Looking for parallel lipo charger schematic

[pldaniels]

Hello everyone,

I'm looking for a schematic, or outline on how to do lipo cell charging in parallel using the existing 'balancing taps' that are found on most packs these days.

From what I can gather, one needs to have isolated chargers but on a correctly staged input supply (ie, charger for cell #2 has to be 4.2V above charger for cell #1 etc)

Looking for hints/guides...

Paul.

[Bruce Abbott]

It can be done with isolated chargers (example (http://homepages.paradise.net.nz/bhabbott/lion.html)) but this requires a lot of circuitry and changing current is tricky.

Another way is to use a single multicell charger combined with a balancer.

[pldaniels]

Bruce,

Surprised I didn't recall your setup - since I frequently visit your site for great ideas.

Thanks for that!

Paul.

[dleroi]

Hello everyone,

I'm looking for a schematic, or outline on how to do lipo cell charging in parallel using the existing 'balancing taps' that are found on most packs these days.

From what I can gather, one needs to have isolated chargers but on a correctly staged input supply (ie, charger for cell #2 has to be 4.2V above charger for cell #1 etc)

Looking for hints/guides...

Paul.

Paul,

Here's a schematic and board layout for the parallel charger that I built. It uses a Microchip MCP73843 LiPo/Li-Ion charge controller and independent 5 volt power supply for each cell. It will charge 1 to 4 cells.

The MCP73843 is a constant-voltage, constant-current, single-cell charger with built-in safety timer, cell preconditioning, and status indication. The constant current is set by the value of an external sense resistor and the constant voltage is a function of the controller itself, which comes in 4.1 and 4.2 volt versions. I pretty much followed MicroChip's application note for the design.

These drawings are lacking in detail, but if you (or, anyone else) are interested, I'll do a more comprehensive post.


- Don

[dleroi]

... if you (or, anyone else) are interested, I'll do a more comprehensive post.

- Don

Ok, then, I'm going to unsubscribe.

[FlyingDan]

Hello everyone,

I'm looking for a schematic, or outline on how to do lipo cell charging in parallel using the existing 'balancing taps' that are found on most packs these days.

From what I can gather, one needs to have isolated chargers but on a correctly staged input supply (ie, charger for cell #2 has to be 4.2V above charger for cell #1 etc)

Looking for hints/guides...

Paul.


Hi Paul and Don,

Please consider as well electron_head's circuit in thread http://www.rcgroups.com/forums/showthread.php?t=130567
In particular, you would find there a similar approach to Don's, but with a much mower budget (i.e. only two LM317 instead of a special IC, per cell). Also, Don's and electron_head's circuits share the problem of the common ground plane, that calls for isolated power supplies (which is expensive). Some of us are still looking for a solution that would overcome this difficulty (as in commercial chargers).

Dan

[dleroi]

Hi Paul and Don,

Please consider as well electron_head's circuit in thread http://www.rcgroups.com/forums/showthread.php?t=130567
In particular, you would find there a similar approach to Don's, but with a much mower budget (i.e. only two LM317 instead of a special IC, per cell). Also, Don's and electron_head's circuits share the problem of the common ground plane, that calls for isolated power supplies (which is expensive). Some of us are still looking for a solution that would overcome this difficulty (as in commercial chargers).

Dan

Hi Dan,

You would think that a dedicated IC and pass transistor would be expensive, but the MicroChip part is just under $1 USD and the MOSFET is just over $1 USD - not much more than LM317s. The rest of the components will cost about the same for the two designs. With the IC, you also get automatic shut off, a built-in safety timer, charge indicator, and precharge conditioning (trickle charge for over dis-charged cells).

Yes, the power supplies are still an issue. For mine, I found some 5V, 13A switching supplies on sale for $5 each at Jamco and purchased a dozen of them. I'm currently building a single switching supply with multiple isolated outputs, though.


- Don

[FlyingDan]

Hi Dan,

You would think that a dedicated IC and pass transistor would be expensive, but the MicroChip part is just under $1 USD and the MOSFET is just over $1 USD - not much more than LM317s. The rest of the components will cost about the same for the two designs. With the IC, you also get automatic shut off, a built-in safety timer, charge indicator, and precharge conditioning (trickle charge for over dis-charged cells).

Yes, the power supplies are still an issue. For mine, I found some 5V, 13A switching supplies on sale for $5 each at Jamco and purchased a dozen of them. I'm currently building a single switching supply with multiple isolated outputs, though.


