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AA4PB

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Battery Power
« on: April 08, 2005, 08:17:19 AM »

I've been experimenting with a true sine wave inverter and 100AH AGM battery. The battery and inverter are out in the garage about 30 feet away from the radio. Very little power lost in the connecting cable because its operating at 120VAC. The radio gets a nice clean 13.8VDC right up until the battery reaches 10V and the inverter shuts off. In addition, I can operate a room light and accessories like the antenna rotor. No RFI detected from the inverter.

The question yet to be answered is whether you get more total life from a directly connected battery (considering the loss in the cable and the fact that the radio doesn't do well below 11V) or the inverter (considering the loss of the inverter and power supply but operating down to 10V).

My thought is that I can charge the battery from the 12V output of the generator when necessary and yet the generator can be shut down for refueling without loosing power. It also opens up the possibility of using solar power during a prolonged power outage. One of the issues with a generator is that you can only get about 24 hours of operation from the amount of gas that you can legally store at a residential location (5 gal in the generator and a 5 gal can). During a power outage purchasing more gas is pretty much out of the question.
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Bob  AA4PB
Garrisonville, VA

KC2MMI

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« Reply #1 on: April 14, 2005, 08:18:21 PM »

If you are running a 12->120V inverter at the battery, and another 120->12 inverter at the radio, or in the radio, you're using two inverters which in the best case are what, 90-94% efficient each? So you're getting
something like 92% of 92%, or 84% efficiency.

If you ran battery cables directly, with a 60 foot round trip, and a 20 amp tx draw, you could use 4AWG (or 2SAE) gauge cable and only have a 3% loss. Net gain of over 10% by getting rid of the AC lines.

Now, if you used a buck booster by the radio to boost the battery voltage up to 14.4 even as the battery voltage dropped...those have some loss too, but your radio might perform a lot better getting full voltage. And still outperform the dual inverters.

You'd need to confirm your rx and tx drains, double-check the wire run length, etc. to detail it, but I'm betting AC is not the way to go. (Aside from it being nice to have in the shack.)
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K2GW

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« Reply #2 on: April 15, 2005, 05:40:44 AM »

>>One of the issues with a generator is that you can only get about 24 hours of operation from the amount of gas that you can legally store at a residential location (5 gal in the generator and a 5 gal can).

Interesting point I hadn't heard of before.  Who's law is that?

Thanks & 73

Gary, K2GW
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KC2MMI

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« Reply #3 on: April 15, 2005, 07:09:32 AM »

Gary-
 <Who's law is that? >

Most cities and incorporated municipalities have FIRE LAWS to prevent devastating fires. For instance, in NYC it is illegal to have a "standard" 20# propane bbq tank stored in a residence. Gasoline must be in a metal, not plastic, approved container.

And over the border in Nassau County, it is legal only if stored outdoors, not in a home.

In NJ, you can't pump your own gasoline, you have to let the attendant do it. All fire laws.

Considering how many cigarette smokers set themselves and gas stations on fire every year...small wonder. Even NYC had two "great fires" before wood constuction was banned here.
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W0IPL

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« Reply #4 on: April 15, 2005, 12:20:17 PM »

If you are having problems getting full output from your radio (shutdown = no output) you might want to investigate running two 12V batteries in series and then an Astron N2412-24 regulator. This produces regulated 13.8V (it is rated at +/- .01V regulation - no load to 20Amp - I see +/- .1V on mine).

This would allow you to run some #4 wire to bring in the 24V and solve the low voltage drop out AND get full output from your transceiver(s).

I have been running this configuration for most of a year now and have had ZERO problems with it. I do run a pair of deep cycle batteries - just in case.

C Ya
 Pat
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KE4SKY

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« Reply #5 on: April 15, 2005, 01:36:23 PM »

F-3201.2 of the Virginia Statewide Uniform Fire Code  prohibits storage of more than 5 gallons of gasoline in residential areas
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AA4PB

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« Reply #6 on: April 16, 2005, 08:50:12 AM »

No doubt that #4 wire and a DC/DC regulator would be more efficient. The regulator here is key in order to keep the radio functioning properly as the battery voltage drops.

The convience of having 120V AC available to run accessories like the rotor, etc. is probably worth the added 10% loss of efficiency. Not having to deal with #4 wire is a benefit as well. I just have to use a larger battery to make up the difference in operating time.

In the real world I suspect that the 10% figure is too low. The inverter is rated at 93% efficiency but that is under full load. I expect that during receive the current usage is low enough that the 150 mA needed to run the inverter circuitry has a significant impact over time.

I've also found that the inverter output is actually 115V rather than 120V. The computer UPS switches over to its own internal battery because the voltage is too low. Perhaps there is a means to either change the UPS threshold or increase the inverter output, but there are no schematics on either.
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Bob  AA4PB
Garrisonville, VA

WA4MJF

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« Reply #7 on: April 17, 2005, 10:12:16 AM »

I would use a generator, because although
batteries may power the radio, you still
gotta eat, keep your coffee maker, freezers, refrigerators,
range, hot water, well pump, lights, heat/AC,
etc running to produce a well fed and
comfortable operator to continue operations.
Alos, in my case, my OES duties require that I
be able to use most all of my radios, my FAX
and computer network.  Lot to ask of batteries.

I don't know about MOGAS storage in NC,
because I don't have any stored here.

Howerver, I use propane for my generator and
have a tank of sufficient size to run the
house for 5-6 days according to the calculations.
I've never been without power for more tha 4
days and I still had some left.  Of course,
after a long outage, you need to promptly
refill.  Exercise the generator weekly, too.

73 de Ronnie
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K2GW

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« Reply #8 on: April 18, 2005, 05:39:47 PM »

>>F-3201.2 of the Virginia Statewide Uniform Fire Code prohibits storage of more than 5 gallons of gasoline in residential areas

Thanks.  It's the first I've heard of it.  

73

Gary, K2GW
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N4HRA

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« Reply #9 on: April 24, 2005, 01:14:49 PM »

I would use a good DC power supply around 20Amp, with a blocking diode between the power supply and the battery.
connect you rig to the battery,
set the power supply output to 13.67Vdc + .7VDc for the diode.
I use the above with a 370Watt 100Ah@20Hr battery
If you deside to use the DC/Dc route the batteries in series MUST be the (a) same MFG,  (b) same Rating, (c) same age so they discharge ar the same rate.
this holds ture for bateries in Parallel

My 2 cents

Lew
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KD5CFS

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« Reply #10 on: June 13, 2005, 02:51:56 AM »

I am surprised no one has said anything about the fact that he is draining his battery down to 11 volts.This is killing your battery.I never let mine get below 12.0 v,this is approx 50% discharged and will give the battery a much longer service life.
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