Chinese 12V 6800mAh Li-Po battery mini review

Lots of these Li-Po battery packs on eBay, going for around £12 from various vendors:

BatPic 122

Nice hand-sized battery pack, with a coax plug and socket on flying leads, and a handy little power switch and LED. Comes with a somewhat underspecced charger (350mA – so, around 20 hours to charge).

The battery specs seem too good to be true, though. 6800mAh at 12V? Nearly 7Ah at a fraction of the size of an old fashioned gel battery. Hmm.

Testing:

To test the battery capacity, I hooked it up to a little LCD telly via a Turnigy power analyser.

BatPic 126

The TV takes about 0.3A, so it ought to run for about 20 hours. Ha! To start the test, I charged the battery fully with the supplied charger:

BatPic 124

12.77V is a little high, but it’s straight off the charger; it’ll relax back to around 12.6V.

About 6 hours later, it was time to switch it off before the battery flattened itself permanently (10.8V is as low as you should go):

BatPic 127

So. Not really 6.8Ah at all, more like a third of that. I think I know what they’ve done, though (assuming they aren’t just out and out dishonest): to create a nominally 12 volt battery, they’ve strung 3 cells together in series – but then they’ve mistakenly added the Ah capacities of the cells together. Connect 3 cells in series, you add the voltages, but Ah stays the same as a single cell; connect them in parallel instead, and you add the Ah up but the voltage stay the same as a single cell. They’ve mixed it up.

The headline, therefore: these battery packs only have a third of their marked capacity. Caveat emptor etc.

The upside (!) is that the little charger that comes with it takes half the time to charge it.

UPDATE: A kind commenter, Unferium, notes below that Li-Po cells can be safely discharged to about 3V per cell rather than the 3.6V I used, which does change the results slightly. The voltage drops off very fast from 10.8V down, so you only get an extra 0.25Ah out of the pack. I think the headline stands :)

Teardown:

Anyway, let’s see what’s inside. Note: Lithium batteries can explode or burst into flames if mishandled, or if they’re faulty. Do not take one apart unless you know what you’re doing, or you’re an idiot. Thankfully, I’m fully qualified in at least one of those categories.

First, off comes the outer blue shrink-wrap:

BatPic 128

… revealing a stiff cardboard “case”. It comes apart easily to reveal:

BatPic 129

The actual battery of cells is just the silver chunk; the dark strip on the left is just dense packing foam. Shame they couldn’t just make the whole pack a bit smaller instead – I can’t see what benefit that padding does given that it’s only on one side of the cells. Even if something bad happens to the battery and the cells start expanding, they’ll blow up like a pillow, not out sideways. Ho hum.

Let’s pull the cells out:

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Yup, three Li-Po cells in series. Thankfully they’ve each got their own protection circuit (which disconnects the cells before they get overcharged, or so discharged they’re unsafe to charge again):

BatPic 143

The 3 cells are extremely securely glued together, so don’t try pulling them apart. If the foil envelope around a cell is punctured, they give off a strangely fruity smell and need to be disposed of safely in a neighbour’s bin. (Not the nice neighbours, the ones on the other side)

In use:

Despite their misleading label, they’re still useful battery packs, particularly for Arduino / microcontroller use. 2.2Ah at 12V is still plenty of juice for some projects. Here’s a little wireless monitor I rustled up to monitor our solar panels:

BatPic 140

It’s just an LCD, an Arduino and an nRF24L01+ radio module, all cable-tied to the battery:

BatPic 145

Lasts for a couple of days between charges, and it’s surprisingly robust. Easy to recharge with the charger that came with the battery (albeit a bit slow).

BatPic 144

Conclusion:

They’re not as good as they say they are, but they’re still handy.

15 thoughts on “Chinese 12V 6800mAh Li-Po battery mini review

  1. That foam padding might not be for safety so much as for a alternate design the original manufacturer planned where the foam padding is taken out so a larger Li-Po battery packs can be put inside and they can sale their new higher capacity battery pack to their customers.

      1. Huh. My next two ideas on that foam were:

        1. Perhaps they had plans for a larger charging circuit or such and the foam was just their as filler so they could maintain the same form factor with the next design.

        2. The battery pack might have been intended to lay on its side (perhaps in a compartment?) with the foam cushioning the Li-Po packs against bumps/impacts.

        Although, neither of those sound quite…….right.

        Perhaps I’m just overthinking this.

        1. You could be right. The way the whole thing’s constructed of sticky-backed card just feels so clunky and home-made. Guess they could have had a load of pre-cut bits already…

  2. Thank you for a Teardown of these cheap packs. I originally jus thought – Nooo – that thing is going to set your house on fire! – But seeing that it employs a safety-circuit on each cell, it’s pretty much idiot-proof – i like that!
    Is it just the pictures, or are the bottom of the cells not square ? It looks angled – This could indicate that the cells are made of scrap-materials (fits with the price)

  3. Hi,
    Sorry about the long comment… Here goes:

    It looks like you’ve only used half of the batteries’ total capacity:
    10.8 / 3 = 3.6v – this is the nominal (expected) voltage.

    Cut-off voltages depending on the load (as a guide):
    1/4C – 3v per cell
    1/2C – 3.15v per cell – sag to 9.1v total pack
    1C – 3.2v per cell, The total voltage sag shouldn’t go lower than 9v Max,

    Also cut off discharging if any cell reaches above 30*C (Just in case).
    All learned from experience and research.

    With the above as a guide, did you see any more capacity?
    Stay safe though!

    1. Hmm… might have to run the tests again. I know the little protection circuit will cut the batteries off at a certain point, but I never noted what voltage it was.

      Thanks for the heads-up!

    2. Well – I’ve done another test, this time in reverse: I discharged a battery as far as it would go (ie until the safety circuit cut the pack off). It hit a low of about 8.2V.

      (Once the pack gets down to 10.8V the voltage falls off really fast – it’s certainly not linear.)

      Then I hooked it up to the Power Analyser and charged it fully, keeping track of how much charge the battery would take – 2.6Ah, a little more than my result above, but not much.

      I’ll amend the article. Thanks for the advice!

  4. Thanks for the great tear down and info. I had purchased one of these but was concerned about using and charging it because of the lack of available info. Nice to know the protection circuit is real. I was hoping you’d be able to answer a question for me. I want to use these inside a portable stereo and will need to leave the battery switch in the on position all the time. My question relates to the led. Do you think having this led on all the time could potentially drain the battery to a dangerous or damaging level if it is not used for a while? Or would the protection circuit kick in at that level and shut off the led too? Any insight would be appreciated.

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