Thanks MX, i really meant to say .7C i was also thinking about using a 15 ohm rheostat http://www.allelectronics.com/cgi-bi...-15&type=store to select charge rate, see any problems with this? im new to electronics, have built a few kits and repaired a few things, any thoughts? the 15 ohm 15 watt is the only pot i found under 100 ohm

Dylan

Originally posted by Dylwad
Thanks MX, i really meant to say .7C i was also thinking about using a 15 ohm rheostat http://www.allelectronics.com/cgi-bi...-15&type=store to select charge rate, see any problems with this? im new to electronics, have built a few kits and repaired a few things, any thoughts? the 15 ohm 15 watt is the only pot i found under 100 ohm

Dylan

I see 2 problems with using the 15 ohm rheostat:

1) the rheostat probably rotates through about 270 degrees
of turn. 15 ohms / 270 deg = .05 ohms per degree. A difference
of just a few degrees will change the charge current by over
150 milliamps. A multiturn rheostat from 0.1 to about 2 ohms
would be better.

2) If you use a rheostat to adjust the charging current, you'll
need an ammeter hooked up all the time. Ideally, you'd rather
flip a switch to select between different charging rates that you
commonly use.

MX

I tried to build this charger today, and have some problems... I put it together, and did it right, even did it a second time... and I got the same problem... it puts out 2.5 volts, but no more...

I used an LM350AT instead of the 317 (to handle more than 1.5A) and I used 1/2 watt resistors instead of 1/4(all I had) And I used a 1K trimpot, but a 15 turn one from RS... what did I do wrong???

Anyone got any good pics of how they did theirs... or any good drawings how its laid out on the pcb? Im at a loss here, and its really annoying... its buggin the heck outta me, since near every project this week has failed! lol, anyhow, thanks for any help...

Phreakish
Check your pinout on your voltage regulator.
If you have that right then take a picture of your board front and back . try to get the picture as high of resolution as you can and I'll see if I can spot anything. Also check your power supply make sure it is 12 volts if you are building it for 2 cells. At the start of this thread there is a pictture of a pcb layout for the circuit.
I have had weekends like that also so I know whay yo are going through. Sometimes it seems I keep on breaking little balsa sticks.
The first time I built this charger I used the wrong size resistor.
And couldnt adjust the output voltage. What size cells are you planning to charge and how many. What did you change R1 and R2 to if you changed them.

hello!

This charger is it realle adapted for KOKAM 145mah??

thanks you

I'm fairly sure I have it right, but lemme double check. the drawing on the website only has them numbered not labeled... so which one is Vin, Vout and Vadj??

oh, I didnt' change anything except on R2 and R3 I used 1/2watt.

R3 is 470ohm 1/2W
R2 is 2.2K 1/2W and R1 is 1ohm 1W
R4 is a 15 turn 1K trimpot

I used an NPN transistor (just like the site said) and two ceramic disc capacitors, 0.1uf 50v

The biggest change was that I used an LM350AT instead of the LM317 suggested on the site, since I have several laying around...

The batteries I want to charge are kokam 1020 lipo. I'm going to be running 2s packs, ad 2s2p packs as well, and would like to charge both with the same charger, as well as integrate the trickle charge (going to wait, and get this one to work first...)

any help is greatly appreciated...

Here's the pinout of the LM317T. Sorry it's somewhat small.

Pin1 = adj
Pin2 = v-out
Pin3 = v-in

thats the same of the 350at... but the numbers on the website for the connection is different... it has the Vadj going down to the cap/transistor and the Vin from the + input, and the Vout to the connection just past the 470ohm resistor...

He numbered his pins differently on the schematic. Just use the
pinout for the LM317T as shown in the bottom left of his
schematic, and you will wire it correctly. That's what I did and
mine works.

MX

Phreakish

On the drawing U1 has the pins rearranged and the numbers on the pins do not match the numbers on the 317 probably so the wires dont cross this may be the problem Just read the VI as Vin, A as Adjust, and VO as Vout
This is the way it is supposed to work don't go by the pin numbers. If you look at the bottom left side of the drawings he has his own pin numbers labeled on the 317 as being from left to right 2,3,1 which matches up to his pin assignment. Look it over again and just go by the function of the pin insted of the numbers.
Make a drawing of your regulator and assign functions to the pins then look at the schematic and see if your functions match up with the functions on the schematics.


maulionc

I posted at the beggining of the thread changes to make to the Scott Henion circuit to charge a single cell 145mah lipoly and have charged my 145mah with no problems with it. So it will work with 145 mah with some changes in components.

I figured it out! I grabbed a pack of 470K *K* ohm!!! oh geeze... whadda week... Im off to get some 470ohmm not K

d'oh! I got a 1K ohm resistor too! isntead of a 1ohm... grrrrr... anyhow, i'm dumb, ignore this...

grr.. still doesn't work. I put in the 470 OHM resistor, replaced the 1k ohm with a 1ohm, and it only puts out a max of 3volts... it adjusts... between 2.5 and 3...

Check across R3, it must have 1.25 volts across it. If it doesn't, good possibility you don't have the regulator connected properly.

Also the info on the pin assignments is true. When I first made mine, I did not get the pin assignment right.

Is Q1 working? Do you have .6-.7 volts between the base and emitter. If you don't then the transistor is not conducting.

Do you have at least 12 volts at the input? The regulator must have at least 3 volts higher on the input.

I'm betting the regulator is not connected correctly or the voltage divider network has the wrong value resistors or a cold solder joint. Are they nice and shiny?

Grant

Don't know if this will help but here are some photos. I used a highlighter as I made each connection so I wouldn't cross anything up.