USB LiPoly Charger - Single Cell

If you need to charge LiPo batteries, this simple charger will do just that, and do it fast! The USB LiPo Charger is a basic charging circuit that allows you to charge 3.7V LiPo cells at a rate of 500mA or 100mA. It is designed to charge single-cell Li-Ion or Li-Polymer batteries. Check the datasheet below to see if it will work with your battery.

The board incorporates a charging circuit, status LED, selectable solder jumper for 500mA or 100mA charging current, external LED footprint, USB input, mounting holes, and various holes for your own connectors. We include a single JST-tpye connector which connects directly to our LiPo batteries. The connector comes unsoldered, so you can use it or not.

There is also a 'SYS OUT' which allows you to connect the charging circuit directly to your project so you don't need to disconnect the charger each time you want to use it.

Replaces: PRT-00726

USB LiPoly Charger - Single Cell Product Help and Resources

Core Skill: Soldering

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Core Skill: Electrical Prototyping

If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.

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Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

  • heathkid / about 13 years ago / 7

    I'm just very glad I bought "PRT-00726" when I did. This seems like a step in the wrong direction. I'd like to see the original brought back. This may be just my opinion... but I really wish I had bought more of the other before this came out. Sorry.

    • bcerrato / about 13 years ago / 3

      I agree. I used the original 00726 as a battery backup for projects that had wall power. With this new design I'll have to get a wall to usb style converter to do the same thing... which is not ideal. On top of that you could provide auxiliary power for "non critical" pieces of a design that weren't battery backed up on the original design.

    • spiralout112 / about 13 years ago / 3

      I agree, having the 2.1mm connector is key to me, I made a modified version of the iphone charger and I always have people asking me to build one for them, but none of the boards available are suitable now. A PRT-00726 with the 500ma/h charging current would be perfect for me.

    • TQT / about 13 years ago / 2

      I'm on the same side. Hope you can, at least, bring the two flavors for us.

    • BillM / about 13 years ago / 2

      I agree. Not having the barrel jack from the original makes it difficult to incorporate a solar panel for charging, battery pack connection for supply, and a load connected all at the same time. I like the old design better.

  • hobgoblin612 / about 13 years ago / 3

    "at a rate of 500mA or 100mA per hour." ??????
    NOOOO amps is the measure of the rate of current flow. ie charge per second. not the actual amount of energy.
    just delete the "per hour" please.

    • Member #107653 / about 11 years ago / 1

      They must have meant the acceleration of the charge, i.e. charge/time/time :)

  • Fixed.
    Note to self: click 'save changes'.

    • FlyByPC / about 11 years ago / 1

      It still says 100mAh per hour in the description. Perhaps an accelerating rate of charge? ;-)

  • Member #200199 / about 13 years ago / 2

    Does this board prevent from over charging and will it slow down when it is almost charged?

  • SomeGuy123 / about 13 years ago / 2

    I don't like the lack of a normal header for power in.

  • yvest / about 13 years ago / 2

    Could you please confirm that it uses a mini USB connector and not a micro USB connector?
    PS. I think that your product page should mention it.

  • Member #156340 / about 10 years ago / 1

    I'm running a test with a pro mini doing a blnk test and a PRT-00341 Polymer Lithium Ion Battery - 850mAh, charging from a USB port.. The first few charge cycles I could run the board while charging, and the charge would go to complete and the charger LED would go out. Now, each time, it doesn't quite make it. The LED does not go out. 4 or 5 charge cycles have been this way. Would this be a charger design or a battery problem? If I were to plan a product around this, would I have to put the pro mini in a low power mode while charging in order for the charge to complete in this configuration?

  • Member #156340 / about 10 years ago * / 1

    See above, I posted twice by mistake.. I though my post would be at the top so I thought I lost it.

  • Chiel / about 10 years ago / 1

    The MCP73831T is a astonishingly easy chip to use, and quite cheap to for what it does. it would cost very little to design and build a circuit using this or to include it in a existing project. i myself am waiting for a set of Printed circuit board prototypes with load sharing based on these little battery wonders as i type this.

