Fully Charging Using SG as the Reference Point for 100%

[Matrix]

So I joined in on a discussion about charging and Battery Life here the other day, and was suggested I start a new thread. After thinking more for a while, re-reading the responses there and processing it all, I decided to start this thread to clarify and correct my thinking.

In the linked thread above, Mike Wrote:

If your hydrometer is reading higher than factory SG, something is wrong. It just can't. When a batch of electrolyte is mixed up, it has a specific amount of sulfur in it, and is what ever the factory says it is supposed to be. Some factories use 1.257, some use 1.3, some use 1.2. But the amount of dissolved sulfur is there, at 100% of what the Mfg used.

If I am understanding this comment correctly, max SG does not change from the original electrolyte level.

So if my Hydro reads a number higher than what the manufacture says is the 100% charge number (for Trojan that number is = 1.277), and no other issues of contamination have occurred in the battery ... does that mean I charge to the highest number that my hydro reaches (the point where the number stops rising) and assume my hydro is off and incorrect?

Or does the manufacture built in an amount of electrolyte that would allow a hydrometer to read higher than the manufacture 100% charge number of 1.277?

Another way to look at it (or say it) .... if the manufacture says 100% is 1.277, but I can charge the batteries to 1.298 according to my Hydro, do I assume my hydro is off ... and charge to the highest number I can reach (my 1.298) until the batteries stop receiving charge, or do I go to 1.277 because the manufacture has built into the SG more acid than they want the user to rise to? (that last part is probably stated incorrectly, but I hope you understand what I am trying to say)

I am using and comparing both a glass hydro (the one often recommended here) and the MidNite Solar Hydro-Volt. Both have temp comp. I am getting very similar readings from both.

Also ... I realize increasing the voltage increases the amps during charging, but does increased voltage hurt the batteries (unless there is heat build up and the batteries get too hot) . My problem is my charger keeps turning off before the max SG is full reached if I use the Trojan 29.6v number unless I increase the volts. Both the solar and AC charger do this. And I have adjusted the voltage of both to reach 1.277 in the highest cells in the battery bank. I have the voltages set about a volt or more higher than Trojan's charge voltages - at about 30.8-31v for absorb. BUT if I have to use my Hydro's highest number reached because that is the real 100% charge number for me, I will have to increase those voltages even more. Is that a bad thing?

(Note: I have never over heated the batteries. Even at my higher voltage levels ... they just don't heat up. And they hardly use any water in 3 months since putting them into service new in Oct 2017)

[Mike90250]

OK, there is one mistake that CAN cause a high SG reading, the electrolyte has been bubbled so much, the remaining electrolyte is more concentrated than the factory fill, and the fluid level may even be below the top of the plates (makes it hard to suck up electrolyte to measure). But if you refill with distilled water to the original factory level, and gently agitate or run at least 1 good absorb cycle to let the bubbles stir / remix the electrolyte, when the proper temperature correction is calculated, the SG is supposed to match factory.

If your cells are not using water in 2 months, you are not recharging enough and the electrolyte can possibly begin to stratify, affecting the SG reading. Usually, water at the top, and the heavier acid at the bottom - so that does not explain the High SG either.

Refill the batteries to the proper level, bubble them for a day, and then try the temperature corrected SG reading.

[Sunking]

If I am understanding this comment correctly, max SG does not change from the original electrolyte level.

Incorrect. It can and will go lower. Example any spillage or loss of electrolyte. You cannot put electrolyte back in. Hard charging for example will make for acid mist from heavy gassing. Ot tipping the battery over and spilling electrolyte.

So if my Hydro reads a number higher than what the manufacture says is the 100% charge number (for Trojan that number is = 1.277), and no other issues of contamination have occurred in the battery ... does that mean I charge to the highest number that my hydro reaches (the point where the number stops rising) and assume my hydro is off and incorrect?

Or does the manufacture built in an amount of electrolyte that would allow a hydrometer to read higher than the manufacture 100% charge number of 1.277?

You EQ until SG quits rising, and that is as high as it can possible get. That does not mean you will read a perfect 1.277. There are a lot of factors to consider. Unless you have a Master Hydrometer, there will be some minor inaccuracies. What you want to do is set a Bench Mark by EQ until SG stops rising when the batteries are new and have had several cycles to form the plates. Initially they will read a bit low. But after 20 to 50 cycles you will see peak, and that is your Bench Mark.

One other thing to consider is Trojan does not activate the batteries normally (add electrolyte). The distributor does that, and depending on the area of the country the mix will vary. In warmer climates they will mix a stronger electrolyte. Deep cycle batteries in a tropical climate can be as high as 1.330

Also ... I realize increasing the voltage increases the amps during charging, but does increased voltage hurt the batteries (unless there is heat build up and the batteries get too hot) . My problem is my charger keeps turning off before the max SG is full reached if I use the Trojan 29.6v number unless I increase the volts. Both the solar and AC charger do this. And I have adjusted the voltage of both to reach 1.277 in the highest cells in the battery bank.

