Re: How to charge a 9V Ni-MH



Fred Bloggs wrote:

He can add a 9.1V zener reference diode and automatically taper it off to float charge at full charge of 1.4V/cell, like so, the series diode prevents battery discharge on loss of line power. At 15mA, the 1.7V will be enough headroom for the '317:
View in a fixed-width font such as Courier.
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. -----
. +12 -+----|LM317|-----.
. | ----- |
. | | [82R]
. | | | 1N4148
. | '--------+---|>|----> To NiMh +
. | |
. | |
. +|10u |
. === | 1N5239B
. |16WVDC -/ 9.1V
. | ^
. | |
. | |
. | |
. | |
. Gnd -+----------------+----------> To NiMh -
.

The characteristic is sharper with the bigger diodes, and it is more likely to withstand a momentary reverse battery connection with a wimpy 150mAH NiMH...all available from Radio Shack.

View in a fixed-width font such as Courier.

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. -----
. +12 -+----|LM317|-----.
. | ----- |
. | | [82R]
. | | | 1N4001
. | '--------+------|>|-------> To NiMh +
. | |
. | |
. +|10u |
. === |
. |16WVDC | 1N4739
. | -/ 9.1V, 1W
. | ^
. | |
. | |
. | |
. Gnd -+----------------+----------------> To NiMh -
.
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