One battery out of twelve seems weak, and they are no longer sold

mevenable

I live in Nicaragua.  I purchased 3 banks of 4 Outback 106NC batteries two years ago.  They have done well, but now one of the twelve seems weak, I first noticed this when battery performance fell around the end of October, and quickly discovered the problem.  While all the batteries charge equally, and perform equally during the day (even if the solar panels are disconnected and a 1.5 kW load is used, they hold up equally well), and work equally for a few hours into the evening, after that one of the batteries starts getting weak much faster - after about 1-1.5 kWh of use.  By morning, if I let it run that way, there is a 0.8 V difference with the other three batteries in the string without a load, and 1.4 or more with any sort of load.  At first I just used the batteries mostly as a backup at night while I tried to resolve this (I do have the grid), and then I disconnected the string with the bad battery and started just using the two.  The string with the bad battery was fully charged when I disconnected it, and all four batteries have held their charge about the same for over 48 hours, going down to 12.7-12.8 V.  I contacted Outback and they told me not to run the string with much charge difference, which I had already guessed, and recommended a few things to try, like increasing the Absorb time, which didn't help.  They told me that the 106 NC has been discontinued, and they could not tell me what other battery if any would work.  They gave me a phone number for the actual manufacturer, who then referred me to one of their engineers, but that fellow does not answer his phone or return calls.  I need to figure out what to do, and whether I need to buy all new batteries in a case like this, or if there is some sort of reconstruction that could be attempted, or whether there is some other battery I can put in the string.  Any ideas?

BB.

A little sad that Outback dumped you to the actual mfg for support... But if they no longer have a relationship, outback may not have any leverage (other than you trying for a check from outback because they bailed, assuming there is still a valid warranty at this time, 2 year?).

If you can figure out the basic battery construction. 100 ah @ 12 volt AGM is were I would start looking.

What asorb voltage are you using. Typical is 14.4 volts for a 12 volt AGM battery.

If you do install a replacement, just watch the per battery charging voltage. If they start to diverge, you can do some tricks to help bring back into balance (such as clipping a 12 volt car brake lamp(s) across the higher voltage batteries to discharge then back to group average voltage).

Bill

softdown

Unfortunate - I'm sure they were pricey batteries. I would try swapping the weak battery into a spot where a stronger battery is. See what happens after two weeks.

I would not, in 1000 years, swap out the whole array. Thats like junking a car because a part went bad. A 100 Ah AGM 12V is very easy to replace. There are likely only a few manufacturers - in this hemisphere anyway. I'd try for one with similar characteristics. Like internal resistance if that is available. Even size and weight is a clue. 

AGMs is supposed to have less internal resistance than FLA. Used AGM may resemble newer FLA in internal resistance. It does here. Anything less than 5 is considered acceptable for a new automotive battery by the way. Internal resistance is a good  indicator of how efficiently a battery accepts a charge. 

I'd also call solar battery sellers as well as battery distributors - they might have a good slightly used and similar battery available.

mevenable

Thanks guys, good feedback.  I am using 57.6 absorption and 54.4 float for the system, as per outback specifications, with temperature adjustment as needed.  That is 14.4 per battery.  I was originally told by outback that a new battery should not be added to the string after about 6 months.  However, recently they said that was just to get the best usage from the new battery, but it wouldn’t really hurt anything to do it.  From what you are saying, maybe there is a problem with just putting in a new battery, even if I could have found one still? What are the issues for the other batteries and the system as a whole?  This is Nicaragua, so my choices are limited and really competent technical support on something unusual like this is hard to come by.  I am thinking to go to the place that used to carry them and see if they know anyone that might have a used battery, but I am not sure that would end up being easy or satisfactory.  The warranty check for the battery is the least of my worries.

mevenable

Btw, how do you measure internal resistance?

mevenable

Just an ohm meter on the terminals?

BB.

The classic method is to measure the voltage (right at the battery terminal) with a light load, and measure the voltage with a heavy(ier) load, and with a little math:

• V=I*R
• R=V/I= Change in voltage / change in current = Resistance
• (V1-Vc)/I2-I1) = Resistance of battery

I.e.:

• (12.7 volts - 12.6 volts) / (10 amps - 1 amp) = 0.011 Ohms (purely made up numbers)

You can get also get a meter that measures internal resistance using an AC signal--But the above should be quick and dirty test that helps you figure out what batteries are good/bad/match. You can use a Brake Lamp (low load) and a pair of headlamps for the heavy load... Or whatever you have handy (power resistors, etc.).

