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$ 6.95

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In stock 1,085 in stock
6.95 1+ units
6.26 10+ units
5.56 100+ units

Description: This is a very small, extremely light weight battery based on the new Polymer Lithium Ion chemistry. This is the highest energy density currently in production. Each cells outputs a nominal 3.7V at 400mAh! Comes terminated with a standard 2-pin JST-PH connector - 2mm spacing between pins. These batteries require special charging. Do not attempt to charge these with anything but a specialized Lithium Polymer charger.

Battery includes built-in protection against over voltage, over current, and minimum voltage. Please use caution when using this battery in wearable projects. When using conductive thread, a short in the thread can create sparks and heat. We recommend using coin cell batteries for beginners.

Note: Due to the requirements of shipping these batteries, orders may take longer to process and therefore do not qualify for same-day shipping. Sorry for any inconvenience this may cause.

Note: Be careful with the JST connectors. They can stick in pretty good and tugging on them can damage the connector. Check this tutorial for an easy way to remove them safely.

Dimensions: 5 x 25 x 35mm

Weight: 9g


  • 2C continuous discharge - very high for low price
  • Excellent long-term self-discharge rates (<8% per month)
  • Robust power source under extreme conditions (-25 to 60C)


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Customer Comments

  • Are these and the other capacities LiPo’s going to be in stock soon?

  • Hello, in the datasheet it seems that the discharge rate is 0.2C, not 2C, could you check it out?

  • Can I wire these in series? I don’t want to charge them in series, just discharge them. I thought you could but then I read a comment that made me think you can’t.

    • You can.. you just don’t want them to be too dissimilar ( and of course don’t charge them in series - I know you said it, just repeating it for those who need to read it twice ;) ) Which comment are you referring to?

      • Thanks. It’s farther down in this feed, by RobertC.

        • Seems like Robert isn’t too convinced that these specific batteries will be consistent in makeup - i.e. they may actually be too dissimilar. I’d take his advice in that case :)

          • Aww… I was so hopeful… But since I’m back to the drawing board, do you have any idea how I should go about getting 8-9ish volts out of LiPo batteries?

            • I’d say either find LiPos that are already set up in series (3S: 11.1V - step down, 2S: 7.4V - step up .. you’ll want a balancing charger, of course) so that you know they should be good in that configuration - or boost from a single cell’s 3.7V up to the voltage you desire. I don’t think there’s any off-the-shelf product for that boost (didn’t google much), but you should be able to find a chip and/or circuit that’ll do it if you’re willing to build it yourself.

              Alternatively, there’s things like 9V Li-ion Rechargeable Battery - 350mAh though a comment there suggests it’s actually just 7.2V, or you could go for a NiMH solution (example link only!) which readily come in 8.4V packs of various sizes and appropriate chargers.

  • Can someone please confirm the pinout of the connector. I assume pin1 is +, pin2 is -

  • Hmm, wow. I was thinking about using one of these in a small outside project with a small solar cell for charging but I just read the datasheet and it appears the operating temperature while charging is 0 to 45c. So I can’t charge it if it’s below freezing or over 113 degrees f… kind of ruins that plan then. It gets below freezing where I live frequently in the winter, and in the summer 113 inside of a sealed container in direct sunlight is very possible….

  • Sparkfun without any LiPo battery ?? How is it possible ??

  • Note that the JST connector link links to a ‘PH’ series connector with 2.0mm pitch. The battery spec says it has a ‘ZH’ series connector with 1.5mm pitch. Jay.

  • I am looking to do a portable project that uses EL and im wondering if this can power it? does anybody know? or is there a better way of powering the inverter?

  • Battery includes built-in protection against over voltage, over current, and minimum voltage.

    Does this mean it will stop supplying power before draining completely?

    • Yes, but a) draining a Lipo completely will permanently damage it (this circuitry prevents that), and b) by the time it cuts off, you’re already at the point on the discharge curve where it’s falling very rapidly - you’ve already used 95% or more of the battery’s capacity.

  • Any idea when this will be back in stock?

  • If I need to run 5V on my Arduino, can I hook 2 of these batteries in series? If so, can will I need a special charger for charging the batteries when connected in series?

    • Check out the LiPo booster. You wouldn’t be able to charge them in series, and they will most likely drain unevenly and get damaged if you hooked them up in series.

  • Nathan, Thanks for listening to my request (probably many, too)! :)

  • What is “2C continuous discharge”? A coulomb is one amp for one second. I could understand discharging continuously at a certain number of amps.

    • C * AH = discharge rate. So, in this case it is 2 * 400 = 800mA.

      • Aha, thanks, I get it now…I was never going to figure it out while thinking that C stands for coulombs here. Reading about C-rate helped.

  • This is precisely what I’ve been waiting for. It does appear to be a bit more thick than the other batteries though.

Customer Reviews

4.2 out of 5

Based on 5 ratings:

5 star
4 star
3 star
2 star
1 star

Great product, even better customer service.

Long lasting, easy to recharge.

Great battery with small issues

Very easy to use, compact and light, but a few issues. Used these batteries with young middle schoolers, and had a few batteries get their wires pulled out. Not sure if it was the kids being too rough or a bad batch, but tell your kids to be gentle and they work great.


If you have bought any of these LiPo batteries you have seen them all but the 400mah fits for me in a ideal compromise on dimensions. These packs are well built, nothing feeling cheap or dangerous. Generous wire lead length.

Grabbed one of these to run ESP8266 project

It’s a power-hungry little chip (WiFi with SOC) and this powered it nicely for over 6 hours. They are right about the JST connectors, thay can be tricky.

Small but strong

A lot of mAhs for such a small battery!