    My question is this: Why don't you carry the charger IC seperately? Surely something as simple, yet handy like this warrants its own product?

  • jcholton / about 10 years ago / 1

    Can this charge multiple batteries at the same time?

    • Chiel / about 10 years ago / 1

      Doubtfull. the MCP73831T is designed to charge a single cell properly. the moment the battery its designed to charge is fully charged the IC shuts off automaticly. Also if 2 rechargeable batteries with a voltage difference are put next to eachother i think you get that one starts charging the other at a unsafe speed. Lithium-Ion Polymer batteries are best to be handled with utmost care and to avoid iffy situations.

  • Member #332966 / about 11 years ago * / 1

    I am trying to use 3 of these chargers to charge a 3 cell lipo from the same 5v source. The negative of the in and out of the chargers are the same. Any ideas on how to connect chargers without shorting anything out?

    Sorry, just read comment before is the same.

  • Member #465977 / about 11 years ago / 1

    There are a lot of questions about using one of these to charge two cells. I understand the answer to that is somewhere between "no" and "yeah, the fire from the exploding battery is really cool."

    And it looks like the system output is electrically identical to the battery connector, so it's probably not possible to use multiple chargers with their system output in series to use them in higher voltage applications.

    So, does anybody have thoughts on how to get ~12volts of battery with in-circuit charging?

  • Maxwell / about 11 years ago / 1

    I'm intending to use this to charge from a 6V solar cell. I am wondering what the best way to clip the cell voltage to 6V would be (I'm presuming an LDO voltage regulator would be the way, but would like something as cheap and simple as possible! Would a simple zener, maybe with a current limiting resistor, do the job as well?) TIA

  • Member #448741 / about 11 years ago / 1

    Hi guys Firstly, I am a noob to electronics, so don't get annoyed by my stupid questions:) I just wanted to know 2 things: 1. How exactly do you use a solder jumper 2. How does the charger indicate that the battery is done charging


    • Chiel / about 10 years ago / 1

      1) You use the jumper by removing the solder between the existing pads(look up Desoldering), then apply new solder between the middle and the other pad. 2) It has a on board led that goes one when charging and turns off when its done. as readable in the datasheet.

  • Member #405003 / about 11 years ago / 1

    stupid question, is it possible to use this battery, with this charger?

    • Chiel / about 10 years ago / 1

      Yes. this charger is built exactly to charge those kind of batteries. just know that the bigger the pack. the longer it takes to charge.

  • wesgood / about 11 years ago / 1

    Will the battery discharge if there is nothing connected to SYS OUT?

    • Chiel / about 10 years ago / 1

      (better late then never, might help others with same question later) Depends on the battery ofcourse. Some discharge on their own faster then others.

      Lithium Ion based batteries (like the Li-Poly) tend to discharge slowly for rechargeable. The ones on sale here on Sparkfun discharge with up to <8% per month at most.

  • Member #427754 / about 11 years ago / 1

    Great stuff! It's charging my nokia bl-5c baterry with 500mA without a problem.

  • Tomotron / about 11 years ago / 1

    It's a bit expensive for what it is but mine worked... for a while. First the LED burnt out fairly quickly. Then the MCP73831T brain smoked and blew itself right off the board. Bummer.

  • shilbert / about 11 years ago / 1

    Is the IC used in this the MCP73831T-2ACI/OT? I think I may have fried mine, and the MCP73831T has several variants that control the various charging thresholds.

    • shilbert / about 11 years ago / 1

      It looks like it is -- the IC has "KD14" printed on it, and according to the datasheet "KD" matches up with MCP73831T-2ACI/OT.

  • According to the Eagle schematic, the JST connector has a pin spacing of 0.1". According to this LiPoly's description, it's connector has a 2mm pin spacing. Which is correct? Or are these actually incompatible?

  • Tresky / about 11 years ago / 1

    This is used for charging a LiPo with a USB input, but can it also be used to charge a device through the USB with the LiPo? In other words, can this board charge in reverse?

