When do you replace your tranceiver batteries?

I change them at 80%.

For me, Aaron, batteries are cheap and, while they may have plenty of charge to transmit for a while at 50% or less, searching sucks down a lot more juice and I'd prefer to have a large reserve in the event of an actual burial.

I'd never heard Ortovox's 10% recommendation, but that seems way, way too low. Certainly too low for my comfort. I'll keep propping up the AAA battery industry.

Thanks Marcus, I was wondering about battery drain in search mode vs. transmit. My first thought was that of course transmitting a signal takes more energy than receiving one but then I began to think that there is probably some amplification involved in searching and, at least with modern beacons, some sort of processing that would take energy as well.

Thanks Marcus, I was wondering about battery drain in search mode vs. transmit.  My first thought was that of course transmitting a signal takes more energy than receiving one but then I began to think that there is probably some amplification involved in searching and, at least with modern beacons, some sort of processing that would take energy as well.

Of course, that's totally my conjecture -- I may be wrong about that, but anecdotal "percentage" numbers after a day of transmitting vs. after a day spent doing beacon drills seem to back that up.

80% with the DSP, which is pessimistic w. regard to remaining battery life.

Always carry fresh spares as well.

Certainly well above 50% on the DSP readout. I found it instructive to put a DSP (at 64%) in the freezer after the 2007 Edith Creek accident - the beacon was dead in a day or so.

The discharge curves (look at the 100 mA one. These are for AA batteries, which have double the current capacity of a AAA) of alkaline batteries are pretty flat with low current draw (to meet the 200 hr spec at 10 degrees C, beacons will draw 5 mA from 1000 mAHr AAA batteries, but most beacons are better), so it's hard for the beacon to make an accurate assessment of battery life. This is especially true with big temperature changes (unless the beacon tries to correct for temperature).

It's also instructive to look at the battery indicator in transmit mode after a few minutes of searching with an old battery; the reading will rise as the battery depolarizes. Searching draws more current. Up to 500+ mA would potentially still meet the 1 hr ASTM spec for beacon life. I expect all modern beacons are better here too.

I believe the Pieps engineers are quite conservative in their ratings, but I match their conservatism with my own and change the batteries early. Even then, I only change batteries once or twice a year.

80% with the DSP, which is pessimistic w. regard to remaining battery life.

Always carry fresh spares as well.

From Pieps -  www.pieps.com/images/stories/products/01.../Manual_DSP_2010.pdf
Marcus is right about consumption in send vs. receive, but I see no reason to change batteries at 80%. An hour of searching at zero is a lot, why not do it when it gets below 20%? That would be conservative.