Battery Supplied Station

[ab5r]

I am thinking about eliminating household AC power and powering my various devices with battery power. My devices included several scanner, seismic digitizer, and dual band transmitter. (I have no HF equipment at the time being.) All of the devices with the dual band consume low current demands.

I thought of Sealed Deep Cycle type battery. I would appreciate any suggestions and/or experience with a battery powered station..

Regards & 73,
Jerry AB5R

 

[jaspence]

If you don't use AC, your choices are solar cells or some type of generator to keep your batteries charged. If cost and local ordinances aren't an issue and you live in a good area, wind power would be a logical choice. Deep cycle batteries or ones designed for use in a solar system are best for constant charge/recharge conditions.

 

[N9PBD]

While you're looking for batteries to power your off-the-grid station, take a look at Lithium-Iron-Phosphate batteries. They're much, much safer than Lithium Ion batteries, 1/2 or less than the weight of lead acid batteries, and when their long life is over, they can be recycled as fertilizer (no kidding). Most have an advertised 1500-2000 charge-discharge cycles (lead acid deep cycle batteries are usually warrantied for 300 or so cycles). I'm going that way with my station. Rather than lugging around a really heavy lead acid battery, I'd rather have light weight, long lasting power. The down side is that they are more expensive right now. Hopefully that will continue to trend down as they are more widely adopted.

 

[prplehz]

I see I'm not the only one wanting to do this. I smell smoke and where there's smoke, there's fire .. I'm just needing to power a few scanners and one laptop.. Myself, I think I am going solar with a deep cycle battery. My hand helds can just charge internal batteries right off the solar panel itself. So those are really easy and mobile if need be. Thanks for the info on those new batteries!

 

[PrimeNumber]

I run my station 100% off of two deep-cycle lead acid batteries topped off by a small solar system. It also serves as my home's "backup generator" during hurricane season or other power outages. The batteries are Duracell 75AH Group 29's, they were about $100 each. For everyday charging, I keep an old Harbor Freight 45w panel (actually 3x15w) in the yard, while the good Kyocera 140w panel is kept inside except when the extra kick is needed. Either way, a 10A Morningstar controller runs things.

There are many good, lighter, and slightly safer alternatives to lead acid batts, but it is hard to beat their price-performance ratio, if you can live with their downsides. Say, if I had a toddler in the house, I'd really consider some of the sealed high-tech options. But with everybody over 18yo, nobody's going to shove the cat into the battery bank. If you go with conventional lead acids, be sure to pop for some good battery boxes to keep the inevitable small spills contained. Some people will try to scare you about flooded lead acid batteries, like they're miniature hydrogen bombs lurking in your home ready to wipe out the neighborhood or some such nonsense, but I assure you, I've been driving around with a lead acid battery in my car for 3.5 decades and without incident. Ordinary care when dealing with them – proper fuses, safety glasses, distilled water, and don't spark the terminals – and you'll be fine.

If you want to design up a suitable solar system from COTS parts, here's a good article to read first: Installing your own small, remote off-grid solar system by Jeffrey Yago, P.E., CEM Sizing a battery & solar system to your particular needs is sort of an art. Too small and you'll kill the battery from deep-cycling it too often, too big and you won't cycle things enough to keep the batteries happy. There are many rules of thumb, but that's a topic for another thread.

I'm really happy with the two years I've been operating on this battery/solar system. Other than topping off the batts with distilled water every couple of months, it's been maintenance free. It's certainly the most stable, noise-free power supply you'll ever find.

 

[ab5r]

PrimeNumber: Excellent information. THANKS I am not actually wanting to power the whole house, but just my radios and seismology gear that I run. BUT, you input is GREAT.
Jerry

 

[PrimeNumber]

Jerry, you're welcome. You can definitely scale things down to fit your application. There's a world of good off-the-shelf solutions out there, and an inexpensive 24 AH deep cycle battery and suitable charger – maybe solar, maybe not – would be all you need. I am running a bit more than you, with a 100w HF rig and a 75w VHF. Do consider conventional lead acid batteries, but there are a lot of good options these days.

