Manually adjusting EQ voltage for higher temps

Riley · August 2022

I plan to do my first corrective EQ cycle next week.
I have learned that my Schneider gear does not perform/adjust the EQ voltage for temp compensation of the battery bank.

I want to make sure I have this right.

Calculation inputs:
Rolls S-550 battery bank (48V or 24 cells)
Rolls manual states EQ voltage at 25C of 62.4 -> 63.6
Rolls manual states temp compensation of: 5mV/*C/cell

So assuming my bank will be running at 35C (10C over nominal), my calculation is:
5mV * 10 degrees * 24 cell = 1,200mV or 1.2V reduction or EQ Voltage for bank temp of 35C

In other words the EQ voltage range for battery 10C higher than nominal is:
62.4V - 1.2V = 61.2V
up to
63.6V - 1.2V = 62.4V

Note: This is a 6 month old battery bank so I assume stay on the lower edge of the EQ voltage range.

The EQ voltage of 61.2 seems low, perhaps too low to be effective if the bank is at 35C.
The voltage of 62.4 does seem reasonable (ie: effective) but as the batteries get warmer, I would have to decrease the voltage even lower.

Do this make sense?
Any thoughts on this?
Should I clarify this with Rolls?
Perhaps I am over thinking this?

Thanks in advance.

Riley

JRHill · August 2022

Riley said:

I plan to do my first corrective EQ cycle next week.

Do this make sense?
Any thoughts on this?
Should I clarify this with Rolls?
Perhaps I am over thinking this?

Hmmm. The bank is 6 months old. What is the basis for your need to take corrective action? A lot of manuals and spec sheets suggest a time interval for performing an EQ but that is a generality. There is a much better reason to perform and EQ and that is that the specific gravity measured at EACH and every cell varies by more than a given percentage. If you have gotten reliable SG readings and they exceed that % then by all means do it. If you are just doing it based upon time then you might put more thought into your battery maintenance procedure.

Doing an EQ can be looked at as a controlled abuse of the battery. You don't want to do an EQ unless you have to do it, in my opinion. And doing an EQ during the heat of the summer without a charging system that does temperature compensation of the battery's charging voltages with the correct limits programmed can do more damage than good.

A few questions? Have you taken SGs? Are you good at doing it? In other words, taking a cell's SG multiple times and each reading is almost identical? Do you write the readings down and have the cells numbered and the ambient temperature at the time?

Hopefully you don't think I am anal but the darned batteries are expensive. And it doesn't take a lot of time to do it right? Here is a spread sheet that I used when I had lead batteries. I'll get it to you with the formulas if desired.

Battery Maintenance

Battery #	Cell 1 (L2R)	Cell 2	Cell 3	Ave	High	Low	Date	Batt Temp
1	1.260	1.250	1.260	1.257	1.260	1.250	3/6/2016	66.2
2	1.275	1.280	1.275	1.277	1.280	1.275			Temp Adj SG
3	1.250	1.245	1.280	1.258	1.280	1.245	Bank Ave	1.265	1.260
4	1.260	1.255	1.295	1.270	1.295	1.255	Bank High	1.295	1.289
5	1.270	1.250	1.280	1.267	1.280	1.250	Bank Low	1.245	1.239
6	1.280	1.260	1.275	1.272	1.280	1.260
7	1.260	1.260	1.260	1.260	1.260	1.260	EQ on Low?	YES	(< .1.250)
8	1.255	1.265	1.265	1.262	1.265	1.255	EQ on Range?	YES	(>. 0.030)

Notes:	Feb 12th: 56%SOC, 48.1v, 1.175 SOC

Riley · August 2022

I have 0.020 or more delta between cells. I have taken lots and lots of SG readings and it's pretty consistent. Some cells are down.

If the cells were close, I would happy to not have to do this. Even when this bank was new, the SG difference was an issue. See my other recent thread.

I too am pretty anal and don't want to damage the bank but I want to get these cells evened out before I mothball for the winter time.

Riley · August 2022

JRHill said:

Riley said:

I plan to do my first corrective EQ cycle next week.

Do this make sense?
Any thoughts on this?
Should I clarify this with Rolls?
Perhaps I am over thinking this?

Hmmm. The bank is 6 months old. What is the basis for your need to take corrective action? A lot of manuals and spec sheets suggest a time interval for performing an EQ but that is a generality. There is a much better reason to perform and EQ and that is that the specific gravity measured at EACH and every cell varies by more than a given percentage. If you have gotten reliable SG readings and they exceed that % then by all means do it. If you are just doing it based upon time then you might put more thought into your battery maintenance procedure.

Doing an EQ can be looked at as a controlled abuse of the battery. You don't want to do an EQ unless you have to do it, in my opinion. And doing an EQ during the heat of the summer without a charging system that does temperature compensation of the battery's charging voltages with the correct limits programmed can do more damage than good.

