Learning curve

HotRod · May 10

Hey all! My battery just finished a bulk/absorbtion charge cycle, so I thought it would be a good time to check temps and SG. Here's what I got:

Temp on top in F. SG on bottom. 58°F ambient temperature.

Is this what I should expect to see?

HotRod · May 10

Forgot to mention the battery is a refurbished forklift battery. It's a 24-85-27, so 24 cells, 1430AH, lead acid.

BB. · May 10

Battery A2 at 1.27 SG would be a candidate for Equalization charging... Ideally, batteries should be within 0.015 to 0.030 SG units from high to low cell(s). Over 0.030 difference, suggest EQ needed.

However, cells to differ and change SG limits over time. Doing EQ once a month, higher voltage charging until SG stop rising (and monitoring temperatures to ensure batteries do not overheat), then log the temperature corrected SG... That is your "new" 100% SoC.

EQ is hard on FLA batteries. You only want to do it when needed (SG differences, some mfg. suggest once a month, especially if "tall cased" cells).

-Bill

HotRod · May 10

Thanks Bill! The battery has only been online since the 27? of last month. Cell A2 was low of fluid when I checked it before start up. Altogether I added 1.5 gallons to top off all the cells. Not sure which ones took the most, I have a flow-Rite watering system on it, I just know that one was obviously low when I gave the thing a visual inspection.

So, should I do a forced equalization charge on it? I'm thinking I should wait til I have the temp sensor to do that though. I don't know. Suggestions?

BB. · May 10

Roughly, a 0.100 SG change from ~1.27x to 1.17x SG units is the difference between 100% SoC and 50% SoC... So, a 0.030 SG difference is about 15% storage difference (State of Charge) between the high and low cell.

If you are not deeply cycling the battery bank at the moment, say down to (typically) 75% SoC (and not going to 40% SoC), everything should work OK--And exercising the bank and EQing after 30 Days of Service and see what you in SG at that time (with full EQ), it should not hurt anything.

Given that you have added a bunch of water, and this is a new (to you) installation, running an EQ to mix the water and electrolyte, and getting your first SG readings for your logs and verifying the battery is in good condition, would not be a bad idea.

-Bill

HotRod · May 10

Thanks again Bill. I have been setting the night time grid support voltage down to 49.5v, but it has yet to go below 50v. in the mornings its usually down around 51.5 - 52v ballpark. the panel says thats ~50% SoC. It's just 5 LEDs on the front of the inverter and at least 3 are lit every morning.

Estragon · May 11

FWIW, +1 on Bill's suggestion for an EQ. Ideally, I'd want a temp sensor controlling voltage vs temp, but if it's going to be a while I'd probably do the eq and monitor temp manually. "Warm" (say 80-90ish °F) is okay. "Hot" (eg. 110-120+°) means stop EQ.

The low cell is likely fine, just a bit of dilution not mixed in from watering, but IMHO it's important to establish a good baseline reading on a new bank. It probably won't take a heck of a lot of EQing to get the baseline reading.

HotRod · May 11

I EQed the battery yesterday as suggested. The hottest temp I got was 79.9 at the center of the bank. The low cell, A2, came up to 1.28SG. should I hit it again?

Few basic questions.
How often should I take SG and temp readings?
How often should I be adding water?
What should I be doing besides that?

Estragon · May 11

I generally check SG on every cell on long weekends (which is just ny way of remembering to do it), so about every couple of months. If I find a range of SGs, which I usually do, I EQ and check SG on the lowest couple of cells every 1/2 hour. When the SG stops rising on the low cells between checks, I stop the EQ. If the 1.28 cell stopped rising, that may be as good as it gets. I sometimes have to EQ over a couple of days depending on sun and loads.

I check water at the same interval as SG. If low, I might add a bit of water to be sure plates stay covered during the EQ, but as the acid can expand a bit I don't fill too full. On my L16s, about 1/4" from full (bottom of the fill tube) seems to work well.

Aside from that, just keeping things clean and getting to know your bank's "personality". Over time, if you watch things, you get to know what normal is for it with your specific usage.

HotRod · May 11

"I sometimes have to EQ over a couple of days depending on sun and loads." Can you elaborate on that a bit? Im assuming you meant that you run EQ on a given day and then do it again the next day, not allow the EQ to run all night unsupervised, right?

BB. · May 11

If A2 stopped and did not exceed 1.280 SG--Then that is the "new" SG level.

Regarding the auto watering... You might want to turn it off and only autowater once a month or something like that (i.e., when doing monthly SG checks and EQ, ... SG first and make sure all plates are covered, do not fill now, EQ with SG check every 30-60 minutes until SG rise stops, then top off water. You do not want to fill to brim, then EQ (gassing and heat, electrolyte may spill out of cell(s).

Auto watering is nice, but I fear over filling and a stuck valve that overflows a cell (uncontrolled filling). Running auto water only when you are there (or at least do this for awhile until you trust that all is good)--Would be my suggestion.

As the battery cycles, SG levels will change, and can even rise over a few months of use/EQ cycles. Normally, you are trying for >90% SoC at least once per week. You are not trying for 100% (basically light EQ) every day--That is hard on the FLA batteries.

-Bill

HotRod · May 11

Thanks Bill. For clarity about the Flo-Rite watering system, it's just the float caps and connecting hoses. I manually water the whole bank simultaneously with a bulb hand pump. So I'm there when the watering takes place. I just have no way of knowing which cells are low and taking water. I've only watered it the one time. From what I'm gathering, once a month should be adequate, once I've learned the behavior of the equipment. I'm still learning and trying to develope my plan. I plan on gathering a set of readings early Monday morning before charging starts. Then do it again after the battery has been in float for about an hour. The temp sensor is going in as soon as my back will let me get back in the swing of things. Probably this coming week.

