additional/backup GPS

[Wobblers]

Garmin Edge 200.
For longer trips I use a Touring with an Edge 200 for back up. Long battery life, over 13 hours. Ok it's only a bread crumb trail to follow, but it works and it works well. Can also be charged on the go,

The man in blue's on the money.

My second hand Edge 200 easily lasts more than 12 hours (come to think of it, I've never actually measured exactly how much longer it'll last) and, apart from the lack of altimeter, ticks all the boxes. You ought to be able to get one for less than £50 - for anyone in Glasgow, the Aldi on Glasgow High Street still had them for that last time I was up in June. Alternatively, look for a second hand Etrex Legend or Vista HCx, or the more up to date Etrex 10, 20 or 30. My Etrex Vista gives over 20 hours on a set of Eneloop AAs, and has proper mapping as a bonus as well as an altimeter. They still seem to go for a fair amount of money on eBay, though.

 

[Aravis]

I can also vouch for the Edge 200. Halfords are still doing them for a reasonable price as long as you don't mind getting a box of gels as well.

Mine is my primary device; I use it in a minimalist way, with all brightnesses and contrasts set as low as possible and not normally touching it once I've set it running. After yesterday's 9 hour ride the battery was showing 59%, which is what I've come to expect, so I think the advertised battery life figures must assume more active use. Possibly they are understated to encourage potential buyers to spend more.

On the previous ride, which was a little longer in duration, I ran it off a battery pack (attached to the end of my handlebars with elastic bands) for the first 3 hours, and it finished on 74% - roughly as expected.

What I don't know is what happens when the battery runs lower, because even after 12 hours it's still been showing 45% or thereabouts. Does it reach say, 30%, then fall off a cliff? Do you get sufficient warning to enable you to attach a battery pack without endangering your data? Whatever, with a battery back it looks as though it will reach 24 hours easily.

 

[Wobblers]

What I don't know is what happens when the battery runs lower, because even after 12 hours it's still been showing 45% or thereabouts. Does it reach say, 30%, then fall off a cliff? Do you get sufficient warning to enable you to attach a battery pack without endangering your data? Whatever, with a battery back it looks as though it will reach 24 hours easily.

Now that I can answer. I usually keep the battery below 50% (because that helps lithium ion batteries age slower) so sometimes it'll get below 10%. The battery fuel gauge seems to be fairly linear: no falling off cliffs or anything like that. The battery warning notice appears once it gets below 5%, I've had that appear once half way round my lunchtime loop. It was still complaining 30 minutes later when I got back to work, so I think you'll have plenty of time to plug in a external battery pack.

 

[Aravis]

Now that I can answer. I usually keep the battery below 50% (because that helps lithium ion batteries age slower) so sometimes it'll get below 10%. The battery fuel gauge seems to be fairly linear: no falling off cliffs or anything like that. The battery warning notice appears once it gets below 5%, I've had that appear once half way round my lunchtime loop. It was still complaining 30 minutes later when I got back to work, so I think you'll have plenty of time to plug in a external battery pack.

Thank you for the information, especially the BIB. It just gets better and better.

As nearly all my rides last 8 hours or more, I've been charging to the hilt the night before (but not earlier). What I've not had the confidence to do up to now is to deliberately run it low mid-ride, but I think I now can...

 

[Dogtrousers]

As an aside, the good news is that, contrary to what I thought, my GPS didn't lose the data points for the first 80km of my ride at the weekend. It had oh so helpfully stored them in a separate file under an "archive" subdirectory.

All the same I think I'll press my old 60CSx into backup "record only" service. The Oregon has a great screen and maps and other features but it burns batteries (probably mainly because of the screen). Even if I have remembered to bring charged-up spares, this still means that I get annoying elevation jumps each time I change the batteries.

 

[Ajax Bay]

I usually keep the battery below 50% (because that helps lithium ion batteries age slower)

This makes interesting reading with regard to the benefits of part-charging a Li-ion battery. There's a trade off between available capacity and number of recharge cycles (ie longevity). I note the OP desires high capacity (ie to run as long as possible - more than 14 hours. This implies maximum capacity at outset, though mid ride charging (from a battery bank, from a hub dynamo, or from mains at a stop) is clearly a workaround.

"Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.0V/cell should deliver 1,200–2,000 and 3.90V/cell should provide 2,400–4,000 cycles.

"On the negative side, a lower peak charge voltage reduces the capacity the battery stores. As a simple guideline, every 70mV reduction in charge voltage lowers the overall capacity by 10 percent. Applying the peak charge voltage on a subsequent charge will restore the full capacity.

"In terms of longevity, the optimal charge voltage is 3.92V/cell. Battery experts believe that this threshold eliminates all voltage-related stresses; going lower may not gain further benefits but induce other symptoms. (See BU-808b: What causes Li-ion to die?) Table 4 (see link) summarizes the capacity as a function of charge levels. (All values are estimated; Energy Cells with higher voltage thresholds may deviate.)

"Most chargers for mobile phones, laptops, tablets and digital cameras charge Li-ion to 4.20V/cell. This allows maximum capacity, because the consumer wants nothing less than optimal runtime. Industry, on the other hand, is more concerned about longevity and may choose lower voltage thresholds. Satellites and electric vehicles are such examples."

 

[Nibor]

I have one of these loggers http://www.i-gotu.com/