Are my batteries toast?

[SirHund]

So yes to get started here I am new to solar but have on and off studied it over the years. I jumped in head first 6 months ago and love it. I have pretty well just been experimenting to see what works.

I managed to acquire some 12v marine batteries from salvage and revive them to a pretty even balance. I am currently using 12 marine batteries that were paralleled but now are run in a 24volt series. They are charged with 4 renogy 100 watt panels also series and 4 Photowatt 50w panels in series.

Question is that on my Renogy Rover 40a CC once the sun goes down....the charge will read out between a 25.1 and a 25.5. I would assume this means my batteries are maintaining a charge but that charge is on the very low end of a life cycle. Is this correct?

also yes I am upgrading to 6 volt batteries just searching out what is best for that type of battery yet cost effective.

[organic farmer]

... Question is that on my Renogy Rover 40a CC once the sun goes down....the charge will read out between a 25.1 and a 25.5. I would assume this means my batteries are maintaining a charge but that charge is on the very low end of a life cycle. Is this correct?

At the end of each day of charging your battery-bank ends with a charge between 25.1 and 25.5vdc, a 90% SOC and a 95% SOC.

If we can assume that your specific gravities are good and even. I would be focused on system loads and how much power you are producing during the day. Some power goes to the loads and some goes to your batteries. Are you sure your batteries are getting enough charge?

[SirHund]

I run little to no load thru the day. I'm usually at work. I am pulling down 600 wh for approximately 5 hrs so 3000 w per day and about to drop off to 4 sun hours. I haven't checked the gravity on the batteries. I simply cleaned and refilled them with fresh acid. My CD does go into a boost mode at 29 volts for 2hrs at a time and when it kicks down to float or even mppt it's running a consistent 27.5 to the batteries. But you can literally watch it drop off as the sun drops and then holds at 25.1-25.5.
Thank you for reminding me though as i have been meaning to run a SG test on these batteries and replace the acid in 4 of them that I did not do this to off the get go because they had a solid resting charge when I found them.

[Sunking]

At the end of each day of charging your battery-bank ends with a charge between 25.1 and 25.5vdc, a 90% SOC and a 95% SOC.

Which means absolutely NOTHING just like your advice is worth NOTHING.

I run little to no load thru the day. I'm usually at work. I am pulling down 600 wh for approximately 5 hrs so 3000 w per day and about to drop off to 4 sun hours.

You worded that incorrectly. I think you meant you use 600 watts for 5 hours and use a total of 3000 watt hours which is not possible with your system. You cannot possible generate 3000 watt hours of usable power in a day with only 600 watts of panels being clipped off at 500 watts. Here is the bottom line. You have 600 watts of panels. At 12 volts the largest battery you can handle is 500 AH, and at 24 volts only 250 AH. There is no way possible you can charge 12 x 12 volt Marine batteries in parallel with just 600 watts. And there is no way you can generate 3000 watt hours in a day. It is just not possible.

Now you are going to say well my batteries voltage says I am OK. They lied to you because they are tired and exhausted. Voltage does not mean much of anything. Just because a battery voltage is in the good range does not mean it OK or indicates State of Charge. It tells you nothing and is only an Indication.

As for used batteries, they are toast. Batteries are like Condoms, don't buy used Condoms.

[organic farmer]

Which means absolutely NOTHING just like your advice is worth NOTHING.

Hmm,aren't you the fella who keeps saying that an off-grid system should cost 'MORE' than a grid-tied system?

Yeah we see how well grounded in reality you are.

[SirHund]

Wonderful, maybe understand I am asking questions and trying to learn here.
Next, no I am not going to say my voltage says I'm fine, so I'm fine. I have noticed enough of a power loss since my change over.
which brings me to my next point, as I stated they are not in parallel they are series 24v. I have read some of your posts looking for information and saw how you jump on parallel groups, to which I agree. There is a diminishing point of return. Also a reason for my switching over, reorganization of my batteries and wiring. Running one 12 volt parallel string of 14 batteries wasn't cutting it and yes you are almost correct on the not possible to charge 12 batteries.
if I hadn't had like 101% prime conditions this summer you would be correct. But when I can pull my logs and look at them to see what I'm taking in and what I'm drawing out....its clear they are charging fine.
Now to the question of used batteries. Yes I know as a used battery they are not optimal. But as a beginning user looking to learn I'm not going to go drop minimum 1k on batteries to have a "whoops" moment. But as far as educational purposes and seeing my need for 6volt batteries theses repurposed 12v marine all 12 in service and 2 on standby that I got for less than 250.00.....they have served their purpose for the past 6 months now I am comfortable and able to move up the ladder.

I was simply curious about the voltage reading on them was all. Figured there would be an intelligent knowledge packed vet out there who at one point had done the same.

[SirHund]

And yes I did typo 600wh when it should have been sun hours

[SirHund]

Also I should mention I am a approaching this from a minimalist out look and a survivalist out look. Everyone should understand top of the line equipment will/should perform. But I needed to see that even in adverse conditions I could make it work and work well, which it has. I'm not coming here for an argument by any means. I know know what I have read and learned from hands on experience.

