I’ve got a longish ride coming up (24 hrs max) and want my Garmin 800 to last the distance (I usually achieve about 12 hours before battery runs out). I’m either going to use my Exposure Revo dynamo or Maxx-D with normal front wheel & wondering if the boost cable will keep the GPS running long enough. Any experiences? Cheers.

If you use the revo/dyno hub combination then you need something to convert the Ac from Hub to DC for the GPS (Think Sinewave/plugII and others)
Easiest would be to boost straight from the MaxxD to GPS as its all DC
Otherwise have you thought about a light supplementary battery? I found these usefull and not too heavy
http://ww2.duracell.com/en-US/product/instant-usb-charger.jspx
Got mine from Superdrug of all places and was only a tenner

Thanks Martin. Yes actually I have a 3rd party charger a bit like that one (runs off 3 x Lithium batteries) and it does work well on my smartphone, but it’s a bit clumsy for attaching to the GPS on the stem (and I’m “racing” so I could do without an extra 100 grams on the bars). Exposure reckon the boost cable straight out of the Revo will keep a Garmin going (although won’t actually charge it) apparently but I don’t want to take any chances.

I’m also interested in anyone’s Revo/boost cable experiences.

Out of interest how is the Revo? For commuting I currently run a Shimano dyno hub with a B&M light unit but would like to power my exposure red-eye at the back also (currently use a Diablo for that).

My commute is largely on road but I can take off road diversions as I fancy. Is a Revo set up overkill? Is there another (cheaper) lamp I can use with my Shimano hub that will drive a rear light?

Well, it performs at least as well as my Maxx-D, and crucially it solves the problem of charging regular lights on long (very long) rides/races, so for that reason the Revo is fantastic. I suppose it could be overkill on a commuter bike, but only if you can’t justify the £££.

Is there another (cheaper) lamp I can use with my Shimano hub that will drive a rear light?

almost any B&M or other german dynamo lamp will take a rear lamp – not a red eye though.

http://www.bike24.com/1.php?product=40920;dbp=28;page=3;content=8;navigation=1;menu=1400,1410,1411;lang=2

looks similar to a red eye

This is the setup that Mike Hall used for last years Tour Divide. There’s some links through to the manufactures sites as well, so you have a look at their equipment.

http://normallyaspiratedhuman.com/?p=1337

I use an Exposure Revo in conjunction with a Lightcharge so I can turn off the light and get all the power into my phone during the day. It’s not quite good enough to run google maps on an iPhone4 with the screen on all the time but it’s not far off.

If you download maps beforehand to limit the data connection demands and keep screen off when you’re not looking at it, you could carry on indefinitely, so I’d be pretty confident the gps should be ok?

For a lazybones like myself, it means you never have to plan your route again!