Posts: 62
Threads: 16
Joined: Mar 2009
quote:
Originally posted by Hotzcatz
If you have any appliances which make a lot of heat for rather a long We ran our house on four 150 watt solar panels for seven years before we doubled our solar array to eight 150 watt solar panels. Some of the panels may be 160 or 170 watts, I think they don't exactly match, but they are close. Much more power now so we don't have to run the "iron sun" (Honda generator) very often and we can plug in more things such as a freezer and that second incubator now. At the moment, there are eight 150 watt solar panels, eight 6 volt batteries wired in series parallel to feed 24V to the inverter which can put out 15 amps max. We do have a new inverter which will be able to put out more amps with a pure sine wave but haven't hooked it up yet. We may increase the battery bank size to twelve batteries pretty soon, too. I don't know if it was that we were so limited in power before that the new array seems plentiful but we like it.
Do you not have a charge controller? The new maximum power point charge controllers are worth their weight in gold 
Posts: 2,014
Threads: 46
Joined: Jun 2003
Great discussion. You can find wire loss charts on the internet that covers most situations, be it running Helco AC power or PV. Generally, DC power from PV are probably more sensitive to wire size/distance/voltage.
I would agree with TY's battery comments. Far better to ruin a cheap set than the really good one. Wanna guess how I know that? As for adding new batteries to an existing bank, prevalent advice seems to be against it, but I think you might want to seriously weigh the situation, if talking the less expensive batteries, the trade off may be OK.
As for the battery cost question - if I recall correctly, my Interstate (golf cart) batteries were around $75 each. These replaced my "learner" set. At the other extreme, my Rolls Surettes were about $800 each, and I needed 12.
As Cat says, if you live off grid, you tend to be aware of your usage. We've spent a lot of nights basking in the glow of our oil lamps
David
Ninole Resident
Ninole Resident
Posts: 30
Threads: 2
Joined: Mar 2009
quote:
Originally posted by Hotzcatz
A Kill-o-watt meter or some such, isn't it called?
If you have any appliances which make a lot of heat for rather a long time - stoves, clothes dryers, etc., then try not to use them at all. Appliances which make a little bit of heat for a long time such as electric blankets, small incubators, etc., are fine. Appliances which make a lot of heat for a small amount of time such as a popcorn popper are good for limited use such as when the sun is brightly shining.
We ran our house on four 150 watt solar panels for seven years before we doubled our solar array to eight 150 watt solar panels. Some of the panels may be 160 or 170 watts, I think they don't exactly match, but they are close. Much more power now so we don't have to run the "iron sun" (Honda generator) very often and we can plug in more things such as a freezer and that second incubator now. At the moment, there are eight 150 watt solar panels, eight 6 volt batteries wired in series parallel to feed 24V to the inverter which can put out 15 amps max. We do have a new inverter which will be able to put out more amps with a pure sine wave but haven't hooked it up yet. We may increase the battery bank size to twelve batteries pretty soon, too. I don't know if it was that we were so limited in power before that the new array seems plentiful but we like it. There is a constant awareness of power usage when you are off the grid, though. I would suspect if folks on the grid were as aware of power usage as folks off the grid there would be a lot less power used.
"I like yard sales," he said. "All true survivalists like yard sales."
Kurt Wilson
Thanks Hotzcatz,
Yep, meter is a "Kill-A-Watt EZ". It set me back about 30 bucks. Sounds like a "1 battery per panel" ratio is a good idea.
Is there a reason why only 6v batteries instead of 12v? First thing that comes to my mind is that the 150w panels were 6v. Or am I totally missing something? Maybe they're just cheaper.
I'll have to go back to my old shop books for series-parallel diagrams but I'm assuming that' the purpose is either for the sake of redundancy or to build up your volts to a level that the 24v inverter needs?
On a rainy day like today (I'm in Pahoa at the moment), would I have enough sun/batteries to run a fridge, my laptop, catchment pump and a few cfl bulbs based on your 1st seven year system config? Oh man, the dreaded "dryer". Wasn't there a time when our parents dried cloths without an electric drier?? [ ]
Posts: 30
Threads: 2
Joined: Mar 2009
FANTASTIC Discussion!
Are there any local shops that offer very small 'turnkey' solar kits for us "off-grid beginners"? I'm also combing the web & youtube. I'm out there looking for a basic newbie shopping list.
Guys, please send me a private email if mentioning company names is not appropriate.
So far it sounds like the parts list runs as follows:
Panels and mounting brackets,
Trainer Batteries,
Signwave Inverter,
multi-meter,
and some way to tie it all into your breaker box.
But there's one more thing that everyone seems to share, and that's the pain of 'battery care'. When I was a kid working on cars for a living they always told me to keep the batteries on a piece of wood or something and to never ever set a battery on the ground. Is that all I need to know or is there more,?, because I love it when you talk about how your batteries can last 10 years if they're cared for 'correctly'.
Thanks!!!!