- Don

Don, that sounds interesting. However the "rest of us" still rely on very simple, ubiquitous parts, as I'm sure I won't find this IC easily in my surroundings.
Mmmh I am very curious about your new design (multiple isolated outputs sounds VERY good)...

Dan

[dleroi]

Don, that sounds interesting. However the "rest of us" still rely on very simple, ubiquitous parts, as I'm sure I won't find this IC easily in my surroundings.
Mmmh I am very curious about your new design (multiple isolated outputs sounds VERY good)...

Dan

Dan,

MicroChip sells directly to the public from their web site, as do many other manufacturers these days. In fact, I order directly from MicroChip because they sell single units, whereas their distributors often sell only in large quantities. You do have to register, but that's a very simple process that greatly simplifies subsequent ordering. Of course, even though they sell single units, it's much better to order more because of the shipping. Here's a link, in case you want to see it first hand:

http://www.microchipdirect.com/ProductSearch.aspx?Keywords=MCP73843

I'm also excited about the new circuit. The parts are ordered. I'll keep you posted.

- Don

[pldaniels]

I actually received my samples of this microchip yesterday.

It's an interestingly simple chip, I got the MSOP-8 type (surface mount - don't get this unless you really want it ;) ). Of all the parts on the board, the most expensive is actually the current/voltage sense resistor (0.1R~0.5R) since it's typically a precision 1% type. They cost me about $0.90 each from RS and you have to buy at least 10, worse, if you want to have variable currents you have to have different resistors or change the supply voltage (according to their formula).

Incidently, those wondering why there are multiple entries on the WWW site for the same chip, you want the -420I version (4.2V).

Paul.

[dleroi]

Of all the parts on the board, the most expensive is actually the current/voltage sense resistor (0.1R~0.5R) since it's typically a precision 1% type.

Paul.


Paul,

I'm glad to see someone else using the MicroChip device. I'm very pleased with my 4-cell charger.

Did you go with chip resistors? I found them to be much less expensive than the other types. I would think the resistors in Electron Head's circuit would be substantially more, albeit easier to find.

At what rate will you be charging? How many cells?

Have you done a PCB layout? If not, are you interested in seeing mine?

Regards,
Don

[pldaniels]

Don,

I'd love to see your circuit/PCB. I was wiring mine up to use the MSOP charger chip and an accompanying IRF7501 P&N MOSFET MSOP 8 pin chip as well (will handle 3~6A no problem). Basically it means the entire circuit should fit within a 15x10mm area without any real issues - the biggest issue will be sorting out these floating-grounds / isolated PSU's.

Paul.

[dleroi]

Paul,

Oops, I used the IRL5602 in the D2Pak. I wasn't concerned with board size. I put 4 chargers on a 99.5 x 63.5mm board. The schematic is above, in post #4.

ExpressPCB doesn't print a nice looking image of the PCB because they don't want us using their software without using their PCB service. I had forgotten about that when I said I'd post it. Here it is anyway, though.

Regarding the power supplies, I found some 5V, 13A switching supplies on sale for $5 each at Jamco and purchased a dozen of them. I mentioned above that I'm working on a single supply with multiple isolated outputs. I'll have more on that when it's working.

- Don


- Don

[pldaniels]

Don,

I see you've gone quite fancy there and using double-sided board with vias. I was doing a single-sided one myself ... only because I'm lazy and like to work purely with SMT (less holes!), even my connectors are SMT. The biggest trouble though (expense rather) when it comes to pure SMT is the larger capacitors.

When I've done my SMT PCB (using Eagle CAD on linux) I'll post it up here.

Paul.

[dleroi]

Paul,

I, on the other hand, was anxious about using SMT components, this being my first SMT project. In fact, had the MicroChip IC come in a through-hole version, I never would have attempted surface mount. As it turned out, it was much easier than I ever thought it would be and now I'm sold. I wouldn't want to go much smaller, though, given I have no special equipment other than an old Pace desoldering station.

I look forward to seeing your layout when you've finished it. Do you make your own boards?

Cheers,
Don

[pldaniels]

Don,

Yes, I do make my own boards using the laser-toner/paper/water-dissolve method, etching in either H2O2+HCl or Ammonium Persulphate.

I much much MUCH prefer using SMT so long as it's SOIC / 12xx size stuff. If I -really- have to I'll use 08xx stuff but it's getting a bit crazy. The MSOP size chips (like the ones we're using) are tollerable but only because they've -only- got 8 pins.

