How does it know....

[RichardW]

Got in the C4 Pic this morning and soon as I turned it on it beeped and the service light come on Uh-oh thinks I, what's up with it now? Was mightly relived a couple of seconds later when the message "Remote control battery flat" popped up, then the service light went out

That's a bit too clever for my liking.... off to buy a new battery now, so my heart doesn't skip every time I go to start it

[addo]

I know how you feel; recently spent a full day fixing the washer (simply couldn't afford a service call or new machine; all good in the end) then yesterday it paused between cycles exactly when the neighbour operated his tailgate lift! A loud electrohydraulic "Whirrr!" and the machine had stopped dead. I damn near had a heart attack.

[RichardW]

Very funny, Addo!

Was tinkering with the Xantia this afternoon - been meaning to relay the headlights for a long time. Got the NS done, but not enough cable / fittings to do the other side, and I wanted to make sure the first side works for a while (see above about heart skipping!). Easy enough - but found that the bottom mount on the NS light is broken - presumably from the car-vs-drainpipe incident a couple of years ago - so I wasn't imagining the light vibrating when driving! On the up side the short battery disconnection has brought the steering wheel radio controls back to life for the first time in a year - they went off in a previous battery disconnection incident

On the C4 couldn't find a battery locally, but then a bit of net research showed that the number quoted in the handbook is wrong. Got some new ones ordered up from the bay for next to nothing

Got to love French electrics

[citroenxm]

I think the battery strength affects the unlock sigal strength, so when the locking ECU detects the signal below a certain level it will warn you so your not stuck with a flat battery...

[Mandrake]

I don't think its determined by received signal strength, if it was unlocking the car from a large distance would falsely trigger it.

I believe that the fob measures the voltage of the battery directly while under load and if its below a certain voltage it sends a slightly different code to the car which informs the car of the flat battery. (as well as commanding it to unlock) All it would require is a single bit of the the code word to be reserved for battery ok/flat status.

Some IR remotes for things like cable boxes use the same technique where the remote sends a slightly different IR code when the battery is flat so that the box knows and can display a flat battery warning.

[Stempy]

'tis electrickery.

[Stickyfinger]

tis electrickery.

NO it is not.....its SCIENCE

[Citroenmad]

Its when it starts shouting at you random messages for no reason which is the point to worry. I don't think earlier C5s have this, I had to replace the battery in one of the C5s remotes yesterday. The car didn't tell me, fortunately I was able to tell for myself as the key no longer worked when it was cold ...

[RichardW]

Random messages - it did that before... started squawking about the handbrake after starting. Presumed the battery was a bit tired so bought a new one (a 'Starting Bull' ) which has fixed that. Old one went onto my Xantia though, and still provides a good cranking speed a year later.... mind you, that has a pretty easy duty cycle - generally cold start then 30 mile trip to re-charge twice a day, rather than the Pic which gets used for more short stuff with the Children.

Fitted a new remote battery last night - first one I was still getting the message, so fitted another one (got 5 from ebay for £1.10 - postage must have been nearly that!), and that stopped the message.