Keyless Kefob

[kmrobertson3]

One of my T180 kefobs only lasts about a day when the Battery is changed. I have had it changed 3 times now in 2 months and it still runs out.

Anyone else with this problem?

Cheers

[shcm]

Obviously it should be lasting a lot longer than that.

First, this may sound like rubbish, but are you keeping the key near any other electronic kit (e.g. say on the top of a pc - running or in standby) or next to a mobile?

Second, when you change the Battery, it might be worth just pressing one of the buttons with the Battery out - Without boring you with the details, just take it from me that digital electronics can sometimes get itself in strange states if it doesn't get a proper reset and this process might help.

Third, I've not looked at the key internals to see how easy this is, but if you can get the Battery such that only one terminal is connected and then connect an ammeter between the other battery terminal and the fob contact it should be touching, that should give an idea of how much current the key is drawing in an inactive (not transmitting) state. I would expect perhaps a few u(micro) amps max, possibly even less. If it is more there is probably a fault, but it is relatively easy to workout how long roughly the battery will hold up with such a current measurement.

Fourth, a good battery should be around 3.1V to 3.0V. Below 2.6V is probably not good, but it depends on the key design. What are the "duff" battery voltages coming out at?

Fifth are the battery terminals and key terminals clean and free of finger "grease"?

With the first point above, the handbook warns against such things. I suspect what they are concerned about is the 125kHz based side of the key. With the keyless entry, my understanding is the car uses 125kHz to "wake up" the key. The key then responds on the normal UHF (434 MHz) frequency. I expect they are concerned that with the key close to stuff that may have something in it oscillating around 125kHz (say a switched mode power supply for example), it may keep the key "awake" i.e. in a much higher current draw state - which will deplete the battery much faster.

I suspect your key has a fault, but proving it may be more difficult. The above is what I'd look at first, if I were trying to prove it.