Nickel Iron vs. Lead Acid - Off Grid battery debate

[Mike90250]

This is my first hard use of the batteries, and till we get sun in the spring time, I'm not able to experiment much with them, because I'd have to charge with generator, and I don't want to do that yet.

[Robert1234]

Purdy much spot on My 150 amphr is based on a 24 amp drain to 1.05 (my current inverter cutoff), followed by a 24 amp drain to 0.90 (the targeted Magnum inverter cutoff), followed by a 5 amp drain to 0.90 (just to see what else might be left). So... C30 will be an arbitrary notation for a 5 amp draw till I otherwise change my definition of the capacity of these regen cells.

I'm pulling another C5 drain from the cell today while I otherwise work. Will full charge up again Monday night and start the first full low power drain on Tuesday. May give a 4 hr short charge some Monday & drain just to see what kind of % ROI one can expect in the lower charge state of the cell.

Not really sure if this will help Mike much though as "it is what it is" for his setup. Perhaps this may suggest he can improve efficiency a bit by part charging? If so, he'll need to repeat all of this on his own setup as the results can be fairly battery specific. Guess let's just see what it says and we'll go from there.

[inetdog]

Gonna take some time though as I'll only be able to drop out maybe 3 tests a week due to the drain lengths.

You haven't figured out how to do an "accelerated" C30 discharge, eh? And I suppose that you have to discharge at what you guess will be the C30 rate, then correct if the cell lasted longer or quit sooner and try the whole thing again from the start?

[Robert1234]

Pretty close to what I already am doing with regards to charge loading for lab tests. On the 150 amp-hr cells I charge at 30 amp overnight. Figuring 15 hr on avg charge, that's 450 amp-hr or right on 3x loading of a C5 charge rate. Would be interesting to compare the percent discharge curve & charge / discharge efficiency as we start dropping the charge loading too (ie short charging the cell to < 100% capacity). Haven't done many full discharges at constant drains as low as C30 since my cells are so small and I don't expect to use them that mildly, but we'll see what it looks like just for grins. Gonna take some time though as I'll only be able to drop out maybe 3 tests a week due to the drain lengths.

[inetdog]

Defining full is the crap shoot when you are working with the Ni-Fe batteries in the field. My experience has been that once at float voltage you really don't add much (if any) more power into the cell even if you go into float with the cell only half charged.

How about something really unambiguous and conservative just for testing: When you have delivered energy equal to three times the cell's nominal capacity (that should allow for more than worst case charging inefficiency) the cell is FULL. Defining full during normal cycle operation is definitely more problematic.

[Robert1234]

what is "Full" ?

Defining full is the crap shoot when you are working with the Ni-Fe batteries in the field. My experience has been that once at float voltage you really don't add much (if any) more power into the cell even if you go into float with the cell only half charged. Perhaps what might be more consistent would be to refer to the number of amp-hrs remaining in the cells to a level of 1.10v once you hit the 1.0v mark at a specified draw? Even that moves around though as the cells like to "recover" back to a higher voltage when the drain is released or decreased. I fear there is no clean answer to your query.

Didn't realize you are on year 2. Do you feel as though you have lost capacity? or is this the first winter of full, "hard" use?

[ursus_maritimus]

"Testing for electrolyte carbonate level is possible via titration.
For the specific procedure see HP #15, page 23. It is more expensive
to test a
cell's carbonate concentration than it is to replace the electrolyte
in a cell. So the test procedure is usually skipped if the cell
is over ten years old. "

Reconsideration: The NiCads he would have been playing with were probably much smaller volume than the cells people are using for serious off-grid installations (I'm not serious, just curious with mine, not nearly large enough to convert to CO2 scrubbers. ), so I doubt the test is more expensive than new electrolyte in that case?

Over the weekend I'll try to find the cells with the dark rings and see if the geometry of the smaller cells permits some sort of coiled swab to access the inside of the case. But it's been dry for over a year, and depending on what affinity this mystery deposit has for the plastic, it may be thoroughly "soaked in".

The plastic on the cells I have is not clear "transparent". It is something like "frosted glass". The plates are only visible as shadows. Sort of like the 70s Tupperware containers.

If these cells are designed primarily for "industrial" and government use, where the users would almost certainly have standard life-cycle plans where fussing over electrolyte to squeeze extra life out of them would not be a consideration, would the designers be that interested in the condition of the plastic beyond 20 years or whatever the official lifespan is? I had read somewhere the factory systems that make these were a German design (Varta) so perhaps that would be a better place to look for answers than the Chinese manufacturers?

[Mike90250]

Mike,

If I understand your question correctly now, you would like to define 100% Power as a C30 drain to 1.0v - then you would like to know what % of that power is discharged via a C30 drain to 1.1v. Have I got that part right?

Well, yeah, that's about it, lets call the battery temperature 70 or 72F, or whatever the spec is, that the charts are published to. And then is the issue of, what is "Full" ? (setting empty to 1.0V seems safe)
Best to go by an amount of dwell time at voltage (which voltage spec), or
when absorb (fixed voltage) amps drop to some % of C.
Or is there a 3 method that's valid ?