[sdold]

Hmm,aren't you the fella who keeps saying that an off-grid system should cost 'MORE' than a grid-tied system?

Yeah we see how well grounded in reality you are.

He's not the only fella, I say it too, because it's generally true. It's also true that most folks on this forum have reliable grid power and aren't depreciating their systems as business assets.. Your circumstances aren't the norm and your advice usually only applies to folks in your situation, which is not most of us.

[SirHund]

Im not trying to be rude or anything but it would be helpful if this remained on topic. I'm simply trying to learn.
I do not have grid power because that defies my point of doing this.
Also to answer a previous response. My batteries are all 109Ah and I have 12 in use at the moment. Wired in series to 24v. Thus bringing the Ah from roughly 1200 down to roughly 600 Ah.

[Bala]

I have a 24v system. As is always said voltage is not a solid method to determine state of charge but once you have run a system for many years it will indicate to you how things are going.

Mine always has a fridge freezer and some other bits running. As soon as the sun goes it will drop to 25.2 or less depending what is running.

It is then the voltage the next morning that indicates to me how the batteries are. If is still close to 25 then all good. If not then there are many other factors I consider but to much info type on a phone at the moment.

[SirHund]

Bala thank you very much for that response. That opened me up to other details I didn't think of. I can see what you mean by voltage now.

There are times that we have run it hard and drained out the batteries but it was because we needed it. By drained I mean we hit out low voltage alarm on the inverter and it was about a 20.2.-22.2, also I informed the lady this could not happen or we risk heavy damage to the system. But with all that said if it is a normal running night with just fans and phone chargers we may go as low as a 24.1 or so. Still not a good number but given it only sucked a volt.out I view that as a pretty stable drop on used batteries.

[SunEagle]

So yes to get started here I am new to solar but have on and off studied it over the years. I jumped in head first 6 months ago and love it. I have pretty well just been experimenting to see what works.

I managed to acquire some 12v marine batteries from salvage and revive them to a pretty even balance. I am currently using 12 marine batteries that were paralleled but now are run in a 24volt series. They are charged with 4 renogy 100 watt panels also series and 4 Photowatt 50w panels in series.

Question is that on my Renogy Rover 40a CC once the sun goes down....the charge will read out between a 25.1 and a 25.5. I would assume this means my batteries are maintaining a charge but that charge is on the very low end of a life cycle. Is this correct?

also yes I am upgrading to 6 volt batteries just searching out what is best for that type of battery yet cost effective.

So to answer your question. Yes your batteries are on their way to being dead weight or as you put it "toast".
First off they were used and probably have little chance of ever getting back to full SOC..
Second 12 x 12v batteries wired in a series/parallel 2 x 6 circuit for a 24 volt system will never get evenly charged.
Third, while you mention you have 8 panels of various wattage ratings that are series wired I doubt they are all in series since your 40A CC probably isn't rated for that much input voltage.
Forth, when you mention a system Ah rating of approx 600Ah you need about 60 amps of charging and the most you can get out of that panel system is 25amps, which is to little for your giant battery system.
Finally, battery voltage readings are never a proper indicator of the SOC value. Only the specific gravity value can tell you what they are doing.

So to give you a truthful answer you have to provide us with a little more detail such as the Voc & Vmp of those panels and how they are wired to your CC. Also knowing the specification of that CC will help us determine if it will work properly for a battery system.

[Bala]

Bala thank you very much for that response. That opened me up to other details I didn't think of. I can see what you mean by voltage now.

There are times that we have run it hard and drained out the batteries but it was because we needed it. By drained I mean we hit out low voltage alarm on the inverter and it was about a 20.2.-22.2, also I informed the lady this could not happen or we risk heavy damage to the system. But with all that said if it is a normal running night with just fans and phone chargers we may go as low as a 24.1 or so. Still not a good number but given it only sucked a volt.out I view that as a pretty stable drop on used batteries.

I never let mine get below 24.5. I can start my generator from the house and charge them. It is easier for me to get diesel that new batteries, I consider the convenience of long battery life over cost.

[SirHund]

Awesome..
SunEagle I will get right on that and shoot the info over.
I understand what you are saying and it makes sense. Again why I am experimenting on used batteries before I hurt good ones. It just got too overwhelmingto sit around and do math. My brain doesn't work that way.

My panels are wired in series (1) and series (2) then linked off into feed wires to the CC that them lead to the battery obvioulsy. It did at first present a voltage overload until I had a nice individual on this forum guide me to the proper connection. Since then charging great and throwing no codes.

I stepped batteries back until I watched the system actually make a notable gain under low Sun conditions to get my bank size so I will not argue that but only say I watched the numbers make sense to me. I had 16 and stepped back to 14 the 12. They gained all the way back and at 12 batteries actually started hitting boost on CC. Now if I stepped down to 10 it may be a better charge rate as far as a full charge but again the numbers were adding up. May have to try this this weekend.

My bank is wired in 3 strings of 4 (12v) that equal 3 strings of 2 (24v) batteries as i was guided to hook up as the optimal running platform unless I read it wrong. Solar load coming in at opposing corners of bank as to the inverter load going out.

Made sense in theory for a good power input as well as draw. Making it all even ish.