Chris
Posts: 62
Threads: 16
Joined: Mar 2009
quote:
Originally posted by chrism
Sounds like a "1 battery per panel" ratio is a good idea.
Is there a reason why only 6v batteries instead of 12v? First thing that comes to my mind is that the 150w panels were 6v. Or am I totally missing something? Maybe they're just cheaper.
I'll have to go back to my old shop books for series-parallel diagrams but I'm assuming that' the purpose is either for the sake of redundancy or to build up your volts to a level that the 24v inverter needs?
On a rainy day like today (I'm in Pahoa at the moment), would I have enough sun/batteries to run a fridge, my laptop, catchment pump and a few cfl bulbs based on your 1st seven year system config? Oh man, the dreaded "dryer". Wasn't there a time when our parents dried cloths without an electric drier?? []
Unfortunately, one battery per panel isn't quite how it's done. There's a reasonable amount of math involved in determining how many batteries you need. The key here is to determine how many watt hours your load list says you require. Once we have that, THEN and only then can we start to properly build your system.
Why are there 6 volt and 12 volt batteries? Because that's how they're made  Let me detail batteries a bit for you:
Lead acid batteries: this includes your 12 volt, ~100 amp hour RV/Marine batteries. For PV, as soon as you need more than one RV/Marine battery on a 12 volt system, 2 on a 24 volt system, or 4 on a 48 volt system, you want to instead move up to golf cart batteries. These have half as many cells (so they're 6 volt) but have twice the capacity per cell, meaning around 200 amp hours. Golf cart batteries are a little more expensive but their lifespan (if properly taken care of) is about twice as long.
If you need more than 16 golf cart batteries then you'll want to look into L16's which are basically double size golf cart batteries. They're 6 volts, around 400 amp hours, and about twice the life span of typical gold cart batteries. WELL taken care of L16's can last 20 years! Poorly taken care of L16's can last 20 seconds.
Would you have enough sun/batteries on a day like today? That depends on a TON of variables Chris. It depends on everything from how energy efficient your appliances are to the size of your system.
Once we have your load list, we can proceed from there
Posts: 62
Threads: 16
Joined: Mar 2009
quote:
Originally posted by chrism
So far it sounds like the parts list runs as follows:
Panels and mounting brackets,
Trainer Batteries,
Signwave Inverter,
multi-meter,
and some way to tie it all into your breaker box.
But there's one more thing that everyone seems to share, and that's the pain of 'battery care'. When I was a kid working on cars for a living they always told me to keep the batteries on a piece of wood or something and to never ever set a battery on the ground. Is that all I need to know or is there more,?, because I love it when you talk about how your batteries can last 10 years if they're cared for 'correctly'.
You'll also want a maximum power point charge controller, wire, fuses, switch gear, and maybe a couple other odds and ends like a combiner box.
Before searching for the solar kit, I'd suggest we properly size your system first and see if we can improve efficiencies there.
As for battery care, I have to run out and want to submit this before I do. I Googled for this battery care site which upon skimming, looks like a decent start. Although they don't talk about venting, how deep to cycle (never more than 50% for most batteries), etc, so it's not complete.
Posts: 3,188
Threads: 216
Joined: Sep 2007
I have done several solar residences and several sail boatsin my 20 years plus of off grid adventures. All the systems relied on a generator back up for cloudy days. I usually buy a little honda 1000, a charger and 4 of the trojan 6 volt (t55 me thinks).
Adding panels and chargers then can be done on an as needed basis.
Bear in mind though that in most of these set ups we still rely on our little honda's when overcast
Your biggest asset for your solar system will be your propane fridge however
pm me if you have questions / want help help with schematics - reasorces
suppliers:
These guys have been suppliers to off grid systems for a long time - they brought in the legendary "china diesel" gensets many of us cut or teeth on
http://www.hardysolar.com/solar-san-diego/
regards
Posts: 30
Threads: 2
Joined: Mar 2009
Thanks Yogi & Bull!!
I'm still working on the list (we've been camping).
However, I hear you guys loud n clear about sizing our load and understanding/changing our consumption habits.
With a little luck, I did find some residential 12v refrigerator distributors. One was called "Sun Frost". I'll keep you posted.
Also the 6v golf cart battery discussion really helped!
By the way there's a solar company called 'Provision' in the industrial park next to Big Isle Moving in Hilo, but they were closed. It probably was a good thing that they were closed, especially after reading your responses.
I won't be able to respond for a couple days but should have "the list" done and posted by Monday.
tytyty
Chris
Posts: 299
Threads: 49
Joined: Jun 2003
New 110 volt refrigerators are efficient. There is no reason to spend the dollars for 12 volt one, unless you have such a small system that you are going to do everything lo voltage and save the expense of an inverter.
Jerry
Posts: 2,484
Threads: 10
Joined: Feb 2008
I can't imagine that it would ever make sense cost wise to stick with an electric dryer for an off the grid system. Get one that runs on LPG. Same for heating water. If you are counting watts that closely, the electric dryer or water heater is likely to use as much electricity as all the rest of the house put together.
|
