Solar Generator Project

[geron]

Found this on another forum and is about the only one I can understand well enough to actually build it.

Would any of you "solar gurus" add any advice, comments or tweaks to the system? (Not to add any cost since this basic outfit would run about $2600- $2800)

app.box.com/s/68v8n6wxadid4s8kfrex

[missasip]

Geron, the guy spent a large amount of money for this homemade system.

I think he is lacking in battery capacity. In the long run 4-12 volt batteries will not hold the charge he is set up for in his inverters. I also think the cart is a bad idea, but that's just me. He spent all that money for the batteries, inverters, charge controllers, etc and pulls in around in a $80 cart.....

I think he may have done better with the batteries had he used 4-6 volt models. The overall amprage may not have been quite as much but they would/could be as close in capacity.

You start pulling heavy loads from those batteries with that big inverter and they won't last long.

Overkill in some areas and underbuilt in other spots. JMWAG

I would like Marc and TJ to look in on this one. Heck I may be all wet about.

Jimmy

[geron]

Thanks for the input Jimmy. This guy was using his for his Ham radio, kinda like a "go box." His idea was "portability" for field days, RACES and ARES. If I built something similar it'd more than likely be more stationary. I'd use it for emergency lighting, computer, TV, Oven glow plug and Ham radio in an emergency. It might occasionally power a power tool as well. Might also use it to run the water pump to fill the pressure tank from time to time.

[marc]

I don't qualify as a guru, so you might want to wait for one......

But I will say: If it does what he expects it to do, for the price that his willing to pay - that’s what counts!

I would go a different direction than he did - but then I don't know what things were most important to him. In other words I don't what his operational/cost expectations are - and ALL SYSTEMS MUST START THERE! It is critical to reread what I just said – because it is more important then everything else I’m about to say!

He has inverters big enough to drain all four batteries to zero capacity in approximately 40 minutes, if he loads them up. If he only wants to run some big loads for short durations (like a 2KW amplifier during transmit) then he may be OK. Having over sized inverters makes them run cool, but it can also cost you a few points of efficiency.

If he drains the batteries down all of the way during operation, it will take 4-5 days of good sun to recharge them - as long as he isn't using any power during that time. If he uses the grid tied charger, it will still take a couple of days – without using any power.

The obvious trap is never getting them fully charged and thereby damaging the batteries. (I see this happen to literally hundreds of batteries per year) When you deep cycle batteries, they need to be charged up at a controlled rate. Spec’s vary with different manufacturers, but a 300 watt solar array for a 400 amp hour battery bank is too small for deep cycling by any standard. Right now, I preach to my customers to buy more PV NOW and come back to me later for more batteries.

Hi four batteries in parallel isn’t a great idea for longevity. Yes it will work, but 1-3 years downstream you will begin to see an ever increasing imbalance between individual batteries. In general, it’s best to use larger batteries (or higher voltage) to stay within 1-3 parallel connections. For example, using Jimmy’s comment about capacity and lower voltage batteries (which forces you to use more SERIES connections in lieu of parallel):

- A standard golf cart size battery is 190-240 amp hours, so let’s use 220 amps.
- They are 6v so you connect two in series to get 12v.
- Then you make another set just like it and get 12v at 440 amp hours.

I’ll draw a diagram later, but you will end up with (4) 60- 70 lb. batteries with only 2 parallel “strings” using Jimmy’s approach. You can buy super-duper high end batteries for $275. each or go to Costco/Sams and buy lower end batteries for $100. each to do this. The concept is the same, the on,y difference is lifespan.

There is so much more to say, but there is also so much beer waiting to be consumed! So, for now…….

Step one is the hardest – but also the most important:
Carefully, thoughtfully and accurately decide exactly what you expect to operate with your “off grid” system. How many watts per, times how many hours? Example: “I need to run this 60 watt device, 24 hours per day. So that’s 60 watts per hour x 24 hours = 1,440 “watt hours” per day. You can do the same thing for any device by reading the “watts” (which means per hour) and multiplying it times the hours.

A light bulb is easier to estimate than a freezer, because most people don’t pay attention to how long their appliances run during each hour of the day. Pay attention and learn your patterns!

If you don't have an energy budget - you don't have a financial budget. Period.

More later if people actually read this stuff!

Marc

[thywar]

I'm reading and learning. Good stuff you guys. And it's in English which helps me a lot.

[geron]

Holy crap! I understood every word of that Marc. Thanks a million! I currently have four 100 watt panels as a beginning. Had already considered the possibility of 6v batteries and you sealed that one for me. Still learning and working on a system. Currently I simply want to provide simple lighting (LED) and communication (brief TV or computer use for news and Amateur radio).

Have a couple PWM 30a Charge controllers but holding off on the inverters for further calculating.

Thanks!

[marc]

IMHO, in a battery based system - the charge controller is the cotter pin of the entire system.

A good one will:
- Provide high efficiency and thereby not waste power.
- Be able to provide EXACTLY the right charging algorithm for the particular batteries being used. (They are not all the same)

A charge controller that does not provide the correct charging sequences can easily destroy a battery bank in a couple of months. Conversely, I've seen a good charge controller make cheap batteries last longer than they should!

Marc

[missasip]

Bet y'all can't guess who I'm hiring when I try solar and wind again???

Jimmy

[marc]

Actually, if you wait a bit - I'm going to have some interesting used batteries coming my way. The City of Dallas has "decoy" cars that they park in certain neighborhoods. Each of these cars use two, very expensive 12v batteries (They are buying them from me for $375.00 each)

The kicker is the contract to replace them annually, even though the systems are well designed which should give the batteries a 5-6 year life under the the conditions being used. (Twice that under normal operational conditions) I am in the process of negotiating with them, regarding the value of them at the 1 year mark.........

[thywar]

Nov 8, 2013 13:50:31 GMT -7 missasip said:

Bet y'all can't guess who I'm hiring when I try solar and wind again???

Jimmy

I bet I can at that. Great info. Just one more case of how great the people and info on this forum is

[marc]

Nov 8, 2013 13:50:31 GMT -7 missasip said:

Bet y'all can't guess who I'm hiring when I try solar and wind again???

Jimmy

Friends don't need to hire friends - they just pick up the phone.

[Besttracker]

I reckon I'm too stupid and too lazy . 120 gallons of diesel stored - 2 generators and marine deep cycle batteries . The inverter on my vehicles do just about whatever needs to be done in a pinch as well.

My good buddy Clint has a steam engine that runs on coal or wood . It will charge batteries in 20 minutes - runs a wood and metal lathe - a metal milling center - a big circular saw and a generator . Takes 1 hour to fire it up and get to operating pressure , but at our age ... we got all the time in the world .

All that stuff said , This solar panel project is fascinating and the idea of generating electricity minus fossil fuel gets me wound up . Thanks for sharing so much valuable info.

Thanks