Nickel Iron vs. Lead Acid - Off Grid battery debate

[Saggys]

I agree, I will be doing an electrolyte change this spring on the remainder. Thanks for posting the graphs.

[Mike90250]

I think 27% is the normal battery solution. To freeze, it had to have been greatly diluted.

koh_freeze_graphs.jpg

[Saggys]

The supposed electrolyte was 9 years old, could it have weakened or stratified? 30577.jpeg

[Mike90250]

The SG of a NiFe battery does not change with state of charge. The KoH electrolyte freezes well below -40F If a case burst, it was not filled with electrolyte.

[Saggys]

Don't ever let someone tell you that NiFe batteries can't freeze, they can. I bought 22 250 amp hour batteries used and stored them in a connex box till this coming spring. 20 received weekly maintenance charge and they are fine. 1 was a never flooded spare, the other was a flooded spare that was discharged, that is the one that froze and broke the case. I spot checked the SG on about 5 of the cells and they were in the correct zone on the hydrometer, so I figured all was good. I understand if the SG is low enough it will freeze, so I should of checked all of them. It gets very cold up in Northwest, WI., -20F is not uncommon. The other batteries are now stored in a warm place till spring and will be in a controlled environment from now on. My lead acids have never broke a case on me, even not fully charged.

[mdagli1]

Hello, so this is where I'm at the moment. Encell has failed to respond to my email so I've turned to my Chinese supplier where I got my 10Ah samples from. Apparently, they make the sintered version as well but they said it won't resolve the gassing issue...

I've asked about what absorbent material can be used between the plates that might help... (like an AGM)

[Saggys]

Is this the same Encell that was supposed to open a manufacturing facility in Florida around 2014?
After checking out their website it looks like Chinese manufactured batteries are still the only reliable source for NIFE cells.

[mdagli1]

Mike90250 Datasheets can be found here: http://encell.com/fused-iron-batteries/

The only bit I'm interested in really is at what state of charge does it start gassing at or if it is the same as pocket. I emailed them directly to see if I could get an answer.

[Mike90250]

nope, just what was in the link a posts ago. Unable to verify any of the claims. Now if the vendor was to offer me a 48V 600ah pack, I could evaluate it against my pocket 800ah pack.
But since the links on their page don't work, I have little hope that it's an actual product.

[mdagli1]

Hi guys, before I start another thread on the developments associated with NiFe, does anyone know the difference in performance between pocket vs sintered? From what I can tell from reading the datasheets and sales descriptions for sintered:

1. Increased charge/discharge rates due to increase surface area (C/4 rather than C/5)
2. Slightly increased charging voltage required (by about 0.05V for the higher rates)
3. Reduced voltage drop during high demand (power curve unknown)
4. Lower minimum charging current meaning reduced self-discharge rate? (C/50 rather than C/20)
5. Reduced physical plate size for the same AH capacity from their picture? (electrolyte volume the same?)
6. Improved charging efficiency (75% rather than 50% approximately)
7. Improved operating temperature range at the upper and lower limits (15oC ether way)
8. Immune to thermal runaway from a CC source (due to improved temperature tolerance?)
9. Increased cycle count for 100% DoD (more than doubled due to reduced need of electrolyte top ups but real cause is unknown?)
10. new patent (Edison patents however have expired?)
11. electrolyte mixture remains the same, 25% KOH and 3% LiOH (any research being conducted here?)
12. gassing rates remain high at above 80% state of charge meaning water loss remains an issue (any info on the thresholds changing on this?)
13. lower mechanical strength so more vulnerable to physical shock?

Could someone verify my comment please as I don't have access to the academic literature on the subject. (most are educated guesses)

thanks

[Mike90250]

I see only a new way of making the porous plates, via sintering powder metal, much faster than the old pocket plate and apparently more exposed surface area.
Made in the USA ( in 2018 ) distributed out of France . Odd combination .

[peakbagger]

Looks like more of advertisement. The article is from 2018 which is ancient history as far as battery tech is concerned.

[johnpearcey]

Useful article about the latest NiFe developments:

https://www.perma-batteries.com/en/product/batteries-encell/#

[Brian1]

Test. Looks like I am back.

Since I last posted I have made some improvements to my system.

A couple of months ago I replaced my Flexmax 80 with a Midnight Solar Classic 150 which allowed me to finally bring out the last 2 BP175 panels so I have now deployed a total of 8 panels. This occurred right after a hurricane and I lived exclusively off this system for 2.5 days.

A couple of weeks ago I installed a 500 farad capacitor across the inverter input to help with the fridge surge when it turns on and the batteries are below 2/3 charged and I am running other stuff. I found the batteries were having trouble supplying that instantaneous surge alone and thought the big capacitor would help. I have not gotten to test that yet. It is made of 6 x 3volt 3000 farad capacitors in series so you end up with an 18 volt x 500 farad capacitor. I recall there was opinions about how to charge this capacitor initially. I gave it it's own fuse so to charge it I had a couple of very large 2.2 ohm resistors in series across the fuse connections without the fuse in there and I waited until nighttime so the battery voltage was around 13.4 volts which gives a current of around 3 amps. I let that go for a couple of hours until the current was less than 1 amp then I moved my connection to a single resistor for a couple more hours until there was no current and then I disconnected that arrangement and put the fuse in. I will let you know how that goes once I get a chance to run the battery down far enough to test.

That is all the improvements to date aside from I am trying to build kind of a pergola arrangement over my back porch so I can mount all 8 of those BP175s in one place in an organized manner instead of scattered around the house in pairs.
Beyond that, the batteries are still working just great.

Unrelated to this I have also installed a 3.96kW grid tied PV system on the roof. This seems to be doing fine.

I made a quick video for the national solar tour I could share if there is interest.

Brian

[nwdiver]

I gave you an example of how NiFe saves fuel. Go back and read it.

You told me how you think it saves fuel and I explained how that's not possible. If you have a battery that's 60% efficient vs one that's ~80% efficient the less efficient battery isn't going to save any fuel. I'm in a similar position now where I don't have enough panels to fully charge my batteries so I go on-grid from ~midnight to noon. Less efficient batteries would just INCREASE the amount of time I would need to be on-grid because NiFe would eat more kWh than lead-acid. Not by a small amount either... ~2x as much. I'm losing ~2kWh/day due to cycling. I'd lose ~4kWh/day if I was using NiFe.

I suppose if you put the batteries in storage for the winter NiFe would save you a bit of fuel since you can allow them to self-discharge to 0 while you need to top-off lead-acid once a month or so... is that what you're doing?