Paul.

[GlennS]

Hi Paul,

I've been using the Benchmark chip BQ2000 for my chargers. The chips were also made by TI. In fact I dont own a commercial charger. The homebrew ones are all I have.
Also use the laser toner transfer/water dissolve method for my boards.
Cheers,
Glenn.

[rclinks2002]

Don,
For your charger design, what is the maximum amperage that it can put out? Thanks

Ben Mitchell

[pldaniels]

Glenn.... almost didn't see you there, with your changed avitar and all :)

I've been a bit busy lately working on some other minor project, including a PC-based volts/amps/temp logger amongst other things. Sadly I fried a couple of vital chips when I was doing the 12v to 240V inverter and that's really slowed up things (microcontrollers let go of their vital smoke when you accidently power them with 12V)

Paul.

[dleroi]

Don,
For your charger design, what is the maximum amperage that it can put out? Thanks

Ben Mitchell

Ben,

The amperage is set by the current sense resistor and is limited by the capacity of the pass transistor. I was shooting for 3 amps on mine, which would have used a 0.036 ohm resistor, but I settled for 0.039 ohms because they were easy to find. So I'm actually charging at 2.82 amps. The IRL5602 MOSFETs that I used have an on resistance of 0.042 ohms and are rated at 24 amps. The manufacturer suggests they can dissipate 2 watts using the PC board pads as heat sinks, the way that I did. Mine are dissipating 1/3 watt and get not quite hot to the touch. 6 amps would put you at 1.5 watts, which I would think would be the practical limit without additional heat sinks. With heat sinks, you should be able to handle 9 or 10 amps.


What charge rate do you want?

- Don

[rclinks2002]

Don, thanks for the information, I am shooting for somewhere around 3 amps. Thanks
Ben

[li_gangyi]

does any1 have got a single sided PCB design?? Would like to try this out myself...
and is there anyway I can get around the problem of having to use 4x isolated supplies??

[Zockolo]

Hey don.

Where did you get the IRL5602 MOSFET? What is the exact number?

And what is the part number of the Sense resistor? Where did you get it?

You could use a PC power supply too, to power the Circuit, because you have multiple 5V outputs and they give 13A each.

I'm powering up my Triton DC charger with an ATX modified power supply for 12V at 9A and it works fine. I could get 4 wires of 5 volts to each input and bingo, you have your multiple power sup.

Oh by the way I made myself shipped 4 saples of the IC from MicroChip and it cost me zippo, since the are samples and you are allow 4 of each type :)

Thanks for your futur reply.

Z

[pldaniels]

Just as a side note - I've ordered in 10 of the new GWS C3 lipo chargers, they do up to 1000mA charge and 3S via a balancer plug. I'll be curious to see how they tick.

Paul.

[dleroi]

Z,

I think I ordered the IRL5602 parts from Mouser and got the Fairchild version, which is NDB6020P. You can also get them directly from International Rectifier. However, if you are looking for 9 amps you may want to use a different package in order to make heat sinking easier. I think they come in TO220, also.

Incidently, I said in my PM that mine charged at 1 amp. That's wrong. I meant to say 3 amps. I was thinking of 1C :confused:!

The sense resistor that I used was the LRC-LR1206-01-R100-F and I got it from Mouser, too. You'll need a different value, though, or to parallel 3 of them. I put extra pads on my circuit board for parallelling, but it's obviously more economical to get the proper value.

I'm sure you can get all of the parts from other vendors. Just check Mouser's site for more info.

I got my ICs from MicroChip, too.

I like your ATX idea. As I said, though, I had these other supplies that were very cheap...

I also built a DC to DC converter that has 6 isolated 5 volt outputs. I used a surplus 50KHZ transformer that had 6 secondaries. I thought it would be a great thing to present in this thread, but when I found a company that would supply the transformer in small quantities, the price was over $100 each! It
still would be a nice way to go for someone that wanted to wind their own.

[pldaniels]

dlerio,

Nice package you've built yourself there. Good job on the double-sided PCB incidently.

[Zockolo]

Hello boys!

Well I have order some parts to be able to start building my own parallel charger. ;)

I order the electronic componets from Mouser and it should shipped this week. :o

I order the MOFSET on the TO-220 form factor so it can handle more AMPS. :D

The only thing I find that is a little of a pain :( is the fact that you connot ajust on the fly, before beginning to charge, the charging amperage.
It yould be fun to have some king of selector for lets say, 1, 2, 3 or 4 AMPS. Then is could work with almost any lipo packs without changing the sense resistor. :rolleyes:

I intend to build a 5S lipo charger since i have 5S cells and with the ATX power supply that should not be a problem.