A few questions? Have you taken SGs? Are you good at doing it? In other words, taking a cell's SG multiple times and each reading is almost identical? Do you write the readings down and have the cells numbered and the ambient temperature at the time?

Hopefully you don't think I am anal but the darned batteries are expensive. And it doesn't take a lot of time to do it right? Here is a spread sheet that I used when I had lead batteries. I'll get it to you with the formulas if desired.

Battery Maintenance

Battery # Cell 1 (L2R) Cell 2 Cell 3 Ave High Low Date Batt Temp
1 1.260 1.250 1.260 1.257 1.260 1.250 3/6/2016 66.2
2 1.275 1.280 1.275 1.277 1.280 1.275 Temp Adj SG
3 1.250 1.245 1.280 1.258 1.280 1.245 Bank Ave 1.265 1.260
4 1.260 1.255 1.295 1.270 1.295 1.255 Bank High 1.295 1.289
5 1.270 1.250 1.280 1.267 1.280 1.250 Bank Low 1.245 1.239
6 1.280 1.260 1.275 1.272 1.280 1.260
7 1.260 1.260 1.260 1.260 1.260 1.260 EQ on Low? YES (< .1.250)
8 1.255 1.265 1.265 1.262 1.265 1.255 EQ on Range? YES (>. 0.030)

Notes: Feb 12th: 56%SOC, 48.1v, 1.175 SOC

I was wanting to do a spreadsheet instead of my paper hand written method. Message me and I can send you my email to send your sheet, looks good!

JRHill · August 2022

Not knowing what your "current'

charge stages are set for voltage and time limits, you could bump your Absorb and soak time a bit until the weather moderates a bit. Day by day it will should improve. You might even stay with that for the longer term as I did. The only consequence would be a very little bit more distilled water consumption. For example I greatly improved my SGs cell by cell by upping the Absorb voltage by ~2 vdc and extending it to more than 2.5 hours or more without doing an EQ. The extended Absorb was like a mini EQ which worked well for stirring up the electrolyte without doing the big voltage hit. Maybe this could work until the summer heat subsides and even further. Have you thought about getting a temperature device with a remote sensor that you could stick between batteries? A bit of thermo paste too? I had my batteries placed 2x4 so with the sensor in the middle it did pretty well. But seriously, I offset the need for EQs greatly by upping Absorb voltage and time by a little bit. Voltage not more than ~58 and I took time out to 4.5 hours. I didn't use that much more water. Didn't hurt the batteries at all vs hitting them hard with the voltage sledge hammer.

My problem was light draw and moderate charging. I never worked the lead hard which they like and need to stir things up - up AND down. After two banks of Trojans I learned the problem I bit the bullet and went with 3 Simplifys, then added a 4th. They don't care about light charge or discharge, partial charges, etc. Plus I get to use the space below 55% SOC. Bt for you with that expensive bank, wouldn't you like to get that 7+ years that others brag about with their Rolls'?

If you adjust things, I'd love to hear your experience; Rolls vs Trojans.

Riley · August 2022

Thanks JRHill. That's effectively what I did (bumped up my absorb time) to get start to get better cell SG matching.
Please see my other thread on this topic: https://forum.solar-electric.com/discussion/357529/sg-cell-difference-in-new-rolls-battery-bank

I have the same problem, my cabin doesn't draw much, maybe 30% SOC draw (so 70% SOC by morning).
My gear does have temp sensors (for both CC and Charger) but as I mentioned, Schneider gear doesn't do temp comp for EQ cycles (so I am told on my other thread).

I also don't have enough panels for this time of year. Tons of power in the late spring/early summer. I plan to design in some extra a panels over the winter so that I can stir things up better (charge at 15% of the AH rating).

I do stir things up by running a heavy generator bulk charge now and then (and finish with long PV absorb).

I rarely do a heavy discharge.... that's just how my cabin power and water systems are designed. Perhaps I just need to work these batteries harder but its hard for me to get my head around that.

I did get 5 years out of my first set with not any noticeable degradation (until I had a unrelated accident which is a long unrelated story).

JRHill · August 2022

I understand.

Riley · August 2022

Just to follow up on this - the Schneider gear (at least the Conext MPPT 60 150 ) does do temp compensation for EQ cycles. Seems to work fine so no need to manually compensate

JRHill · August 2022

So how are your SGs looking?

Riley · August 2022

I did a temperature compensated EQ for 3 hours. The delta in SG values is now 0.015 instead of 0.030.

As others have said (repeated from Rolls support), run for a few weeks at this point and cycle then up and down.

I can always do another EQ in a month's time before mothballing for the winter time (until sometime in Jan). Rolls documention states that as well.

And thanks for asking.

JRHill · August 2022

Mothballing.... Sigh. Can't you just stay there?

Riley · September 2022

My wife would leave me if I lived here year round. Pretty cloudy and isolated here in the winter time.

Manually adjusting EQ voltage for higher temps

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