Portable power for a ham station

Regional 2016 National Preparedness Month Logo
National Preparedness Month 2016

This post is the 6th in a series – Especially since this month is national preparedness month, investigating off-the-grid power is my next stage of going portable. I’d like to have something light, rugged, safe, cheap and that can run my ICOM 7100 for at nearly a day (but not at full power). There are clearly going to be some compromises involved in this choice.

I settled on 35 Ah battery as my benchmark to cost against. An amp-hour is the ability to pull one amp for one hour, or 10 amps for 1/10 of an hour… It’s not quite that simple, since you can’t pull too much power from certain kinds of devices reliably. If you have a device that pulls 20 amps, and you use it for 20 minutes, then the amp-hours used would be 20 (amps) x .333 (hours), or 6.67 AH. Therefore, if you plan to transmit 20% time on HF: 20 amps x 0.333 hours = 6.67 amp hours and on receive the radio pulls 1.5 amps x 0.66 hours = 1.0 amp hours that means the radio will consume almost 8 amps in an hour. My ‘back of the napkin’ calculations say: I should be able to operate for about 4 hours at higher power levels.  Sounds like I better plan on having an amp meter in my circuit if I want to have predictable usage.

For batteries, there are a number of possibilities in the marketplace:

Weight

Rugged Safe Cheap

Powerful

Example
Traditional Lead acid

+

+

Example
AGM

OK

+ + OK

OK

Example
Li-Ion

+

+

+

Example
LFP

+

+ +

+

Example

This table is based on some quantitative analysis but I’d call it primarily a qualitative perspective. Feel free to comment with better info if you find have it.

The decision

battery-51tnl6zn1rl-_ac_ul115Since I don’t know how often I will use this portable solution yet, I didn’t want to invest in higher cost batteries or solar recharging… They’ll be time for that later, if I become addicted to being in the field. Right now I just wanted something ‘good enough’ to be usable and get started, so I went with the AGM solution.

Other considerations

Once you go with a battery based solution, you need to think about charging. Do I want to have a solution where I can switch over to battery if there is a power outage or will I depend on remembering to charge the battery before I need it? Although the switching option is appealing, I think I’ll hold off on that as well since it should be easy enough to add later.

How about connecting to the various devices? I want something flexible, standard and commonly available. I convinced myself that Anderson Powerpoles from Powerwerx are the way to go. Besides there is an HRO in Plano (near my house and they have a huge selection of options).

Next time, I will cover the circuit and configuration I ended up putting in place, as well as what Powerpole based options I purchased to get started.

Humor you may get a charge out of:

Did you hear the one about the radio operator arrested for battery? The charges were dropped because he only resisted a little.

#natlprep  #amateurradio #hamradio

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4 thoughts on “Portable power for a ham station

  1. Check out KF7IJZ’s YOU Tube channel for an in depth comparison of batteries for portable operation. Jeremy also experiments with Solar Power for Ham Radio.
    I do SOTA and Picnic Table portable at QRP power levels with a KX3. As soon as I can I’m retiring my 12V 9.5 aH SLAB and replacing it with a LiFePO4 battery.

    Like

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