Off-Grid remote radio powering

K1UO Larry · November 2023

Is anyone on here powering a remote radio location using solar and batteries and what about powering a legal limit amp?

Geoff AB6BT · November 2023

Quick calculation...assuming amplifier in 50% efficient, 1500W*2 = 3000W

You'll probably be using an inverter to power the amp...if inverter efficiency is 80%, 3000W/0.8=3750W.

So 5000W inverter?

3750W/13V= 288A. So from there you can calculate battery capacity and runtime for the amp.

i'm sure others have real world experience.

KD0RC · November 2023

The chemistry of the batteries also needs to he taken into consideration. Lead acid batteries typically cannot be used below about half of their rated capacity. Lithium batteries can be used to 80 or 90 percent of their rated capacity.

It is a crime that a 100 amp-hour deep cycle battery is a 50 amp-hour battery for all practical purposes.

I changed my 5th wheel camper over to a pair of 100 amp-hour lithium batteries and put 400 watts of solar panels on the roof. I have a 2000 watt inverter. While I can run my KPA 500 this way, I find it impractical, so now I just run my Flex 6400 barefoot when I take it on the road.

You need to factor in rainy or cloudy days, shadows from trees, etc when determining solar capacity. I live in CO and get a lot of sun, but wouldn't you know that FD weekend was rainy the whole time and I needed my generator...

The percentage of night time vs day time operations is also a factor. The extra oomph that you get while the panels are producing power can really help.

WX7Y · November 2023

Hi Larry, I am 98% Solar here so pretty close to being off Grid and the Amateur station is 100% off grid on running on Solar.

The size of batteries really depends on the Duty cycle at which your running in TX.

The Amp at 240V is probably fused at 15A per leg and probably draws less then 12A per leg or less on the Voice peaks and CW key_up and how much are you Transmitting and how much Receiving time.

The Inverter needs to be large enough to handle the PEAK load for a tube amp drawing 12A per leg is a total of 2,880 Watts total ( IxE=P ) 120V x 12A = 1,440 Watts x 2 =2,880 Watts.

I have a LARGE (60KW) battery bank here and I can run the whole House/Shop for a few days with no sun without changing my wifes power hungry habits, probably more than a week if we went to conserve mode with out the Central air or Christmas decoration's going.

The key is get a 220V Inverter that is large enough to handle any future add on's AND that you can Parrel more than one inverter together to give you room to grow.

I use the MPP 6500 Inverter Chargers here which give 6500W @120V per leg and so for 240V you need two of these to give you 220V. This is give you equivalent to nearly a 60Amp @220V service. I have 4 of these inverters for 120A @ 240V service.

Of course if your just wanting to power your Shack you can get by with much smaller inverters to give you 240V @ what ever current your after.

ALL IN ONE Solar Inverters/chargers are NOT very expensive if you ONLY do it once and get a system you can grow both battery's and Inverter size.

I run my Flex PGXL and half the house and I never had a issue even when I was running a 3000W per leg inverter

KD0RC · November 2023

Wow... I'm coming to your house when the apocalypse hits... 😁

WX7Y · November 2023

Amen on trees and Winter months, I built my system for Winter solar time which is only about 8 hours on a good sunny day at 39* Latitude.

Off-Grid remote radio powering

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