Last week I experienced an unexpected depletion of my mobile phone battery near the end of a day’s walk in a very remote mountain valley (Cwm Eigiau) in North Wales. My mobile had a fully charged battery and I knew of no reason to switch it off even though the valley probably had poor or no mobile phone signal coverage. Near the end of my walk I must have regained mobile coverage because my mobile bleeped to tell me that someone had left a message for me. However, when I tried to phone the messaging service, my mobile display flashed “battery empty” and went dead. Later on I was able to use the mobile while it was being re-charged. Subsequently the mobile has operated as normal so it seemed that the battery depletion wasn’t due to a fault or sheer old age. When I mentioned the depletion to others later their consensus about the cause was that my mobile had simply used up considerable amounts of battery power in the valley constantly trying to find and communicate with possible mobile phone masts. Has anyone else had a similar experience and a similar explanation? Also, my mobile was in an outer pocket on top of my rucksack in very cold conditions. Thus, it is possible that perhaps its battery capacity that day was reduced by being at low temperature for a prolonged period. My recent experience reinforces existing advice to those who venture into wild and remote places about not depending on mobiles because reception in such areas can be patchy or non-existent. In addition it also appears to show that the absence or very low strength of signals can cause mobiles to use up excessive amounts of battery power and even render them inoperative. Therefore, it seems prudent for people to be wary about leaving their mobiles switched on if they are in such areas for significant lengths of time and away from recharging facilities. Graham Bullough

I recently learned that leaving the Blue Tooth switched on uses more battery power, so if you had blue tooth on in the car and left it on while walking that could have added to the usage?

I haven't seen anything as dramatic as Graham, but I have experienced shorter-than-expected battery life on my mobile while walking in the Lake District. Brett's explanation tallies with what I thought was the situation, so it seems reasonable that this would happen.

One of the more unusual but nevertheless interesting threads that does provide some practical advice to a real situation. I have been doing some research on lone worker systems and the polling issue also arose, and the subsequent affect on battery life, as Brett has mentioned. I was also introduced to the 'roaming sim', which as far as I can work out, will roam all of the major networks to try find a signal. Something that might prove helpful in the sort of thing being discussed here, but seems to me that you should keep the phone off until needed and keep it close to the body to keep it warm.

Phil, I find your comments on roaming sim cards interesting. I have always got very bad signal strength on my mobile and when I get no signal what so ever, my phone flashes up with emergency calls only. I always thought this was strange as I have no signal. I wonder if emergency calls are not limited to the network you subscribe to but can go through any network. If this is so, it may have some impact on your lone working systems.

Yes, that's right - as long as you can connect to a network, you can still make emergency calls. Don't forget there will still be some remote areas where there's no coverage at all, and then of course even emergency calls won't work. Another thing I've heard is that if you dial 999 from a mobile, you connect to a national emergency call centre who then have to connect you to the appropriate local control centre for where you are. But if you dial 112, the connection is to a centre local to where you are. Anyone know if that's an urban myth or not?