# System overview with NiFe cells.



## Guy_Incognito (Jul 4, 2006)

Somebody eyeball this and check my math - It's been a while since I've done this kind of stuff in earnest.

It's a system for my new place - a 4 bedroom house.
House load has been estimated at about 3-4kWh/day on average, 7kWh worst case (using large operating times for appliances). 

Basic specs:

About 1500-2000W of panels, likely kyocera 120W ones, wired in 4 strings of 4 (probably) for 48V nominal. At about 16 degrees south of the equator, panels on a roof that faces north at a 14 degree or so slope. There'll be an frame for seasonal angle adjustment. Temps range from 15-33 degrees celsius over the year.

An outback power MX60 charge controller, two 24V 2000W inverter/chargers paralleled, plus the display,hub,etc. Pretty much the complete setup using the outback power range. Surge load for an hour or so might exceed the capacity of one inverter, and seeing as it's a pretty remote area, I'd prefer the extra redundancy of twin inverters anyway, so I'm not left sitting in the dark whilst some crucial bit gets freighted to me.

A listeroid 6hp single-cylinder diesel, manual start, driving a 3kVA gen head. It'll also have a heat exchanger for the solar hot water system, seeing as when I need to run the genset, I'll probably need to boost the HWS. Measured consumption is about 0.5gal/hr at 3kVA.

17-19kWh of usable capacity supplied by 40 Nickel-Iron cells of 400Ah each, in two strings of 20. Or 19 maybe, the boost/float voltage is a bit high. 

Why would I go off and use something like that? I'll put that in at the end.

A pentametric energy meter, with shunts to measure panel input, inverter load/charge and battery current/voltage. Probably will measure raw panel voltage before the MPPT gets to it as well.

I've crunched the numbers and it all seems reasonably sane. Probably have to top up the system via the genset for a few hours a week in winter... and a day or two a week in summer.

So, the batteries? Insolation is about 5-6 hours a day in summer, 8-10 hours a day in winter. On average, of course. There have been periods of extended overcast conditions there in summer. One period extended over the entire wet season - about 5 months. Not too good for your standard lead-acid setup, as the place might be unattended and still ticking over for more than a few days at a time sometimes. I'll be using the pentametric to gauge the charge efficiency of the NiFe cells. If they're hideously wrong for the system, I've the ability to replace them with gel-cells after about 3 months of hard work. 

From all my research, the advantages of the NiFe cells are :
- 100% DoD cycles without drama.
- Can be held flat indefinitely.
- Abuse tolerant.
- Life. 20+ years cycling the bejesus out of them is not uncommon.
- Able to slot new cells in fairly easily without upsetting the bank too much.

Disadvantages:
- Inefficient. Really inefficient. Although it occured to me today that if the inefficiency comes into play in topping up the last 20% of capacity, then one could simply not do that. That's what the pentametric's for, to suss it out. But if anyone's got any hard data let me know. No hearsay please, the internet's full of it already.
- Rumoured issues with voltage sag under load, although the specs for the cells say that 200A is the max continuous discharge and short circuit is around 2100A
- Matching cell voltage and the pretty big swing between float and flat voltage. Bit tough to match to lead-acid equipment sometimes.

But the lure of being able to, well, pretty much abuse the heck out of them without much drama is pretty strong. I'm quite willing to sacrifice a fair bit of efficiency in the process to be able to do that. Price/capacity wise, they're a little cheaper than lead-acid here. The price offset seems to be enough to get extra panel capacity to take into account their inefficiencies.

Anyway, let me know what you all think.


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## mightybooboo (Feb 10, 2004)

My first question is the Listroid,heard the Chinese versions are complete total junk,someone at another forum I think just went through almost completely remachining one,so stay away from the newer ones.I say,see it start and run before you buy,I would.

Im thinking you need more panels for so many amp hours batteries,but Im terrible figuring those numbers when you get away from straight 12 volt system and 6 volt batteries.I want to hear what the pro's say.

Beyond that little bit,thanks for sharing,this should be a good learning thread.

Not even sure I should have posted,out of my league,but Im curious and the listroid advice is something Ive read more than once.

