Backup power (photo and description)

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System
System Posts: 2,511 admin
in Solar Beginners Corner #1
Hi Everyone, first post here but have been visiting for a little while.
I had a nice descriptive post all written up here earlier with all the details and then got logged out somehow and lost the whole thing before I could preview it...so I don't know how much I really feel like re-typing right now...but you'll get the idea ;-)

Anyhoo I've seen a few topics regarding back up power systems and figured I'd show what I've been using. I'm in a rural area and the power goes out here surprisingly often, but most occasions are in the summer and not generally for more than a few hours at a time.

It's really more of a battery backup than a solar system for anything more than light and infrequent loads, but it does give me a lot of convenience when the grid is down.

I have;
- (1) Sunforce 15 watt panel with 7amp charge controller $99 on sale
- (2) 12v no name brand marine "deep cycle" batteries wired in parallel $112 each
- (1) PowerBright 1100 watt MSW inverter $120
- (1) Eliminator 300 watt inverter $30 on sale

I realize I probably only get 30 watt/hrs/day out of the panel
The batteries are 120 mins RC @25amps so I figured roughly I could draw a couple hundred watt/hrs out of them without worrying about sulfation while the panel brings them back up slowly...but can also just recharge from grid power if I need to use more.
That's what I have, here's what I use it for, listing wattage from the spec plate;

- Small 5 cup coffee maker (650 watt) but the inverter says it draws 550...takes about 7 mins to run.

- 19" LCD tv/dvd combo (0.6 amps)

- Small microwave (1050 watt) seems to run slow but it does work

- CFL (13 watt) lamp

- Charging iphone

Some other potential uses could be;

-Computer/wireless internet...but would probably just use my cell phone if I wanted to do a bit of web browsing

- Cordless phone...again probably just use my cell

- Charging AA's for flashlights...but generally have enough of them charged up anyways, so probably wouldn't be needed.

Again, this is really only a "solar" backup for very light/infrequent loads.
Also, it is definitely not portable. Just from reading online there seems to be a lot of people looking for tons of power for SHTF or B.O.B to fit in a backpack and go indefinitely ;-)
This is not one of those magical systems...but it does give me a lot of conveniences when the power is out- make coffee in the morning, lights/radio/movies in the evening.
If I did it again(after finding this forum) I would probably make some changes...but for less than $500 I certainly don't regret it.

img0081gk.jpg
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Comments

  • TnAndy
    TnAndy Solar Expert Posts: 249 ✭✭
    #2
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    Re: Backup power (photo and description)

    First thing I'd do is get more PV, because a 15w panel won't even keep up with the self discharge of those two batteries.
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  • System2
    System2 Posts: 6,290 admin
    #3
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    Re: Backup power (photo and description)
    TnAndy wrote: »
    ... a 15w panel won't even keep up with the self discharge of those two batteries.

    Maybe my multimeter is lying to me...but before hooking up the panel a few days ago the batteries had read 12.7 something volts and this morning before the sun came up they read over 13v (can't remember the exact numbers)
    Like I said, it's not much of a real "solar" system...but it would appear that the panel has been keeping up with self discharge and then some.

    What would be a reasonable self discharge rate to expect from these batteries ?
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  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    #4
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    Re: Backup power (photo and description)

    I have little doubt a 15W panel will maintain your two batteries. I used a 5W panel on a boat battery for a year, zero issues. Details about that project here:

    http://2manytoyz.com/solarcharger.html

    That said, 15W isn't enough to recharge your batteries. While it might replenish the energy used over a course of days, there's another issue. Batteries (obviously) contain a fluid. It requires a certain amount of movement, whether it be mechanical (on a vehicle), or stirring from bubbles. Not talking about boiling a battery, just a hard enough charge to gently bubble the battery.

    I trickle charged a battery to death over the course of a year. It was a battery tied to an inverter, only to be used during an outage. I'm in hurricane prone FL, and this was a basic emergency power backup. So much for that. My battery solution stratified. Very strong solution at the bottom, and very weak at the top of the cell. A proper charge prevents this.

    At least with the boat, it did get some periodic use - not so much during the Winter months. Never sat long enough to worry about. And when driven, the alternator charged the battery.

    For battery charging, I recommend reading this article: http://www.windsun.com/Batteries/Battery_FAQ.htm#Battery Charging
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  • System2
    System2 Posts: 6,290 admin
    #5
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    Re: Backup power (photo and description)
    2manytoyz wrote: »
    I have little doubt a 15W panel will maintain your two batteries. I used a 5W panel on a boat battery for a year, zero issues. Details about that project here:

    http://2manytoyz.com/solarcharger.html

    That said, 15W isn't enough to recharge your batteries. While it might replenish the energy used over a course of days, there's another issue. Batteries (obviously) contain a fluid. It requires a certain amount of movement, whether it be mechanical (on a vehicle), or stirring from bubbles. Not talking about boiling a battery, just a hard enough charge to gently bubble the battery.

    I trickle charged a battery to death over the course of a year. It was a battery tied to an inverter, only to be used during an outage. I'm in hurricane prone FL, and this was a basic emergency power backup. So much for that. My battery solution stratified. Very strong solution at the bottom, and very weak at the top of the cell. A proper charge prevents this.

    At least with the boat, it did get some periodic use - not so much during the Winter months. Never sat long enough to worry about. And when driven, the alternator charged the battery.

    For battery charging, I recommend reading this article: http://www.windsun.com/Batteries/Battery_FAQ.htm#Battery Charging

    Thanks for the link, I have read the charging info and know that I will still need to use my charger to bring the batteries back up after any real usage.
    Nice write-up on the boat BTW

    I do have a question, now over winter it's less likely I will need to use my batteries for a while. How often should I put my charger on to bubble the electrolyte when not being cycled ? Monthly ? 3 months ?
    How long until stratification will become an issue ?
    Thanks
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  • System2
    System2 Posts: 6,290 admin
    #6
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    Re: Backup power (photo and description)

    Another thing, as stated earlier, if I were to do it again I would make some changes...the first thing I'm thinking is when I need to replace the batteries I would go with something like a Universal Battery 22 ah sla since it would be a better match with my panel. But we'll see how long these ones last, I may have more solar input by then. Anyways, I just wanted to show what I'm using since I think there is a lot of people out there looking for similar solutions to similar situations. There is also a lot of ready-made booster/power inverters out there that do basically the same thing...
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