On 3/10/2017 4:52 PM, Joerg wrote:

With or without dynamo I'll never ride without a battery because then
it's lights out when waiting at an intersection. Very bad at night.

I've been doing a lot of design with Li-Ion batteries lately and I
realized that a dynamo is almost a perfect match for two series Li-Ion
batteries when I was helping a colleague charge his Magicshine pack with
a lab supply set to 8.4VDC.

Think of a dynamo putting out 6VAC, with a full wave Schottky rectifier
you'll get about 8V (8.4V - 0.4V of voltage drop. 8V is just about right
to charge two series Li-Ion batteries. Just in case of high speed
riding, stick in an VLDO like a LT3022 with 145mV drop and you're at
7.855V, still enough to get two series Li-Ion cells to full capacity.
The losses are very low, even lower than a switcher.

The reality is that with protected Li-Ion cells you don't even need the
VLDO since the batteries are protected from charging over 4.2V per cell.

At lower output levels, a dynamo could even run a 2 cell battery powered
light if the batteries were removed.