was to clean up the fuses. The 50amp light fuse was corroded quite a bit but I don't see how that should drain power if everything is switched off. I also got an AccuMate charger and have screwed a lead onto the battery so it is simple to re-charge if required. as amatter of interest, has anyone tried to drill a screw hole into a battery terminal? The metal is soft and easy to drill.....yes? No it is quite hard and chewy and breaks dril bits easily. I think the idea for the AccuMate cames fron this website so thanks for that.
Regards.

[Corranga]

Rather than screw the lead into the battery, I used a couple of larger O type terminals and simply added them to the bolts already on the battery terminals.
Tamiya connectors on the other end of the lead / charger, and it's easy to plug in or remove.

I reckon get 2-3 weeks out of my 3-4 year old budget Eurocarparts Lion brand battery when I forget to plug it into the conditioner, so your new Bosch should be at least the same, assuming it's charging properly/has no drains.