Re: How to charge a 9V Ni-MH

On Wed, 02 Jan 2008 13:15:16 -0500, Fred Bloggs <nospam@xxxxxxxxxx>
wrote:



Jim Thompson wrote:
On Tue, 01 Jan 2008 17:08:20 -0500, Fred Bloggs <nospam@xxxxxxxxxx>
wrote:



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.
.
.
.
.
. -----
. +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.

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


I doubt that any off-the-shelf zener is accurate enough for long
battery life.

I'd use a TL431 (or CMOS equivalent) and a pot.

...Jim Thompson

You can always adjust this one in, state of charging indicators added:
View in a fixed-width font such as Courier.

.
.
. -----
. +15 -+--|LM317|---. ~~ 1N4001
. | ----- | .--|>|-----|>|----------> To NiMh +
. | | [82R] |
. | | | |
. | '------+------+
. | |
. | | ~~ IRF510 D--> To NiMh
. | '--|>|-+-------------G
. | | S
. | |1N4739 |
. | |9.1V |
. | -/ |
. | ^ |
. | | |
. +| | |
. === | |
. 10u| | |
. | | 50R |
. | '----/\/\/\ ---
. | ^
. | |
. | |
. Gnd -+---------------------------------'
.
.

Yep. Poor man's equivalent to a TL431 ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

America: Land of the Free, Because of the Brave
.

Relevant Pages

  • Re: Lenovo/Thinkpad "A battery error has occurred"
    ... Jim Thompson wrote: ... Lenovo/ThinkPad "A battery error has occurred" ?? ...
    (sci.electronics.design)
  • Re: relays
    ... much "poop" the controlling circuit must deliver on a pulse basis. ... ...Jim Thompson ... "Poops" required per desired battery lifetime. ...
    (sci.electronics.design)
  • Re: OT: telephone black box
    ... Jim Thompson wrote: ... Be advised that the majority of SPAMcalls "id" as "UUU UNKNOWN CALLER" or as "PPP PRIVATE CALLER" and the so-called trace does not work. ... A selection of pre-programmed responses that the user can "piece together" would seem to be ideal, and definitely should include those 3 magic tones. ...
    (sci.electronics.design)
  • Re: Need Circuit Design -- Cheap...
    ... suggested voltage capability higher than 5V. ... Donate in the name of Duane Lee Thompson, my youngest son, who died at ... GND GND ... ...Jim Thompson ...
    (sci.electronics.design)
  • Re: No More Dependence on Foreign Oil- Coming to Your Neighborhood Soon
    ... Jim Thompson wrote: ... Let me remind everyone here that the "leftist weenies" claimed global ... huge amount of liquid methane embedded deep in the oceans which will be ...
    (sci.electronics.design)