Garmin Edge 305/705 charging on the go

[Greenbank]

I've been considering one of these (which one depends on whether I really want mapping or not) but the fact it's powered by a non-replaceable internal battery (and therefore has a finite battery life of about 15 hours) is a bit of a limiting factor for long (>20 hour) Audaxes.

Has anyone used one of those AA battery powered USB charger thingies on one of these whilst it is being actively used for navigation/tracklog-recording?

I've heard a rumour that although they can be charged/powered like this, they can't be used for navigation when they are being charged/powered. Anyone confirm or deny?

[Lonewolff]

My Edge 305 works perfectly fine when being powered and charged from one of those AA usb battery boxes, had it turned on for about 30 hours on the 'Chapman last year.

[Greenbank]

Excellent. That's what I was hoping for.

My plan is to power it via a USB AA-battery dibbly-dobbly and then when I notice those batteries have gone (and the power icon flicks over to internal battery) I'll replace the batteries in the USB box thingy.

Do you use one of those triathlon-style top tube bags for the battery pack, or something else?

[delthebike]

Do you use one of those triathlon-style top tube bags for the battery pack, or something else?

Handle bar bag used here with just enough USB cable hanging out to connect the device. But I don't see why a plastic bag around the dibbly dobbly and taping to the frame wouldn't work either.

[Greenbank]

Don't use a bar-bag as I've got aero-bars: http://www.greenbank.org/bikes/tempo/tempo6.jpg (chain is tight thanks)

I was going to go for battery pack dibbly-dobbly in a plastic bag inside one of those triathlon style top-tube bags, but strapped to the underside of the stem, or to the bottom of the tri-bars.

[Lonewolff]

I had mine in a plastic bag cable tied my stem, but top tube bag sounds like a good idea.

[Seineseeker]

Never knew you could do that, good tip.

[Cyclops]

I've got a charger I made myself with a AA battery holder and USB cable. I stick it in a poly bag, wrap with parcel tape and zip-tie it under the stem. Rechargable NiMH's lasted 36 hours on the Daylight last year.

You can also extend the battery life of your Edge by:

• turning 'Smart Recording' on
• switching off the beeps
• using the backlight sparingly

[Greenbank]

I don't have an Edge at the moment, but this was/is one of the deciding factors.

The next question is which one (305 or 705).

One question is whether I need/want mapping or not.

When the 705 comes out there should be lots (or at least some) of 305s appearing on eBay as people flog them to help fund the upgrade. I might see if I can snaffle a cheap 305.

Another reason is the data recording. For a 305 you get 3.5 hours at 1 data point per second. That'd be enough for analysing my training laps of RP. With the 705 you can shove a 2GB SD card in and record one data point a second for weeks on end.

[Lonewolff]

When the 705 comes out I will definitely be considering an upgrade.

[bobajobrob]

Are there any USB chargers that charge from a dynamo hub? If not, is it possible to make one? I'm considering a GPS for touring but I don't want to be changing the batteries every day.

[RichForrest]

I did notice that B+M do a hub - AA NiMH charger for their IXON lights.
Busch & Müller KG - Ride & Charge

The PDF page http://www.bumm.de/docu/download/492rk-e.pdf does mention output but I don't know enough about electrics to know if this can be used or adapted for anything else.

Rich.

[TimO]

I'd be fairly careful about experimenting with USB power supplies.  USB power is essentially 5v, it is meant to be between 4.75 and 5.25v (ie ±5%).  Whilst going below this probably wouldn't do any permanent harm, exceeding it could quite easily fry delicate electronics.

The problem is going to be with making a power regulator circuit which can take a substantial variation in voltage and efficiently convert this to 5v.

Simplistically you could just rectify and smooth it, and bung it into a suitable zener, although this would be wasteful, since you are just going to be dumping the excess power as heat.  It should be possible to build a small switch mode supply, but I suspect it would be relatively inefficient.

I think I'd rely on a battery pack, since they seem to be fairly easily available.  A very quick Google found this Li-Ion power pack.  I'm sure there are cheaper devices available.

[Chris S]

You could try USB power from your dynohub , if you have a Maplin nearby (for bits) and you're handy with a soldering iron:

USB power from dynahub? - Bike Forums

The key phrase appears to be - "You just need 4 NiMH batteries between a bridge rectifier and USB connector".

[bobajobrob]

The problem is going to be with making a power regulator circuit which can take a substantial variation in voltage and efficiently convert this to 5v.

Couldn't you wire a NiMH battery pack into it?

Edit: what Chris S said.