Off-grid home building adventure!

When I changed out 8, L-16 lead acid for 42 Nife, it required about 4x the floor space for a slight increase in storage capacity. But the plan is because the NiFe does not sulfate in 2 week cloudy weather. And have a good source of distilled water for NiFe.


solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
battery lugs http://tinyurl.com/LMR-BigLug
Setting up batteries http://tinyurl.com/LMR-NiFe

gear :
Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV || || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

Interesting. So how much water do they really end up using? I actually have the lab equipment to get my own distilled water if we go that route...
Did you size the system based on being able to have a deeper drawdown? Do you actually use them that way (80% DOD)? I was wondering how bad the voltage drop really is (I think I read that even though they have lots of charge left in them, the V drops lower than other batteries...)

Sounds like you must have domestic water storage that you pump into occasionally, is that right?
We have a deep, but very full well, so our 400+ gallons of water storage is all just in the well where it can't freeze and cause problems that way in the winter. Plan is to just hav a pretty large pressure tank so it doesn't run often. And even though it is a 1hp pump, the depth is usually less than 100 ft, so it isn't drawing that much...

-eq

Oh, and this might be a silly question, but why 42 cells? I thought the 48V systems were done with 40 cells?

FLA cell voltage is 2 volts, NiFe 1.3 volts

We have +300 fruit and nut trees, 2 dry wells, and water source is a 1.5af pond. So I pump daily, 2,000 gallons into 12,000 gal of elevated (160') tanks, and gravity feed from that.
In my cells, I go through about 10-15 gallons monthly. I keep the batteries in the top 50% of charge even in winter. I went with 42 cells, because if one dies, it's months to get a replacement. Having the spares "sitting idle" appeared to not work, so I put them all into use. NiFe has a LOT of internal resistance, I replaced a 400ah bank, with the 800ah NiFe, just to have the surge capacity. And, the recharge efficency is not good in the top 20% either.

Thanks for your responses Mike.
I have actually read the whole 25 page debate thread about NiFe vs lead acid... Sheesh. And other threads too. Which took a lot of tenacity to get through for the occasional gems of useful information (as with all things online, but still). I think I'm probably ready to just go with the flooded acid (Sunking would be proud that I've "come around" ). I like the idea of using a somewhat obscure technology and I'm not afraid of the maintenance and chemistry required, as long as it is something fantastically worth it... But I'm feeling more and more unsettled about it the more I learn. And if I'm not afraid of careful maintenance, the flooded acid should last us well...

And I'm also considering moving up to a 48v system.
Current ideas: 2kW panels, the Apollo t80, the magnum 4448, and probably Rolls batteries (~500Ahr)

We have a big diesel welder generator...and auto gen start. I know it's way bigger than most generators, but we needed the welder anyway. It can power anything (and everything). We've used it this summer and the thing just barely sips fuel. So we feel pretty comfortable that it is our backup. And could happily run it for the 5 days a year that the sun doesn't come out (instead of doubling battery bank to last 3-4 days, we'd go for a smaller bank and burn 5 gallons of diesel on the days we'd need to). And heavy shop tools wouldn't run off the solar, we'd run the generator to plane boards and the like...so we'll be using it anyway...

For details that I know some of you would ask about. Solar insolation here is 5.7. Highest temp I've seen is 85, long stretches of very cold and snow. But even when cold and snowy, the sun usually comes out. Daily use is calculated to be ~200Ahr/day. Pretty low, but we already live on solar, and are mindful about how we use it; do all the heavy energy usage stuff early in day, don't suck it dry on cloudy days, only LEDs, etc...

So, it seems like the system would be more efficient at 48V. And 48V would be easier to charge from a 2KW array. I can switch my planning for going towards a 48V system pretty easily... I was a bit surprised at how much the price of the Apollo T80 has gone up lately. And seems harder to find. Does anyone know if there's something going on with that model (being discontinued or ?).
Now, about wiring the batteries (and therefore picking sizes and models)... I had really liked the idea of being able to replace bad cells with the NiFe. No luck with that anymore. So then I thought it might be nice to have parallel strings. But I understand they don't charge evenly and are shorter lived that way. A back-up isolated string (or bank) would make me feel better in terms of redundancy, but I doubt the cost/benefit is worth it...

This back-up-string of batteries idea comes from our current setup. We can switch between a 2x6V bank, and a spare bank of 2x12V. Easier to swallow when it's just a two batteries, and not a string of $1000s.

We will keep the old 12V NiFe set on the wind generator to play with...but for nothing more than non essential lighting. Who knows. Maybe we'll be so impressed we go for NiFe when replacement time comes, but until we really experience it, I'm not feeling ready to jump in.

So that's what I'm currently thinking on... Shoot holes in it, ask questions, give ideas if they come I you...
Oh, and happy long weekend of course!

-eq