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Author Topic: Backup power  (Read 2547 times)

Posts: 1042

« on: February 19, 2007, 07:00:38 PM »

I'm curious as to what most of you do for backup power in your home stations.

I've just finished installing a relatively simple system that provides seamless switching between AC and battery backup w/out relays or any drop-out during change over.

We don't often get power outages in our area, but when they come it's handy to have.

I also have a generator if we get a long duration power outage, but the battery is good for at least 8-12 hours of local operations.

What, if any, provision have you made for losing the mains?

Posts: 2415

« Reply #1 on: February 19, 2007, 10:35:27 PM »

Simple. Get a marine deep cycle battery (The AGM sealed batteries are better, But cost more) Along with a good FULLY AUTOMATIC 10 amp battery charger.
Run nice heavy copper wire with a large (50 amp or so) fuse right near the battery to a buss behind all your radio equipment (And LED lights for power outages) It is nice to have one of those marine plastic battery boxes with the cover to put the battery in also.
Hook all your equipment up to the battery and you are always on stand by power. IF commercial power fails you will keep right on operating.
Generator size varies with your situation. If you live out in the country and have your own water well, You need a generator large enough to operate your well pump for water. A 5KW is a nice size to run an entire household (As long as you dont try to run everything at once!)  
If you live in a city and dont need to run a well pump, A little one to 1.5KW generator that would just run a few items in the house and charge the battery would be big enough.
This is the KISS way of doing it and works great. I have been running all my radio equipment on battery power for over 15 years now. NO elaborate switching systems to fail, NO inverters to suck up power.
I see more and more commercial tower sites with equipment operated the same way.
With a reasonable T/R duty cycle, A single battery should power your radios for at least 8 or so hours until you need to start the generator to charge the battery.
Deep cycle battery about 60 bucks, Fully automatic 10 amp charger, Around 40 bucks.

Posts: 14499

« Reply #2 on: February 20, 2007, 10:40:54 AM »

I have both a sealed battery backup and a generator. My way of doing the battery backup is to use a true sine wave inverter. That provides several benefits:

1) It means that the power line to the radio carries higher voltage (120V) and lower current. Less loss in the line between the radio in the house and the battery/inverter in the garage. If you want to spend the money it is possible to purchase inverters that include automatic AC changeover and a built in automatic charger.

2) It provides a low voltage warning and cut out. I can't discharge the battery below the minimum safe voltage (10 volts).

3) The radio gets a nice regulated 13.8VDC until the battery voltage reaches 10V and the inverter cuts off. The radio puts out full power and is stable, even under varying battery voltage.

4) I have 120V AC power available for accessories like antenna rotor and remote switches.

Bob  AA4PB
Garrisonville, VA

Posts: 21764

« Reply #3 on: February 20, 2007, 01:58:41 PM »

If the RV is fueled up, I can step outside and start its generator, and just operate from there.  Its tank holds 55 gallons and that will run the generator for an entire weekend.

Of course, then I won't have any gas left to go to the station and refuel...hmmmm...well, there are a few kinks to sort out.


Posts: 3746

« Reply #4 on: February 20, 2007, 02:53:41 PM »


I have three 12v 38 ah sla batteries that were removed from large datacenter UPS systems.  I use these to run fluorescent camping lights and stuff for the kids.
You can get these at most hamfests.

For the radios, I use Liebert sinewave UPS that were removed from supermarket point of sale systems, just needed fresh batteries.  We change out the same type battery in the ups in the datacenter at my office so I used them at home and give away the rest to field day operators, club members who do public service events.

I also have a small 5kw genset but have never needed yo use it since I purchased it three years ago.  If I did not have it, I would have needed it several times !

73 james

Posts: 548

« Reply #5 on: February 20, 2007, 04:37:25 PM »

I use a whole-house UPS system rated at 5.5 KVA continuous, 10 KVA surge. It pretty much powers the entire house (minus a few non-essential, power hungry loads) with no problems, including the fridge, window air conditioners, etc. In fact, it's built-in transfer switch transfers the load so quickly I often can't even tell there is a power failure, unless I happen to try running one of the non connected loads, like the clothes washer/dryer. It's powered by a bank of 24 2V/660Ah batteries good for about 30 kWh. Full description available at:

Before I got the system up and running, I used an Astron 25A power supply with the battery float charger mod with six 12V/25Ah gell-cells under the radio bench. Still sitting under there, in case all else fails!

73, de Tom, KA1MDA

Posts: 11


« Reply #6 on: February 22, 2007, 11:23:19 AM »

I have changed my battery set up as I used to keep the battery floating off the power supply all the time. The problem is if the power goes out and you have something on they battery might be drained when you need it. I now keep my battery charged with a stand along charger, and have a large manual switch so I can switch between the power supply and the battery. This also eliminates the problem of the PS dumping too much current into the battery when it needs to be recharged. Just my 2 Cents on the subject.

73 e KB9JJA

Posts: 1042

« Reply #7 on: March 31, 2007, 12:22:08 PM »

Free batteries:  Is there any other great kind?

I was just given two 34 Ah/Hr AGM's, pulls from a mobility cart.  Replaced early to upgrade the cart to 50 Ah/Hr's.  

These beauties are just about perfect for field day as they have handles and weigh about 25 lb. each so are not too hard to carry around.

I guess I can add as many as I can collect to the array.
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