Battery life lessons

[Matrix]

Thanks SunKing and Mike ... excellent info as always. Not trying to hijack the thread, just realizing that my real life inexperienced example and questions could possibly add some detail and (hopefully) additional clarity to the OP's initial question. So @Woutah, I hope this discussion has helped you with your batteries as much as it helps clear up some thoughts in my mind. My apologies if I hijacked the thread.

[Sunking]

Manufacturer says 100% = 1.277. But ur saying I need to go until all cells stop rising in SG... Regardless of my hydro reading (assuming everything is working correctly)??


And then when my cells all stop rising while charging.... I can assume That number according to my equipment (whatever that number is) will be my fully charged SG? So I should charge all batteries until all cells stop rising? And what ur saying is, that then all SG numbers across all cells will b the same. (at least in the same battery)?

Yes.

I agree with what Mike is saying, I just interpret the results differently. True your hydrometer may have some inaccuracy, no big deal as long as you are aware of it. Lets back up a bit and rehash what Trojan told you, and what any battery manufacture instructs you on how to EQ batteries.

Trojan told you the difference in SG is normal for new batteries because the plates have not fully formed right? A spread of 15 points is normal and nothing to worry about and expected right? So relax.

Mike is right in saying the SG can only go so high, and that happens when the batteries are fully charged up. It cannot go any higher. Trying to do so is a significant over charge that only corrodes the plates. So now look at Trojan's or any manufacture EQ instructions. What do they say? EQ until SG stops rising right?

So even though your hydrometer may read a bit to high, who cares as long as you know what that number is. Now if you want a very accurate hydrometer I can help you with that. It will cost more than $8, more like $50 to $90 using a lab qual;ity hydrometer and if you demand exact accuracy a Master Hydrometer but now we are talking $100+ and a good battery thermometer. Not really needed as long as you know what your hydrometer reads when SG is saturated.

So relax, I am positive you are OK. You just need some time and experience to gain confidence and knowledge. You are way ahead of 90% of folks who come here. Those folks do not know how to spell a hydrometer or what it does.

For now lets not hyjack the thread. Start another one and I will help you.

[Matrix]

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.

Manufacturer says 100% = 1.277. But ur saying I need to go until all cells stop rising in SG... Regardless of my hydro reading (assuming everything is working correctly)??


And then when my cells all stop rising while charging.... I can assume That number according to my equipment (whatever that number is) will be my fully charged SG? So I should charge all batteries until all cells stop rising? And what ur saying is, that then all SG numbers across all cells will b the same. (at least in the same battery)?

[Sunking]

SunKing, I see what your saying about float and Solar chargers ... but I run into the problem of not getting fully charged according to SG with my inverter-charger too ... UNLESS I set the volts higher than manufacture. I have no realistic absorb time cut off, the system just stops charging too soon unless I have the volts set to 30.8v

I understand what you are trying to say, I am right. .

You are getting there but still not quite on the same page. When you turn the voltages up, you are forcing the controller to stay in BULK or more technically correct is called Constant Current. Bulk is just a catchy marketing term. To be completely accurate with solar it Bulk is really constant power, as much as the panels can possible generate under the current conditions.

Here is a KISS example using a 100 watt model panel on a discharge 12 volt battery. Current = Power / Voltage. So initially the battery voltage is 12 volts and thus initial charge current is 8.33 amps. In a few hours later the battery voltage is 13 volts and charge current is 7.7 amps. When we reach say 14.3 volts current is down to 7.0 amps. Power remained Constant. An AC Charger is constant current. So if it were say 8.33 amps charge power is 100 watts if the battery under charge voltage is 12 volts, but at 14.3 has to be 120 watts.

By turning the voltage up you are forcing the controller to stay in Bulk or Constant power from sunrise to sunset harvesting every watt possible. That will minimize undercharging, but may or may not fully charge the battery by sunset. It just gets you every bit of power possible. Otherwise as you have experienced if you use 3-stages, you never come close to full charge.

Once you hit the Absorb stage, charge current will taper to 0 amps when and if the battery ever fully charges. Duing Absorb, you are NOT harvesting al the power, something less, much less. There are not enough sun hours in a day to ever get fully charged in winter unless you have more panel wattage than required. Very rare anyone has enough panel wattage. That has to be deigned carefully. In a DIY environment, 99% are grossly undersized. Tuff even for a pro because of the guess work involved, but pros are better guessers.

