Re: proposed circuit for bicycle battery recharger



mike wrote: 
Fred Bloggs wrote:



Tom (at tomsweb.net) wrote:



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

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

This doubler circuit I found at:
http://www.kwarc.org/bulletin/99-04/tech_corner.htm


What's the matter with the conventional full-wave doubler, not enough diode drops? :

             View in a fixed-width font such as Courier.
.
.
.
.
.
.      dynamo
.      2.5-5V
.      RMS
.       .-------+--o-->|--o---+---------------o-------------.
.       |       |             |               |             |+
.      .-.      |             |+              |            ---
.     ( ~ )     |            ---              |             -
.      '-'      |            --- 4700uF       |+           --- 4 cell
.       |       |             |              ---            -  NiMH
.       '---------------------+              --- 4700uF    --- (4.8V)
.               |             |+              |             -
.               |            ---              |            ---
.               |            --- 4700uF       |             -
.               |             |               |             |
.               +--o--|<--o---+---------------+-------------+
.                                             |
.                                             |
.                                            ===
.                                            GND
.




Please explain the purpose of the rightmost cap????
Then explain why we need ANY of the caps????

Pleas explain how you can double the dynamo voltage without ANY caps???? If the dynamo wasn't the dynamo, the two series caps can function as ballasts, limiting the current. But the dynamo is all wrong for this, increasing output voltage with frequency.


Depending on the load vs available charge current, there may
still be the problem of overcharging and the pedaling effort
to just overheat the batteries.

Right- he needs to put an N-Channel in series with the return to doubler and cut this off when the average Vbatt indicates full charge. That would be an LMV431 type circuit with zero drain when the dynamo is not charging the capacitors. Why don't you draw that up????


Then there's overdischarging...

I wouldn't worry about that- if the lights are a safety issue then you don't want them to shut off.



.

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