DIY simple lipoly charger - Page 2 - RC Groups
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Feb 14, 2003, 06:25 PM
Registered User
I just finished building one and it works great. You have to be careful with the pinout on the schematic it is wrong. Use the pinout on the package for the LM317.

I can't gett my LED to work. It never comes on but the charger works great. For about $15 in parts you can't beat it.

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Feb 14, 2003, 07:11 PM
RIP "Long Shadow Flyer"
crvogt's Avatar
Getting ready to build a few of these boards, I was dreaming of a li-po charger for 4 packs/ cells, variable charge rate, and variable cell charging... looks like you have it....
Was having trouble converting the Schematic to acutal parts, found a program (FREE) to do Schematics and board layout. The company will also make boards "inexpensivly" from the drawings. Could not figure out how to copy the circuit 3 more times on the blank boad, with out having to redraw it 3 more times...

here is the site for the Free program:

here is a Jpeg of the board I created, to help in making one on perfboard, will be using snappable headers and shorting jumpers to select, charge rate, and voltage....

perhaps Scott Henion would like to actuall make up some blank boards, and sell them...

Last edited by crvogt; Feb 15, 2003 at 06:15 AM.
Feb 14, 2003, 10:28 PM
Registered User

SHDesigns Charger

Hey Parkflier:

The pinout on the LM317T IS CORRECT as drawn on the schematic. From the front of the 317, the left terminal is the Adjustment terminal, the middle terminal is the Output, and the right terminal is the Input.

If you look at the schematic, I think that the pins are numbered 1, 2, 3 on the schematic representation of the part. These numbers are not in numbered sequence on the pin locater on the part in the schematic. I think this is why some have had problems or think that the pinout is not correct.

If you don't have yours wired this way, it may be miswired, although I don't know how it would work if you didn't have it wired correctly. Although, you do mention that your LED doesn't work.

You could have it miswired, or maybe your LED is in backwards, or your Q2 is bad. Check your led for turn on by shorting across the Q2 emitter to collecter and see if the LED turns on.
Feb 14, 2003, 10:37 PM
Registered User

Sample PCB Layouot Won't Work

Hey Carl

The layout you have shown does not have the LM317T wired correctly. You have the center lead of the 371 tied to the adjustment voltage, and the outer leads tied to the input and output voltage leads.

This is not correct. I cannot tell the indended orientation of your part on the component side from the outline, but no matter which way you have it on the component side, the adjustment lead IS NOT the middle lead. The middle lead must go to the output.

Check out that wiring before building!
Feb 14, 2003, 11:00 PM
Registered User

PCB Layout of SHDesigns LiPoly Charger

I have done and tested a prototype PCB layout of the SHDesigns LiPoly charger (650 ma, 8.2V version).

I have artwork that I'm still perfecting. While the circuit works perfectly, there are a few things I want to correct before I post the artwork.

1. I'm not at all happy with my original placement of the LM317T regulator because its heatsink extends outside the edges of the board. Also, the 317 is mounted vertically and has a heatsink, and therefore is succeptible to bending (and eventually breaking) the 317 solder leads. I will reposition the 317 so that it and the heatsink can lay flat on the PC.

2. I am currently using an EIAJ class 4 coxaial barrel connector on a pair of wires for the input because I connect to a 12VDC wallwart with this type of connector. I will also connect to a Cigar lighter cable with an EIAJ Class 4 coaxial barrell connector on the other end for car use. I want to get a pc-mount jack to eliminate this wire and plug, so I need to redesign the layout to accomodate that.

I have taken a design approach that involves taking the artwork and using it as a template to predrill the component holes onto a single sided PC. Then I use Sharpie-like permanent marker to form the etch resist for the circuit nodes, drawing by hand. There's only 10 nodes to draw. It's really easy and beats all the muss and fuss of photo resist and other methods. Then I etch with ferric chloride. So on my PCB all components are connected with amorphous blobs of copper, not lines of copper. Etches faster that way too.

So keep posted. I may even offer PC boards and part kits.

I can get the wall warts for the power supply attractively priced, too. But only 12 V for now, so that limits me (not the design) to 2 cell chargers.
Feb 14, 2003, 11:32 PM
Registered User

Check it again...

The pinout on the LM317T IS CORRECT as drawn on the schematic. From the front of the 317, the left terminal is the Adjustment terminal, the middle terminal is the Output, and the right terminal is the Input

This is correct, as stated on the package the LM317 comes. The schematic uses a different pin assignment than the package which is what I used. If you use the pinout as shown on the layout in the lower left of the schematic it will match. I didn't use this at first and went with the package pinout which isn't the same as the schematic pinout. Scott told me his CAD program self assigns the pins.

It is easy to get confused here, so be careful.

As far as the LED not working, I think Q2 is bad. My LED worked before I installed. I'll try shorting across the transistor.

Feb 15, 2003, 06:20 AM
RIP "Long Shadow Flyer"
crvogt's Avatar
Thanks for the feedback, went back and rechecked the to-220 pin out and have corrected the drawing.... other input or corrections are appereciated...

Last edited by crvogt; Feb 15, 2003 at 06:35 AM.
Feb 15, 2003, 07:55 AM
Oxford Panic
AndyOne's Avatar

A simpler Li-poly Charger

I decided to make my own charger for Li-poly cells and a good choice of regulator seems to be the L200 because it has current and voltage controls in the one IC. This circuit only uses a hand-full of components so it does not have all the features of the LM317 circuit.

See attached zipped PDF file...
Feb 15, 2003, 12:16 PM
Registered User

It seems this circuit will do everything you need, adjustable current and voltage.

Does the current go down as it approaches full voltage?

Feb 15, 2003, 12:31 PM
Hornet Basher
@ MX

I am not by any means an expert on electronics, but to vary the voltage, why couldn't you simply adjust R4 for the correct voltage?

If the voltage wouldn't go low enough, you could simply increase the value of R4 to say 3kohm or so.

Am I missing something?
Feb 15, 2003, 01:51 PM
Registered User
billystiltner's Avatar
I have an old radioshack package for the LM317T its pinout is as such. To keep from confusion just match up the function of the pin
instead of the numbers i guess.

Last edited by billystiltner; Feb 15, 2003 at 01:54 PM.
Feb 15, 2003, 02:11 PM
Registered User
billystiltner's Avatar
You do adjust the voltage with R4.
A higher value for R4 might work with a 15 turn pot(i would have to do the math on it maybe someone allready has). But you get the precision by changing R2. I know if you use too high a value for R2(i accidently used a 22kohm when i first built the charger) you loose the voltage out swing and you dont get the desired decrease in current near the end of the charge.

The current does go down as the battery gets full.
Check the data i posted.

Thanks for the link to the pcboard layout program. I was looking for something like that when i put mine together. I was in a hurry so I just threw mine together and soldered.
Feb 15, 2003, 02:25 PM
Registered User

I was talking about Andy's L200 circuit.
Feb 15, 2003, 02:33 PM
Registered User
billystiltner's Avatar
That is a nice and simple design. Does Radio Shack stock the L200?
Feb 15, 2003, 02:34 PM
Oxford Panic
AndyOne's Avatar

Simpler Charger

It seems this circuit will do everything you need, adjustable current and voltage.

Does the current go down as it approaches full voltage?

Grant (parkflyer)

The answer is yes, the current tapers once the voltage of the battery reaches the charger output voltage. It can be considered as a constant voltage supply with a current limit or a constant current supply with a voltage limit, it amounts to the same.
These are the characteristics you need for charging recahargeable lithium batteries.


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