If it is a 10 watt panel and if it really does put out 10 watts when aimed perfectly at the sun on a cloudless day, your 19.2 amp hour battery pack is probably in the 60 to 70 watt hour range. Thus, perfect conditions, 6 to 7 hours.

My bike tour six years ago, my dynohub was not keeping my battery up like it should. Ended up plugging a charger into an outlet in a laundry room at a campground and found that my charger was not charging as fast is it should. At that point I started checking cables and found that I had a bum cable, half my power from the dynohub did not make it thru that cable. Changed cables, and I was self reliant for power with my dynohub for the rest of my tour.

Lesson learned, use good cables.

I also carry a meter so I can see how much power is going through my USB port, but if you don't know what the numbers mean, a good meter might not be of any help. In my case, the meter was how I discovered a bum cable was my problem, changed cables and the charger plugged into the outlet started putting twice the power into my battery pack.

That's a sunny and cool day; heat reduces a solar panel's efficiency, up to 25% by some accounts.

Cables. Cables. Cables. I try to be redundant, but mixing and matching USB-A and C and micro USB is a minor PITA. I actually have some devices that require USB-A to micro USB; they will not charge with USB-C to micro USB.

I've been contemplating a dynohub but I hear mixed reviews. The most common criticism is that it just doesn't produce a lot of power. I'm a power hog because of my cameras. On the GAP/C&O last year, with my 19.2k bank and using my laptop to charge some devices (see USB-A to micro USB, above), I was able to go about 2.5 days of filming, backing up at the end of each day, and recharging overnight before needing a wall outlet.

I think on flat ground I am getting about 2 watts out of my dynohub on average when touring. I base that assumption on an hour long exercise ride where I measured roughly 2.5 watts on average. Touring, I am slower than an exercise ride. A couple of watts is not much. And in hilly terrain, I generate much less, the downhills do not last very long and I get minimal charge on the uphills. That is one reason why I have such a big powerbank at 44 watt hours of capacity. A hilly day, I generate less power than I use and a few consecutive hilly days and the number of lights on my powerbank for charge level are getting fewer.

I am quite frugal with my power usage. A dynohub would probably be of little help to you. There are different dynohub powered USB chargers with different outputs. Even with a really high output one like the Forumslader (spell?) you would probably not have enough. I am using a Cycle2Charge V3, it has maybe 50 percent more output than the Sinewave Revolution that I used to use.

A 20 amp hour powerbank that charges fast is pretty cheap, thus you might be best off having enough powerbanks to last between opportunities to plug into an outlet somewhere.

Before I had a dynohub, on a bike tour, every time I walked into a restaurant I looked for a seat near an outlet to charge things, and that was in the era where USB chargers did not put out a lot of power. Now with high output chargers and powerbanks that will accept a fast charge, that looks like the way to go.

Because my phone might use a lot more power than my old one, I plan to carry another powerbank on future bike tours, as a backup. It is a fast charging Anker 72 watt hour powerbank.

Thanks for sharing your experiences. I'm probably going to hold off for now. My battery bank uses standard 18650 cells (like oversized AAs). I like the idea of being able to replace cells should they wear out. I may look for another, smaller bank for redundancy's sake.

Can you expand WRT your charger? I have a couple of 18650s and the Fenix X11 single-cell charger. A couple of 3500mAh cells + the X11 makes for a lightweight kit. (136g). Slow (re)charging, though

I believe that I will change the way I use the panel. Instead of charging while riding, I will charge the battery pack while I break camp and during longer mid-day stops as well as at the end of the day when making camp. Of course, common sense dictates bringing a wall charger with me

Oh wow, I've never seen that X11 before - how do you like it?

Regarding my battery bank - the Goal Zero Venture 75 uses 18650s. I haven't opened it up yet to see if the cells are replaceable, but it would be cool if they are. The bank is larger than battery banks of similar capacity but I'm hoping to reduce e-waste. I charge it with an oversized Anker dual USB-c wall wart that can output 65 watts through a single cable.

FWIW, here's the charging times of my Goal Zero Venture 75 with solar panels of various capacities

It does the job, and is compact. Actually, I was using a Wurkkos FC13 (apparently discontinued), a rugged flashlight that doubles as a power bank. I was carrying the X11 as a spare, rarely used.

The Venture 75 has impressive performance (19Ah recharged in 90 mins) but overkill for me. I consume barely more than 1Wh/day.

I like their battery packs, but I haven't had luck with their solar panels. I forget which one I have, and I can't find it at the moment, but I have never had any luck getting it to charge anything. I put it outside on a sunny day and a cell phone didn't charge. It does out put energy, but it never charged anything I have hooked it to. I keep trying it occasionally but no luck. I am going to try again if I find it. I have tested it with a meter and though I forget what it read, it has been at least eight years since I experimented that in depth, but it never put out even close to what Goal Zero claims. If I find it, I will put it in the sun for an extended period of time to see if I can wake it up.

Some phones and some other devices are very picky about the power supply and won't take a charge if they do not like it. You might have to charge a power bank and then charge the phone from that.

My nerd son, told me not to charge an iphone directly from a solar panel, instead use a battery pack to charge the phone. Tourist in MSN may be quite right.

