mobile_simon

Hi everyone,

I recently upgraded to a Schmidt dynohub and wondered how everyone went about charging their devices. I heard that dynohub charging causes added stress on batteries because the charge is always in flux. Should I get a cache battery instead of hooking my smartphone up directly? I am using a Sinewave Revolution USB charger.

Thanks

fietsbob

I'm curious , looked anywhere else? or this the place, where you are dependent for all your info?
can you share what your owner's manual says, for those that dont have your same Kit?

mobile_simon

Honestly don't remember where I got the concern from, maybe it was over at Thorn Cycles Forum. The Sinewave has nothing to do with my question, just thought I'd share my entire setup.

boomhauer

I thought the literature says you don't need a cache battery to charge your phone. I bought one but haven't tried it out yet.

wahoonc

I like the cache battery, it can be used to power up other things as needed.

Aaron

LuckySailor

I've just added a Schmidt dynamo hub and Luxos U to my touring rig. Haven't used a dynamo in years, and don't have any experience with this one presently. However, in my reading, the cache battery was to keep constant power going to the device being charged-ie, an iPhone, which will give an error message everytime voltage drops below (3V?) It makes sense to me that it would stress out the device, having power fluctuations all the time-so therefore a cache battery is a good idea me believes.

LuckySailor

mobile_simon

Ok thanks for the replies. My Android phone is less fussy over power sources than my Apple was. Might go without a cache and see how it fares.

mark03

I'm fairly certain there is nothing in the battery itself that's bothered by fluctuating charge currents during a charge cycle. And I'm a EE (though not an expert on Li-ion chemistry and pathologies).

One problem is that your smartphone/tablet/etc has its own charger built in, which is stateful. That is to say, when you connect a DC source, it goes through a sequence of states as it verifies the source quality, then initiates pre-charge (in case one of the battery cells has a short), and so on. That state machine may well be confused by the dynohub output, so I would agree that a design incorporating a cache battery or supercapacitor is a good idea.

You also want max-power-point tracking (MPPT), which dynamically varies the load applied to the dynohub to extract the most power at any given instant. Good luck finding out if widget X supports this from the marketing literature! If you break open the widget and look at how it's built, you can sometimes tell if it is a linear or switching regulator as the presence of an inductor implies a switching regulator. This is a necessary (but not sufficient) condition for MPPT.

Unfortunately, as long as we are stuck with non-removable batteries, there are always going to be multiple voltage conversions in this kind of application: dynohub -> [cache storage] -> 5V USB -> battery. You are probably lucky to get better than 80% power efficiency end to end.

And now you know why engineers suffer paralysis when forced to pick which high-tech gadget to buy.