    • MikeGrusin / about 11 years ago / 1

      Nope, this one doesn't work in reverse. But do take a look at the Mintyboost, which sounds like exactly what you need.

  • Do you have a Tutorial of how to connect the LiPoly Charger to an Arduino and also to the 5v? I want to charge my system and when the baterry is full, the charger turs off, thanks

  • Member #2972 / about 11 years ago / 1

    Great little board, the chip is pretty stand alone, but as its an SOT23-6, it can't dissipate much heat so don't expect to get more than 300mA charge current out of it. It'll limit the current if it over-heats so the chip will only be damaged by over-voltage. Whilst you can of course connect your application circuit to the 'SYS OUT' - this is directly across the battery. So if your application draws more than say 30mA, it will never indicate 'end of charge' because it detects when the battery is full by when it stops drawing 7.5% of main charge current. When jumper is set to 500mA, it will average the charge current of 300mA, and 'cut off' during constant voltage phase when the battery AND application circuit draw less than 37.5mA. Not a project breaker, but if you're wondering why the LED never turns off with your circuit attached - that'll be why.

  • Member #379210 / about 12 years ago / 1

    Is it possible to use this to charge a double cell setup ? (Two 3.7v batteries placed in series?)

    How would you charge double cell setups if you can't do it with the above? I need something that's easy to charge since the end-user isn't that technical.

    • Kamiquasi / about 12 years ago / 1

      Is it possible to use this to charge a double cell setup ? (Two 3.7v batteries placed in series?) No

      How would you charge double cell setups if you can’t do it with the above? You would need a balancing charger and appropriate wiring.

      Li-Ion/Polymer Battery Charger/Balancer - 50W, 5A

      wiring primer

      I need something that’s easy to charge since the end-user isn’t that technical. Depending on exactly what your batteries are and how they are wired (fixed in series or otherwise), the 'simplest' solution would be to charge in parallel rather than in series.

      series charging

      parallel charging

  • Sam Bredeson / about 12 years ago / 1

    If I didn't want to use USB power for this, could I remove the USB port and solder in my own power source? I'm assuming only the power pins from the USB port are being used, but I could be wrong!

  • Member #147729 / about 12 years ago / 1

    Will this charge a 18650 cell? The nominal cell voltage, 3.7 and max charge voltage 4.2 seem to match but there's no mention of it in the datasheet unless I missed it.

  • Member #319420 / about 12 years ago / 1

    Does anyone know if this would do fine if I charged it from a 5.5v solar panel, or would the voltage output from the panel be too high for the charger?

  • Member #319420 / about 12 years ago / 1

    Does it come set at 100mah or 500mah? If I have a 5.5v 250mah solar panel, what would I have the jumper at?

  • igeorge / about 12 years ago / 1

    Does the charger stops when battery full ? I like to prevent overcharging the battery or explosion Thank you

    • Member #319420 / about 12 years ago / 1

      No it will not overcharge- It automatically switches to trickle charging and then shuts off.

  • Bajaj / about 12 years ago / 1

    Hi, I'm using a board with the IC MCP73831, when connected to USB port only thing it does is light the LED every 30 seconds, also if you connect the battery. the supply current is minimal, we note that not charging. know what that means?. thank you very much.

  • Member #308135 / about 12 years ago / 1

    I'm slightly confused. So would I need a separate connection between the battery and the device in case there's no external power? or does this charger already handle it, so I'll only need to connect the battery and the device to this charger?


  • Member #15428 / about 12 years ago / 1

    Is it possible to connect Vin directly vs. using the USB connector? There appear to be 2 pin connections above the USB connector & below the charging LED -- Can a direct Vin be connected here? If so, what is the polarity of the pin connections? If this is possible, what is the high limit of the input voltage? What are the current limits? I'd like to power this from a 6V/100mA solar cell (possibly several in parallel to increase available current). Is this possible with this board?

  • johnelle / about 12 years ago / 1

    Anybody seen issues with USB3? I noticed it wasn't charging on my new computer (red light not on) but when I moved it to my original machine with USB2 it worked fine. Front USB on both machines (wired directly to the MB).

