USB charging from dynamo or solar

[Kim]

See, what would be good would be a cycling GPS designed to connect to a dynamo directly, perhaps using one of those clever mounts with a connector in it.

If you eliminated the faff and points of failure (extra stuff to mount on the bike, USB connectors, charging logic that assumes a continuous supply), it would be as convenient as dynamo lighting.  As a bonus, free speed sensor.

[D.A.L.E.]

I've got something like that (the now legendary UM25C) for bench-testing things.  In my touring kit I have an older version of https://portablepowersupplies.co.uk/product/dual-usb-power-monitor

Well this is excellent, thank you for the tip. It turned up yesterday and I have now measured everything (except my dynamo, because it's pissing it down). Surprising how awful some of my powerbanks are.

[Audax1]

Useful no nonsense post! Dynamos are great for convenience but think they batteries are going to make them redundant, and by the sounds of it already have. Guess having battery lights and one of these battery packs would mean that you’d be sorted for quite a long time touring or cycling in the winter.
Do like dynamos but definitely a plus for batteries here!

Gonna suggest a different approach.

Don't fuck about with dynamo to usb charging. It's not worth it.

If you have a 3w dynamo, the realistic amount of power you're gonna put into a battery pack is 2Wh, if you ride for 10 hours that's 20Wh per day. An iPhone 14 has a battery of just under 12Wh. A wahoo bolt is ~6Wh. That's most of your 20Wh gone there.

By comparison, Anker make a 26800mAH battery which is 98Wh (so as to be under the 100Wh max allowed on an aircraft). This has a pair of 2.4A inputs, which at 5v allows you to put in that same 20Wh in about an hour plugged into a cafe's wall outlet. Or if fully empty, in under 6 hours plugged into a hotel power outlet while you sleep.

This is going to be quicker, easier to use, and not cause you to put 5w of your own energy into charging you gadgets.

Unless you are going somewhere really off the beaten track where you'll be more than 5 days without access to a power socket. I don't think it's worth trying a dynamo to usb charging setup.

And solar is even more variable, it's better to just use the same weight in lipo packs.

J

[Kim]

I've got something like that (the now legendary UM25C) for bench-testing things.  In my touring kit I have an older version of https://portablepowersupplies.co.uk/product/dual-usb-power-monitor

Well this is excellent, thank you for the tip. It turned up yesterday and I have now measured everything (except my dynamo, because it's pissing it down). Surprising how awful some of my powerbanks are.

Note that because bigger numbers == moar betterer, powerbanks quote the Amp-hour capacity of the battery at the nominal 3.7V cell voltage, not the 5V USB output.  So you'd expect a "20Ah" powerbank to give you a capacity of about 14Ah as measured by that kind of meter.

[quixoticgeek]

Useful no nonsense post! Dynamos are great for convenience but think they batteries are going to make them redundant, and by the sounds of it already have. Guess having battery lights and one of these battery packs would mean that you’d be sorted for quite a long time touring or cycling in the winter.
Do like dynamos but definitely a plus for batteries here!

Let's do the maths on that.

Assuming the light is the same 3w of an LED Dynamo light.

If you were to ride the whole of a night in the middle of December, in the UK, that's 16 hours of use.

16 x 3 = 48Wh.

Let's bring back that 98Wh battery pack mentioned above, we get 2 nights of illumination from the battery pack, with approximately enough charge left over to put a tiny amount in the phone.

For 500g.

Obviously that's a UK worst case scenario, tho it may be even harsher usage if you are in the North of Scotland on the same day.

In Audax, or ultraracing, the balance tips back to a dynamo for lighting. But for everything else on the bike a big battery pack is great.

J

[ElyDave]

I still maintain the utility of charging device A from the dyno hub, which leaves more Watts for charging other things from the powerbank(s)

[D.A.L.E.]

Note that because bigger numbers == moar betterer, powerbanks quote the Amp-hour capacity of the battery at the nominal 3.7V cell voltage, not the 5V USB output.  So you'd expect a "20Ah" powerbank to give you a capacity of about 14Ah as measured by that kind of meter.

Every day is a school day. I told you I was terrible at electronicals.

Still though, my fancy 10,000mAh powerbank puts out about 4000mAh. Which is good to know.

[Cudzoziemiec]

I suppose there's an element of what might be called "energy management" or "power accounting" to be made here. A balance between providing all the power you want and restricting the power you use to match your provision. My attitude is that cycle touring is about riding the bike, eating, sleeping, seeing places and things, and just spending time wherever I am and going wherever I'm going. My phone gets used about two minutes a day, the rest of the time it's in airplane mode. In a fortnight last summer I topped it up maybe twice – certainly I didn't need to recharge the 10,000mAh powerbank I took with me, and I didn't have any other means of device-charging. But that's not going to please everyone, and I tend not to use the phone for navigation. We'll all find our own balance points between power and consumption, which themselves will vary from trip to trip.