I am aware of that. It wouldn't charge a power bank either. The phones I tried were very old ones that are not really picky about the power source. It was basically unless. I'm fairly decent with electronics. I grew up in a TV/radio repair shop. I do all my own phone and computer repairs as well. Portable solar power leaves a lot other be desired, though I still like to experiment with it. I have had old solar panels that either didn't perform well, or stopped working. I have gotten some to work by leaving them in the sun for an extended period of time, weeks. If I can find the Goal Zero I have, I plan on doing that, though here in Western Pennsylvania getting a good streak of sunshine is difficult.

Regarding hub dynos: Think about an e-bike, the thrust it provides, the time duration, and the battery size; Charging a similar battery size, over the same time duration, would impose about the same thrust in *drag* on the bike, an insurmountable amount on a manual bike. Half the battery, half the drag, but that's still a lot. Even a quarter the drag. I think a hub dyno *might* be able to keep up with the drain rate on a smallish phone or nav device, a constant display on bright is the biggest draw on that.

For my anticipated need of a multiday battery to power my CPAP, a hub dyno is not enough, and that's with running the CPAP with no humidifier (uses heat) or tube heat, as those both suck more E than just the blower motor. So my plan will be to 115VAC charge the battery every couple of days. Leaving it plugged in overnight at a campground bathroom is too susceptible to theft. I'm hoping to map out public libraries, coffeeshops, etc, to fast charge the battery, hopefully with multiple AC plug inputs. Or find people via that org that I forget, for scheduled backyard camping, with charging at an outside plug.

If the phones are really old, maybe you can access the battery? Some Li Ion batteries that drop below a certain voltage level have a circuit inside to prevent them from taking a charge in the future, that is a safety feature. If your battery is really low, you may have reached that point.

I store some of my Li Ion battery devices and spare batteries in the fridge (not the freezer), as I think they self drain slower that way. I check them twice a year to see if they batteries need to be charged up some. And one of my Li Ion batteries would no longer take a charge when I checked them a few weeks ago. Added it to the others that I need to take next time I go to a place that recycles them.

Last spring I replaced the battery in an old laptop, the battery was swollen, which means that it was at the dangerous level to use. Photo below:



When you see stories on the evening news about a laptop computer catching fire in an airplane, it is the batteries that look like the one above that are the problem.

In case it might be of interest, this is a comparison of power banks, found somewhere when searching for fast recharging banks

[EDIT]
In the context of bike touring, the battery bank acceptance rate is perhaps the most important feature (i.e. how fast can you recharge the bank). Perusing the sheet, trade-offs become apparent. The larger the bank (i.e. capacity) the larger the acceptance. 10Ah banks usually can be charged at 18W. 20Ah can accept much larger wattage. ex: the Sanberg PD 100W ingests 60W. OTOH larger banks are much heavier. A Nitecore 10Ah weighs 150g whereas the Sandberg weighs 550g...

The sheet provides an estimate of the time it would take to recharge from empty to 75%. These data are probably misleading. We see a fair bit of variance in output efficiency (68-100%). Variance in recharging efficiency is likely to be similar. There's also a few ways to look at recharging speeds. ex: (1) 10 mins recharge: morning trip to a camping bathroom (2) 1hr recharge: having lunch in a restaurant.
[/EDIT]

take some thin straps and attach it on top of your panniers. I even saw cyclists with backpacks and solar panels attached to the backpack.

In 2016, I rode an electric motorcycle from San Francisco to New York City with one of these on my back.




The panel was facing the wrong direction every morning and the right direction every afternoon. I stayed in hotels, so it ultimately was of dubious value. But it sure did look cool. One guy asked me where I was from. I responded, "The future!"

The batteries were fine. They charged perfectly well with any other charger I used. I am well acquainted with batteries, and have replaced the one in my old Macbook Pro four times. My lack of knowledge is not what is at issue. What is at issue is the specific Goal Zero panel I own.

Additionally, the panel would not charge a known to be good power bank. As I said before, I love the concept of solar charging, but I am speaking specifically to my experience with Goal Zero. I have not had good luck with their solar panel. Others I know also have had bad luck with them. My experience with them is a few years old though, and I have not tried a newer model, mainly because I feel I wasted my money buying the panel I have. Their newer panels may be better. I do not know. For me, and what is more important for my touring needs, is that power banks make more sense for my use, since I can carry extras and have plenty of power for my needs.

My phone would not charge well from my hub, a combination of hilly terrain and feeble legs. It beeped in protest when my speed dropped too low. The Battery pack, however, was much less picky. The phone would charge from the solar panel, but not fully.

Another power option is the Velogical dynamo. I recently purchased one, have put a few miles on it, and am impressed. Excellent customer service. I plan to use it for charging a backup battery for a tour on the GDMBR this summer. Two big advantages I see are that it can be completely disengaged for zero drag and it is way lighter than a dynohub. There is a fairly extensive thread on them (I think in the electronics sub-forum) that I read before making my purchase.

I looked at the Velological and it is a legit product with plenty of good things said about it. Unfortunately the price is well outside my comfort zone. It is a slick product and seems it is a better alternative than a generator hub.