 

[Token]

Years ago California had some pretty frequent rolling blackouts. Although we actually only ever lost power once as a result of these they were a concern, and for a while there was very real potential for them to become frequent in nature. Since they were in the summer, and since we live in the desert, my wife asked if it would be possible to build a small backup power system to take the load of say the cooling system, the refrigerator, and maybe a fan or two, for the duration of the longest anticipated blackout. Seemed like a good idea to me, and being in the desert Solar was the solution I gravitated toward.

Although it was originally intended as backup power the system needed to be cycled periodically, and I found it was actually better for the system to have a small load on it all the time. So I ended up moving all the radio (and associated) gear in the house over to the system full time. The house itself is on grid and the system is a very seldom used backup for some of the household stuff, but my radio stuff, including the computers, have been off grid since about 2004 or so.

I selected used / surplus when possible (except the lead acid batteries) and was not in a rush, so I built the system up over time. I am sure the design is far from optimal, but it does work.

Although I built pretty small to begin with I selected a pretty large charger/controller and inverter, intending to scale everything up over time. The models I used are no longer available (and I picked them up used then from a local utility), but the inverter is a true sine 4000 Watt, able to take “extended” surge use of over 6000 Watts, 24 VDC input. The charger controller is dual circuit, 12 and 24 Volt.

The solar array started pretty small, something I picked up used, I think it was initially 6 panels and about ~250 Watts. I have added to this over time and I think today it is about 2 kW. Photovoltaic power density has really come a long way, I know when I started a 45 to 60 Watt panel was killer, today you can push 250+ on a single panel and cost are well under $1.50 per Watt for new stuff.

A small bank of deep cycle lead acid batteries provides 12 VDC (~1000 AH). A larger bank provides 24 VDC (~1900 AH). The battery banks are in a small shelter outside the house, yes the shelter is insulated (to prolong battery life) and ventilated (for obvious reasons). I built these banks up a few batteries at a time. 1900 AH is unusually large for a 24 VDC system, and most would recommend you go 48 VDC or higher at those kinds of levels, but the inverter I initially picked up was 24 VDC, so I have stuck with it.

For initial cost vs power density lead acid is the way to go.

The 12 VDC is used pretty much only for radio gear, and goes to a 12 VDC buss at both radio locations in the house (the radio room and the living room). Running 12 VDC a distance can present some interesting issues, but nothing that can’t be overcome with planning. Most of the radios here run on 12 VDC.

The AC power from the inverter is taken to both radio locations and a couple of other locations in the house. For radio applications the computers, the amplifiers, and some radios / ancillary gear that will not operate on 12 VDC, are on the AC. I do have a couple of legal limit amplifiers here. I can operate them, however I do have to remember I am on solar when I do. Extended operation can really draw down the system and exercise it to the max. But other than when using those amplifiers I never have to really think about the fact I am on solar.

T!

 

[ab5r]

PrimeNumber: I have a hang-up when deciding the proper selection for AH for the batteries and what solar wattage would be needed to charge the batteries. Also, is the charging a trickle type or cycles when needed?

Token: Thanks for you input. It sound great. I guess all this DIY stuff kinda scares a person, not to mention costs. Of course, doing it over time would alleviate that pressure somewhat.

Thanks to BOTH of you.

 

[PrimeNumber]

Tolken, it sounds like your solar system is in the general vicinity of where I want to build toward. Congratulations for being there already.

ab5r, let me take the easy question first. Off of my small solar system, it's basically a slow-but-not-quite-trickle charger. The 45w HF panels can put out about 3.5 amps at full-tilt in the sunshine, and the charge controller bumps that down to what the batteries need at that moment. When I'm transmitting at full power, my radio pulls ~22 amps straight off of the batteries, but it's an intermittent load. Think of the battery bank as a water storage tank that can dump a lot of water fast or a little at a time, while the solar system keeps it topped off at a slow, steady pace. (And if I need more, there's the 140w Kyo panel ready and standing by.)

Now for the harder question: how big a power system for your needs? First, figure out how many AH your system will draw over the course of an average-to-hard day's use. Remember, when you transmit you may be pulling 20A, but even when actively talking you're probably not transmitting more than 1/3 of the time. You want about 2+ days' reserve of batteries when fully charged, drawing down to no more than 50% over those two days, so multiply your daily AH estimate by 4 and round up to the next bigger size of battery. When in doubt, go a little bigger.

