Nickel Iron vs. Lead Acid - Off Grid battery debate

[russ]

I'd like to thank everyone who participated in this discussion, especially Old Bill with his funny bashing style and Robert1234 for the scientific approach. 21 long pages, but a very interesting read.

Hi Neven - Welcome to Solar Panel Talk!

Russ

[Neven]

Thanks

I'd like to thank everyone who participated in this discussion, especially Old Bill with his funny bashing style and Robert1234 for the scientific approach. 21 long pages, but a very interesting read.

I'm very much a novice when it comes to everything electric, but willing to learn as I'm planning to install this year or next year what I believe in English is called a grid-tie with power backup system. I want to use most of the electricity that the 5 kWp system generates, and thus a 5-7 kWh battery system might be interesting. There are certain aspects of the NiFe battery that appeal to me, such as the environmental aspect and longevity. I'm not so enthusiastic about changing electrolyte, especially if it's every 2-3 years. But this depends on the quality.

In this respect I have one question: the discussion has been about old Edison batteries and modern Chinese versions, but how about the Russians? Are they doing anything differently?

[Robert1234]

The "place in New York" was probably my source, but he has no more. Zappworks bought them all.

[AzSun]

edison Battery Source

How are you guys sourcing your used batteries? Ebay, Craigslist? I would love to find some to mess around with.

I've had mine since the mid 1970's and never used them until recently. I purchased the set I am using now from a rancher in Nebraska. The rest came from Pullman cars being restored by a railroad historical society. Ebay does have them once in a while. There are usually only 1-4 cells which are not good for much. There was a place in New York that was selling larger sets on eBay for a while. I will dig around and try to find their address.

[Saggys]

How are you guys sourcing your used batteries? Ebay, Craigslist? I would love to find some to mess around with.

[Robert1234]

The data I have (again not official Edison documents) says KK series cells are from 1941. Like you, my NiFe's are performing non-critical duty right now as I need a whole lot more to put them into main service.

I have answered the questions I originally had, and now it all comes down to sourcing and availability of the cells for me now on the decision to go NiFe or LA at the cabin. Based on the data I have I am looking to get 100 more C6 cells to add to my existing 20 so that I can run 3 parallel banks of nominal 48v. That will give me about 22 kWh of high efficiency storage with a peak capacity of about 45 kWh. Unfortunately, my source has sold all he had so I am on the lookout for more. Might have a line on some C8's but that is yet to be confirmed.

Bottom line, I want to go NiFe, but unless I can find more cells at my previous investment, it's gonna have to be LA.

[AzSun]

Thought I'd drop in an update for posterity. I did a couple dozen tests over the holidays with the nickel irons I have. I'll post raw data if anyone cares to see it, but here's a quick summary of what it says to me...

My test bank is made up of Edison C6 sells. My cells are between 50 and 60 years old and had not been reconditioned at the point when I got them. Using my reconditioning process without opening the cells, I got them up to about 300 amp-hr when overstuffed with "juice". The only reference I can find on these cells are that they are said to have an original capacity of 337.5 amp-hr (but that a single source with no Edison reference). So I'm about as good as I can expect for what I've done to revive them.

The coulombic efficiency of the cells on charge / discharge was very surprizing high when only using the bottom half of the batteries' amp-hr of storage - 90%+ efficient (perhaps 95% or even more at low amp draws). Since this was from scores of tests, I deem it to be real. This efficiency is much higher than anything I have seen reported before and suggests the batteries indeed might be quite useful for solar applications if you operate in these ranges, but it means you need even more cells (and $$ to invest). NOTE: As one should also suspect, the water consumption by the cells is also dramatically reduced when operating within this improved coulombic efficiency range.

There are two major "watch outs" that these experiments point out....

(1) The discharge-charge efficiency takes a major nose dive as you continue to pack the cells. The more you try to store, the worse the incremental efficiency gets. This makes it very wasteful to attempt to utilize all of the stated capacity. While this might be fine for on-line backup power devices, efficiencies of 30% and less are most assuredly way too low for most of us attempting to store electricity being generated from from solar panels. NOTE: I should emphasize, I only know the coulombic efficiency break point for the cells in my possesion. That same point of diminishing returns for other cells would have to be independantly determine, and it would be unfair to generalize that other cells should also only be used to 50% of stated capacity.

