I sort of winged it on my calcs for power for my first solar site. Anybody have some input?
My system draws under 1amp (at 13.8v dc) on standby and 3 amps on transmit. On a day to day basis, I am guestimating that the repeater will be in use for 3 hours maximum.
24 amps + 9 amps = 33 amp hours a day.
I have been running battery banks of 1600 amp hours with two 120watt (7.1 amps) panels. Site is located at 12,000 feet at 39.01'884" 106 22' 043" (Twin Lakes, Colorado) is that enough power for a worst case scenario? It worked well throughout the winter (no battery freezes).
Just wanted to know what you all think...
Howard
Calculating power needs/backup at solar site...
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Not to be too picky on your calcs, but it will be 21 hrs x 1 amp equals 21 amp hours/day standby. 3 hrs x 3 amps equals 9 amp hours/day TX.
21 + 9 = 30 Amp hours/day input power.
Other things to consider:
- Battery tempeature (batteries de-rate as temp. drops
- Days of autonomy required. In our area we use 30 days (autonomy = total days without any charge such as pacific northwest winter).
- Maximum allowable depth of discharge (typiclaly don't discharge a battery more than 80%).
Your 1600 AH of batteries = 1280 AH at 80% discharge. Derate that 1280 AH by 20% for cold temp. = 1024 AH.
30 AH/day times 30 days = 900 AH.
Looks good.
you might also checkout the newsgroup alt.solar.photovoltaic
21 + 9 = 30 Amp hours/day input power.
Other things to consider:
- Battery tempeature (batteries de-rate as temp. drops
- Days of autonomy required. In our area we use 30 days (autonomy = total days without any charge such as pacific northwest winter).
- Maximum allowable depth of discharge (typiclaly don't discharge a battery more than 80%).
Your 1600 AH of batteries = 1280 AH at 80% discharge. Derate that 1280 AH by 20% for cold temp. = 1024 AH.
30 AH/day times 30 days = 900 AH.
Looks good.
you might also checkout the newsgroup alt.solar.photovoltaic
I'd quibble with the notion that a depth of discharge of 80% is acceptable. If these batteries are flooded cells, discharging to 20% remaining will pretty much give them a terminal illness. If they are quality gel cells, they might take this once or twice, but not on a regular basis. The rule of thumb is to limit depth of discharge to 50%.
Note that if flooded cells are discharged without recharging for 30 days, they will sulphate, and this will result in a permanent loss of capacity. Some of that capacity can be regained by a timely "equalization" charge, but this requires specialized equipment and operator presence on site. Gels are far more tolerant of discharged-state storage.
If your installation is important enough, note that you can substantially improve battery life (while reducing the size of the required bank -- batteries are expensive) by installing a comparatively small genset connected to a battery monitoring system with a genstart switch. (Xantrex makes these.) The monitor will start the genset at any pre-defined depth of discharge (50-60% is typical) and shut it down again at a pre-defined higher depth (85-90% is typical; there is a point of diminishing returns trying to recharge deep cycle batteries with a genset; let the solar get you back to 100% next time the sun comes out). The genset has to feed a "smart" charger, which can be an additional component of the monitor system. Finally, if you have a phone line available to the site, you can hook a modem to the monitor and periodically check the cumulative commanded genset runtime, which will tell you when it is time to refuel (if the genset is liquid fueled).
Note that if flooded cells are discharged without recharging for 30 days, they will sulphate, and this will result in a permanent loss of capacity. Some of that capacity can be regained by a timely "equalization" charge, but this requires specialized equipment and operator presence on site. Gels are far more tolerant of discharged-state storage.
If your installation is important enough, note that you can substantially improve battery life (while reducing the size of the required bank -- batteries are expensive) by installing a comparatively small genset connected to a battery monitoring system with a genstart switch. (Xantrex makes these.) The monitor will start the genset at any pre-defined depth of discharge (50-60% is typical) and shut it down again at a pre-defined higher depth (85-90% is typical; there is a point of diminishing returns trying to recharge deep cycle batteries with a genset; let the solar get you back to 100% next time the sun comes out). The genset has to feed a "smart" charger, which can be an additional component of the monitor system. Finally, if you have a phone line available to the site, you can hook a modem to the monitor and periodically check the cumulative commanded genset runtime, which will tell you when it is time to refuel (if the genset is liquid fueled).
