notenoughdaylig 

I’m in the dream stage of building a bike for my son-in-law’s 30th birthday. Would it be possible to charge a di2 system with a 6v/3w dynamo hub thru a sinewave reactor and a usb cord? Is that enough wattage?

Does anyone have any real world experience trying something like this?

tia

choddo

Caveat: I do not fit the criteria of respondents you specified but I find the question interesting.

Sounds like 20% too high a voltage to me but that might be within what Di2 can handle. What happens to the excess current when you produce more power than the load? And not sure it will be too happy with the intermittent supply. Also you can’t charge and change gear afaik, read something the other day, but could be wrong. Maybe varies with generation of Di2. Current rear mech connection version says



And … why? Is he an ultra-distance tourer?

rm -rf

Is this a tour far away from plug in power?
Charge up a power bank from the bike, then it can be used for phones, GPS, Di2, etc.
Any USB recharge source will work, but you need the original charger.

Di2 is charged by a USB charger brick. The charger has a non-standard plug that connects to the Di2 charge port. The other end of the brick is a stock USB cable. I use an old 1.5A USB plugin with this. No idea how long it takes, I check it after a few hours and it's done. I normally recharge when the battery light shows "under 50% battery".

Di2 lasts a long time
Di2 doesn't need charging very often. The shortest time for me was about 400 miles of continuous rolling hills at a fairly fast pace. I was shifting "all the time" to keep a good cadence at a brisk pace. Pedal downhill in the big ring, shift to the small ring, shift the cassette half way across, climb up, and repeat. Shifting at least a few times a minute! That's approx 3000 to 4000 shifts in 25 hours!

Normally, it's probably 800 to 1200 miles, since I do shift a lot anyway. I'll shift for a couple of pedal strokes, then shift again. So easy. I don't track the miles, I just check the battery level indicator light every few rides.

BTinNYC 

I think you're a couple years ahead of the industry, but I'm sure it's coming.

rm -rf

Di2 dream bike:
I have the older Di2 with the junction box that has the charge port. It's mounted under the stem. Now, there's an alternate configuration,with the charge port and status lights in a bar end plug. I suppose it needs compatible handlebars to run the wire, or perhaps it can be under the bar tape?

For the junction box version, I got this K-Edge mount. It's less than 1mm thick and sits on top of the steerer spacers. A lot nicer than the Di2's plastic strap that wraps around the stem.

Barry2 

12sp Di2 does not function while charging.
The charge socket is on the RD and the cord just clips on.

If battery life is really an issue, plan on wiring the brifters and not going wireless.



Barry

Iride01 

It probably won't produce enough amperage to charge it. How many watts does your dynamo hub produce? AC or DC?

veganbikes

So I would ask Brian Chapman formerly of Circle A Cycles and now of Chapman Cycles fame he has done this in the past. It is a neat concept but I would say less needed except maybe someone touring all the time with no chance to charge ever and does a lot of shifting. I think keep a battery perpetually charged is not generally great for the battery. However the concept is super neat and one I had thought about back in the day and Brian was a super help in that regard.

notenoughdaylig 

Thanks for all the input.

I should have said this will probably be an 11s setup with an ultegra/grx mix. I didn’t plan on having it connected all the time, just when needed, or as an emergency charge.

I like the k-edge mount, much cleaner than zip ties.

I’ll keep this idea in the development stage for now.

Barry2 

Just tested my 11sp R8000 Ultegra with it charging from an under stem port..... It does change gear while charging.

Barry

grumpus

You'd want a full bridge rectifier with smoothing capacitor to produce DC, and a regulator to limit the 6 V or more output to 5 V. Then you'll probably only have 0.5 A output - Di2 requires 1 A to charge. Can you even charge Di2 when you're using it? Maybe better to use the dynamo to charge a battery when you're riding, and plug that in to charge the Di2 when you're done. Make it a general purpose USB supply and use it for sat-nav and other stuff too.

dedhed

https://custompurple.com/product/shi...-dynamo-usb-c/

notenoughdaylig 

Based on the knowledge here, I was looking for a shortcut. As suggested, the safest route would be to charge a battery bank and use that to charge the di2. Not dream-ideal, but not far from it. Thanks everyone. -Greg

notenoughdaylig 

this is cool!

veganbikes

That thing is neat!

jgwilliams

Are you aware of just how far you can go on Di2 between charges. I reckon between 500 and 600 miles on my 12-speed setup, and I live in a hilly area where I change gear a lot. I find it hard to imagine going that far without finding some power.