batteries for avalanche beacons...
Here's some advice on battery choice and care for avalanche beacons which I put together when a clients unit mysteriously appeared to stop working even though the batteries were new. On inspection the terminals had been corroded by the leaking of previous batteries and causing the fault to occur.
CAN I USE ALKALINE BATTERIES? - YES
Alkaline batteries are the universal option for all avalanche beacons. This is because the circuitry which detects how much battery life remains is tuned for this kind of cell.
The capacity of alkalines degrades gracefully.
Lithium and rechargeable cells have a relatively flat discharge curve. One minute your beacon is saying 99% full, the next it is on zero.
Avalanche transceivers have relatively low power requirements on transmit. With a new set of batteries they will go at least 200 hours and some will continue another 20 or so hours even when the display shows zero battery life. In search mode power requirements are much higher and a beacon with flat batteries may not work for very long and this is where lithium and rechargeable batteries could cause problems.
CAN I USE LITHIUM BATTERIES? - MAYBE (depends on your beacon)
The motivation for using lithium batteries is that they are designed for electronic equipment (such as digital cameras) and resist cold much better than alkaline batteries. However, having said this, lithium batteries can only be used in some but not all transceivers - it depends on whether the unit has the ability to detect what type of battery it is and adjust accordingly.
For example, the Mammut Pulse can use alkaline & lithium whereas the Mammut Element can only use alkaline - always read the manufacturers advice for your model.
Beginning with software version 3.2, the Mammut Pulse can accept either alkaline or lithium batteries. Lithium batteries are lighter, last longer (according to Mammut, in normal conditions the batteries will last 50% longer than with alkaline), don't corrode, but are more expensive.
CAN I USE RECHARGEABLE BATTERIES? - NEVER
Never use rechargeable batteries in a transceiver. As well as the discharge issue, they also tend to put out a lower initial voltage than their alkaline counterparts, which is exacerbated the more cells you need.
GENERAL BEACON BATTERY ADVICE:
- Always renew all the batteries at the same time. The variance in voltage can promote leaking in alkaline cells.
- Use the same brand - don't mix brands. It doesn't matter so much in a headlamp but digital transceivers are quite sensitive to differences in ampage etc across the cells.
- Use the same type (e.g. all alkaline).
- Believe it or not, sizes vary, check that the brand you buy cannot shake loose. Negative and positive terminals should be proud of the casing and covered by insulation at the edges. I would recommend using a good quality brand and avoid cheap no-name batteries.
- Replace the batteries before they get too low - generally before 50%. Check with the manufacturers advice for your model.
- The batteries should be removed if you are not going to use the transceiver for a long period of time (e.g. at the end of the winter season) to prevent damage due to battery leakage. You should also remove the batteries if you ship your transceiver, because the cells may be exposed to extreme temperatures and pressure changes during shipping, this includes putting the beacon in hold luggage on airline flights.
- With all this in mind, there is value in checking the batteries and contacts not only of your own transceiver but also those in your group. As it may be their unit searching for you!