I don't have float oil, just relying on the check ball valve in the flip caps. (useless flip caps I might add, the port in them is too narrow to add fluid, I have to unscrew the cap to add water.

Original fill was distilled water with the chemical mix, in the ratio supplied.

Not able to sample the "bath tub ring" the fill port is too long and narrow to get to the edge of the cell.

I have a titration kit, and will try it when the weather warms up. If I have to replace electrolyte after just 2 years, it will be a sad day indeed. The bio-diesel grades are not too pricey, but un-carbonated lab grade, looks to be real expensive.

[ursus_maritimus]

Several things come to mind immediately:
1. Are either of you using any kind of magic float oil on top of the electrolyte?
2. Is the ring below, above or straddling the space between the lowest electrolyte level and the highest? And is it darkest at the top?
If so, it could result from the electrolyte clinging to the plastic as the level boils down and drying on the side.
3. Or the result of a reaction between the electrolyte and the plastic in the presence of high oxygen concentration just above the electrolyte surface? The hydrogen will rise and be dissipated, while the oxygen will just replace the nitrogen-oxygen mix which is normal air.
4. Possibly some impurity in the electrolyte or something dissolved off the plates at the initial fill is just rising to the surface of the electrolyte and being deposited on the plastic as the level goes up and down?
5. Next???

Can you safely reach into the cell through the fill hole with a non-conductive alkali-resistant probe and rub the surface of the case to see whether it is an insoluble deposit that will rub or scrape off or a change to the plastic itself. (Either one would be worrisome to me.)

In my case, this ring was in some of the cells when I took them out of the crate dry. I know they fill the cells and must do some sort of testing before emptying and shipping (there is a residual amount of fluid in each of the cells when shipped; it would be wise to assume it is caustic). Assuming the cases and cells were new, these deposits must be created very early during the operation of a cell.

The Changhong manual I had (via internet) didn't mention float oil, and it also seems unlikely they would put this in the cell for the short time needed to test them. I do have some of the float oil but didn't get it from Changhong. (I might use it in some of the cells this spring) According to some of the threads on various sites the past year it is a special grade that was made by Chevron, but no longer in production. In one of the help columns in Homepower magazine Richard Perez advised putting a layer of mineral oil USP in cells after changing the electrolyte. In some of the earlier years of that publication, they went through a period of enthusiasm for NiCads, but that seems to have vanished. They must have gained some experience dealing with float oil and carbonate formation. (In his earlier "Battery Book" R Perez did have a chapter on NiFe, but was not very enthusiastic about them at the time.) It might be worth contacting them for their experience with electrolyte chemical quality, carbonation and float oil.

ftp://sunsite.unc.edu/pub/academic/e...s/29/29p44.txt

One interesting excerpt from link above

"Testing for electrolyte carbonate level is possible via titration.
For the specific procedure see HP #15, page 23. It is more expensive
to test a
cell's carbonate concentration than it is to replace the electrolyte
in a cell. So the test procedure is usually skipped if the cell
is over ten years old. "

[Robert1234]

Mike,

If I understand your question correctly now, you would like to define 100% Power as a C30 drain to 1.0v - then you would like to know what % of that power is discharged via a C30 drain to 1.1v. Have I got that part right?

[Sundetective]

Nope, no battery monitor included.

I've never claimed what my generator setup is, and it's NOT state of art. It's old enough to be art.
I get my usage and harvest from the internal logs of the inverter and charge controller, and have no reason to suspect they are anything other than good commercial grade monitoring, within +-5% or so.

When the water pump is not running, I have little daytime loads, since I've had no good sun, I've actually gone to laundromat to save power and generator runtime. Fuel costs are negligible.

and Bill B, I'm just not getting the reference to the Rolls batteries.

Mike

No free battery monitor means you must have the previous Ni-Fe guarantee.
A person wanting to learn can pick up a bit from reading that guarantee as well.
I posted it a long time ago in the Fieldlines forum and the Wind-sun forum.

I thought you had Lister Pictures posted on the Internet and also post in a forum about the Lister.
To many people Lister Generators are a big deal.

The Rolls reference is to give newer people a reference point as to what were talking about.
Sometimes it sound like a man on the moon project going on around here instead of (8) Eight
Six Volt Rolls 5000 Cells at 820 Amp Hours each.
$999 each delivered where I live.

If your fuel costs are low and you use such little power - what's to worry?

The 700's you have take less than 1/2 the electrolyte that the 800 series uses.
They are small batteries in comparison to the 800's.
Price wise buyers Lose and the sellers Win comparing the two series.

Now that we know what we know about the electrolyte problems you may actually be better off
to the tune of thousands of dollars over the years having the small reservoirs.

Getting the 1/2 measure of the Lithium Hydroxide is a big problem according to the
Changhong Battery Doctor. Then it's a cheap 1/2 potency grade on top of not being enough.

Changhong may have had some heat problems with the small reservoirs back in the day but
those guys were pushing a C4 or C5 Charging Rate.

I'm starting back into a research project for my son so good luck.
You should be able to figure it all out.
It may not have to be so bad.


Bill Blake

[Mike90250]

Nope, no battery monitor included.