(2) Coulombic efficiency is NOT total efficiency - ie even if amp-hr out is equal to amp-hr in (100% efficient), you still have to take into account the volts necessary to charge the cell versus the natural volts the cell runs at during discharge. WHile there is no one specific set of values I can give you because charge rate comes into play, typically my charge source was at about 1.6v when the cells were at their 50% capacity level (150 amp-hr). Using 1.2v as the average discharge volts, that gives us a "real" wattage efficiency of about 75% as the best we can expect to achieve (compare that to 90% for LA cells using the same type of analysis).

Finally, after reviewing all these experiments I'll expand my initial generalization to Mike and sugest there is about 15-20% power remaining at the 1.1v level as you continue the discharge to 1.0v.

Robert,

I have some original Edison documents in a 3 ring binder. It states C6 cells are 338 AH, with a normal charge rate of 67.5 amps. The list price per cell was $62.90 each from a sheet dated July 12, 1948.
I have 18 C6 cells with serial #'s around 3336KK, not sure how old they are. I did test one a little over a year ago and have been using it with some other NIFE types to power my garage and landscape lighting.
I don't think I am getting the capacity on the C6's you are, but some of my other Edison types are near 100% of new performance as shown on Edison sales brochures. Test data for a cell below.

Battery Model Battery Serial Number Date Log I.D. Load Amps Start Volts End Volts Time Notes Decimal Time Calculated Amp Hours @ 1.3V

C6 3336KK 10 25 11 C6 3336KK 5AD1 5 1.4 1.1 29:47 00 End charge 1.654V 7.6A
C6 3336KK 10 23 11 C6 3336KK 10AD1 10 1.45 1.1 13:20:10 13.336 133.36
C6 3336KK 10 22 11 C6 3336KK 15AD5 15 1.4 1.1 10:32:50 10.547 158.21
C6 3336KK 10 17 11 C6 3336KK 20AD1 20 1.35 1.1 8:25:10 8.419 168.38
C6 3336KK 10 20 11 C6 3336KK 20AD2 20 1.35 1.1 8:12:20 8.205 164.11
C6 3336KK 10 15 11 C6 3336KK 60AD1 60 1.25 1.1 2:56:00 2.933 175.98
C6 3336KK 12 24 11 C6 3336KK 60AD2 60 1.3 1.1 2:30:10 End charge 1.650V

[Beanyboy57]

I should have looked more closely at the title of this thread "Nickel Iron vs. Lead Acid - Off Grid battery debate". The DEBATE word should have cued me in that firm opinions had already been set. Going forward, I'll try to limit my discussions on this board to more non controversial subjects such as array configurations, charge controller settings, etc. For the record, I'd like to leave this thread with one last thought as it has served me well over the years in my career:

"It is a good morning exercise for a research scientist to discard a pet hypothesis every day before breakfast." - credit Konrad Lorenz - 1973 Nobel Peace Prize recipient.

Don't quit now, we are finally getting into decent research and asking serious questions about this technology!!

[Robert1234]

Thought I'd drop in an update for posterity. I did a couple dozen tests over the holidays with the nickel irons I have. I'll post raw data if anyone cares to see it, but here's a quick summary of what it says to me...

My test bank is made up of Edison C6 sells. My cells are between 50 and 60 years old and had not been reconditioned at the point when I got them. Using my reconditioning process without opening the cells, I got them up to about 300 amp-hr when overstuffed with "juice". The only reference I can find on these cells are that they are said to have an original capacity of 337.5 amp-hr (but that a single source with no Edison reference). So I'm about as good as I can expect for what I've done to revive them.

The coulombic efficiency of the cells on charge / discharge was very surprizing high when only using the bottom half of the batteries' amp-hr of storage - 90%+ efficient (perhaps 95% or even more at low amp draws). Since this was from scores of tests, I deem it to be real. This efficiency is much higher than anything I have seen reported before and suggests the batteries indeed might be quite useful for solar applications if you operate in these ranges, but it means you need even more cells (and $$ to invest). NOTE: As one should also suspect, the water consumption by the cells is also dramatically reduced when operating within this improved coulombic efficiency range.

There are two major "watch outs" that these experiments point out....

(1) The discharge-charge efficiency takes a major nose dive as you continue to pack the cells. The more you try to store, the worse the incremental efficiency gets. This makes it very wasteful to attempt to utilize all of the stated capacity. While this might be fine for on-line backup power devices, efficiencies of 30% and less are most assuredly way too low for most of us attempting to store electricity being generated from from solar panels. NOTE: I should emphasize, I only know the coulombic efficiency break point for the cells in my possesion. That same point of diminishing returns for other cells would have to be independantly determine, and it would be unfair to generalize that other cells should also only be used to 50% of stated capacity.