Sun is pretty plentiful here. All charts that I have seen give an equivlant of 4 hours of sun per day. I would imagine that 4-5 days would be the outside of not receiving a full day of sun. We average 250 days of full sun. I have been using flooded cells. Genset is out of the question as these sites are located in USFS land.
The adjacent "wealthy" county neighboor to the west (Aspen) has full telemetry on their solar sites.
Within the last year I took this county from using CSQ to voted repeaters....
As for the temps. Yes they wil be darn cold, but in a smaller cabinet I am hoping for a little warming. Daytime summer temps never exceed 75 degrees and running under 15 watts is not going to generate much heat.
Howard
The adjacent "wealthy" county neighboor to the west (Aspen) has full telemetry on their solar sites.
Within the last year I took this county from using CSQ to voted repeaters.... As for the temps. Yes they wil be darn cold, but in a smaller cabinet I am hoping for a little warming. Daytime summer temps never exceed 75 degrees and running under 15 watts is not going to generate much heat.
Howard
Solar Powered Repeater
While 1A standby is OK for grid powered systems, you can see that it eats heavily into your solar budget as a load that has to be supplied 7 x 24 x 365. Anything you can do to reduce standby current is likely less expensive than the solar panels and battery. For instance, consider that radios made specifically for mountain top / solar use (Daniels Electronics. Glenayre used to make this stuff too) have a standby current of ~ 50 mA.
Of course, then you have other equipment, and controllers that draw power too....
I've had a solar powered repeater on the air since the early 90s with nothing more than a 100Ah 12V battery with no power related interruptions. (see http://www.qsl.net/va3pla for technical details). But of course, it is only hobby radio, so I can take my chances with a small accumulator size.
RFDude
Of course, then you have other equipment, and controllers that draw power too....
I've had a solar powered repeater on the air since the early 90s with nothing more than a 100Ah 12V battery with no power related interruptions. (see http://www.qsl.net/va3pla for technical details). But of course, it is only hobby radio, so I can take my chances with a small accumulator size.
RFDude
Unfortunately I was have a short build season at this site. Grant funding was awarded in August and I had to have this done by the end of September.
The reps for Daniels were non too helpful (i.e. didn't seem to want my 70k worth of business) Plus with all of the federal grant money floating around there lead time was 12-16 weeks.
I emailed an Icom dealer at 9pm on a Sunday night. He called me at 8am Monday. I had the repeater in my hands by noon on Tuesday
I never even got pricing on the Daniels. I bought the Icom for $2500. Now I am paying the price in Solar panels and batteries
(well not me, my employeer 
)
The reps for Daniels were non too helpful (i.e. didn't seem to want my 70k worth of business) Plus with all of the federal grant money floating around there lead time was 12-16 weeks.
I emailed an Icom dealer at 9pm on a Sunday night. He called me at 8am Monday. I had the repeater in my hands by noon on Tuesday
I never even got pricing on the Daniels. I bought the Icom for $2500. Now I am paying the price in Solar panels and batteries
(well not me, my employeer )Solar Powered Repeater
Too bad about the Daniels non-response....
Look at the schematic of the Icom and see if there are circuits that you can de-power. Perhaps wire them into an extra switch you install, so that you can turn these parasitic loads back on when you need them.
One of the gov't agencies around my area that have lots of solar powered sites use Motorola Desktrac of all radios... but they go into the radio and disable the LEDs and anything else that draws unnecessary standby current.... This can also include the audio amplifier stage. Just some ideas for you.
Good Luck.
RFDude.
Look at the schematic of the Icom and see if there are circuits that you can de-power. Perhaps wire them into an extra switch you install, so that you can turn these parasitic loads back on when you need them.
One of the gov't agencies around my area that have lots of solar powered sites use Motorola Desktrac of all radios... but they go into the radio and disable the LEDs and anything else that draws unnecessary standby current.... This can also include the audio amplifier stage. Just some ideas for you.
Good Luck.
RFDude.