[Mike90250]

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.
The battery box has only lead plates in it, no sulfur, till the acid is poured in.
If the hydrometer reads overcharged, something is wrong, either the SG you are assuming is incorrect, the electrolyte is contaminated with something, or the Temp Comp is inaccurate. When you recharge a battery and drive all the sulfur back into solution, you can only get to 100%. It's real hard to dissolve lead into weak battery acid, so getting more than 100% indicates something other than "overcharge".

[Matrix]

I just went outside and did a full SG on all 12 cells. (4 batteries) Yes I have temp compensation set in my solar CC.

Conditions:
- 12:30pm / 45* F / Cloudy
- My 2.5kw array can produce at best 350 watts today
- Batteries started the day at 97%
- CC says batteries are at 100% by 12pm

SG readings
- Highest single cell 1.291 (all 3 cells in that one battery were over charged)
- Lowest single Cell 1.273
- On average, 3 batteries are at 100% or better
- 1 battery is over charged at an average SG of 1.289
- all batteries are at 100% or higher when SG is averaged per battery (not for the whole bank)

Do I lower my Absorb from 30.8v to 30.6v to not over charge the 1 over charged battery ... or keep it at 30.8v to insure all 4 batteries are at 100% even though one battery is getting over charged?

[Matrix]

I see wide variations in voltage meter accuracy. Have you taken a voltage reading AT the batteries with a known accurate DVM? Could be different than your CC or inverter/charger is reading.

Yes. While Charging, in Float and Resting ... They all match. I have a fairly accurate DVM

[littleharbor]

I see wide variations in voltage meter accuracy. Have you taken a voltage reading AT the batteries with a known accurate DVM? Could be different than your CC or inverter/charger is reading.

[Matrix]

I understand your dilemma. I have been there ( I usual AM there - Constant state of consfussion.) I have set my Absorb times to max on both my solar CC and my gen powered / AC powered inverter-charger. And if I set my voltage to the manufacture voltage of 29.6v (for a 24v system) I NEVER get a fully charged battery according to SG ... and I have 2 different hydrometers. The CCs never time out, they just reach a point and turn off charging, but the batteries are never fully charged. So have gone to upping the voltages until charged. Presently I am at 30.8v for absorb and my end amp setting (one of the 2 CCs has an end amp setting) is set to 5.7 amps on a 435 AH battery (which I know is low ... but it allows the CC to stay in absorb longer) on the system and at this point I seem to reach fully charged according to SG. But I have never had a time issue concerning the absorb timer. The system stops charging way before i hit absorb time ... based on amps.

SunKing, I see what your saying about float and Solar chargers ... but I run into the problem of not getting fully charged according to SG with my inverter-charger too ... UNLESS I set the volts higher than manufacture. I have no realistic absorb time cut off, the system just stops charging too soon unless I have the volts set to 30.8v

[Sunking]

Back to my questions. I'm asking as I don't want to make false assumptions!
1. I set bulk = absorb = float. I understand absorb is not a timed event, but I have to set a time. So what do I put here?

You are asking good questions. Enter max time like 4 or 6 hours. Essentially you will not have any Absorb phase. By setting Bulk = Absorb = Float converts your charge controller from a 3-Stage Charging Algorithm to a simple CC/CV charger. There is NO Absorb mode so it is a moot point other than you must set it to something.

2 & 3. "If it is low, raise the voltage" If at the end of the day the specific gravity is not at its maximum, I just up my Voltage levels?

Correct. However you may very well exceed the manufactures maximum range for Bulk/Absorb. Keep in mind in summer months you might very well be able to switch back to 3-Stage charging where you can set Bulk/Absorb to say 14.8 volts and Float to 13.5 volts. But in winter months despite going to maximum allowable voltage of your controller, it is possible you never reach full charge and have to use the genny once a week.

In winter months despite say setting the voltage to 15 volts, you may not ever see the battery get close to 15 volts. Example 14 volts may be the highest you see by sunset. If that is the case, you never reached gassing voltage (14.4ish). Next day the voltage may struggle to see 13.9 volts. That is called deficit charging with each passing day your battery is getting weaker and weaker and sulphation is growing robbing you of cycle life and capacity.

What you are doing is forcing your controller is to stay in Constant Current Mode (aka Bulk) which means it is harvesting using every watt the panels can produce from sunrise to sunset. The Controller never reaches the Constant Voltage Stage aka Absorb/Float/Equalize. Ideally what you are shooting for is at some point in the afternoon the batteries reach the set point voltage of say 15 volts and charge current starts to taper off before sunset, and specific gravity indicates full charge. When you see that happen, lower the voltage a bit and see what happens the next day.

