Over on QRPer.com, I just published a post on portable power that was The Spectrum Monitor magazine’s April 2021 cover article.
This article is essentially an overview of a few different types of rechargeable batteries including pros and cons of each chemistry.
While this article focuses on use in ham radio field applications, it also applies to anyone powering receivers–especially those without an internal power supply–in the field.
Good article Thomas. Since I live in a condo and do not have access to a proper bonding/ground rod, I run the Kenwood 590S (with attached LDG tuner) off of a 20ah Bioenno battery with anderson connectors and just run the charger after a session. I have yet to modify my car setup to handle it but that part is not expensive. Got a cheap case for the battery from Harbor Freight, too.
I am now very leery of lithium ion batteries when a small AA sized (14400) one almost melted. Lithium Iron Phosphate is the safe way to go but you need a compatible charger or you can overdrive the LiFePO4 battery during charging. I think I bought both the battery and charger from Ham Radio Outlet.
Nice summary of portable batteries.
I have been experimenting with using the Power Delivery (PD) of the compact USB-C batteries that are normally used to charge up phones, tablets and laptops.
I have several PD power supplies, but just recently acquired an Anker PowerCore III Elite. This a 25,600 mAh battery that can produce 5V, 9V, 15V and 20V at 3 A through the USB-C port. To get the higher voltages, you use a PD sink that communicates with the battery to select the voltage. There are many PD sink boards. I used one from Amazon:
This module has a USB-C at one end and screw terminals for attaching wires to the device you wish to power. There’s a button on the board which will cycle thru 5, 9, 12,15 & 20v. A LED changes color to show what voltage is selected. There’s also a way to just lock it at a particular voltage.
The Anker battery I’m using does not provide 12v (just 5, 9, 15, & 20).
I’ve been testing it using a Yaesu FT-817. The FT-817 can run at 9v and up to 16v. At 9v, it produces about 2.5 watts. At 15v, it will produce its full 5 watts. I used a USB Digital Tester to measure Voltage and Amps being delivered.
Started with a fully charged battery.
1. Called CQ on FT-8 with FT-817. 15V @ 1.88A
Worked a station from Nebraska on FT-8
Played FT-8 for about one hour.
2. Decided to really test the battery by running WSPR with the FT817.
Used 9V, which is about 2-2.5 watts out.
Set up 20% transmit duty cycle. Average of one two minute transmission every ten minutes.
Transmit at 9V, 1.76A, receive at 9V, 0.4A
Did WSPR for three hours.
3. At this point I changed it to 50% transmission.
Did that at 9V for one hour. Sometimes, it did three transmissions in a row. (almost 6 minute)
4. Switched it back to 20% and did another hour of WSPR.
5. Called CQ ten times on FT-8 at 15V, 1.76A
6. At this point battery showed 50% capacity.
7. Charged the Amazon 10” Fire Tablet from 20% to full capacity.
8. Charged my Motorola Power G Phone (which has extra large battery) from 20% to full capacity.
9. Battery now showed one light (10% capacity)
10. On Sunday morning, I checked into the PA NBEMS net running 15V
11. At this point the battery single light started blinking warming that it was near empty.
12. Took about 3-4 hours to recharge the battery back up.
Overall, very impressed.
Some of the other battery packs will also do 12v out the USB-C. For some reason, the Anker batteries skip the 12v. You need to be careful that you don’t end up supplying too high a voltage to the radio.
Fortunately, the FT-817 will handle the 15v. But I still used a USB tester to ensure that I didn’t accidentally place the battery in 20v mode.
How RF noisy is the Anker battery? Many times the different voltages are supplied with very noisy conversion circuits inside battery-side the USB connector. Would be very convenient if it is proved to be RF friendly!
There’s two ways of looking at the noise that can be generated by these batteries.
The first: If you place a radio within several feet of the battery and the PD sink, then you can definitely hear noise being generated, The noise falls off fairly quickly – within 6-8 feet, it’s mostly gone. So if you are using it with a radio who’s antenna is in that range, then, yes, you do get some noise. So you should use some coax and have the antenna a distance away from the battery.
The second: Does the battery and PD sink introduce noise through the power connection. As far as I can tell, this is no. At least on the FT-817, no noise is introduced directly from the power.
I did all my testing on an outside antenna, so I did not detect any noise from the battery.
I just did a quick test using my indoor antenna, and did notice noise when I was in the same room as the antenna. But noise disappeared (or was a lot lower) when I hooked up some coax and moved to a separate room from the antenna.
From my testing so far, I think it is definitely a viable option. A couple of these batteries would last for many hours of QRP operation in the field. Add a solar panel to recharge them, and you might be set for days of sunny operation.