Not reaching Absorb or Float stage -- all of a sudden

[dalyxxdj]

Hi, I'm new to the site and sort of new to solar. We have an off-grid system here in Colorado that has been up and running for about 18 months now without any problems until just recently. I can get more specific if need be, but it's a 48V system, with 8 6V deep cycle, flooded lead acid batteries, a Midnight Classic Controller and a Xantrex XW Hybrid Inverter/Charger. 6 Sun Power panels. It's connected to a Kohler 14KW backup generator (which we've never really had to use -- we get great sun here!) The system was professionally installed and we had another installer come out and QC it about a year ago and gave it the thumbs up. We've faithfully watered the batteries with distilled water as recommended. We could go 2-3 cloudy/semi-cloudy days and be fine. In fact, even on lightly overcast days, we'd still make it to Absorb/Float stage.

In the past few days, we've noticed that after a full day of sun and once the system was Resting and it started getting dark, the voltage would drop off dramatically, even though we have a very small, continuous load most of the time -- maybe 150 watts, with the occasional spike to 250 when the fridge cycles. Whereas a week ago the system would rest at about 51 V and in the morning it was still at 49.5 - 50 V, lately it drops to 49 V or less by the time we go to bed and in the morning it's at 48 V or less.

The suddenness of the problem makes me think I accidentally adjusted something, or some wiring is loose, but I'm not sure. The panels are obviously doing something and the batteries do get somewhat full and as long as it continues to stay sunny during the day we can make it day to day.

Any thoughts? We're tired of having to wait for the sun to be fully shining before we can turn on our coffee maker! Thanks for any help!

Dan

[Bala]

If you do not know how to adjust all your settings you need to find out how, so that if you accidentally adjust something you know how to set it correctly.

Check all your connections for loose or corroded parts.

Hydrometer test your batteries, you may well have a bad battery.

[Sunking]

Do a load test. Fully charge the batteries via generator.

After batteries are fully charged up on genny. Measure open circuit voltage which means nothing connected. Then apply at least a C/10 load and measure the voltage again on the batteries. If they drop more than .2 volts, buy new batteries. I bet the voltage falls off a cliff.

Please tell us you have hydrometer readings made at least weekly. If you did you would know exactly what is wrong and could have prevented it.

I suspect you have several issues going on like low end batteries and 18 to to 24 months is all you are going to get. Over discharging them too deeply each day. And the worse sin of all with FLA not using your generator to EQ them monthly or when the Specific Gravity via hydrometer indicates a problem.

[dalyxxdj]

Thanks to both of you for the quick feedback.

Should I bother with the load test if the batteries are, in fact, toast after testing them with the hydrometer (more on that below)? I assume that if they are bad, I'll need a new battery bank, and a good one at that. The reason I ask is that I'd have to figure out how to do an open circuit voltage test with nothing connected and then how to apply a C/10 load and do another test. Any thoughts on that would be cool, too. We are so far off-grid up here (literally and figuratively) that there are very few knowledgeable and trustworthy resources to turn to, so thanks for any help you can provide.

Embarrassingly, I do not have a hydrometer (anymore -- I had one when I was making beer!) and therefore have not taken any measurements since the system was installed. I'm not especially naive (but am feeling stupid now), but we were trusting that the system would be fairly no-fuss and work well for some time to come with weekly watering of the batteries, and regular equalizing. We also trusted that the batteries we were buying were decent and would last us more than 18 months!

If it helps and you know anything about batteries, they are Deka Pro Master batteries, 6V and I have 8. I couldn't find any particularly relevant rating information on them except a box that said "190 Min." in it and a part number: 8L16/T875. I'll go online and see if there is any other rating information about them. Not that price is the best indicator, but I thought they were fairly decent batteries at $180 per.

Anyway, thanks again for any and all help.

Dan

[Willy T]

Having and using a Hydrometer is almost a must on FLA Batteries. Doing a Equalization Charge is another fact of life. There two types : Maintenance and Corrective. Once you get the SG readings it will tell you the way you need to go. You can adjust the Absorb voltage and time to help you keep it within limits once you understand what the readings are telling you. As batteries age, things will change as they have with yours. you have to watch for the changes.