You want to error on the over charge side if possible. Most likely you will see undercharging in winter which is telling you your panel wattage is too low. If you have a genny, chronic undercharging is not a big deal because it can be corrected with the genny. Just do not get in the habit of running the genny every day as that results in chronic Over Charging which needs to be avoided. If the panel wattage is correct, you should only have one month out of the year you need to run the genny once a week to top the batteries off. If you find yourself needing to run the genny every few days in winter is screaming telling you do not have enough panel wattage.

[Woutah]

Only difference is voltage set point. Absorb, Float and Equalize are Constant Voltage modes. Absorb is not a timed event. Thus why solar charge controllers fail to completely charge batteries. Absorb is a Current Event. Full charge is achieved when charge current tapers to 3% of C. That can take 6 to 10 hours. Equalization can take up to 24 hours.

Three stage charging does not work with Solar because the sun does not shine 24 hours. You have to use you hydrometer to set voltages. You want to force your controller to be a simple CC/CV charger and the way you do that is set Bulk = Absorb = Float. Start at 14.4 volts. As the sun sets check specific gravity. If it is low, raise the voltage. This time of year you will likely find there is no voltage high enough. There is simply not enough sun. This is why you must have a generator.

Take Mike's advice and read the stickies. Starting with this one.

Thanks - believe me, I read the stickies multiple times. A year ago I understood absolutely nothing of them, now I understand the concept and am learning every time I re-read them. Believe me, they are hugely appreciated!
I understand I need to use my generator on a regular basis to fully charge my batteries - clear.
Back to my questions. I'm asking as I don't want to make false assumptions!
1. I set bulk = absorb = float. I understand absorb is not a timed event, but I have to set a time. So what do I put here?
2 & 3. "If it is low, raise the voltage" If at the end of the day the specific gravity is not at its maximum, I just up my Voltage levels? I can keep increasing till either I've reached the max level allowed by the battery manufacturer or till I'd reach the max spec. gravity (probably won't happen without genny, but in theory...)

I hope my questions are more clear now!

[Woutah]

What stickie says set "Absorb = float" ? That needs correction or further investigation. Bulk=Absorb, Float is for long term idle, and generally not useful in solar, or in winter

Setting BULK=ABSORB=FLOAT is valid, for short sun hours, but you can overcharge batteries in the summer with that setting.

my previous post got cut off - the questions came from the you're killing your batteries sticky thread.
The question does indeed related to the winter period, I understand that if there's more sun I should lower my voltage points.

[Sunking]

What stickie says set "Absorb = float" ?

This is 1 or 3 of them.

That needs correction or further investigation. Bulk=Absorb, Float is for long term idle, and generally not useful in solar, or in winter

Mike you can fully charge a Pb battery with a Float Charger. In fact it is the best way and maximizes battery life. It just takes up to 24 hours which is useless for solar and daily cycle applications. I really dislike names like Bulk, Absorb, Float etc because they are meaningless terms. Every charger made, with the exception of some nickel base chargers. are CC/CV. Only difference between Bulk/Absorb/Float is a voltage set point. Regardless of what voltage you use to any charger is CC/CV and all behave the exact same way. Float voltage ranges from 13.2 to 13.8 volts. Bulk/Absorb voltage ranges greatly from 14.8 to 16.2 volts

Setting BULK=ABSORB=FLOAT is valid, for short sun hours, but you can overcharge batteries in the summer with that setting.

I agree with a caveat. That assumes the system was properly sized to begin with. Rarely does that ever happen. Without a hydrometer, a user has no clue what is going on.

Bottom line is a user has two charge options.

1. Under charge
2. Over charge

Under charging yields shortest battery cycle life and lowest capacity. There is no such thing as perfect for solar. You want to error on the over charge side of the razor blade. The only way to balance on the Razor's edge is with a precise Float Charger using temp compensation and a hydrometer like a telephone or utility uses.

[citabria]

Mike , you suffering from old timers disease like some of us? https://www.solarpaneltalk.com/forum...ge-controllers
This is how I found this forum.

[Mike90250]

What stickie says set "Absorb = float" ? That needs correction or further investigation. Bulk=Absorb, Float is for long term idle, and generally not useful in solar, or in winter

Setting BULK=ABSORB=FLOAT is valid, for short sun hours, but you can overcharge batteries in the summer with that setting.