proposed circuit for bicycle battery recharger

Everyone,

Based on suggestions from the previous thread I came up with the
following simple circuit for charging 4 NiMH cells from my dynamo, it
is a full-wave voltage doubler with Schottky diodes:

4700uF
||+
.------------|---o--||----o-->|--o-----o-------------.
| | | || | | | |
| - | | | | |+
| ^ | | | | ---
.-. | '-->|--. | | |+ -
( ~ ) GND|-o | | | --- --- 4 cell
dynamo '-' | | | | --- 4700uF - NiMH
2.5-5V | - .-->|--|-' | | --- (4.8V)
RMS | ^ | | | | -
| | | | | | ---
| | | ||+ | | | -
'------------|---o--||--o---->|--' | |
|| | |
4700uF | |
=== ===
GND GND

created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

All diodes are schottkies. I simulated this and it appears to work
relatively fine for the expected voltages >=2.5V RMS. The NiMH
batteries are fed a ripply and unregulated rectified DC and I am
relying on the cells themselves to regulate this to their required
voltage (the theory is that when the voltage wants to go higher, the
batteries will demand more current and limit the voltage, and vice
versa).

Any opinions about whether this simple circuit will work? Will my NiMH
batteries like it? I realize I will have to make sure the batteries are
not overcharged.

FYI, a quick repeat of the specs of the dynamo:
* biking speed 10 km/h: 5.6VRMS unloaded, drops to 2.5VRMS at 0.5 amp
load, available power 1.25W
* biking speed 20 km/h: 9.9VRMS unloaded, drops to ca. 4VRMS at 0.5 amp
load, available power 2W
* did not measure the AC frequency but I expect it to be in the range
10..200 Hz, and pretty much sinusoidal

greetings,
Tom

.

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