[Sunking]

Dan I have re-read your thread and follow up questions. Lets start with a good hydrometer because no matter what from this point forward you need one, and a good one. So first thing you do is click the link for a Deka Temperature Correcting Hydrometer. break out the credit card, and spring a whopping $8 on one OK? Will not take you but a minute and is a Must Have. At $8 or less no pain. Buy 2.

Something I should have caught earlier is you said your system will not get up to Absorb or Float is telling me you have a shorted cell or battery. If you had sulfated batteries or bad wiring what you would notice is the charger gets to Absord and Float way too quick, and the batteries could not carry any load. Get a volt meter out and measure each battery voltage and see if you have one or more really low compared to all the others.

I am familar with Deka Pro Master batteries. Do you know what AH they are? You mentioned T875 which is a Trojan battery 8 volts so that is throwing me off. They should have a number on them like:

GC25
GC15
GC10
GC45

Is this your battery and which one?

They are budget Golf Cart batteries and honestly 18 months to 2 years is all they got in them. Before I make a recommendation replacement model I need to know a few more details about your system and usage. So if you could, answer these questions please as best as you can. It is important.

• Location like near what city or region? Like Boulder, Denver, or COS
• Total Panel Wattage?
• Charge Controller manufacture and model number?
• Inverter manufacture and model number?
• Now the tough question, do you have any idea of how many watt hours you use in a day?

I am thinking something from the Trojan RE Line up or maybe Industrial line up as they should be available in CO. You might have to go to Denver or COS to pick them up. Or maybe even a gold course if you have any buddies that run a golf course or golf cart shop. The Trojan RE line is a good medium end product that should serve you for 5 years with PROPER CARE.

So lets get you fixed up and educated going forward OK?

GET YOU A DAMN HYDROMETER NOW.

[Mike90250]

...they are Deka Pro Master batteries, 6V and I have 8. I couldn't find any particularly relevant rating information on them except a box that said "190 Min." in it and a part number: 8L16/T875.......Dan

Uh Oh. sounds like 2 years is all you are going to get. 190min is the reserve time to run a car that has blown an alternator.

[dalyxxdj]

Hi again and thanks for your feedback. I appreciate the help. To respond to some of Sunking’s questions/advice and to clarify a few other things:

1) Hydrometer – check. Education – check, check. That’s why I’m here!

2) Measured each battery this morning before anything was happening and they all measured equally at about 4 volts. Should I be concerned that it isn’t 6V, or would that be natural given that it is first thing in the morning and the total voltage was low? I suppose it’s a good thing that they were all the same, no?

3) The batteries are not the golf cart series of batteries. From the spec sheet, my batteries are the 8L16 batteries. Here is the link to the spec sheet -- http://www.bornay.com/en/products/pr...-batteries.pdf. They list two AH’s – one is Ah C20 = 370, and the other is AH C5 = 295. It also says the time to discharge at 75 amps is 190 minutes.

4) The nearest big city is Colorado Springs or Pueblo. I go to Denver regularly as well, and if I have to get something up there, it’s no problem. We are at 38.38 N, 105.13 W and 7,100 feet if that helps.

5) Our solar array is 6, 327 watt, Sun Power panels for a total of about 2,000 watts. I didn’t see anything amiss with any of the wiring on the panels the other day when I looked. It is oriented due south (not magnetic) and tilted at about 33 degrees if that helps. Like I said, we generally get great sun and up until earlier this week, we were cycling normally.

6) Our charge controller is the Midnite Solar Classic 250.

7) Our inverter is Xantrex XW Hybrid Inverter/Charger, Model No. XW6048.

