Garmin 705 Extending Battery life

[frankly frankie]

I dunno anything about the Gomadic thingy but NiMH rechargables are nominally 1.2V under load.  Alkalines may start out at 1.55V but this drops very rapidly under load, after 30 minutes they will be lower voltage than the NiMHs would be.  The (expensive) solution might be Energizer Lithiums - these will maintain a higher voltage for much longer than Alkalines (maybe 5-6x as long) and do have the merit of weighing much less - they are half the weight of NiMHs so you can pack twice as many.
7Dayshop sell a pack of 6 for £5.70 so its worth experimenting with them.

[Manotea]

The (expensive) solution might be Energizer Lithiums - these will maintain a higher voltage for much longer than Alkalines (maybe 5-6x as long) and do have the merit of weighing much less - they are half the weight of NiMHs so you can pack twice as many.
7Dayshop sell a pack of 6 for £5.70 so its worth experimenting with them.

I used Lithiums in my eTrex Vista HCx gps for the Brian Chapman. Very Impressed. Easily 45hrs+ and half the weight of a piair of nimh rechargeables. I'll be using them for my longer rides from here on.

[Jaded]

Just noticed that I left my 705 on after a long walk yesterday. The thing was still going, with 14 hours on the clock.