  • renato gallo / about 12 years ago / 1

    anyone has an idea on where to solder that white connector ? why there aren't two of those ?

  • renato gallo / about 12 years ago / 1

    is there a tutorial that can explain where to solder what in order to use this?

  • magrin / about 13 years ago / 1

    Hi there! Is it ok to charge a nominal 3.6V cellphone battery with this charger? Thanks

  • Member #265016 / about 13 years ago / 1

    Just purchased this product and was wondering what the status light indicated?

  • Member #143562 / about 13 years ago * / 1

    Sorry if this is a stupid question....If i have 2 LiPo batteries connected in series, can this circuit handle recharging them? I need a bit more than 3.7v (I need enough voltage to drive a 5v voltage regulator) so connecting 2 of the readily available 3.7v LiPo's would be ideal, but I need a recharging solution.
    edit: just found the Li-ion 9v battery on your site (PRT-10053). Can this charger handle this particular battery?

    • bratib / about 12 years ago / 2

      For 2 - 3.7v LiPo batteries in series you would need 2 of these and connect one across each battery. Each one would charge its own cell, which is actually more desirable with LiPo cells anyway. A slight difference in their internal resistance will cause different charging rates in series. This causes lots of problems in the life of series cells unless they are matched. Even then, for the long life of the cells, they should be charged individually.

    • MikeGrusin / about 13 years ago * / 2

      Sorry, no. This charger can ONLY handle 3.7V LiPo batteries. It can handle two in parallel, which is still 3.7V, but cannot handle 2 in series, which is 7.4V.
      9V is right out.

  • TheWaddleWaddle / about 13 years ago / 1

    "We include a single JST-tpye connector which..."

  • Ace! / about 13 years ago / 1

    The datasheet for the MCP73831T says the max supply current is 1500 MICROamps. Did they mean 1500 MILLIamps?

  • turnavies / about 13 years ago / 1

    From the MCP73831T datasheet, it looks like this IC regulates the output voltage to one of 4 options: 4.20V, 4.35V, 4.40V, 4.50V. Correct?
    If so, how is it suitable to charge a single cell 3.7V li-poly battery? The datasheet for the batteries you carry says 'Charge cut-off Voltage' is 4.20±0.03V. Seems really close.
    What am I missing?

    • turnavies / about 13 years ago / 1

      I figured it out, so I'm going to answer my own question here: 3.7V in the battery datasheet is the average voltage, 4.20 is the maximum 'starting' voltage of the battery. It will stop charging at that point. Since the MCP73831T regulates to 4.20V, this is a suitable charger.

  • LouwH / about 13 years ago * / 1

    Looks cool! I am planning on powering my project from a car-battery (lead-acid 12v) If I use a 5V regulator and then connect this board, will the connected LiPo act as a backup when the 12V is n/a and my device is connected to the SYS OUT?
    Another Q: Is this device capable of powering two batteries at once? (Since it has two connection spots for batteries)

  • Nilson13 / about 13 years ago / 1

    Hey everyone,
    I am completely new to electronics and have a few simple questions. By connecting my project to the "SYS OUT" and then my battery to the "BATT IN", will the following situations occur:
    1. Will my project be powered by the battery when I am NOT charging?
    2. Will my project be powered when I am charging?
    3. Will my battery be charging AND will my project be powered at the same time when I am charging?
    Forgive the elementary question, but I will greatly appreciate it if anyone can help me with this.

    • Maxim / about 13 years ago / 3

      Actually I'm also confused why the SYS connectors exists. The charger CAN'T charge and power the project simultaneously because it needs to be able to either charge in either CC or CV and this depends on the parameters of the battery. The correct way to load share is to sense when Vusb is connected and trigger a FET to disconnect the battery (to allow it to charge alone) and to power the project thru Vusb.
      See App Note AN1149 from Microchip for details.

      • DogP / about 12 years ago / 2

        That App note is very helpful. I agree that SYS OUT on this board isn't ideal, because the charger IC is expecting just a battery cell, not the whole system load plus battery. I'd imagine this is worse when the system load is larger.