8) I’ve always had a hard time figuring out our watt hours usage, so I’ll tell you what I know. At any given time, the meter reads about 175 watts during the day, a little less in the summer when we take off the heat tape that keeps our water from freezing. When it’s sunny (or going to be sunny), we run the coffee maker – 900 watts or so for 3-4 minutes. Occasionally, the toaster. When the fridge cycles, add about 100 watts for 4-5 minutes at a time. We have a well pump that comes on once a day and draws about 1200 watts for about 4 minutes (thankfully, we have a good well!) Occasionally some power tools, but mostly we have cordless stuff for that.

I think that answers most of your questions, but if not, please feel free to follow-up. FYI, I did water the batteries this morning since it was almost time for my monthly feeding of them. The levels were low, but none of the plates were exposed in any of the cells.
Again, thanks for any and all help. Now, I’m off to buy a hydrometer (or two)!

Dan

[Mike90250]

2) Measured each battery this morning before anything was happening and they all measured equally at about 4 volts. Should I be concerned that it isn’t 6V, or would that be natural given that it is first thing in the morning and the total voltage was low? I suppose it’s a good thing that they were all the same, no?

measuring 4V on an unloaded 6v battery means that it is dead.

[dalyxxdj]

Hi Mike,

"Thanks" for the info I kind of hope it is the batteries and not the panels or the controller. I had asked my installer separately what they thought could be the problem and they didn't mention anything about the batteries and assumed that it was a problem with the controller. I can't see how that is the case, but could it be?

I guess I have a basic battery question, though. If the batteries are dead, how is it that they will store some power during the day, enough to get us through the night at least? Also, I ran the generator yesterday for a bit and it was able to charge the battery bank up to the Absorb stage and to 57V. Once I turned it off, it went back down to 51V, but stayed there for awhile until ultimately ending up at 48.5 this morning. Now that the sun is out again today, it's back up to 51V. If it is the batteries, am I simply going to have to do this dance every day until I get new batteries?

Thanks for your help in advance!

Dan

[Willy T]

Dead would be a term to describe them as useless. Almost total loss of capacity might better description for their condition. If they were 100% when new they may be at 10% capacity now. They are like this because there is so little plate material exposed to the electrolyte and the electrolyte is so weak because the plates are covered with sulfate that has crystallized that very little charging takes place.

Can these batteries be rejuvenated ?? Hardened Sulfate is almost impossible to remove. There ways with certain chemicals to do it. ( EDTA ) but it's not worth the effort and it's complicated to do.

You could try to do a Equalization Charge @ 62 V to see if you can break any loose. You have to keep the temperature below 115 ° F and use your hydrometer to look for a rise in the SG level. You may be able to get them to a higher level than they are now, it depends on how many $$$ you want to spend in gas trying. I have tried them for 24 hrs and got nothing in return and some will recover a little.

Bottom line, when you get new batteries, pay more attention to them.

[Sunking]

2) Measured each battery this morning before anything was happening and they all measured equally at about 4 volts. Should I be concerned that it isn’t 6V, or would that be natural given that it is first thing in the morning and the total voltage was low? I suppose it’s a good thing that they were all the same, no?

OK Dan I have a pretty good idea what is going on. You are not going to like a lot of what I have to say, but at least you will have an idea os what and how it happened.

You have a 48 volt FLA battery system, and there are some voltages you need to know especially when they are setting there doing nothing or being discharged like at night. A fully 100% charged 48 volt battery with no or little load should measure 51 volts (50.91 to be exact). At 80% State of Charge (SOC) 50 volts. At 50% SOC the voltage you never want to go under is 48.4 volts. At 0% SOC is 46 volts. See where I am going with this Dan? If you have 8 batteries x 4 volts = 32 volts.

3) The batteries are not the golf cart series of batteries. From the spec sheet, my batteries are the 8L16 batteries. Here is the link to the spec sheet -- http://www.bornay.com/en/products/pr...-batteries.pdf. They list two AH’s – one is Ah C20 = 370, and the other is AH C5 = 295. It also says the time to discharge at 75 amps is 190 minutes.