Just a question Dan what is the capacity of the input capacitor? It is not specified in your schematic. :confused:

Can I abuse of you Dan and ask for the pcb file layout so I can burn my own board without having to redraw everything? :rolleyes:

Oh by the way you are correct saying that you are charging at 1amp if you use the LRC-LR1206-01-R100-F resistor that you gave me.
If you do the maths .110/.1 =1.1amp ;) unless you have a different resistor in place like a .03x in place you are not near the 3 amps you think your outputing ;)

Thanks again.

Z

[Zockolo]

Sorry to bother you again, but how's the molicell doing for you ?

Where did you get them ?

Is there a difference between them and the Lipo?

Do you charge them the same ?

Thanks.

Z

[dleroi]

Z,

The value of the input capacitor is dependent on the maximum charge rate. MicroChip says to use a minimum of 4.7 uF and that 4.7 uF should be good for up to 1 amp. I was originally planning for 9 amps, so I used 100 uf.

I gave some thought to how to vary the charge rate without changing resistors and came up with a scheme that puts a PIC in the sense loop. I never got around to building it, though, because I decided to stick with a 1C charge rate.

Sorry for the confusion over my charge rate. I used the LRC-LR1206-01-R040-F, not the LRC-LR1206-01-R100-F that I typed before. So, I'm charging at just under 3 amps.

I'll be happy to post the PCB layout. Do you have ExpressPCB? If so, I'll just post the files. Otherwise, I'll post PDFs of the top and bottom. If you don't have ExpressPCB, you may want to download it - it's free. Then, you could just copy and paste to make a 5-cell board. Also, you may want to change the layout slightly for the TO220 packages. Anyway, let me know.


Regards,
Don

[dleroi]

Sorry to bother you again, but how's the molicell doing for you ?

Where did you get them ?

Is there a difference between them and the Lipo?

Do you charge them the same ?

Thanks.

Z


Z,

It's no bother at all!

I like the emolis and that's all I use, now. I build the packs from the Milwaukee V28 power tool battery packs. They weigh a little more, but they are less expensive, safer, and more durable than LiPo. They're charged the same way. Check the threads for V28 and/or emoli and you'll find lots of info.

- Don

[dleroi]

I intend to build a 5S lipo charger since i have 5S cells and with the ATX power supply that should not be a problem.
Z

Z,

Just one more thing. Are you certain that your ATX outputs are completely isolated from each other? They can't have common grounds for this charger. If you have rewired to make them isolated, I'm sure lots of people here would like to hear more how you did it.

- Don

[Zockolo]

Are you serious?

They have to be completely independant? :confused:

Geee that blows up my baloon... :censored:

Where the heck did you get the 5v power supply so small to fit into that box?

I found theses
http://www.trcelectronics.com/Meanwell/nfm-20-5.shtml
but 25$ a pieces this is nowere economical :)

Well well well

Z

[dleroi]

Where the heck did you get the 5v power supply so small to fit into that box?
Z

Z,

I got lucky and found them on clearance at Jameco for $5.95 each, so I bought a dozen. I just checked and they don't have any more. I should have bought 100 of them!

Since I got you interested in this, if you can't find them elsewhere, I'll sell you five of mine for what I paid, plus shipping, if you want. Where are you located, anyway?

- Don

[Zockolo]

I have search everywhere and I did not find a proper small power supply at a reasonnable price :(

I even went to a friend of mine where I work who is an electronic engineer and ask him for another solution. He told me that is could usa an isolated DC to DC converter and power 4 or 5 of theses from the same source, but isolated DC to DC converter are no where near modes in price :eek:

So yes I will probably resort in buying 5 of yours since I want a parallele charger good to 4 amps and I am buying soon big capacity packs so I want something robust to charge them up.

I will give you some news soon, I'm waiting for my electronic components to arrive and we should be able to arrange some sort of paiments to you.

I'm near Montreal in Quebec, Canada you should be able to send the package to me by USPS as a gift and it should pass custom with no problems.

Thanks again and I will be triing to find some other means of powering up this beast.

Z

[z-matrix]

Hello everyone,

I'm looking for a schematic, or outline on how to do lipo cell charging in parallel using the existing 'balancing taps' that are found on most packs these days.

