P38 key fob

I have 2 working key fobs. One I use regular and the other twice a week . The one I only use twice has over the past 6 mnths flattened one of the batteries in the fob. The first time I put down to dodgy batteries and replaced, these were Duracell. The second time panasonic, same thing happened. Then Ever Ready then some off the bay I've never even heard of the make. The longest the fob has last has been about 6 weeks. Saturday I put new batteries in and have used it daily and today message on dash low key fob battery again. On testing one battery again nearly flat. This is always the battery that is nearest the board. I have tried cleaning the fob out with electrical cleaner, no difference. This fob was repaired several years back by some one we all know and trust and has been fine until these past months or so.
Any one got any clues or ideas for what could be causing it. Its really weird it is only one battery that goes flat and not both

I thank you

the batteries are stacked, in parallel. unless there is an intermittent short i dont see whats going on.. once is a duff battery, twice is unlucky.. i dont believe in coincidence

kermit_rr said:

the batteries are stacked, in parallel. unless there is an intermittent short i dont see whats going on.. once is a duff battery, twice is unlucky.. i dont believe in coincidence

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Series not parallel surely ?

kermit_rr said:

the batteries are stacked, in parallel. unless there is an intermittent short i dont see whats going on.. once is a duff battery, twice is unlucky.. i dont believe in coincidence

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Totally agree. It's weird

pwood999 said:

Series not parallel surely ?

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yes, sorry

@Rubberknees It's odd that only one battery goes flat. The batteries fit inside the cover, there is a metal strip the connects the positive of the battery furthest into the cap to the PCB. Looking at one of mine, if that metal strip is loose, it's just possible it may cause a short. As only one battery goes flat, that would seem to rule out a fault on the PCB.

Datatek said:

@Rubberknees It's odd that only one battery goes flat. The batteries fit inside the cover, there is a metal strip the connects the positive of the battery furthest into the cap to the PCB. Looking at one of mine, if that metal strip is loose, it's just possible it may cause a short. As only one battery goes flat, that would seem to rule out a fault on the PCB.

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If you remember you sent me a replacement strip as mine broke in two. This is whats in and it looks OK compared to my other fob. Whether its not seated properly I don't know. I'll take it out and refit, see if that does any thing

You could try a bit of tape round the outside of the battery's so they are as one, i seam to remember Tomcatalan doing that to sort out battery`s going flat.

brianp38dse said:

You could try a bit of tape round the outside of the battery's so they are as one, i seam to remember Tomcatalan doing that to sort out battery`s going flat.

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Good call that. Will try that.
My old mate I still miss him

Rubberknees said:

Good call that. Will try that.
My old mate I still miss him

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Yep do miss his humor, as well as the tech stuff, a great loss.

Batteries taped together and refitted into fob. Lets see how it goes

Nice to hear tomcats name mentioned again great knowledge and even better humour and his mate wammers greatly missed on here a mountain of Range Rover knowledge

Right update time. Same batteries now been in for 2 weeks and still working. Both batteries showing 3.1 volts on multimeter so fingers crossed.
One pointer whilst battery holder out of fob shone a light on it and went over with magnifying glass. Have found a tiny piece of metal embedded in the battery holder where one battery would touch it. Could this be the reason only 1 battery drained. Have taken tape off just to see and will feed back

Rubberknees said:

Right update time. Same batteries now been in for 2 weeks and still working. Both batteries showing 3.1 volts on multimeter so fingers crossed.
One pointer whilst battery holder out of fob shone a light on it and went over with magnifying glass. Have found a tiny piece of metal embedded in the battery holder where one battery would touch it. Could this be the reason only 1 battery drained. Have taken tape off just to see and will feed back

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I would have left the tape on.

Right another 2 weeks passed. The fob has been left in drawer unused . Took out and used today. No problems Locked and unlocked twice Never lasted this long before so appears we are getting there (still keeping fingers crossed)