        Pg. 5 of that app note explains in detail, but also suggests if you want to connect it directly like this SYS OUT pin, to use a charger with no auto-termination, like the MCP73811/2. The MCP73812 would adapt to this board with very little change.

        I believe adding a FET and Diode is a better, and still simple method though, because auto-termination should be better for the battery (it's not good to hold the battery at full charge like the MCP73811/2 would). This does add the requirement of verifying that you don't draw too much current from the USB port though (if the load draws 300mA and the charger is trying to charge at 500mA, you'll overload your USB port by using the FET).

        I don't think that there's anything dangerous about this design though... just not ideal.

  • Member #221868 / about 13 years ago / 1

    Sorry for askign a newbie at this charger
    For the SMD LED and also the normal LED what is those two purpose? If the SMD LED kept on blinking what is the problem?

    • Member #221868 / about 13 years ago / 1

      and how much voltage and current is needed to charge the Lipoly battery? How do i know it is charging?

  • Gizmo E. / about 13 years ago * / 1

    Can one of these be rigged to charge two of the following in parallel?
    I realize the charging time would be a lot slower.

  • ideeas / about 13 years ago / 1

    Can I use this same board to charge a Ni-MH battery, also?
    I want to be able to use the USB connection to charge this battery, too.

  • kamp0145 / about 13 years ago / 1

    The mcp73831 on this board gets very hot. I can only hold my finger on it for around 4 seconds. Is this normal?
    Also, I trimmed off the section of the board that reads " Lipo USB Charger". Will this have any effect on how it performs?

    • You should try heat sinking the IC, with a proper heatsink or just place tin foil on it to help disapate heat. And it should not matter if you have cut the board as long you hae not cut a trace.

  • Calce / about 13 years ago / 1

    Do not buy this charger. The second I plugged in my single cell Li-Ion 3.7V battery into this, I saw a puff of smoke and the transister on it blew. What a piece of garbage.

    • was your polarity correct?

      • Calce / about 13 years ago / 1

        polarity was correct, I soldered the connector to the BATT IN pins, the two furthest left in the picture

        • FoxxCommand / about 13 years ago / 1

          You shorted it by bridging the sys out Vcc and Gnd together or the Bat In, how do I know this? I just did it myself, but seems like the board is still giving out the same voltage it was before I shorted it so it seems like mine is still usable, let's hope so before I hook my LiPo in.......

          • Well, i disagree that this is a peice of garbage... I thought that it worked fine even the colour of the board was great!Thanks Sparkfun.

  • Member #154878 / about 13 years ago / 1

    how do you do the jumper for the 500 mA current?

    • you cut the coppertrace connecting the two pads, then you solder the other two pads togehter

      • firegeek / about 12 years ago / 1

        Huh? From both the schematic and the physical board, the 500mA pad is already connected to the center pad -- and verified with my ohmmeter.

        So it seems like you should just leave everything alone if you want 500mA. Whereas if you want 100mA, it seems like you should cut the trace connecting the 500mA pad to the center pad, and solder the 100mA pad to the center pad.


        Or have I completely misinterpreted everything I'm seeing?

  • dab / about 13 years ago / 1

    I'm looking at this device, but would like to integrate it with an arduino board with usb connectivity. Once complete, users will need to connect the arduino to their computers via usb. So, I want to use a rechargeable li poly battery in the project, but I don't want multiple usb jacks (one for charging and one for communication).
    Does anyone have a strategy for how to integrate the charging with the connectivity?

    • attach the usbin power to the charger, then the sysout to the arduino (arduino runs fine on 3.3v@16MHz), then the datalines to the usb datalines of the arduino. If you wanted to go technical, you could add some auto shifting so it would change from battery to usb power when pluggin it in.

  • ClayBratt / about 13 years ago / 1

    This may be a dumb question but Im assuming SYS OUT puts out 3.7v Would that be correct?

    • jrossetti / about 13 years ago / 1

      SYSOUT puts out whatever the battery is, since it's directly connected to it; check out the schematic.