I've never claimed what my generator setup is, and it's NOT state of art. It's old enough to be art.
I get my usage and harvest from the internal logs of the inverter and charge controller, and have no reason to suspect they are anything other than good commercial grade monitoring, within +-5% or so.

When the water pump is not running, I have little daytime loads, since I've had no good sun, I've actually gone to laundromat to save power and generator runtime. Fuel costs are negligible.

and Bill B, I'm just not getting the reference to the Rolls batteries.

Mike

[russ]

Bill - Your assistance and 10$ will allow one to buy a cup of Starbucks coffee. Forums are nice bu most have more BS than useful information.

So you didn't get the free E-Xpert Pro Battery Monitor that is now standard, required equipment
when dealing with your Nickel Iron Battery Dealer.

http://www.tbs-electronics.nl/products_expertpro_features.htm

If you had it your Ni-Fe Guarantee would rise and set around that - and only that - Meter.
Period.

Since you have a state of the art generator set-up we have no way of knowing how much power you use
per day based on your solar panels unless you say.

The first daily figure you quoted sounded good to me since it works out to around $3 per day
where I live. That's less than 1/2 of the latest bill here.

Now your talking less than 45 cents per day plus a little tax - if it was here.

What kind of generator fuel costs are you looking at ??

So if I take $7992 worth of Rolls 5000 Series Batteries (including delivery)

and charge them just one time for the entire week

and then discharge them by 78% only one time for the entire week

I will equal your entire Ni-Fe trip for the whole week. Wow.

Seems hard to believe - don't it.

Let me at's it.


Bill Blake

[Sundetective]

Actually, Correction DAY should be WEEK, so I'm using 32 kwh a week, and in the same week, 79 kwh was used to recharge. I had to go through my logs, looking for a week that started full, and ended full.

I'm not getting 79 kwh daily, out of a 3kw array in winter !

I suppose there is some incidental daytime usage mixed in there, but at the most, 1KWh per day, or 7KWh total so my recharge efficiency goes up a fraction, 32kwh out, and 72kwh replacement.

So when I'm not in summer mode, pumping water for ag usage, I'm burning about 4.5 kwh per day, which includes 2, energy star fridges. (that's about 140kwh per month for city dwellers).

****

So, the lowest my bank (42 cells) has been, has been 46V, [ 1.095V per cell ] which was, with a 6KW inverter, nowhere the 130 amps the inverter could have possibly drawn. Say a 1Kw load, would be no more than 25A from a 800ah bank, should still be a pretty light load for them.

Both meters, in the Tristar, and the Xantrex, agree pretty well, along with my 2 DVM's, so I'm not too concerned about metering.

So you didn't get the free E-Xpert Pro Battery Monitor that is now standard, required equipment
when dealing with your Nickel Iron Battery Dealer.

http://www.tbs-electronics.nl/products_expertpro_features.htm

If you had it your Ni-Fe Guarantee would rise and set around that - and only that - Meter.
Period.

Since you have a state of the art generator set-up we have no way of knowing how much power you use
per day based on your solar panels unless you say.

The first daily figure you quoted sounded good to me since it works out to around $3 per day
where I live. That's less than 1/2 of the latest bill here.

Now your talking less than 45 cents per day plus a little tax - if it was here.

What kind of generator fuel costs are you looking at ??

So if I take $7992 worth of Rolls 5000 Series Batteries (including delivery)

and charge them just one time for the entire week

and then discharge them by 78% only one time for the entire week

I will equal your entire Ni-Fe trip for the whole week. Wow.

Seems hard to believe - don't it.

Let me at's it.


Bill Blake

[inetdog]

Originally Posted by ursus_maritimus
....

I am considering getting another set that won't have spent two years in storage (On some of the cells I received there was a noticeable dark bath-tub-like ring on the interior of the case, near the fill lines. What does that mean?)
I noticed all my cells developed that same dark ring shortly after I started using them, but vendor suggested I was seeing things. There was only about 2 months of factory sealed storage in my case, before they were filled and activated.

I noticed all my cells developed that same dark ring shortly after I started using them, but vendor suggested I was seeing things. There was only about 2 months of factory sealed storage in my case, before they were filled and activated.

Several things come to mind immediately:
1. Are either of you using any kind of magic float oil on top of the electrolyte?
2. Is the ring below, above or straddling the space between the lowest electrolyte level and the highest? And is it darkest at the top?
If so, it could result from the electrolyte clinging to the plastic as the level boils down and drying on the side.
3. Or the result of a reaction between the electrolyte and the plastic in the presence of high oxygen concentration just above the electrolyte surface? The hydrogen will rise and be dissipated, while the oxygen will just replace the nitrogen-oxygen mix which is normal air.
4. Possibly some impurity in the electrolyte or something dissolved off the plates at the initial fill is just rising to the surface of the electrolyte and being deposited on the plastic as the level goes up and down?
5. Next???

Can you safely reach into the cell through the fill hole with a non-conductive alkali-resistant probe and rub the surface of the case to see whether it is an insoluble deposit that will rub or scrape off or a change to the plastic itself. (Either one would be worrisome to me.)