Well technically they are the exact same battery series. Nothing wrong with that just a larger version. So now we at least know you had a 48 volt @ 370 AH battery. You need to know what this means and how to apply it. To find the battery Watt Hour Capacity is easy = Battery Voltage x Amp Hours at the 20 hour rate. So you have 48 volts x 370 AH = 17,760 watt hours of 17.76 Kwh. That is a moderately sized battery. But here is the catch, you cannot use that much in a day, not if you want the battery to last more than a year or two. To maximize battery life you want to limit your 24 hour day discharge to 20 to 30% of the capacity and under no circumstances let your battery go below 50%.

What this means is want to limit your daily usage to 3.5 to 5.3 Kwh per day. It also means your panels must be able to deliver more power than you use in a day to over come system inefficiencies and make up for some cloudy spells. It has to be able to do this year round even in the short days of December and January.

4) The nearest big city is Colorado Springs or Pueblo. I go to Denver regularly as well, and if I have to get something up there, it’s no problem. We are at 38.38 N, 105.13 W and 7,100 feet if that helps.

5) Our solar array is 6, 327 watt, Sun Power panels for a total of about 2,000 watts. I didn’t see anything amiss with any of the wiring on the panels the other day when I looked. It is oriented due south (not magnetic) and tilted at about 33 degrees if that helps. Like I said, we generally get great sun and up until earlier this week, we were cycling normally.

6) Our charge controller is the Midnite Solar Classic 250.

7) Our inverter is Xantrex XW Hybrid Inverter/Charger, Model No. XW6048.

OK so you have 1920 watts of panels. How are they wired up? I assume 3 in series in parallel with 3 in series. Only other possible workable config is all 6 in series, depends on the Voc of the panels.

OK in winter for your area your best tilt angle is Lattitude plus 15 degrees gives you 4.1 Sun Hour which is excellent. That means your panels can generate at least 5.3 Kwh per day. It also means you batteries are just a bit small as 1920 watts @ 48 volts generates up to 40 amps. Idea battery size for you is 400 to 440 AH. 370 is OK but your panel wattage and sun hours can support larger batteries so you get a passing grade on equipment sizing.

8) I’ve always had a hard time figuring out our watt hours usage, so I’ll tell you what I know. At any given time, the meter reads about 175 watts during the day, a little less in the summer when we take off the heat tape that keeps our water from freezing.

OK this is where you are likely where you get into trouble. 175 watts x 24 hours = 4.2 Kwh in winter months. What is using 175 watts around the clock? Whatever it is is using 80% of your daily total only leaving you 1 Kwh a day to play with. You really need to nail this down as to how much energy you use in a day.

OK in closing your batteries are toast. Based on panel wattage and equipment you have A Trojan IND9-6V a 6 volt 460 AH battery with a 8 year warranty. Take care of them and do not let them go below 50% DOD and you got a solid 5 to 7 year battery. Next after you digest this we will talk about proper maintenace like EQ charging with your generator and how to use a hydrometer.

FWIW here is a SOC chart. This will let you know where you stand.

[Mike90250]

A 6v battery has 3, 2v cells internally (thats why the 3 caps for water) Either all the cells have some damage, or one 2v cell is dead. in a large battery bank of 48v, it's likely both things have started happening.

Do you monitor any of the logging functions of the Classic ? it's data logs (if you configured them) can tell you a lot about the charge and discharge characteristics of the batteries.

Regardless, you are looking at new batteries, get a hydrometer and practice with what's left of this bank, to learn to protect the new bank.

[paulcheung]

I think he has a faulty volt meter, it is no way that the battery bank at 36 to 40 volts on a 48 volts system still can operate, he need to get a different meter to check the battery's voltage.

[Sunking]

I think he has a faulty volt meter, it is no way that the battery bank at 36 to 40 volts on a 48 volts system still can operate, he need to get a different meter to check the battery's voltage.

Paul if you read he put the batteries on generator and got them up to 51 volts at rest, but quickly discharge with a load applied. Classic sulfated battery. That tells us the batteries are done, but can also indicate he has a faulty charging system which needs to be checked out before replacing the batteries.

Hoping he gets back soon as I have a few more questions.