  • Jw1223 / about 13 years ago / 1

    I made one of these, only with a 5v regulator onboard, dc barrel input, no USB, and 3 max1555 to charge 3 batteries at once. If anybody wants the eagles or the link to the batchpcb version, let me know. I've also done it in both pth and smd.

    • jhpankow / about 13 years ago / 1

      Jw1223, I am interested in your 3-MAX1555 PCB. Is it available on batchpcb?

      • Jw1223 / about 13 years ago / 1

        Here's the link to the SMD version.
        And here's the PTH version.
        These designs are for charging only, so no SYS output. If you need the eagle files to add the SYS output, let me know and I'll shoot them to you.

        • jdeboi / about 11 years ago / 1

          Hey. Don't know if you'll get this since your post is 2 years old, but I'd love to see the eagle files for SYS output + 5V boost. jdeboi at gmail dot com. thanks a mil!

        • jenesaisdiq / about 12 years ago / 1

          Hey Jw, was just about to design a really similar board- only with a microUSB and a boost convertor on it! Would love to use your eagle files as a jumping-off. You can hit me via dick{at} . Thankya!

  • bdodds / about 13 years ago / 1

    So with this board I now am forced to use MINI USB as my 5v input?
    I'm not sure why there is no regular power in jack or even a power in JST connector like on the old board...

  • pstemari / about 13 years ago / 1

    The MAX1555 is discontinued?? Maxim shows its status as active at
    The dual wall-wart/USB input is a nice feature.

  • N.Poole / about 13 years ago / 1

    Oh good, I was gonna build this... now I don't have to, lol.
    Oh, and don't mean to pick nits here but you have a "Tpyo" on this page, if you catch my drift.

  • BigBen710 / about 13 years ago / 1

    Please forgive my ignorance as i'm a complete beginner to electronics but i'd planned on using the old MAX1555 charger with a solar cell and Mintyboost kit for a college project but guess i'd now be better off using this circuit?
    My problem is i have to produce the PCB myself and as i intend to use a solar cell to charge the battery, can i omit the usb and just connect my solar cell striaght in instead?
    Thanks in advance!

  • jrossetti / about 13 years ago / 1

    datasheet says supply voltage range is 3.75-6. So, theoretically, I could slap a 6V solar panel on the front of that and call it good, right?

    • SomeGuy123 / about 13 years ago * / 2

      You could. The battery would take forever to charge though.

  • c60278 / about 13 years ago / 1

    Is this board capable of powering a circuit and charging the battery at the same time, or is that not possible with this new IC?

  • Quick question...
    1. Why is this board so big?
    I made a similar board which is really small, 1.2" x 0.6" and it even has a 3.3v @ 300mA regulator on board. Not to mention it cost me about $3-4 to make... ($15 is a good price tho since its made and is plated through hole and stuff!! i do like the price :D)
    Just askin...
    Also may i suggest you make 2 version of this ... one with a 3.3v regulator and one with a boost to 5v reg... like a MAX751 or something ...

    • Electrumpeter / about 10 years ago / 1

      Nobody reacted on this one but I was looking for exactly the same and it would also be nice if you could use a switch to turn the battery power on and off and it would also be nice if there was some sort of battery indication. That would be really useful.

      • you said a switch to control battery power... do you mean to control battery to the output sys header? Also Indication? meaning battery is plugged in ? If possible contact me via email AtomSoft @ gmail .com

  • dcormier / about 13 years ago / 1

    The title on this product indicates it's for charging single-cell LiPo batteries, but PRT-08484 (a 3-cell pack) is listed as a related item. I'm assuming that's not going to work.

    • yes, it will work. they are still arranged as a single cell, just in parallel.
      "These three cells have been match for internal impedance and can be fully charged and discharged in parallel."

  • LukeW / about 13 years ago / 1

    The schematic link is actually linked to the datasheet.

  • Cute board ,
    There seem to be some trouble in the "Shematics" & "Eagle Files" links
    "Our server gnomes couldn't find the page you are looking for"

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