Increasing the charge voltage does not increase charge amps. Get that out of your head. The current is controlled by the charger current regulator. If I were to put a 20 amp charger on your batteries, set the voltage to 29 to 32 volts, the charger will provide 20 amps and not 1 amp more. I can then put your batteries on a 100 amp charger set to a lower voltage like 28 volts and it will charge at 100 amps period.

With solar you will have to use higher voltages simply because of the fact power is not constant, it varies, and there are not enough hours in a day to fully charge a Pb battery unless you designed it to do so in the short months of winter, and even them can fall short because ABSORB takes more hours than you have sun light.

By turning up the voltage forces your Controller to stay in BULK mode for the whole day or most of it. BULK mode harvest every possible watt the panels are capable of given the conditions. Absorb phase is Constant Voltage and current will be no greater than Bulk for a few seconds, and then tapers toward zero despite the fact the panels can generate a lot more power if demanded. By turning up the voltage, especially in winter months, forces the controller to pump in as much power as possible from sunrise to sunset.

Last thing to consider all voltages and SG you have mentioned are at 77 degrees F. As the temp drops, you have to raise the voltage and perform a Temp Corrected reading.

Over charging can and will cause damage mainly in the form of corrosion, and wil use a lot more water. There is NO SUCH THING as a perfect voltage or SG. You have two choices: Undercharge or Overcharge. 95% of all batteries failures are from undercharging. You will get longer cycle life and more capacity on the overcharge side of the fence. Jus tdo not push it. Look it is winter, cold, and maintaining full charge is challenging.

[Mike90250]

.......
Increasing the charge voltage does not increase charge amps. Get that out of your head. The current is controlled by the charger current regulator. If I were to put a 20 amp charger on your batteries, set the voltage to 29 to 32 volts, the charger will provide 20 amps and not 1 amp more. I can then put your batteries on a 100 amp charger set to a lower voltage like 28 volts and it will charge at 100 amps period.

With solar you will have to use higher voltages simply because of the fact power is not constant, it varies, and there are not enough hours in a day to fully charge a Pb battery unless you designed it to do so in the short months of winter, and even them can fall short because ABSORB takes more hours than you have sun light...........

I'll note an exception here:
1) Charging from Solar Charge controllers, while in Bulk and sometimes even in Absorb, there is no "current limit" for the charger, except it's max output (or an artificial lower limit, manually set if the controller is overpaneled) Every bit of power it can harvest, is used for charging (Sunkings Max Smoke mode)

2) Once the batteries reach the preset Bulk/absorb voltage [this is the same voltage, not 2 different settings] then the current starts to tapper off in Absorb.
If the Bulk voltage is raised and sufficient solar power available, the current limiting device is the batteries internal resistance - When deeply discharged, they will accept much higher rates of charge amps than when they are 90% full), so some conditions could see higher amps, when voltage is raised. This happens when a foggy morning suddenly clears at 11am, and solar power slams into the low batteries. Usually, as the sun rises, the solar power slowly ramps up charging the batteries gradually, and by 11am, the batteries have had a couple hours of slow charging and their voltage has risen from the overnight low.

3) Power. If you only have 300w of panels, the best MPPT controllers can only manage 285w of power into the batteries. PWM controller may only dispense 120w, depending on the panel vs battery voltage mismatch.

[Matrix]

Thanks. Always helpful

[Matrix]

You EQ until SG quits rising, and that is as high as it can possible get. That does not mean you will read a perfect 1.277. ... What you want to do is set a Bench Mark by EQ until SG stops rising when the batteries are new and have had several cycles to form the plates. Initially they will read a bit low. But after 20 to 50 cycles you will see peak, and that is your Bench Mark.

OK so I have had several cycles on these batteries (in operation since Oct 2017). Probably 50 or more. But most likely never fully charged consistently after each discharge. Also, 5-6 EQ charges as well over the past 3 months, most of which did get the batteries fully recharged.

Yesterday and today I took the batteries totally off any discharge, charged and EQ'd them. Tested, and EQ'd again. From there they went to float for 10 hours at 29v over night. Tested again, EQ'd one last time to confirm the SG has quit rising. It has.

Average cell Results per battery for these Trojan L16H-AC 435ah 6v batteries - 24v system
Battery 1 = 1.292
Battery 2 = 1.286
Battery 3 = 1.295
Battery 4 = 1.292

The highest cell was 1.298 (in battery #3) lowest was 1.286 (in battery #2)

All the cells in #2 were at 1.286 and all the cells in #4 were at 1.292. The Other 2 batteries had modest 7 point variances.

So I assume this would be some sort of base line.