BooBoo


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## Guy_Incognito (Jul 4, 2006)

The listeroid is an indian-made clone, imported by a guy here in Australia. They're from the same place the guy at Utterpower.com gets them from, and he lays it out pretty straight as to the reliability of them eg. making sure to clean out all the casting sand before use, a quick tear-down before comissioning them etc. Actually in this case it's probably not a reliability issue, more of a quality control issue from the factory. And I like the sound of a big old 650rpm diesel chugging away much more than something else at 1500/3000 rpm.

For panel capacity, I've a spreadsheet here with all the variables plugged into it and a 70% estimate of battery efficiency. Time to full charge from flat with a 5kWh/day house load is between 3 days in sunny winter to 1.5 weeks (!) in cloudy summer. But that's what the genset's for. 

The NiFE cells apparently self-discharge at a pretty quick rate (a few percent a day). With 1500W of panels, and say, 6 hours of sun gives 9kWh in. Factoring in losses should result in about 320Ah into the batteries each day without the house load attached. With the house load in the equation, it's about 180Ah in a day.

Real-world results may vary of course. It's the solar variability that's got me worried... which is why I'm looking at NiFe cells in the first place I suppose.


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## WisJim (Jan 14, 2004)

I've known a few people who used Ni-Fe batteries some years ago (well, 30 to 10 years ago), and all of them are now using lead acid batteries. The self-discharge rate and high overcharge voltage necessary to fully charge them were both difficult to deal with in a home system. If I recall correctly, it was necessary to disconnect the batteries from the loads, or at least the voltage sensitive loads, whenever completing the charge on a battery. Of course you could switch back and forth between battery sets, using one while the other is charging. 

But I wouldn't use them myself-- didn't pick up a free set a few years back because I figured that they would be more trouble than they are worth.

If I remember more about the systems using them, I'll post the info.


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## Jim-mi (May 15, 2002)

Is it assembled yet ... ??

If not--why not ... ??

NiFe cheaper than lead acid there........wow
shipping is a killer..........and getting worse.
But hey if you've got a mindset to go NiFe---have at it
Be aware of the Outback FX's upper and lower bat limits.

You might consider going 72 volts into the MX60....works great.


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## Guy_Incognito (Jul 4, 2006)

I was thinking of upping the panel voltage, but it's a little tricky - there'll likely be 8 panels on each triangular roof section when fully expanded, which gives 96V and the OCV might be a little high for the MX 60. So I was thinking two strings of 4 on each section. If I go with 6 on each section, I'll probably run at 72V.

And as for the battery prices, it was a bit suprising, but I am comparing them to pretty high-end gel cells I suppose.

For those of you playing along at home:

- I can get 1.2V 400Ah NiFe cells new for $260 each, giving 480Wh/cell.
- Using 2V 875Ah Sungel lead-acid cells at 50% usable capacity for good life gives 875Wh/cell and they're $1050 each. 

To reach the target of 19kWh usable storage:
- You need 40 NiFe cells, two strings of 20 to get 24V. 
- You need 20 Sungels in series to reach that target.

40 * $260 = $10,400
20 * $1050 = $21,000

I haven't priced the larger NiFe cells as I was thinking of a 48V system and you need 40 cells for 48V. It would probably be more cost-effective to get something in the order of an 800Ah NiFe cell if I was sure of sticking to 24V.

I can buy a fair few panels to offset the efficiency loss with the $10,000 difference.


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## mightybooboo (Feb 10, 2004)

Guy_Incognito said:


> - I can get 1.2V 400Ah NiFe cells new for $260 each, giving 480Wh/cell.
> 
> 40 * $260 = $10,400


So for 12 volts at 400 amphours it costs 1300 dollars? 
And youre buying 3800 amphours at 12 volts for 10,400?

BooBoo


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## Jim-mi (May 15, 2002)

Just recently Outback raised the OCV rateing on the MX60, so yes the OCV of 8 pannels would be overlimit.

Got to tell ya that from the network of dealer\installers that I'm on it seems to be the consenses that nobody sells\sets up a new system with gells or NiFe bats.......(with very few exceptions)
I thought you were comparing NiFe to lead acid costs----not to gells.
Wis-Jim pointed out well the hi/lo voltage issue with NiFe.
Again--check out the hi/lo voltage limits of the FX's.
(I could reach in the file cabinet and find out--but I'll let you do that for your self)


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## Guy_Incognito (Jul 4, 2006)

Jim-mi said:


> Got to tell ya that from the network of dealer\installers that I'm on it seems to be the consenses that nobody sells\sets up a new system with gells or NiFe bats.......(with very few exceptions)
> I thought you were comparing NiFe to lead acid costs----not to gells.


