In Part One, I wrote about the interaction between portability and capability with a focus on the radio transceiver itself. This time around, I would like to discuss how to pair a battery to your chosen radio.
Again, portability and capability are paramount. Batteries are among the heaviest and bulkiest elements of any portable radio station. It is worth your time and trouble to optimize the amount of battery that you bring for any given outing.
My portable batteries: the Bioenno 12Ah LiFePO4 and the TalentCell 3Ah LiIon
These days, few people carry Sealed Lead Acid batteries because of their weight and low, 50% discharge capacity. Whenever I go out and about, I now reach for either the Bioenno 12Ah Lithium Iron Phosphate or the TalentCell 3Ah Lithium Ion battery.
The Bioenno 12Ah battery is the larger of the two in every way. It weighs in at 3.3 pounds (1.5kg), measures 8.5″ x 2.2″ x 3.1″ (215mm x 56mm x 79mm), and can deliver 12V at 20A continuously via Anderson PowerPole. I originally bought this battery to power a QRO radio that I no longer own, the Kenwood TS480SAT that I talked about in Part One. It’s a bit pricey as well, costing close to $150 with a charger. It has provided me faithful service the five years that I have owned it.
The TalentCell 3Ah battery is new to me but I have owned its larger 6Ah counterpart for three years and it is also reliable. The 3Ah TalentCell matches the size of my smaller QRP equipment, costs $28, measures 4.2″ x .9″ x 2.5″ (105mm x 24mm x 63mm), and weighs 0.4 pounds (190g). Inside are three 18650 cells and a battery management system. Conveniently, it outputs 12V via a barrel jack and 5V via USB.
The Battery Capability Formula
In my quest to extend my outings with minimal weight, I’ve come up with a formula. To make the calculation, you need to know the following:
- the amp hour capacity of your battery,
- the amp draw of your radio for both receive and transmit,
- a rough estimation of your duty cycle while operating.
All of these elements can be plugged into one equation:
To work this formula, I’ve used the numbers the manufacturers have given for amp draw on transmit and receive for each radio, which you will find below. The folks at Bioenno have stated that I can discharge my battery to 80% of capacity, so I’ve plugged that into the formula. For simplicity’s sake, I’ve done the same for the TalentCell batteries. I’ve also assumed a “relaxed contest” transmit/receive duty cycle of 60% receive and 40% transmit which takes into account band changes, logging, and lulls in activity.
If the formula above seems like a lot to take in all at once, the formula can be simplified like so:
To demonstrate the formula, I’ve come up with a few scenarios involving the three radios I’ve shown in Part One.
FT-818 and 12Ah Bioenno Battery
The first setup involving the Yaesu FT-818 and the 12Ah Bioenno battery is what I call the “car camping” setup. Basically, the furthest I’m going to haul this is from my truck to the picnic table or to the tent.
After plugging in the numbers of 12Ah battery at 80% discharge, then 60% receive time at 450mA and 40% transmit time at 2.4A gives me a Bioenno battery run time of 7.8 hours with the FT-818. Definitely enough for a weekend’s worth of POTA outings without charging between activations.
MTR3b and 3Ah TalentCell Battery
Next up, we have the most common setup that I take out: the MTR3b and the 3Ah TalentCell. It gives me multiband capabilities in a light and small package. All that I have to change in the formula are the amp draws on both receive and transmit, 20mA and 700mA, and the battery capacity, 3Ah.
I tend to operate for an hour, give or take fifteen minutes. After plugging in my numbers, I can be comfortable operating up to eight parks on a single charge of this system. As an added bonus with this particular radio and battery setup, I get a voltage readout on the display in addition to the five-dot charge indicator on the TalentCell. With this combination, I know where I stand, charge-wise.
QCX-Mini and 3Ah TalentCell Battery
Now for the QCX-Mini with the TalentCell battery. While reviewing my manuals for this project, I was surprised to learn that the transmit current draw was only 350mA, half of the MTR3b. On the other hand, the radio draws more on receive at 70mA. Not extreme by any means, but still worth noting. It could be lowered if I dimmed the screen, I bet. Let’s do the numbers.
Halving the transmit draw more than makes up for tripling the receive draw. I must say, I’m surprised that I can get that much time out of the QCX and TalentCell battery! I’ve got to build an 80m antenna for this rig and get out there this winter.
Now for two setups that I will probably never press into action: the extremes of my radio/battery lineups.
QCX-Mini and 12Ah Bioenno Battery
That is an incredible battery life! Over two days of continuous usage would be a marathon session of radio for sure. Considering that the pileup would probably taper off, and that I would eat, sleep, and walk around a bit, I bet that I would get even more time out of this setup. If I ever go out to a remote place and don’t relocate for a week (or go canoeing, maybe) this battery combined with the QCX could be worth lugging into the wild.
FT-818 and 3Ah TalentCell Battery
And here, I wouldn’t pair these two together for a more practical reason: battery damage. Even though the TalentCell label says that I can draw up to 3A continuous out of these cells, I am reluctant to approach that. I’ve read that lithium ion batteries can catch on fire if not treated nicely and I don’t want to create an emergency situation while out and about.
What a useful exercise! I wish that I had done this sooner, but there is no time like the present. I hope that you can use this formula to crunch the numbers on your own setups.