Rover 200 R reg Battery problem?

The main earth connection is the thick black cable attached to the battery. It connection has to be clean and tight at both ends.

Tenner? :)

You could also get the car checked to see if something is draining the battery when it's off.

Si

By clean, that means electrically clean.

Undo it, sandpaper or scratch the hell out of both surfaces so you've got lots of shiny metal, then bolt it back on tight. Cover it with something waterproof then like vaseline.

I had a perfect *looking* connection once that was electrically crap. Car would run fine from a jump but refused to start - the earth connection dropped so much voltage with starter motor sized currents passing through it that the sparks disappeared.

Cover it with something waterproof like vaseline, then bolt it back on tight. The other way you don't get any corrosion proofing where it's important, at the contact points.

Hmm. I suppose bolting it back *tight* will let the high spots touch, but as an electronics engineer the idea of coating your contacts in something non-conductive before connecting them seems a bit nasty...

Wot he said.

Si

If the battery is ok and charging properly to you need to measure the current draw when the car's parked up. Common cause of this being excessive is a diode failing short circuit in the alternator and taking about 5 amps when the engine isn't running which is enough to flatten a battery in a day or less of not running the car. But it doesn't show up in a causal charging test.

Really a job for a decent auto electrician.

ATS are talking rubbish. In the winter I was doing only 3 miles each way to work both in the dark with everything on and never had a flat battery.

Before searching for the leaky component, I'd first disconnect the cable from the negative terminal of the battery. Then bridge the disconnection with a digital multimeter to measure the current, if any. With all the electrical devices turned off (also, if there is a bonnet light, remove its bulb), the current should not be more than 500mA (the small current going all the while is for the immobiliser, the clock...etc.).

When a higher read out is registered, you have a positive confirmation.

Unplug the fuses in the fuse box one by one systematically while the meter is still connected. Any unplugged fuse that reduces the current drain points to a leak in the system of connections monitored by that fuse. Your car owner's handbook should tell you which fuse is monitoring what. Then track down the leak in that system of connections, again systematically.

An alternative, a short cut, is to examine (the connectors and wires) the commonly affected end electrical devices individually to look for 'short' ( electrical contact which should not be present). These are out of sight normally so that a leak is not immediately apparent.

Disconnecting or remove the suspected offender to see if the current drain improves.

Thanks guys for all your replys, we have run a few simple tests and nothing is draining the battery, the alternator gives out 14 - 17 volts is this enough to maintain the battery?

Also the indicators are slow to respond when cold and damp, when car has been running for 10 or so mins they are fine, the air bag light on the dash has also been coming on whilst driving along but it's not consistant are these conected in any way?

Jayne 0_9

I suppose you've mostly worked on clean stuff :)

The contact pressure needs to be quite high. The idea is to exclude gas from the metal-metal joins. If it does, then corrosion only happens at the edges. The idea is to prevent air getting to the metal-metal joins, and prevent corrosion. A light smear of grease will do this, but will not stop metal-metal contact, when set to the normal pressure.

The alternator should not be charging the battery at anything that much above 15V. Its regulator (inside its housing) needs to be looked into. Any 'quick exhaust and battery place' can check that out for you, often free of charge. It is possible just to replace the regulator/rectifier assembly.

Since the battery may have been repeatedly overfed -- Any acrid fume and also topping it up with distilled/ionised/demineralisedwater repeatedly? -- there may well be some internal damage already. Inspect through the fillers to see if the 'plates' are not warped or even touching one another. Check each individual cell (there are 6 of them) with a hydrometer. If the difference between the highest and the lowest reading is more than 0.050 (specific gravity here, so no unit), the battery is terminal. That also explains why it cannot hold any charge for long.

Also, as pointed out already, the earth-straps need to be checked carefully for loose connection, damage, corrosion (perhaps from spilled bubbling acid electrolyte from the overcharged battery),...etc.. Don't forget to check the engine-to-body earth trap as well.

"...the air bag light on the dash has also been coming on whilst driving along..."! I would have it sorted out pronto! Yes, it could be related to the poor earthing but since it is a vital safety component, you need to have it examined by a professional eventually anyway, no matter what you do.

Less. 14.4V is usually quoted as the maximum, and should die back to 13.8 or so when the battery is charged. Modern 'maintenance free' batteries don't take kindly to being overcharged.

Whenever I had to do stuff for harsh environments (bolted to the outside of a helicopter at low level over the North sea in winter - does that count as harsh?) I used conductive grease for that sort of connection - or potted it.

Your way means that only the high spots touch, which doesn't give you much surface area to handle 100A or so for starting. But cars do seem to manage!