We must do things differently on this side of the world - most large-ish installs seem to tend towards gels here. Either something like Sungels or Sonneschein. From the discharge charts I've seen for the Sungels and Sonnescheins, they're both good for 1500 100% DoD before they're down to 80% of their original capacity. Which is pretty good, no doubt about it. But again, the long periods of no sun there are the real issue which is why I'm wandering off the beaten track.



> Wis-Jim pointed out well the hi/lo voltage issue with NiFe.
> Again--check out the hi/lo voltage limits of the FX's.
> (I could reach in the file cabinet and find out--but I'll let you do that for your self)


Yeah, the voltage limit on the FX is borderline when you're charging 20 cells.
Might have to drop back to 19.



mightybooboo said:


> So for 12 volts at 400 amphours it costs 1300 dollars?
> And youre buying 3800 amphours at 12 volts for 10,400?


(thinks)

12V = 10 x 1.2V cells at 400Ah.... $2600

3800Ah at 12V = er, 45.6kWh.
3800/400 = 9.5(!) strings of 10 1.2V cells = $24700

I'm buying 19.2kWh of capacity for $10400.
19.2kWh / 24V = 800Ah capacity (two strings of 20 400Ah cells )
19.2kWh / 12V = 1600Ah capacity (four strings of 10 400Ah cells)

This is why I tend to work in watts instead of amps. Watts or watt-hours allows you to compare different packs or loads at different voltages without much drama.


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## mightybooboo (Feb 10, 2004)

Yep,Ive noticed that too,Aussies tend to think watts while we tend to think amps.You guys DO do it a bit differently.
I really like the NiFe idea,hope its a winner,you need to keep us updated when you get numbers real world.

BooBoo


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## Guy_Incognito (Jul 4, 2006)

Once I get it all setup with a good chunk of data from the pentametric I'm going to post it all, in multiple places, all over the internet. All the data I get, efficiencies, pitfalls, any good points.

I've been searching around for 3 months now, and there's no hard data on NiFe cells. In Google's results, 90% of them are a straight cut-and-paste of one 10 page article/FAQ, that deals with NiFe cells in about two paragraphs.

- There's vague mention of their use in EV's (!?).
- There's vague mention of theoretical capacities (pretty good, really).
- There's plenty of references to the 100-year old edison cells, but no mention of anything more modern. (Compare a 1915 lead-acid battery your typical car one today.)
-There's a lot of hearsay, but nothing - absolutely *nothing*- that says "Oh, I charge my 400Ah NiFe cells at 1.65V / 80A for 8 hours to get 100% charge and they self-discharge 3% overnight."

If I do finally go down this route and splash the cash for a set, I intend to record and document online as much detail and info as possible, even if it's only to serve as a warning to other brave fools.

(And so ends today's rant  )


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## mightybooboo (Feb 10, 2004)

Did my search too.Are you getting em from Hungary or NIFE?
Supposedly a supplier of Hungarians in Ca.
I knew I read about east Europe somewhere,sho nuff it was Hungary.

Did you come up with the 20 or 40 batteries from a site page,I read a guy went to 40 from 20 and was happy,was that where you came up with the 40 idea?

You got it right,very little on the web

booboo


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## Guy_Incognito (Jul 4, 2006)

I'm actually getting them from China - there's a local distributor here.

Their site: 
http://www.changhongbattery.com/english/index.asp

Checking it right now, it seems they've broken the battery section on their website. Tsk.
There's a company at www.beutilityfree.com that sells the Hungarian ones. I think. The photos and model numbers look suspiciously like the ones I'm getting from China.

I was thinking of 40 cells to reduce the current load and alleviate any issues with voltage sag under heavy current draw, which is rumoured to happen. But two strings of 20 cells has half the current through each string anyway, and it's easier to match voltage to lead-acid cells when you've less cells - the voltage spread (1.0v flat - 1.5V float - 1.7v max charging) gets pretty wide when you multiply by 40.


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