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DIY Powerbank with 18650 cells - anyone tried these ?

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.

I had a USB powerbank with 3x 2.5AHr 18650 cells in it. The cells were in parallel and there was the standard dual USB A socket outputs and a USB microB input along with 2x 5V outputs at 1A and 2A. I ripped it apart, removed the charger+inverter and wired the cells in series and brought out the individual cells so I could balance charge it.

Now I have a 2.5AHr pack that can drive an 817 to full output that looks identical to a normal USB powerpack. The kind of thing airport security people see in the millions every year and don’t care about. I just need to remember not to plug my phone into it !

It seems like it’s very easy to homebrew a spotwelder:

That goes a bit easier on the cells than a soldering iron; does a nice looking job too. I keep meaning to knocking one up for myself. I’ve taken apart a few old laptop batteries now, and the cells were all in perfect working order. It’s possible that the circuitry is failing, rather than the cells.

Here’s something I’ve been playing around with for backup for my KX2. Batteries https://www.all-battery.com/tenergyli-ion1865037v2600mahrechargeablebattery-30005.aspx same folks who make the battery pack for the KX2 and for a holder/tray https://www.batteryspace.com/Battery-holder-Li-Ion-18650-Battery-Holder-3S1P-With-2.6-long-20AWG.aspx. Voltage is set at 11.1 have not tested extensivity-has built in PCB module. Waiting for my holder to come in but I’ve work with the parallel version and seems ok. The 3S1P is in series and will put out 11.1 volts (3 cells) according the Battery Space, expecting today. They also make a tray that holds 4 cells that puts out 14.8 if you need/want more power. The batteries have to be the “flat top” to work with the tray. Also for a battery charger https://www.all-battery.com/UniversalSmartChargerfor3.7-14.8VBatteryPack-01281.aspx (same one used by Elecraft)

All items chosen to keep your pack light.

Update, 3S1P arrived (3 cell in series) activated PCB at full charge output at 12.52 v. No soldering, easy cell exchange, KX2 compatible, convenient external power pack when Anderson powerpoles attached. Could not be happier.

73, John-W5FLY

I have been using this 6 amp hour version of the “TalentCell Rechargeable 12V 6000mAh/5V 12000mAh DC Output Lithium Ion Battery Pack For LED Strip And CCTV Camera, Portable Li-ion Battery Bank With Charger, Black (Multi-led indicator)”. I use it to power my FT-817 and charge the cellphone. I have also used one to power my Tinker board running WSJT-X. I have not noticed any serious RFI from the 12 volt to 5 volt converter.


73 Burke

I am coming late on this, sorry but here is another example of bad bttery banks, which are popular on eBay.

6800mAh printed on the label but below the blue coat you’ll find a Chinese 3000mAh battery and some foam to make you thinking it is a real 6800mAH battery.

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If your interested in the performance of certain cells you will find this site useful:

More on ultrafire:

I always stick to NCR, Samsung, Sony etc for 18650.

That is blatant misrepresentation, though I do think there is a misconception among some retailers who think that if one cell is 3000 maH, then 3 cells make it 9000. That is, they think the maH ratings add like the voltage does. Doesn’t excuse it, but it may be the reason in some cases. Not this one, which shows a smaller battery being repackaged to look like a larger one.
Thanks for posting the pic.
73 Andrew VK1DA/VK2UH