DIY Powerbank with 18650 cells - anyone tried these ?

I bought one of those cheap 2-3 amp step down converters with an led readout from Ebay. Like your unit, I found no noticeable noise on 7MHz where I tested. However, there was a very narrow signal about 10 KHz below my QRG on transmit which matched the CW I was sending. I doubt whether it would cause any interference to either the op or other users. It would have been very local in effect, and was tiny considering the antenna was only 4m over the source. Perhaps someone with more technical knowledge knows what it might be. When I get round to making an enclosure for the pcb I will use it with a 6s pack I made from recycled laptop cells.

This is the 1 Amp test curve. Of interest is the capacity - only a little over 1Ah.

That looks bad, I would’ve expected about 30Wh (4 cells * 3.7V * 2200mAh real capacity * 0.9 step-up efficiency). The efficiency can’t be too bad because at more than a few W of dissipation the IC would melt off the PCB, so I’m guessing either there’s something off about those cells or the low cut-off voltage is too high ?

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Having had a similar device back in 2015 I would say performance is 100% dependant on the quality of the source voltage ie the batteries you use. If you use elcheapo LiION cells then chances are you will get poor performance.

At it’s core it is a DC-DC converter and as far as I was aware at the time on mine (looks very similar) it runs all 4 LiION cells in parallel to source the input voltage for the converter. These things will run warm if you are running at a high current and higher voltage (They were designed originally for 5V I think, might be wrong,the option to go to higher voltages was seen as a ‘useful option’) also any radio might be susceptible to RFI from such a device and common mode chokes usually can deal with any issues. To be honest I never saw issues with mine I set the output to 11V for the ATS rigs.

I used to power ATS3/ATS3B and even a KX3 (at low RF powerout).

Basically it works.


For info… M1KTA's QRP ham radio blog: Possible ATS-3/ATS-3B power source These Richard has looked at seem to use the batteries wired in a different combination perhaps. Mine used them all in parallel and the charge was 1.6A 5V.
Perhaps look at the review Review of USB battery box 6x18650 Qidian of another in the comments off the blog as well.

I do not know this unit, but I can recommend you the xt power bank.
It can be recharged in the car while traveling. … and it fits very well in my lowepro cs 80

IMG_2507 IMG_2509 IMG_2510

That looks interesting. Looks like it can handle the DC input from a solar panel as well. I’ve looked at a few other types of these chargers, and none of the ones I’ve seen could handle the input from solar. Wonder if anyone has tried this out with a solar panel for extended outdoors field operations?

73, Todd KH2TJ

Hi Todd

Take a look at the manual:

As i understand: You can charge it via the DC Input as your Solar panel puts more than 12 V to it (they sell a 18V panel / 18V panels are often used for charging vehicle batteries) … while you take 12V/max. 2A at the usb qc2 socket… but i’ve no experience

For me it’s the power backup… normally i use built-in cells

Thanks for the link to the manual. Might just work…

73, Todd KH2TJ

Okay - so the problem here is the cells. Ultrafire 4000mAh = 1100mAh. They are being returned and replaced with Samsung cells.

There are a lot of fake 18650s out there. I think the highest capacity 18650 is about 3600mAh, but generally over 3000mAh you get all kinds of trade-offs: less cycles, too sensitive, higher internal resistance, slightly large physical size etc. Probably the best bet is something around 3000mAh from a reputable manufacturer. Also, there is no genuine Ultrafire over 3400mAh and even that is really expensive.

Agreed. Clearly what I bought is not as described. Incidentally, if any UK activators want their batteries characterised on our system, PM me.

Thinkpow Powerbank - Ramp Current Test (Samsung Cells)

Okay up to 1.4 Amps - not enough to power an FT-817.

Ouch … so it looks like it’s not of much use after all. Thank you for testing this for everyone.

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Probably okay for some radios - but not the 817. BTW just did a test on a Samsung 2600mAh 18650. The measured capacity was 2660mAh.

One further thing that I have discovered about this unit is that it has no charge balance circuitry. Thus, if you put in one discharged cell, as I did after my cell capacity test, the Powerpack then fails to charge properly. All in all a bit rubbish.

Yes, it’s a cheap design, just 4 cells in parallel. In the mean time, I found something better:

There is also a 8300mAh version with 12V/6A output for £54.

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There are millions of BM’s available online and they arent that expensive.

Get the soldering iron out…

  1. There is no room for an additional PCB (or PCBs) inside
  2. Even if there was, the unit would have to be extensively modified as it seems to run two sets of two 18650s in parallel.
  3. It does not deliver sufficient current anyway.

Not worth the effort…

Ordered. Report to follow.