Easy Project

System

New here and new to Solar power.

I have a little project I've been working on and I'm trying to size a small solar panel and battery to use, maybe a charge controller, if needed.

My load is approximately 600mA @ 12vdc. I was looking at a 5 watt panel and a small sealed lead acid battery, like a security system battery.

I need to have power around the clock.

Thanks for any help!

mike95490

Re: Easy Project

todds wrote:

My load is approximately 600mA @ 12vdc. I was looking at a 5 watt panel and a small sealed lead acid battery, like a security system battery.

I need to have power around the clock.

Does that mean you need to power the load 600mA, 24/7 ? or are you using the battery to backup another primary power source?

If 24/7 .6A x24hr = 14.4 AH load over 24 hrs.
Recharge needs 17.5AH min ( battery recharging losses )
5 hours of prime sun @ 15V & 3.5A = 52 watts of solar output, needing about an 80 or 100 W panel

Your battery, to run only over a 24 hr cycle, avoiding lower than 50% discharge, would need to be at least a 35AH capacity, but the first cloudy day will not recharge it. How many cloudy days will you want to accommodate?
You may then need to get a larger panel to recharge the battery in 1 day after a cloudy day.

Your Mileage may vary

System2

Re: Easy Project

Thanks Mike for the response. The whole cloudy day, night thing is confusing. Yes, I would like to have the power there 24/7, but I could turn the devices off during the night (camera 160 mA and wireless video xmtr 440 mA).

My first thoughts were to just use the 5 watt panel that outputs 600mA to power my devices.

System2

Re: Easy Project

If you can turn the load off at night, GREAT!! Energy conserved (not used) costs you nothing.

Re your 600 ma output panel - - that 600 ma, would be for best conditions, at mid day bright sun, which only lasts for a couple of hours or so, if that. All other times, the output will be lower and on a cloudy day, you will get little or nothing from the panels. They need bright sun on a clear day to produce anything close to their rated power. So. even if you had bright sunshine 24/7, your panels still couldn't run your load. And no, the panels won't charge by moonlight.

System2

Re: Easy Project

Thanks, Wayne.

I think I need to find a smaller power consuming video transmitter. That 440mA is killing me!

niel

Re: Easy Project

todds,
what video transmitter are you using just for my curiousity? specs on it if you know? 440ma is a great deal of current for a low power transmitter unless it's possibly not a low power transmitter.

mike95490

Re: Easy Project

todds wrote:

Thanks Mike for the response. The whole cloudy day, night thing is confusing. Yes, I would like to have the power there 24/7, but I could turn the devices off during the night (camera 160 mA and wireless video xmtr 440 mA).

My first thoughts were to just use the 5 watt panel that outputs 600mA to power my devices.

Because the voltage and current will vary over the course of a day, you will need a charge controller and battery to even things out. A small gell battery will work, but they are not made for cyclic use, only for a couple of deep cycles, and then they are expected to be "tossed". Whe it dies, replace it with a 12V deep cycle gell battery.
You will need more solar, at least 2 of the 5 watt panels, and maybe 3. depending on your local conditions, you may be able to get by with 10W of panel, but I suspect you'll need at least 15watts, of REAL panels, not some of the junk toy panels sold by surplus tool stores. I saw someplace, Morningstar had a nice charge/load controller, with programable load timer, dusk to dawn - dawn - dusk, and all sorts of varied combos.

Brock

Re: Easy Project

Not to get to far off topic, but the X-10 home series stuff runs on 12vdc and pulls about 30-50mA.  The power supply for them is rated at 400mA.  I have run them fine from a 9v battery for a couple of hours.  They transmit out in the open a good 1000 feet if line of sight.  In a house between floors they are OK.

crewzer

Re: Easy Project

I saw someplace, Morningstar had a nice charge/load controller, with programable load timer, dusk to dawn - dawn - dusk, and all sorts of varied combos.

This is probably the controller to which Mike is referring: http://www.morningstarcorp.com/products/SunLight/index.shtml

HTH,
Jim / crewzer

niel

Re: Easy Project

brock,
you may have hit right on the head here what the problem may be. it may be the supply is rated at 440ma and the load may indeed be something else lower. only todds can verify this for us.

System2

Re: Easy Project

yeah, hopefully Brock hit it.. I wanted to take some measurements this weekend, but didn't get chance. It's not an x10, but pretty much the same type. I've had it for years , plugged in, of course. I was just trying my foot in solar..

Thanks for all the replies, and advice..

Brock

Re: Easy Project

If you get to take a look see if it is really running on 12vdc If it is you can skip the inverter which would save you a bunch in power loss. Basically you could avoid going from 12vdc to 120vac and back to 12vdc again.

mike95490

Re: Easy Project

or even use a small DC-DC converter, they often are in the 90% efficient, better than a 75% inverter and an 95% wall wart. Sometimes hard to find, but they exist

TI: $8 90% efficiency adjustable output voltage
http://focus.ti.com/docs/prod/folders/print/pt6101.html

( These are not simple linear regulators, that need a heatsink and get hot, True DC-DC converters with 1MHz osc inside to run the magnetics. )

Brock

Re: Easy Project

Mike good point I have a bunch of our cordless phone and other similar items on 12vdc to 9vdc adapters right from the bank. Works great!

System2

Re: Easy Project

Brock wrote:

Mike good point I have a bunch of our cordless phone and other similar items on 12vdc to 9vdc adapters right from the bank. Works great!

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Interesting about your cordless phones operating right from the bank. I've never had the courage to try that, as any cordless phones I've checked out have not had electrical isolation between the phone line input and the DC input, so I was always very concerned about feeding the phone lines through the phone to ground, via the PV / battery system and causing problems with the phone company.
Wayne

Brock

Re: Easy Project

Hummm, hadn't thought of that. I did check it when I first installed it to see what it was pulling both at 9vdc and 12vdc before the adapter and it was really low, like 20mA just sitting and about 100mA in use and while charging afterwords. I am not sure but I have never had an issue, could just be lucky?

System2

Re: Easy Project

Yeah, maybe you are just lucky. or perhaps it's just me being overly cautious.
Anyone else running cordless phones powered directly from of-grid systems?
Thanks
Wayne