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'[EE]: NmHi charger chip recommendation required'
2003\05\02@083547 by Tim Box

Hi All

Can any body recommend a battery charger chip to charge 4 AA NmHi 2000ma
batteries  (4.8v total)?

I can feed it any voltage required 3 to 12 volts and if necessary it can be
current limited (rather not though as no room for a heat sink).

I would like it to have an output to indicate charging, full and top/up. It
would be nice to also  have a signal if no or duff battery

Lastly not to expensive and not to many ancillary components

Many many thanks


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2003\05\02@101540 by M. Adam Davis

It may not be worth it to build one yourself.  If you go to your local
hobby shop you'll find a wide variety of NiMH and NiCd chargers for RC
car use.

The one I purchased has ten custom settings (for ten different packs),
will fast charge up to 6A, and handle packs up to 12V.  It uses a small
character LCD and three buttons to handle all settings.  It tells you
when it's done charging, how much current the pack accepted before
finishing, and the current voltage of the pack.  It also tells you if
the pack is shorted or reverse polarity.

I got it for ~$50, which isn't as cheaply as I could have made one, but
it certianly has more features than I would spend the time to put into
one, and the fact that I can define 10 different packs means I can
simply plug in any of my packs and start charging with a few button
presses, rather than re-configuring the thing.

There are cheaper ones available as well.


Tim Box wrote:

{Quote hidden}

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2003\05\02@105032 by fred jones

picon face
Hi Adam,
I'd be interested in what charger you are referring to.  I have the
Superbrain949 from MRC which was $48.  I thought this was what you were
referring to until you started mentioning capability that the 949 doesn't
have.  I had been contemplating the Titan but its a lot more than what you
are talking about.  Would appreciate a specific model.

{Quote hidden}

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2003\05\02@111508 by Tim Box

The device is fed from a wall wort or car socket etc so it has to manage the
charge it's self.


{Original Message removed}

2003\05\02@123900 by

M. Adam Davis wrote:

>It may not be worth it to build one yourself.

Well, Tim didn't wrote that his plan was to build just
*one* charger. He might have plans for a million, who knows...

Anyway, earlier this week I got an issue of Dallas/Maxim's
"Engineering Journal" that had charging as it's special topic.

There are a couple of "In-depth articles" and "Design Showcases"
about charging batteries, primarily Li types, but anyway.
Such as "Designing a pulse charger for use with unregulated
power supplies".

Tim, I just picked up my issue from the paper recycling bin,
and, if you can't get hold of one, I could send you my copy.

Just note that, for *some* reason, they seems to like the the
chips from Dallas/Maxim best :-)

Jan-Erik Söderholm.

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2003\05\02@140716 by Tim Box


I am away on buisnes now so my copy should be there waiting for me on my


Ps I do intend to build many.

I you so desire an off the shelf charger, has them inc 4 AA
2000mah bats for <20 GPB

{Original Message removed}

2003\05\02@151726 by Harold Hallikainen

picon face
    I designed a charger around the LTC1733. This is a really simple linear charger for single cell lithium ion batteries. We used it for two 2AH cells in parallel. The charge current is programmable with a single resistor. The timeout is set with a capacitor. You can pull the charge current resistor pin high to shut down the charger. You can also measure the voltage on the charge current resistor pin to see what the charge current is. It also has some LED drivers for state of charge. I'm using it with a PIC that turns the charger on and waits for charge current, indicating a battery was inserted. It then watches the charge current and puts up a display showing how fast the battery is charging. If the charge current falls to C/10 (400mA for this design), the PIC shuts down the charger and puts "full" on the display. The PIC then measures the battery voltage (with a large pull-down resistor) and waits for it to fall, indicating the battery was removed. The display then goes back to the "waiting for battery" m
ode, the charger turned back on, and we go back to waiting for charger current indicating a battery was inserted.
    The LTC1733 does constant current and constant voltage charging, as appropriate. If the cell voltage is very low, the cell is trickle charged first. The constant current charge is (as mentioned above) set by a resistor and can be up to 1.5A. The chip contains thermal sensing to back off the charge current as the chip heats up in case charge current is high but cell voltage is low (dissipating a lot in the chip). The chip heat sinks to the ground plane on the board.

Works well for us!


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2003\05\02@160259 by Dave VanHorn

I used an AVR :)

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2003\05\04@005826 by Frank Collingwood

Dallas/Maxim MAX712 (NiMH) or MAX713 (NiCad), depending on what type of
battery you are charging.

A little bit of circuitry around it, and off it goes.........

{Original Message removed}

2003\05\04@172841 by M. Adam Davis

Duratrax Piranha
$59.99 from a local hobby shop, Rider's Hobby
AC/DC (only 3A on AC)
Peak charges 1-8 cells (not 10 as I had previsouly said)
Current - 0.1 to 5.0 A
2x8 LCD
Displays battery voltage, peak detection in mV, charge time, current and
Adjustable peak detection threshold 3-20mV
Automatic charge mode to charge batteries if a specific setting is not used
Adjustable trickle charge rates of 0, 100, and 200mA
Displays errors for improper input voltage, poor battery connections,
and reverse polarity on the output
Store pre-set charge parameters for 10 batteries
Multiple sound cues and melodies (gotta have bells and whistles, or it
won't sell!)
Solid state reverse polarity and short circuit protection on input and
Fast charge termination: zero delta peak
Part number: DTXP4005


fred jones wrote:

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