Fusing Battery Strings? HELP PLEASE! -ANYONE???

littleharbor2

It's a little more complicated than that. Of course there's the, minimum 5%, Max 13% charging rate for lead acid rule of thumb But there's also the location factor. If you're in the costal, Pacific Northwest you will need substantially more PV than if you lived in Phoenix, for example. If you are in the lower latitudes you are going to get more sun, year round than if you live in Alaska. 
 Battery chemistry clearly affects your allowable charging limits. If you are using AGM batteries you can charge them with up to 20 % of their Ahr. rating. This could be useful in sun challenged areas being that you can have a very large array and get those batteries charged faster than typical lead acid.

BB.

Given that common battery bank voltages are 12/24/48 volt... You cannot have one Watt Array to Battery Bank AH number for charging (a 100 AH 48 volt battery bank is 4x larger than a 100 AH 12 volt battery bank). Also, depending on your needs, 5% to 13% rate of charge for solar is common (5% weekend/summer place, 10-13% is common for full time off grid).

In reality, you really need to start with your loads... A 3.3 kWH per day system is a good start for a very efficient home/family (lots of conservation). Run a fridge, lights, efficient laptop computer/TV, well pump... But for a family of 5, will the family be OK with that level of conservation (especially as the kids grow).

Generally, loads define the battery bank AH and Voltage. And battery bank defines the minimum solar array. And location gives you the amount of sun you have to support your loads/energy needs.

I asked if you were up around Kelowna, British Columbia, Canada... Location is critical to system planning. Solar only works with sun, and as you get farther up north, you are stuck with darker winters and possible loss of sun from trees/mountains, etc.

Why do you want to go off grid solar? Are you planning on taking your current home off grid (save money, go green) or do you want to move to a location where utility power is no available or costs to much to bring to the property?

Off grid solar is not cheap... It is typically somewhere around $1-$2 per kWH (with generator backup). Some people can get cheaper ($0.50 per kWH seems possible. And others pay more--Generally for weekend cabins where not using power >9 months per year).

-Bill

Dave Angelini

Yes others do pay more! I am working on a system that the lady paid 70+ K$ for a 4KW radian and 4KW of solar. The guy is gone and the system has never really worked right.

Excellent post 33 Bill !  Amazing that with this many strings in the thread that the why, where, when, and how many is still unknown.

Estragon

The calculator in the link doesn't appear to account for "days of autonomy" (ie days of gloomy weather before you need to fire up the genny). Using 3kw/day (a bit less than my actual use) it came up 150ah(48v) bank, so you'd be at ~60% SOC after the first cloudy day.

In my case, I also have to consider temperature effects. In an insulated but unheated crawlspace, by spring the bank can be cold enough to reduce apparent capacity by 25-30%, so my 350ah bank is more like 250ah. Even in summer, it may never get to 25°C so it's rarely, if ever really a 350ah bank.

mike95490

You size the Battery to fit your loads, and then you size the solar PV to be able to recharge the batteries completely on a average winter day.   Don't calculate to fit the sunny days, you will run out of power in the winter with shorter days and stormy weather.  Don't forget you will need a generator for a couple of winter months, unless you really oversize your solar.

ligwyd

appreciate all of your guidance. Thank you very much.

Yes in Kelowna, but looking for land now. Always wanted to live off grid so I thought I'd take some power with me. Want about 20 acres or more, a big garden, some chickens, maybe a cow. Live a simple life and raise a family the old fashioned way

I think at this point I may work with what I have, gain some invaluable experience and if what I have built does not function to our needs or expectations, modify and sell equip I may swap out for cost minus and keep on trucking. What a journey and the journey has not even yet begun. Who ever thought being a Dad would be this much fun hey

Looked for No Ox ID Special and found it for $40 (CAD)including shipping off Ebay.ca but picked up a similar product from a wholesaler here in town. Should work fine I'm hoping ?

http://www.nsi-sales.com/ox-4.htm

I'll use a little wire brush or emery cloth on every copper wire connection and lightly coat with the compound and torque up. I will not use it on the battery terminals. I'll shine up the contact side of battery terminals and coat lightly coat with vaseline and torque up.

Re: PV wire. I can get 7 or 19 strand. I imagine 7 is easier to work with and terminate? I don't mind a little stiffness getting it through the short runs of conduit I will have.

I'll try to stop bugging you guys and get to work. Just waiting for some bus bars and battery lugs to show up so I am trying to get some planning and thinking done while I have the time.

Thanks again for any and all critical feedback and support. Amazing !

John

littleharbor2

Wow! You pay a hefty penalty for living in Canada it seems. The highest priced No ox Id I found on eBay was $25.00 and as low as $5.00.  
 Anyway hope it all works out well for you.

mcgivor

littleharbor2 said:

Wow! You pay a hefty penalty for living in Canada it seems. The highest priced No ox Id I found on eBay was $25.00 and as low as $5.00.  
 Anyway hope it all works out well for you.

It's also that price in Canada.......... before taxes

littleharbor2

If I lived a little closer to the US/Canadian border I'd have to start a No-Ox-ID Special smuggling ring. 

BB.

No-Ox on battery terminals is fine.

Regarding power--Keep an eye on costs of bringing power in (or if some is already local to the properties you are looking at). Even $40,000 for the power company to bring in power may be a "better deal" than going off grid. Also, when you (or your descendants) sell the property in the far future--Having utility power may make the property more valuable/easier to sell.

Selling (even working) solar power systems as part of a home/property generally does not add much value (and can actually bring the value down as the new buyers may not like "all of the wiring" on the roof.

-Bill

ligwyd

I heard anything conductive on the battery terminal posts was not good but I'm sure if I'm clean with it it'll be fine. Probably better to have conductive lube on the terminal eh.

Off-grid for me is more of a lifestyle choice than dollars and cents. Property I am considering won't have power ran for along time. Also, my systems are self contained. Drop it off - hook it up to home and take it with you when you leave or sell it if it makes sense.

But I get it, may be an expensive lesson I call it adventure. Just gotta keep the wife happy too

http://gotsolar.ca/projects/

a few jobs we've done recently and my cans are the 18 panels near the bottom

Have a good night Bill

John