For V1 (first voltage check), you can do with zero current... However, I would want to have the battery(ies) set for something like 3+ hours without charging, or be slightly discharged... A surface charge (higher voltage on battery after just removed from charger--Would give you less than accurate results.

-Bill

softdown

mevenable said:

Btw, how do you measure internal resistance?

I use this one: https://www.amazon.com/ANCEL-BA101-Professional-Automotive-Motorcycle/dp/B01M0ARG3X/ref=redir_mobile_desktop?_encoding=UTF8&aaxitk=zWS3dUx4LsbE3AFhf34f3g&hsa_cr_id=7570646790301

It was cheaper on Ebay when I purchased. There are many to choose from. 

mevenable

I changed the position of the battery as suggested.  Would there be any point in moving the weak battery to a different string?

softdown

mevenable said:

I changed the position of the battery as suggested.  Would there be any point in moving the weak battery to a different string?

The point is to find if there is an issue in the charging "parameters". A greater change would help isolate a potential issue. Yes - I would move the questionable battery into the current position of your strongest battery - in a different string. 

mcgivor

What I would do is remove the low battery and charge independently observing the voltage and current, if the voltage increases rapidly and current drops correspondingly the chances are that it has become sulfated, the other possibility is it has a cell or cells that have dried out, 

Unfortunately with AGM there is little that can be done to remmidy a sulfation problem unlike flooded, which can be equalized, or the electrolyte diluted to premote the desulfation process. Some say the vents can be removed from AGM batteries and water added, though this is not something I personally have experience with.

mevenable

One thing that puzzles me. At the end of the night, the “weak” battery has for example 11.7 V remaining with no load, the batteries around it have 12.4, and the batteries in other banks generally have 12.2.  But, if I disconnect one of the terminals, then the batteries all have about the same charge, 12.3 to 12.4, when the batteries in the banks that are connected have about 12.2.  From my observations, when battery banks are connected they sort of equalize things, for want of a proper way to say it.  Just being connected puts a sort of “load” on the weak battery. Question: would running all three banks for a few weeks damage the remaining batteries, in the bank it is in or in the other banks? I am trying to decide whether to move it to another bank and try it for a few weeks while I am gone over Christmas, or just disconnecting until I can get another battery after I get back.  I leave in less than a week.  Thoughts?

softdown

Sounds like that battery has a serious issue. 

Our host may ship to you - have you checked that out?

There are a bunch on Ebay and Amazon of course. The challenge will be shipping the battery. AGM should ship easily but rules are often dumbed down. 

Estragon

What can happen leaving a bad battery mixed in with good, is under/overcharging the good ones.  The charging source only "sees" the average bank voltage.

Personally, I wouldn't leave a bank with such a problem battery in service while I wasn't there to monitor the situation.

Like Mcgivor suggested, it would be best to charge the weak battery by itself, and observe behavior to get a better sense of the degree to which remediation might help.  

mevenable

I am hoping to buy one here, importing is horrible, but there is a service through Pricemart in Managua that might be able to do it.  On the question of the internal resistance, I used the tables of data recorded by my control panel, which give A if current to the nearest A and average V for the entire battery set and got about 0.055 on the average.  However, I tried doing the measurement running a current of 1.9 kW (measured to the nearest 0.1 kW on the control panel) and then a current of about 0.3 kW, and got a 0.4 V difference, or 0.03 for internal resistance (same for all the batteries).  I will try this again in the evening, since there could be some issues since the batteries were charging at the time, I cut of the solar panels and waited for the system to settle into a steady voltage, about 5 min, but even so. . . better to try in the evening I suspect.  It is amazing how hard it is to get anyone in the stores that sell the batteries to tell me what the internal resistance is for their batteries.  One place sells "yoko" batteries, 100 Ah, 12 V, another sells "deka marine master", also 100 Ah 12 V, another sells Ritar RA12-100D (12 V 100 Ah) and "RA12-80D" with 12 V 85 Ah, also "Trojan 27TMX" with 12 V 105 Ah.  I guess I will have to start calling manufacturers.  Sigh.

mevenable

I actually found spec sheets on line for the Ritar batteries - they say the internal resistance is around 5 milli ohms which seems to be a tenth of mine?  so that would be entirely incompatible. I see that the Trojan battery is sold by NAWS, so maybe someone there can tell me what the internal resistence is?  There is a PDF specs spreadsheet online, but I can't get it to download.   I have sent messages to the other manufacturers, we will see what they come up with. 

mevenable

It just occurred to me.  I am measuring what happens to 12 batteries when I apply a certain current.  However, that has to be quite different from what that current would do to one battery.  I think in fact my internal resistance might be somewhere around 4.5 milliohms, which is something like the battery that is for sale.

