HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

Any thoughts, suggestions?

Phil Gardner wrote:
HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

Any thoughts, suggestions?

Yes, get a decent 'intelligent' charger ready made unless you want to
build one yourself for the educational side of it. If you want to DIY
then get a chip that provides the 'intelligence'.

Maha make quite good chargers (among others), see:-

http://www.nevadaradio.co.uk/acatalo...-chargers.html

--
Chris Green

On 15 Oct, 20:33, wrote:
Phil Gardner wrote:
HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

Any thoughts, suggestions?

Yes, get a decent 'intelligent' charger ready made unless you want to
build one yourself for the educational side of it. If you want to DIY
then get a chip that provides the 'intelligence'.

Maha make quite good chargers (among others), see:-

http://www.nevadaradio.co.uk/acatalo...-chargers.html

--
Chris Green

When you look at the spec for this one from La Crosse, it would be
hard to beat as a DIY project.

http://www.batterylogic.co.uk/techno...-i-charger.asp

Great machine. The capability to Refresh cells is very useful. The
only DIY worth doing is an adaptor so that you can charge C and D size
cells.

Rob

On Mon, 15 Oct 2007 15:02:15 UTC, Phil Gardner wrote:

HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

Any thoughts, suggestions?

LM317 voltage regulator IC set up for constant current.

Googling on "LM317 constant current" produced this:

http://users.pandora.be/davshomepage/current-source.htm

remember to mount the regulator on a heatsink - a square of 1/8 inch
aluminium a couple of inches square should do the job

--
Jim Backus running OS/2 Warp 3 & 4, Debian Linux and Win98SE
bona fide replies to j dot backus the circle thingy jita dot
demon dot co dot uk

Jim Backus wrote:
On Mon, 15 Oct 2007 15:02:15 UTC, Phil Gardner wrote:

HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

Any thoughts, suggestions?

LM317 voltage regulator IC set up for constant current.

Googling on "LM317 constant current" produced this:

http://users.pandora.be/davshomepage/current-source.htm

remember to mount the regulator on a heatsink - a square of 1/8 inch
aluminium a couple of inches square should do the job

.... but it won't do nearly such a good job (as in treating the cells
well so they last well) as a proper NiCd/NiMh battery charging chip.

You can buy the chips or beg a couple free off the manufacturer as I
did, problem is I can't rememeber the manufacturer's name now.

--
Chris Green

On Oct 15, 10:55 pm, "Jim Backus" wrote:
On Mon, 15 Oct 2007 15:02:15 UTC, Phil Gardner wrote:
HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

Any thoughts, suggestions?

LM317 voltage regulator IC set up for constant current.

Googling

No need, the circuit is in the data sheet where you'll also find
useful info like package choices and thermal data.

MBQ

wrote:
Jim Backus wrote:
On Mon, 15 Oct 2007 15:02:15 UTC, Phil Gardner wrote:

HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

Any thoughts, suggestions?
LM317 voltage regulator IC set up for constant current.

Googling on "LM317 constant current" produced this:

http://users.pandora.be/davshomepage/current-source.htm

remember to mount the regulator on a heatsink - a square of 1/8 inch
aluminium a couple of inches square should do the job

... but it won't do nearly such a good job (as in treating the cells
well so they last well) as a proper NiCd/NiMh battery charging chip.

You can buy the chips or beg a couple free off the manufacturer as I
did, problem is I can't rememeber the manufacturer's name now.

But a fast charger only costs a few quid.

You canhave my old one f you like. Ex model car racing charger. Does 4-8
cells at about 3A fast, dropping back to trickle when the delta peak is
detected. Runs off 12v or the mains. Can';t sell em for love nor money.

On Mon, 15 Oct 2007 21:55:23 +0000 (UTC), "Jim Backus"
wrote:

On Mon, 15 Oct 2007 15:02:15 UTC, Phil Gardner wrote:

HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

Any thoughts, suggestions?

LM317 voltage regulator IC set up for constant current.

Googling on "LM317 constant current" produced this:

http://users.pandora.be/davshomepage/current-source.htm

remember to mount the regulator on a heatsink - a square of 1/8 inch
aluminium a couple of inches square should do the job


Thanks but the problem with the 317T and also the L200 is R=1.25/I
Fine for a fixed current but hard to achieve a variable one.

On Tue, 16 Oct 2007 11:24:39 +0100, The Natural Philosopher
wrote:

wrote:
Jim Backus wrote:
On Mon, 15 Oct 2007 15:02:15 UTC, Phil Gardner wrote:

HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

But a fast charger only costs a few quid.


£35 ?
Were is the fun and DIY in that

You canhave my old one f you like. Ex model car racing charger. Does 4-8
cells at about 3A fast, dropping back to trickle when the delta peak is
detected. Runs off 12v or the mains. Can';t sell em for love nor money.


Thanks but I don't want or need a quick/fast/Gadget lovers DREAM
charger.
also what I failed to say was I will also be using this for
AAA,D,C,and subC cells.

On Oct 16, 1:02 pm, Phil Gardner wrote:
On Mon, 15 Oct 2007 21:55:23 +0000 (UTC), "Jim Backus"





wrote:
On Mon, 15 Oct 2007 15:02:15 UTC, Phil Gardner wrote:

HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

Any thoughts, suggestions?