[quixoticgeek]

I suppose there's an element of what might be called "energy management" or "power accounting" to be made here. A balance between providing all the power you want and restricting the power you use to match your provision. My attitude is that cycle touring is about riding the bike, eating, sleeping, seeing places and things, and just spending time wherever I am and going wherever I'm going. My phone gets used about two minutes a day, the rest of the time it's in airplane mode. In a fortnight last summer I topped it up maybe twice – certainly I didn't need to recharge the 10,000mAh powerbank I took with me, and I didn't have any other means of device-charging. But that's not going to please everyone, and I tend not to use the phone for navigation. We'll all find our own balance points between power and consumption, which themselves will vary from trip to trip.

Conversely on Sunday I rode 211km back from my holiday in the Mosell over night. During which I finished off an Audiobook, and over 700MB of podcasts. I also had about an hour's worth of phone calls while I was riding along. All of  which required me to charge my phone up when I stopped for dinner. Even tho I was riding with data turned off.

I also had to top the wahoo up cos I was riding so slow.

Riding downhill during the night at speed on unknown roads. I also had my helmet light on in addition to my dynamo light.

I'm sure it's possible to be parsimonious with the power, and no doubt many people do enjoy that kind of riding. But there's also those who's power budget is a little higher.

You are right to do the maths on how much power you actually need for all devices, including lighting, trackers, navigation, Comms, entertainment, etc... And use that to inform your choices regarding what power options you take.

Just remember, from a dynamo, full cycle (charging and discharging a battery) you will get about 2Wh per hour of riding.

Use the data to inform your decisions.

J

[Cudzoziemiec]

I have a dynamo and have considered getting some sort of charger but for now it seems it would, for me, add complexity and cost for little practical gain. OTOH I know at least two people who use a dynamo for charging but not lighting (and both ride at night a lot, though one mostly in town).

[mzjo]

I have a dynamo and have considered getting some sort of charger but for now it seems it would, for me, add complexity and cost for little practical gain. OTOH I know at least two people who use a dynamo for charging but not lighting (and both ride at night a lot, though one mostly in town).

One thing this thread is teaching me is that I am going to have to go back to trying to learn to use the eTrex rather than navigating with RWGPS on the phone for going away from home ('cos the garmin uses batteries that I can buy rather than needing recharging). And that I have not yet finished with paper maps!
I am going to have to get a meter for the powerbank; its 13000 mAh may actually be quite a bit less. In my case it's charging phone, a front light (for use in the tent as well as for riding) and at least one camera (don't like taking pictures with the phone - but at least my old school film stuff uses throw away AAs, or no battery at all!)

[andrew_s]

Let's do the maths on that.

Assuming the light is the same 3w of an LED Dynamo light.

A dynamo is only a 3W supply when powering a light with a filament bulb.
The better LED dynamo lights contain electrickery that provokes the dynamo into supplying more like 5W when at a regular flat road riding speed.

[aidan.f]

Correct, testing data below. To summarise depending on hub the Spanninga Nomad will supply 5 6 Watts of actual USB power at 30 kph
https://www.cyclingabout.com/dynamo-hub-power-drag-testing-schmidt-son-shutter-precision-shimano/

[321up]

Hi,

Last week our new Cycle2Charge V3 Plus got it's first use with a Son28 Neu dynamo and an old Zendure A2 6700mAh battery pack on a 4 day trip.  The only indication of our power usage was the four LED's on the USB power pack than indicate it's charge state so I can't say much about the first two days when we used 25% or less of the capacity each day charging the phones.  By the end of the 3rd day I managed to deplete the 7.5Wh camera battery so I charged that, our two phones and all our lights and got the battery pack capacity down to 25% or less and it seemed to be fully recharged from the dynamo by the end of the 4th day (146km, moving average 20.5kph).  My guess it that it might be capable of keeping everything charged with our minimal power usage with a daily distance of 100km @ >17kph.  Aside from the Garmin running on AA batteries we were otherwise self sufficient.  I now need to look at options for charging AA batteries, preferably from the USB battery overnight.  With a 2nd dynamo and powerbank on C's bike we could possibly generate enough power even if we had the occasional day off the bike.  The real test will be when we are heavily loaded and riding into a headwind day after day.

A.

[D.A.L.E.]

I now need to look at options for charging AA batteries, preferably from the USB battery overnight.

Ikea Vinninge is what I use

[Kim]

Two approaches here:  Something that charges pairs of cells slowly and regulates by overcharging^[1], of which there are many cheap USB powered options available, or the more elusive USB powered smart charger.

The former usually has a size advantage, but the latter is more useful if you want to make use of time-limited access to a mains socket or solar power or whatever.

FWIW, I use an older model not listed on https://international.gpbatteries.com/pages/recyko-battery-chargers but functionally similar to one of the faster models.  It works well enough, but has infuriating LED status indicators that blink arcane combinations of indistinguishable colours to report the charging status.


_{[1] Which is a perfectly legitimate thing to do to NiMH cells, as long as the current is low enough.}