Having the battery size now estimated, the next question is how much solar panel do you need? Probably enough to recharge your batteries in one day when they're down 50%, maybe a bit less. Use an insolation map (here's one: US Solar Insolation Map) to guesstimate the number of average hours you'll get sun. Then divide half your battery bank's AH capacity by that number, and that's how many amps of panel you'll need. Multiply that by 17 (real volts from a nominal 12v panel) to get the panel watts. If you can find a panel that's close to this you're golden, but if you go as much as a factor of 2 down it's no disaster. You can always another matching panel later if it turns out to not be enough.

Then pick out a charge controller. They come in two types, pulse width modulation and maximum power point tracking. PWM's are cheaper and probably better for small systems like you're contemplating, but the MPPT's are a bit more efficient which counts on bigger systems. Pick out a controller that has a tad higher amp rating than your panel, or maybe 2x that if you're thinking you may later expand the system.

There, that wasn't hard, but there are a lot of steps. Earning your ham ticket at any level shows that you've got more than enough technical savvy to pull this off. Start with an estimate of a day's load and work it from there. Do the calculation once, sleep on it, and do the calculation again from scratch. After a while when you're pretty comfortable with the numbers, buy your stuff and wait for the Big Brown Truck of Happiness to show up, then have fun wiring. Good luck, and feel free to ask any more questions.

 

[nanZor]

I have a hang-up when deciding the proper selection for AH for the batteries and what solar wattage would be needed to charge the batteries. Also, is the charging a trickle type or cycles when needed?

PrimeNumber has done an *excellent* job of describing the task at hand! Most notable is the mention of insolation hours at your geographical location, which is far different than just sunrise-to-sunset hours. Not using insolation hours is what kills most solar projects from the start, so good going PrimeNumber. But by far the biggest issue is not knowing how much power you actually NEED each day and winging it with a random battery choice.

What I would suggest is to divide up the project into smaller pieces and work your way up rather than throwing a whole wad of cash at the project.

For instance:

Your dual-band transceiver probably draws about 1a on rx only. Want to power that for 24 hours? Since you don't want to exceed about 50% of a battery's capacity during any one cycle (that is if you want any sort of decent cycle life), you would need a battery of at least 50ah capacity. (1a for 24 hours = 24ah, about half the capacity of a 50ah battery). Add a few short qso's per hour, and perhaps you'll only be able to run 20 hours.

Many would recommend a very nice TRUE deep-cycle battery like golf-cart batteries, BUT when just starting out, you are likely to make mistakes and an inexpensive "dual purpose" deep cycle makes a good "learner" battery that usually ends up being abused at some point. Do your abuse on inexpensive batteries first! Dual-purpose batteries are not true deep cycle, but fare much better than "SLI" or starter-batteries not intended for deep discharge.

If you find a dual-purpose that has an "RC" rating common to most starter batteries, then multiply the rc value by about 0.6 to get close to a "20 hour capacity rating."

I won't even get into solar at this point, but perhaps get a good battery charger and see how things go. My personal favorite is the Tecmate-Optimate 6 model TM-181 (5a smart charge), although this usually spawns a whole host of what everyone thinks of as their favorite. Note that most chargers from the auto-parts dealers are pretty bad, lack precise charge voltage details etc, will actually overcharge a good battery since they are usually designed to hammer abused batteries etc etc. At least with the Optimate, it is up to you if you want to hook up and walk away, or geek out and get into all the blinky lights.

Anyway, before even getting to solar, just think batteries at this stage. Add up all the current your 12v devices need, multiply that by hours of use each day, and double that value for your battery capacity. Amazingly, just a few scanners and other radios that have low current draw like only 1ah, can add up FAST over time. You may need a FAR bigger battery than you think when you add it up, and now you can plan what it takes to charge it via solar.

It is better to find out that your battery needs may be too big to be practical from the outset, but of course anything can be done.

 

[ab5r]

Hertzian: Excellent advise as-well-as PrimeNumber's. Thank you very much.

Now to throw a monkey wrench into the whole scenario:

I also have a seismology hobby which requires ultimately a 24/7 computer display, A/D Digitizer/Amp and sensors. While I WAS referring to maintaining my radios; I also have to supply 15-24vdc to my A/D digitizer. This paints a whole NEW picture. I was thinking of maybe TWO 12v batteries in series and running radios off one an the digitizer off BOTH. Recharging may present another challenge.