BB.

You are correct... The internal resistance of each series wired battery, cable, cable connection, adds up to total series resistance per string.

4x 0.005 Ohms per battery + 3x 0.010 Ohm jumper wiring = 0.070 Ohms total resistance (made up numbers)

-Bill

mevenable

Uh oh. So I. Would have to know the resistance of the jumper wires and probably the connections to the inverter as well?  I might as well pin photos of the available batteries on the wall and throw darts at them to choose one.  I had thought I could bring a battery with me from my set when I shopped in Managua  and the battery stores would have something for measuring internal resistance for that and for their products.  However, none of them has even heard of it, let alone possesses a means of measuring it.  I guess I could bring back a meter at Christmas then go around measuring batteries.  However, it is the only occasion I would probably ever have for using it.

softdown

You really jumped on internal resistance. As I recall lead acid batteries are around 4,5ish when new, AGM closer to 3.5ish when new. I  doubt there will be huge differences from mainstream manufactuer to manufacturer. 

Nice thing about knowing your batteries internal resistance is it makes matching much more accurate. If you are running at 4,5 and toss in a new 3.5, that new battery may be in for a bit of a time I would surmise. 

Project Farm delves into it here: https://www.youtube.com/watch?v=h7rTcBanpMk

BB.

I would not worry about the internal resistance of a one off replacement battery--Just pick something of similar size/construction (in your case, AGM), and put it in... And home the rest of the string gives you a reasonable lifetime.

Yes, cable resistance matters (as well as battery resistance)... AGM batteries have very low and wiring resistance can become an issue... That is why we suggest following the wiring recommendations here for multiple parallel strings of batteries... If you keep all of the wiring "paths" the same length, the batteries charge/discharge in a more balanced manner.

http://smartgauge.co.uk/batt_con.html

-Bill

mevenable

Actually, it seems that so far the only batteries I have found information on all have 5 milliamp internal resistance. The company that makes the deka got back to me, that one is also 5. Really, I guess I will just have to roll with that, unless I can find a strong reason not to.  I will compare details of the other aspects of the different batteries and make a choice on that basis 

mevenable

Thanks you guys. You have gotten me up to speed on all this!

mevenable

I think most that are for sale here would be Standard deep cycle lead acid, not AGM.  I finally figured out what you were saying.  So, if I ever could find a way to measure my current batteries, it might turn out that a FLA is a better match. Otherwise, I can try to find an AGM for sale here, and let it take its lumps adjusting to the other batteries and hope to get a few more years out of the whole lot.

mevenable

Ritar is AGM but 5 milliohm. "RA series is a general purpose battery with 12 years design life in float service. It meets with IEC, JIS, BS and YDT standards. With advanced AGM valve regulated technology and high purity raw material, the RA series battery maintains high consistency for better performance and reliable standby service life." If I could figure out what the internal resistance on the 106NC supposedly was when new, and it was a tad less than 5, then maybe this would be the ideal choice

Raj174

@mevenable
Found two vendors who apparently still have these batteries. Maybe call and verify stock and shipping possibilities.

https://www.freecleansolar.com/EnergyCell-106NC-Deep-Cycle-AGM-12V-100Ah-p/energycell-106nc.htm

https://www.solarflexion.com/product-p/106nc.htm

softdown

Raj174 said:

@mevenable
Found two vendors who apparently still have these batteries. Maybe call and verify stock and shipping possibilities.

https://www.freecleansolar.com/EnergyCell-106NC-Deep-Cycle-AGM-12V-100Ah-p/energycell-106nc.htm

https://www.solarflexion.com/product-p/106nc.htm

Both were functional when adding to cart. 

Shipping Policy Solarflexion ships to domestic and, in some cases, international addresses

softdown

Seems that solar batteries have higher internal resistance than automotive starter batteries. My high quality AGMs are similar to my been around the block lead acids FWIW. 

mevenable

good news on 106 NC!  I will get down Monday to see what can be done 

BB.

Charge all the batteries in the string to fill charge or charge the new battery is about the same resting voltage in the rest of the string.

You want to match state of charge in all the series string batteries. Otherwise they will be out of balance and require more EW charging.

Bill