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Author Topic: Opinions on Campsite power solution...  (Read 1381 times)
KI4BUM
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« Reply #15 on: September 17, 2003, 04:50:26 PM »

> http://www.hondapowerequipment.com/gensup.htm

True, but it takes fuel (not solar friendly) I cant learn by openning my wallet and the big kicker...I can buy pieces parts without the wife complaining. Dropping a grand on a generator gets the wife upset Wink
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N6AJR
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« Reply #16 on: September 17, 2003, 05:57:16 PM »

75 AH is 1 amp for 75 hours, so I'm told.. but not 75 amps for 1 hour.  the higher the load the faster it drops. Good thing is 2 batteries in parrallel last longer than twice the time of one  as the plates don't get as hot.

I suggest a portable box with wheels and you can mount a small solar cell on the top, and a charger and a couple of batteries  and an inverter inside. put wheels on the bottom so when you tilt it, it rolls.

I have a 800/500 watt inverter  in my truck next to my radios ( for the coffee pot when I am working mobile)and a couple of deep cycle batteries and a 400 watt generator that puts out 110 or 12 volts, and a couple of more inverters here and there at the house.

 I think I'm ready for most power outages. use what you need to do what you want.

How about picking up and old travel trailer ($400- $500) and putting all yout mobile power and radio stuff in there with solar on the roof, and a generator, a couple antennas mounted on the roof, and an outside plug for 110 and 12 v, so you can use it at home when the power goes out, and mobile when going on a dxpedition to the local area.
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KF4MKJ
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« Reply #17 on: September 17, 2003, 07:40:29 PM »

I can buy pieces parts without the wife complaining. Dropping a grand on a generator gets the wife upset


Y'all get more snow and ice up there than we do here in Alabama.  Tell her the generator is an investment for this winter.  Hmmm I may see if I get away with that myself.  Wink

73
KF4MKJ
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KD7KCR
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« Reply #18 on: September 17, 2003, 10:23:51 PM »

this is another solution, and the price is right

http://theepicenter.com/tow082099.html
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WA9SVD
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« Reply #19 on: September 17, 2003, 10:39:08 PM »

If all you want to run is a handheld and a laptop, then yhe battery you describe may suffice, depending upon the amount of time you wish to operate and how often you can recharge the battery.  For a few hours operation one or two evenings, it might suffice.  For longer periods of operation, you need to consider a recharge strategy.  (And the inverter for the laptop may be necessary; many laptops will not work on 12 V (or below) from an external source, whwther it's the original AC supply or an external battery.

    And a "75 Amp" or more correctly, a 75 Amp-Hour battery is just that (sort of.)  It's the total amount of energy the battery can store.  At 1 Amp. draw, it will supposedly provide 75 hours of service before the voltage drops below the usable/safe discharge voltage, usually considered 10.5V.  The 75 Amp-hour rating is generally determined by the rate at which it can provide voltage for a period of 20 hours, thus:   75 / 20 = 3.75

    So that 75 AH battery can provide 3.75 amps for a theoretical 20 hours.  IF the draw is less, it may be able to provide a bit more operating time than the 75 AH rating, but if the current draw is high, it can be less.  A 75 amp draw would not be sustained for a full hour!

    The only drawback is that the inverter (if needed for the laptop) may emit considerable interference, and the laptop adapter plugged into the inverter can also cause considerable interference.  (I'd suggest running the inverter and laptop supply to charge the laptop's battery when not operating, and running the laptop off battery while on the air.)  Check things out at home before you take it on the road.  (Or off road.)
    Good luck, and have fun!
 
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KG6AMW
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« Reply #20 on: September 18, 2003, 12:36:19 AM »

The trick to maintaining these deep cycle batteries is to  not over charge them and not run them down too far.  Run a deep cycle battery down to 10.5 volts and you will shorten its overall life considerably.  Discharge it to no more than 50% of charge or 12.24 volts.  That will allow you 37.5 amps.  How you use the 37.5 amps is only limited by the Peukert Effect.  Finally, an AGM battey can do anything a Gel-cell can, only better. However, since they are also sealed, charging has to be controlled carefully or they can be ruined in short order. Check out Power Sonic Battery.