From what I can gather, one needs to have isolated chargers but on a correctly staged input supply (ie, charger for cell #2 has to be 4.2V above charger for cell #1 etc)

Looking for hints/guides...

Paul.

hi Paul,
your question is a bit inconsistent,
parallel li-po charger wuth series connected li-pos ?
it is only possible if you can connect the series packs in parallel, using an isolated voltage path for electrical current, it is possible though, it whould be a bit expensive.

for a parallel li-po charger you whould only need to connect your cells inside your pack in parallel, then charge as single cell, so a simple single cell charger is what you need.

or if you mean charging cells through balancing taps, as single cells, you need N -li-x chargers with isolated power supplies.

[village_idiot]

Just to add something... Almost every PC power supply that I have ripped apart has had common ground and common 5 volt outputs. Some of the really good ones have multiple 5 volt regulators, but the ground has always been common. So they would not work for this application.

Thanks for the Microchip reference, I'll look and see if they have what I need. Right now I need NiCad/NiMh but will want to go to LiPoly in the near future (after I'm done crashing every flight).

[Zockolo]

Can I ask of you the PCBExpress file for the charger board?

I have received my components so will begin building my PCB and should be in contact with you soon for the 5 PWS.

Thnaks.

Z

[dleroi]

Can I ask of you the PCBExpress file for the charger board?

I have received my components so will begin building my PCB and should be in contact with you soon for the 5 PWS.

Thnaks.

Z

Here you go, Z. Good luck!

- Don

[Tarz]

Hi all,
I can't find MPC73843 on my electronics shop http://rswww.com/ . Is there any equivelent chip (European one)??
I found this one BQ24200 but i think it only outputs 0,5A.

[dleroi]

Hi all,
I can't find MPC73843 on my electronics shop http://rswww.com/ . Is there any equivelent chip (European one)??
I found this one BQ24200 but i think it only outputs 0,5A.

Tarz,

You can get them online directly from MicroChip. You have to set up an account, then you can order any of their devices. You do have to pay the shipping, so I try to order other things (PICs, voltage regulators) at the same time to save. Here's the link for the MCP73843:

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1953&device=en010554

Note that it comes in either 4.1 or 4.2 volt versions.

- Don

[Tarz]

Thanks a lot dleroi
I'll check it.

[Takao Shimizu]

I have used this for 3 years.

Takao

[chichisport]

That´s really good , another takao hit.

[ueliisa]

hm very intersting!

I am looking for something like the shemantic from Don. with an output of about 8 to 10A what should be not a problem as discussed befor, I like to use it for 6 or more (up to 12) cell's

Now I want ask about 2 modifikation:

1) ir should work with an central power source of about 10 to 15V (powersupply, car battery, [perhaps ir posible 24V lorry battery]) and as addition a 110/220V source.
then it coud be prepared for the needed voltage and lead it insulated (transformer?) to each chanel

2) it should handle all three Lixx Typ EndVoltage
switching between Voltage could set ones for all together or per singel loader both way are ok.

setup voltage and current per single loader would be my favorite.

are this modifikations possible?
or is a completly new design needed?

in the end the cost should be as low as possible.

[dleroi]

Ueliisa,

The cell voltage can not be easily changed in my design because it is built into the integrated circuit. For different voltages, you must use different charger chips. If you need flexibility, you will be better of to use a different design.

Cheers,
Don

[ueliisa]

Hei Don
Thanks for you answer.

Hm thats what I was expecting as answer - after reading of the 4.1V and 4.2V Chip :(

How could an other design be?

perhaps allready discussed or built ... then pleas link it
I found many designs but most of them can not more then about 1A or max. 2A -> the design I am looking for should be able to support at least 6A better up to 10A or more but this I wrote befor

[dleroi]

Parallel chargers like mine (see above) require an independent power source for each cell being charged. Every once in a while, these go on clearance at a great price. Here's a link to one that popped up today:

http://www.mpja.com/prodinfo.asp?number=17640+PS

I've just ordered some of these for myself.

- Don

[rsmithaa]

Hi Paul,

I've been using the Benchmark chip BQ2000 for my chargers. The chips were also made by TI. In fact I dont own a commercial charger. The homebrew ones are all I have.
Also use the laser toner transfer/water dissolve method for my boards.
Cheers,
Glenn.

Glenn, I'm looking at the bq2000 chip for a charger I'm building up and was wondering if you have a schedmatic you can share or any design tips you can recommend.

Thanks, Rod