-Jason

Estragon · May 11

I never EQ unsupervised. Sometimes if loads and/or weather means the sun goes while SG is still rising, I continue (ie by checking SG on the low cell(s) every 1/2 hr) the next day after bulk/absorb is done.

I'm sort of tempted by watering systems, but I do like to see if any cells are using more water than others. I guess I could still check with a system, but hand watering kinda makes me notice.

BB. · May 11

You have 24x "identical" cells. You are, at first look, trying to find cells that are "different" from the rest. That could be low SG, could be high SG. Could be cell(s) using too much or too little water.

Ideally, you want to check the SG and water levels before your fill (and EQ).

When you see something "out of balance", then that is an indication to check further.

-Bill

HotRod · May 11

Thanks Estragon, my watering system came on the battery. I thought it sounded like a good idea, so I paid a $100 for the seller to leave it in place. And it's great for watering. Very easy, clean. The drawback is the need to remove it to check the SG and temps.

Thanks Bill, I believe I'll just start eyeballing the water levels weekly for a few weeks while checking the SG and temps. That should give me some idea of which cells are using water before I water the whole bank simultaneously.

-Jason

HotRod · May 13

" I plan on gathering a set of readings early Monday morning before charging starts. "
I didn't make it. got up too late, cause GoT.....LOL

HotRod · May 15

The water levels looked good. All the plates were covered plus some. It was in the mid 40's last night so I'm not surprised by the battery temps. The little + and - signs are for when the reading was just above or just below the mark. Temps shot three times with an IR gun and took the average. The battery scale on the front of the 6848 says I'm at about a 50% SoC.

HotRod · May 15

Da panels.

HotRod · May 15

Cell D1 is a misprint. It was 1.305

HotRod · May 15

If a .100 drop in SG is equivalent to 50% SoC, can i assume that every .01 drop is 5%? If true, is my battery actually only discharging to 85-90% SoC? After shopping digital SG meters, that $450 Schneider battery monitor aint looking so bad.

BB. · May 15

Very roughly...

https://www.trojanbattery.com/tech-support/battery-maintenance/

TABLE 1
State of Charge as Related to Specific Gravity and Open Circuit Voltage
Percentage of Charge	Specific Gravity Corrected To	Open-Circuit Voltage
		6v	8v	12v	24v	36v	48v
100	1.277	6.37	8.49	12.73	25.46	38.20	50.93
90	1.258	6.31	8.41	12.62	25.24	37.85	50.47
80	1.238	6.25	8.33	12.50	25.00	37.49	49.99
70	1.217	6.19	8.25	12.37	24.74	37.12	49.49
60	1.195	6.12	8.16	12.27	24.48	36.72	48.96
50	1.172	6.02	8.07	12.10	24.20	36.31	48.41
40	1.148	5.98	7.97	11.89	23.92	35.87	47.83
30	1.124	5.91	7.88	11.81	23.63	35.44	47.26
20	1.098	5.83	7.77	11.66	23.32	34.97	46.63
10	1.073	5.75	7.67	11.51	23.02	34.52	46.03

-Bill

HotRod · May 15

Are there any "affordable" precision SG meters that can be reliably read to .001? I'd even go to float bulbs if I can gain accuracy.
If I am using less than 15% of my battery daily, how often should I be equalizing? Am I really using that little or am I fooling myself?

-Jason

MrM1 · May 15

Consider a Refractometer for about $20 large

https://smile.amazon.com/gp/product/B01CQVHTCW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

And I dont know if you call it "Affordable", but I really like the HydorVolt. Big numbers, Easy to read, Auto Temp comp. Mine agrees with both my refractometer and my float type hydrometer.

mike95490 · May 15

Refractrometers are generally pretty accurate, no bubbles, floats. Just make sure the temp offset is set right

But generally, after a couple months of living with the system,, you should be able to interpret the voltage and get close to your state of charge.

BB. · May 15

You need a 1.265 (or similar) sg equivalent sample solution to calibrate the hydrometer.

I don't think most will calibrate to 1.000 sg units pure water and measure 1,2xx sg.

Bill

HotRod · May 15

MrM1,

Image: https://us.v-cdn.net/6024911/uploads/editor/8g/nc2kfwv1dg02.jpg

I like this. It happens to be the exact one from the link, LOL! But I'm still gonna order the bulb mentioned as well. It just looks easier to use.

Mike, thanks. I'm with ya on the couple months of watching it. I'm trying to build up a data base now. It's a steep learning curve.

Estragon · May 15

I considered a refractometer, but I'm waaay to much of a klutz to be holding something containing battery acid up to my eye

HotRod · June 21

Well folks, here's what it looks like now after seven weeks in operation and 2 monthly EQs under it's belt. After charging and in float all the cells are around 85°F. My spread is .04 from highest to lowest and I'm not sure I'll be able to close that gap.

Last night, after 2 EQ cycles, A2 and B3 managed 1.29 SG. They were 1.29 after both the first and second EQ cycle so I stopped. Am I doing this wrong?

Estragon · June 22

I think you're doing it right. Assuming adequate EQ voltage, when your weakest cell(s) stop rising, that's about as good as it gets. No point stressing the stronger cells if you aren't improving the weak ones

Learning curve

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