SP Dynamo Hub is great, but ..

Does not work so great when you are crawling up hills in Dartmoor and Exmoor on a bike packing trip where your average speed is 4-5 mph.

I stupidly left the AA battery flash charger at home. Won’t make that mistake again.

But then you don’t need much light when you are only travelling at 4mph

Maybe I should have been a bit more explicit with my question. The SP worked a treat at keeping my Garmin Edge 305 charged, but could not keep up with the demands of my Galaxy S2 with GPS and data switched on. I use ViewRanger on my S2 so that I can

a) Use the buddy tracker so the Wife and Daughter can check my progress
b) Useful for when you can’t find the Bridleway the 305 tells you is there

I suspect the only other option is to just have multiple phone batteries and an AA battery flash charger so that you can recharge the phone batteries overnight.

No, i dont think they are really designed for that tho? Out of interest, what charger are you using?

Or a Garmin Dakota.

This isn’t some sort of flaw of SP hubs, it’s just a fact of life. At 4-5mph any hub will be barely powering the lights, let alone have enough left over to charge a device, especially a hungry one like a large-screen phone.

If your rides don’t involve a significant amount of time above about 10-12mph, you’ll really struggle to get away with the dyno as your only long-term USB power source.

Can’t you include some kind of rechargable battery pack in the system to harvest surplus energy when you’re travelling above 10-12 mph?

I convert the output of the hub using a USB-WERK by Busch & Müller http://www.peterwhitecycles.com/b&musbwerk.asp

I also have the inline Li-ion battery that stores excess charge. Obviously, that only gets charged if you either don’t have any USB device connected OR the devices you are charging are fully charged.

Like Bez mentions, relying solely on the dyno hub for powering my devices is not viable as my average speed fully loaded is in the region of ~ 8mph

Only option is to utilise AA batteries and a flash charger as well.

Or get a more efficient GPS (instead of the phone I mean). And then you’ll also have a working phone should you actually need it for emergencies.

For tracking, I use a SPOT tracker. That runs for aaaages off 4 x Lithium AAs so isn’t a concern.

What are good lithium AAs and where to buy them? For use in a garmin etrex. Presuming rechargables don’t last as long?

Just to clarify, since I am about to order this generator, for similar bikepacking.

At 4/5mph gen will not keep a smart phone charged if running gps and data and phone. No lights on.

Presume it would keep phone charged with data off during the day. Phone running stored maps but not gps all the time. Just when needed at unsure junctions.

At 4/5mph gen would probably not produce enough lights to ride at night, with phone on, data off.

Have read Shinamo generators produce slightly more output at low speeds.

A bit off topic, but where’d you go? Thats my neck of the woods.

yup, just use a buffer battery to store the excess from during the day. We use an inexpensive Anker one from Amazon.

@mocha that’s a brilliant idea! So you just get one of those big anker power packs, plug it in during the day, fill it up then use it later? Sound a bit too good to be true! 😀

Check that the “buffer” battery can handle both incoming and outgoing power simultaneously for the best flexibility. Not all do.

Not really necessary as you’ll use your light at night and run the gps off the battery. We’ve run a Garmin 800 all night with the backlight on and it’s only used a third of the reserve. That’s on a small battery the size of a smartphone, sorry forget the exact capacity but it was only £26.

I am either missing the point here or others are. Are people saying that you will have more success charging a buffer battery which you then use off the bike to charge the phone rather than trying to charge the phone whilst you ride?

I don’t quite get this as if you have the phone connected whilst you are riding the charge is going into the device and not the buffer battery.

yup, just use a buffer battery to store the excess from during the day. We use an inexpensive Anker one from Amazon.

All well and good if you do have excess and you are travelling at a speed that generates more than electricity than your devices require. The post was originally about not travelling fast enough to generate enough charge. Regardless, that issue will exist even if you do charge a buffer battery

The big problem is that when you plug a phone in to charge, normally the screen will light up, confirming that it’s receiving power. Obviously running off a wall charger, the screen will light then go off until the phone is full or unplugged. When you’re running off a dynamo that keeps dipping in and out of providing sufficient power, the screen keeps lighting up, switching off, then lighting up again and so on. This wastes most of the energy that your generating. By charging a cache battery, you don’t get this issue as it has no other functions than power in & power out. Hopefully this makes sense… There is an app which can stop the screen lighting up on the phone, but I can’t remember what it’s called.

to solve the on/off problem without a cache battery and to let me have the phone in my pocket etc, i used a standalone battery charger and a spare battery (obviously only works if your battery is easily replaceable) – it was quicker to charge too.

The big problem is that when you plug a phone in to charge, normally the screen will light up, confirming that it’s receiving power. Obviously running off a wall charger, the screen will light then go off until the phone is full or unplugged. When you’re running off a dynamo that keeps dipping in and out of providing sufficient power, the screen keeps lighting up, switching off, then lighting up again and so on. This wastes most of the energy that your generating. By charging a cache battery, you don’t get this issue as it has no other functions than power in & power out. Hopefully this makes sense… There is an app which can stop the screen lighting up on the phone, but I can’t remember what it’s called.

Now I understand. My phone was doing this continuously, and also emitting a beep to indicate it was charging.

Thanks for that. Next time I will try what you suggest