LM317 voltage regulator IC set up for constant current.

Googling on "LM317 constant current" produced this:

http://users.pandora.be/davshomepage/current-source.htm

remember to mount the regulator on a heatsink - a square of 1/8 inch
aluminium a couple of inches square should do the job

Thanks but the problem with the 317T and also the L200 is R=1.25/I
Fine for a fixed current but hard to achieve a variable one.- Hide quoted text -

Due to the low value R not available as a variable one? How many
different currents do you want? Just switch in different resistors.

Alternatively use a simple transistor as a current source.

MBQ

On Tue, 16 Oct 2007 13:21:48 -0000, "
wrote:


Thanks but the problem with the 317T and also the L200 is R=1.25/I
Fine for a fixed current but hard to achieve a variable one.- Hide quoted text -

Due to the low value R not available as a variable one? How many
different currents do you want? Just switch in different resistors.


Yes that's how I do it now with fixed value resistors
But I would like to build a completely variable supply as per the
original post !


Alternatively use a simple transistor as a current source.

MBQ

Great can you point me to a circuit that works and I can build.
Electronics is just a diy hobby I am not a design engineer.

On Oct 16, 2:42 pm, Phil Gardner wrote:
On Tue, 16 Oct 2007 13:21:48 -0000, "

wrote:

Thanks but the problem with the 317T and also the L200 is R=1.25/I
Fine for a fixed current but hard to achieve a variable one.- Hide quoted text -

Due to the low value R not available as a variable one? How many
different currents do you want? Just switch in different resistors.

Yes that's how I do it now with fixed value resistors
But I would like to build a completely variable supply as per the
original post !

Alternatively use a simple transistor as a current source.

MBQ

Great can you point me to a circuit that works and I can build.
Electronics is just a diy hobby I am not a design engineer.

Google "transistor as current source" gives the first hit as
http://en.wikipedia.org/wiki/Current_source which has a circuit for an
NPN transitor that will sink current from the load (battery). Not sure
if you can charge like that. A similar circuit can be made with a PNP
to source current.

Basically you control the base voltage and assume the Vbe to be 0.6 V
which gives you the voltage across the emitter resistor. That sets the
current through the emitter resistor. The same current (to a first
approximation) flows through the load.

MBQ

robgraham wrote:

When you look at the spec for this one from La Crosse, it would be
hard to beat as a DIY project.

http://www.batterylogic.co.uk/techno...-i-charger.asp


You just know that one is going to be copied and be available from all
good local Grocers & DIY stores before long ...

Next addition will be some Flash memory and a USB interface, so you can
view the charge rate and the condition of the cells graphically.

And now that I've mentioned it, the odds of anyone placing a restrictive
patent on the idea should be zero.

--
Adrian C

In message ,
writes
Jim Backus wrote:
On Mon, 15 Oct 2007 15:02:15 UTC, Phil Gardner wrote:

HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

Any thoughts, suggestions?

LM317 voltage regulator IC set up for constant current.

Googling on "LM317 constant current" produced this:

http://users.pandora.be/davshomepage/current-source.htm

remember to mount the regulator on a heatsink - a square of 1/8 inch
aluminium a couple of inches square should do the job

... but it won't do nearly such a good job (as in treating the cells
well so they last well) as a proper NiCd/NiMh battery charging chip.

You can buy the chips or beg a couple free off the manufacturer as I
did, problem is I can't rememeber the manufacturer's name now.

Maxim ?

--
geoff

geoff wrote:
In message ,
writes
Jim Backus wrote:
On Mon, 15 Oct 2007 15:02:15 UTC, Phil Gardner wrote:

HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

Any thoughts, suggestions?

LM317 voltage regulator IC set up for constant current.

Googling on "LM317 constant current" produced this:

http://users.pandora.be/davshomepage/current-source.htm

remember to mount the regulator on a heatsink - a square of 1/8 inch
aluminium a couple of inches square should do the job

... but it won't do nearly such a good job (as in treating the cells
well so they last well) as a proper NiCd/NiMh battery charging chip.

You can buy the chips or beg a couple free off the manufacturer as I
did, problem is I can't rememeber the manufacturer's name now.

Maxim ?

Yes, that's the one, you can (or could) ask for sample chips on their
web site. I got a couple of their deltaV charger chips this way,
along with loads of documentation.

--
Chris Green

In message , Phil Gardner
writes
HI
Just bought 4X 2700mHa Ni-MH AA battery's my old charger is not up to
charging these in a reasonable time C/10 so im looking to build my own
charger.

I have a 1.5 amp power supply what I need is a variable current
circuit add-on- about 150-800 mA but cant find anything Simple! as in
DIY simple.

Any thoughts, suggestions?
Simplest add on would be the Maplin charger I bought for a tenner a few
months ago, PIC controlled with -delta V charge termination, does AAA,
AA, C, D and PP3. Trickle charges the PP3 types only though. Runs off a
12V 1 amp wall wart or a car adapter (fag lighter socket, it came with
one!).
--
Clint Sharp