My question is:
1. should my target be to charge the battery bank until battery number 3 hits 1.295
2. or should I average all 4 batteries together for a target SG of 1.291
3. or charge to the lowest battery so that battery does not get over charged and charge the whole bank to 1.286

My first instinct would be to go for #1 given my interpretation of all the info you gents have previously given me.

But from this I guess I can say that the manufacture 1.277 is low given my hydrometer, and that using my hydrometer to 1.277 has been under charging the batteries. So I should be charging to at least the lowest number I have now established which was 1.286 on my hydrometer.

[Sunking]

Average cell Results per battery for these Trojan L16H-AC 435ah 6v batteries - 24v system
Battery 1 = 1.292
Battery 2 = 1.286
Battery 3 = 1.295
Battery 4 = 1.292

The highest cell was 1.298 (in battery #3) lowest was 1.286 (in battery #2)

All the cells in #2 were at 1.286 and all the cells in #4 were at 1.292. The Other 2 batteries had modest 7 point variances.

So I assume this would be some sort of base line.

Correct. FWIW and do not take it wrong, but you cannot see the forest because the trees are blinding you. A 7 point spread is excellent. Your done.

Don't worry about EQ until you have a 30 point spread as Trojan instructed you. SG can only go so high, and will not go any higher. That is why you EQ until SG stops rising for 60 minutes. Going any further will damage your batteries, and it is impossible to take them any higher. So relax, your done.

[Matrix]

Correct. FWIW and do not take it wrong,

Ha ha ha ... not possible.

... relax, your done.

Good to know. And while I understand the "7 point spread is excellent" thing, and the "Don't worry about EQ until you have a 30 point spread" ... are you saying, now try to set my Solar CC to daily reach this discovered battery SG baseline in normal charge cycling ... correct? At least somewhere between 86 and 95.

OK ... I have some bigger "fish to fry". Have some electrical trouble shooting to do and some peculiarities with my Conext SW 4024 Inverter to figure out. Once I trouble shoot all I can, I will probably be on here asking about the Inverter behavior before I actually contact Schneider ... again. This SW has been a bit of a disappointment. I finally got them to admit it will never do some of the "features" it was advertised to do. A topic for a thread to come. Out.

[Sunking]

Good to know. And while I understand the "7 point spread is excellent" thing, and the "Don't worry about EQ until you have a 30 point spread" ... are you saying, now try to set my Solar CC to daily reach this discovered battery SG baseline in normal charge cycling ... correct? At least somewhere between 86 and 95.

Pretty much close within .010 is good enough. Monitor water usage, If you find yourself adding water frequently back off a bit.

Are you compensating for temp?

[Matrix]

Yes. I am armed with enough info to do it now. Thanks again

[Matrix]

Pretty much close within .010 is good enough. Monitor water usage, If you find yourself adding water frequently back off a bit.

Are you compensating for temp?

Ok, so after several full days of sun and watching my SG each day and adjusting my Solar CC ... I am getting a full battery. BUT as we have discussed before in other threads, I am having to set my absorb to 2.60v per cell to get there. Sunking ... you noted in another thread recently ...

Corrosion of the grids are created by voltages above 2.45 volt @ 77 degree F for extended periods of time. That does not happen with a Solar system.

So in my Solar charging, At 2.60v per cell, I don't need to concern myself with grid corrosion - Especially if I am not exceeding 77 degree F?

I've tried lower absorb voltages with loner times or end amp settings, but the charge current gets so low (like 2 amps) that the SG stops rising before the batteries are fully charged even though I am in an absorb charge. So lower volt absorbs for longer times seemed useless. To get to the SG need to read fully charged, I have had to run higher voltages in absorb. Upwards of 2.60v per cell

[Sunking]

Back it off to 2.45 vpc for a week or two.

[Matrix]

Backed it off to 2.45v for a season, the AC charger is Not getting fully charged in Absorb. Only work around I can figure with that charger is to set the Bulk/Absorb/and Float to same voltage, then it finishes on float, but you have to watch it because it would never end or time out. I guess at some point the battery bank would stop receiving current, but wouldn't that be a recipe for over charge?

[Mike90250]

There are 2 types of float.
AC charging, like in a computer UPS, the batteries get charged and stay in float for 90 days. Called Standby Duty Cyle, and the voltages are a half volt or so lower than :
Solar Charging, where you rely on 5 hours of sunshine to cram as much power into the batteries as you can. Called Cycle Duty charge, and voltages are a bit higher than Standby
Float seldom serves much purpose in off-grid, as there are not enough hours to make it matter, unless the batteries are not being used.

[Matrix]

As long as it does not harm the batteries to solar charge (and occasionally AC charge them) at 2.6v /cell ... I'm good to go. I set the absorb to 2.6v /cell and current to 45 amps (about C/10), the charger walks the voltage up to that voltage in bulk, Spends about an hour at that 2.6v /cell and is pretty much full according to SG. If it's not hurting the batteries, That is what it takes.