(2) Coulombic efficiency is NOT total efficiency - ie even if amp-hr out is equal to amp-hr in (100% efficient), you still have to take into account the volts necessary to charge the cell versus the natural volts the cell runs at during discharge. WHile there is no one specific set of values I can give you because charge rate comes into play, typically my charge source was at about 1.6v when the cells were at their 50% capacity level (150 amp-hr). Using 1.2v as the average discharge volts, that gives us a "real" wattage efficiency of about 75% as the best we can expect to achieve (compare that to 90% for LA cells using the same type of analysis).

Finally, after reviewing all these experiments I'll expand my initial generalization to Mike and sugest there is about 15-20% power remaining at the 1.1v level as you continue the discharge to 1.0v.

[Robert1234]

Mike,

Other data that might be useful to you since you are only partially charging from an almost dead battery set...

Short Charge Data 1
30 Amp @ 0.62 Hr = 18 Amp-Hr

Draw Rate - 5 amp
AmpHr to 1.10v - 12.35
AmpHr to 1.00v - 13.66
AmpHr to 0.90v - 14.22


~ 9% of Power Left Between 1.0v and 1.1v
~ 77% Efficient Delivering Power Used to Charge

[Robert1234]

Test finished with a total drain of 296 Amp-Hr. Very different shape to this curve versus the high draw tests I have run. The majority of the power was drawn out of the battery before the volts fell to 1.10 (see data below). It's also interesting to note that the battery open circuit voltage was back up to 1.26 volts this am once the draw was halted and the battery was allowed to rest.

So based on that, at very small draw rates there is very little power left in the cell between the 1.0 and 1.1 volt interval. Will be interesting to see how this repeats as I raise the discharge rate at 5 amp intervals. But first, I think I will do some short charge - discharge efficiency measures as I work my way back up the discharge rate curve.



Draw Rate - 5 amp
AmpHr to 1.10v - 286
AmpHr to 1.00v - 295
AmpHr to 0.90v - 296


P.S. For those that might want to do storage cost comparisons, at this amount of storage my Ni-Fe bank cost me $96 per KWh. I have Trojan L16RE-B's priced at $128 per KWh (based on a 4.1 amp draw). Using my 25 amp draw data, my Ni-Fe are $190 per KWh with the Tojans at $142 at a 18.5 amp draw. Costs are VERY similar, but the Edisons beat the snot out of the LA on longevity (the "youngest" Edison's in my bank are 50 years old). But.... like I say, the efficiency question still has me leaning towards the Trojans for our NC install.

[Robert1234]

Mike, You've got a lot of storage capacity there. You think a 21 kWh harvest peaks out the capacity in your bank? I'd think you'd probably have "more room in the inn" so to speak (if I may use a seasonal analogy )

[Edit on reread - my bad - you plainly say they are definately not recharged]


My personal hesitation with the Ni-Fe isn't the longevity nor the electrolyte changes nor even the high investment cost. It's what is going to be my kWh out vs kWh in. Doing some out vs in ratio studies at low draw rates involving various states of charge will be interesting and perhaps beneficial. My panel locations at our cabin will not be optimal, so being able to store and retrieve as much power as possible from the array is really important to me. I may need to rethink some of my early work as perhaps I've been too hard on my little bank making my decisions at C5 draw rates?

I'm charging up the cell now and will start the full C30 discharge tomorrow am when I get back to the lab. It will be Wednesday am before I have the first data points to share - assuming my network administrator doesn't intrude on the test.

[plataoplomo]

if it takes me 5 years to decide, then it may not have been a bad choice. If I decide in less than 5 years, that means I've made a poor choice

Thank you very much.

[Mike90250]

May I have your impressions so far? Worth it? Not worth it?

Thank you

I've only been pushing them for a month.

they take a lot to recharge, 2 sunny days (21 KWh harvest) and still not recharged after several cloudy days. Had a 13 day run of clouds, recharging with genset kept system running safely, and with less fuel than having to get a Lead/Acid bank up to 80%.

regular maintainance will include electrolyte change outs, which is going to be a several day job,
in my case, 100 gallons of new juice to mix, and 100 gallons to dispose of. (Maybe I'll make a monster batch of bio-diesel with it)

So, currently, undecided. With luck, if it takes me 5 years to decide, then it may not have been a bad choice. If I decide in less than 5 years, that means I've made a poor choice

[plataoplomo]

till we get sun in the spring time

May I have your impressions so far? Worth it? Not worth it?

Thank you