KG6AMW
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KD7EVS
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« Reply #21 on: September 18, 2003, 12:40:52 AM »

I'd suggest you use a DC adapter for you laptop instead of AC.


here is why...

setup A)

Battery (dc) > inverter (DCtoAC) > (ACtoDC) laptop adapter

B)

Battery (dc) > laptop adapter (DCtoDC transformer)


anytime you change from ac to dc or dc to ac you are losing energy in the form of heat. as stated earlier inverters aren't perfect.

in setup b you have less conversions and less components.    at home, my laptop uses the ACtoDC adapter, in the truck it uses the DC adapter which is mostly a regulator.... laptops are picky about power.


73
kd7evs
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KC7YRN
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« Reply #22 on: September 18, 2003, 01:32:21 AM »

>3.75 amps

"75 amp-hours" means amps times hours, 75 of them. If batteries were mathematically simple, it would mean you could get 75 amps for 1 hour or 1 amp for 75 hours. Unfortunately the real-life capacity of a battery depends on how fast you pull current out. It's as though your car's gas tank got smaller when you went faster! That battery will run more than 75 hours at one amp, and less than an hour at 75 amps.

So the amp-hour rating is only meaningful if you know how fast current was being drawn when the capacity was measured. Most of the time it's quoted at a rate which flattens the battery in 20 hours. 75 amp hours, divided by 20 hours, is 3.75 amps. The battery would supply you 3.75 amps for 20 hours. Draw less current, it lasts disproportionately longer. Draw more, disproportionately quicker discharge.

Except that in real life you'll wear out the battery quickly if you cycle it that deeply. If you want the battery to last, keep normal use to 50% of capacity or less.

>if you can run the laptop off 12V

Unfortunately a lot of laptops want strange voltages like 16 volts. The laptop's factory-supplied car adapter will have a DC-DC stepup circuit. N4UAU makes nifty RF-quiet stepup boxen for running laptops from 12V.

>flooded lead acid

For a battery that's going to get moved around a lot I'd prefer a sealed one myself.

>generator

The littlest Honda is about the size of a lunchbox and quiet enough for most applications. To minimize RF noise, you might run it as a charger and shut it down while operating.
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KI4BUM
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« Reply #23 on: September 18, 2003, 09:50:45 AM »

> I'd suggest you use a DC adapter for you laptop instead of AC.

Jeez...I didnt even think of that. Thanks!

-Tyler
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AD7DB
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« Reply #24 on: September 18, 2003, 10:31:29 AM »

Generators are noisy. Who wants that El Cheapo converted lawn mower engine project running at a campsite?  I read about a ham group that went to a Forest Service camground for Field Day, armed with a nice "quiet" commercial generator. They thought they were all set. At 10:00pm the ranger came by and told them they had to turn off the generator. The rules about "quiet hours" apply to all generators. QRT until morning because they had no fallback plan.

Solar panels must have a charge controller. You can't just draw all the power for your radio straight out of them. For one, the voltage is too high; it's good for charging a battery but not to run your rig. Secondly, the panel can't put out enough current at once to allow your rig to transmit with any decent power. The panel's for slow charging a battery which can handle the demand.

And solar panels are expensive. You also need to keep them in the sunlight. If you're under trees or have cloudy skies, your panel output will be greatly diminished.

No one solution applies to everything. I hope you find what will work for your needs.
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AA4PB
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« Reply #25 on: September 18, 2003, 10:47:54 AM »

I've never seen a transformer that could pass DC to DC. The auto/air adapters I've seen have some type of switching regulator in them because the output voltage has to be higher than the 12VDC input. That means a DC to AC to DC conversion inside the adapter. Still more efficient than doing two conversions with an inverter and separate AC supply - but it doesn't eliminate the DC-AC conversions.

By the way - some of those adapters can generate a lot of RFI which you may want to consider if operating it near a receiver.
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KC7YRN
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« Reply #26 on: September 18, 2003, 08:24:47 PM »

>By the way - some of those adapters can generate a lot of RFI

Absolutely right, some friends on a sailboat had their radio disabled when running a laptop from a commercial Dc-DC stepup converter. They're the ones who told me about the N4UAU RF-quiet converters. When they installed one the RFI problems went away.
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KC7YRN
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« Reply #27 on: September 23, 2003, 02:08:31 AM »

Oh, you asked for a link on self regulating solar panels. http://www.solar-electric.com/sm46.html describes one and how it works.
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