Oversized Battery Bank - Is that a Problem?????

Dan-A-Canuck · September 2015

I've constructed a system for our off grid camp (cottage) in northern Ontario, Canada. I use it pretty late into the fall and a little in the winter so, I've size the battery bank for those periods where it might be well below freezing in October/November (with 4 or 5 consecutive no-sun days) during my extended stays. I have about 1100 amp hours of storage at 12 volts (oops) using 6 - 6v Trojan L16's. For 80% of my year, I'm typically fully charged and floating by noon. For a lot of the days, my battery voltage does not drop below 12.7 (just burning surface charge I assume). The system has been in service for about 2 years, I've been at the camp about 150 days in that time (so it gets used). I have not had to add 1 drop of water although I noticed that there has been a slight drop in the level.... still well above the pates. I equalize them about once a month May to November then once or twice in the winter. I'm guessing the winter isn't so much an issue since they sit at -20 F fully charged most of the time. If the voltage drops to 12.5, I use an Iota charger to bring the voltage back up, but that might be only 3 times late in the fall. My real question(s) after that rant: is not "working" my batteries a problem? Will it shorten the life span? or extend it? Opinions appreciated!

oil pan 4 · September 2015

Should only be a problem if you run the batteries down and cant bring them back all the way up.
Sounds like you are well prepared for 4 or 5 days of no sun, by day 3 or 4 a lot of people are sitting on a pile of dead batteries or running the generator out of gas.

Vic · September 2015

Hi Dan, Welcome to the Forum,

Flooded Deep Cycle batteries should be cycled -- initially to help Finish them, and build Capacity, and then, discharging them below 90% State Of Charge (SOC) on many/most of the discharges will be healthy for them, as it helps remove or avoid Lead Dioxide clumping, which can be mechanically damaging to the battery.

Using essentially no water in about two years, seems to be a wonderment, especially as you note that you EQ frequently.

How about some details of your system? Battery maker and model, amount of PV or other charge sources, your Charge Controller, etc.

Also, what Absorb and EQ voltages are you using?
Are you using a Battery Temperature Sensor? What do you suppose the deepest discharge percentage that the batteries have experienced?
How is the end of the Absorption stage triggered -- by time, ending current, etc?

Keeping batteries cool is very good, and will extend their lives, and will generally reduce water consumption, but almost no water use in two years seems strange ...

Thanks, Vic

Photowhit · September 2015

As Vic noted, if you're equalizing monthly, even using the automated equalizing, and not using some water, I would guess the bank is not fully charged when equalizing, hence little is happening, how under paneled are you? What size of array do you have?

softdown · September 2015

Just a note.....charging and equalizing at lower voltage rates does lower the consumption of battery water. Plus there is the coolness of the location to consider.

Photowhit · September 2015

softdown wrote: »

Just a note.....charging and equalizing at lower voltage rates does lower the consumption of battery water. Plus there is the coolness of the location to consider.

Not sure if you are confusing voltage for wattage, but in terms of wattage.

While this is true of charging, You are creating less heat, hence less loss, This is NOT true of equalizing. Equalizing does not take a lot of current if done correctly! Equalizing can only be done on a fully charged battery, so requires much less current than charging, but at a higher voltage. Last time I measured, perhaps 10% of the potential current was flowing to the battery,

Equalizing, by definition, requires higher voltsge.

vtmaps · September 2015

Photowhit wrote: »

Equalizing, by definition, requires higher voltage.

I wish there was a definition of Equalization. For some AGM batteries, EQ is just an extended absorb. Iota uses the term Equalization that way... their automatic weekly EQ is just an extended absorb, at absorb voltages.

--vtMaps

westbranch · September 2015

here is a document that may help you see just what you need to do to install and use your AGMs, in general. From the makers of my batteries

http://www.cdtechno.com/pdf/ref/rs_2061_0514.pdf , their instructions for PV charging etc...

and a more general one on AGMs http://www.cdtechno.com/pdf/ref/41_2128_0212.pdf

Mountain Don · September 2015

I am confused.... why the references to AGM batteries when the OP states he has 6 - 6v Trojan L16's and also states "I have not had to add 1 drop of water although I noticed that there has been a slight drop in the level" So it seems he does not have AGM's.

OP is a newbie; we shouldn't be making things confusing for him, IMO.

Dan-A-Canuck · September 2015

Thanks for all the thought guys, I'll provide some info in bold below in the questions. Thanks in advance for any insights.
I will add that the system performs pretty well, I have worked it a couple of times hard and it hung in there,

Vic wrote: »

Hi Dan, Welcome to the Forum,
Thanks, I learned a lot here when I was designing my system.

Flooded Deep Cycle batteries should be cycled -- initially to help Finish them, and build Capacity, and then, discharging them below 90% State Of Charge (SOC) on many/most of the discharges will be healthy for them, as it helps remove or avoid Lead Dioxide clumping, which can be mechanically damaging to the battery.

Using essentially no water in about two years, seems to be a wonderment, especially as you note that you EQ frequently. The first 8 months of service they were not EQ'ed but were kept well and timely charged.

How about some details of your system? Battery maker and model, amount of PV or other charge sources, your Charge Controller, etc.
6 - 6v Trojan L16 Batteries @ 12v(a rookie mistake in hindsight) Bulk charge at 14.8v, float at 13.8v, Summer I run 3x250 watt Canadian Solar Panels in series - in the fall I put 2x195 watt BP panels into service as well. I'm typically charging at 35 - 40 amps on a decent day. My consumption is typically 1.3 kWh a day according to my controller, an Outback FM80. Searched long and hard for efficient TV's, lighting etc. if everything in our camp is on (46" TV, A 110v RV pump, hefty powered stereo speakers, powered yagi antenna, lighting, etc, we don't break 600w AC by much, and everything is never on all at once). I run an Iota 30 amp charger for the odd time I get the voltage down to 12.4-12.5.

Also, what Absorb and EQ voltages are you using
15.5v for one hour timed about once a month between ice out and ice up. Once or twice in winter for the odd time I'm up.
Are you using a Battery Temperature Sensor?
Yes, I am using sensor with the FM80
What do you suppose the deepest discharge percentage that the batteries have experienced?
Once, maybe down to 35%/12.3ish v. Perhaps a half dozen times down to 12.4v, Most times, I'm at about 12.6 at the end of the day, and some of the time still at 12.7v. Always promptly charged.
How is the end of the Absorption stage triggered -- by time, ending current, etc?
Absorption is triggered by end current at 13.7v??? (don't know if I have that right). Bulk charge is 14.8v.

Keeping batteries cool is very good, and will extend their lives, and will generally reduce water consumption, but almost no water use in two years seems strange ...
Winter is cool (what am I saying??? It damn cold - down close to -40 on occasion, that's why I don't go much in winter), but summers are warm. Some days into the mid to upper 80's, Mid to high 70's are more common. My "Solar Hut" is well vented in summer.

Thanks, Vic

Thanks to you Vic

Dan-A-Canuck · September 2015

Hi Photowhit: I don't think I'm under paneled (Summer I run 3x250 watt Canadian Solar Panels in series - in the fall I put 2x195 watt BP panels into service as well) but opinions are appreciated. I equalize manually when batteries have floated for a couple of hours and I know that there is going to be an hour of good sun. 15.5v per Trojan guidelines,afterward my batts usually show a charge of 13.9 or so.

Thanks: Dan

Photowhit wrote: »

As Vic noted, if you're equalizing monthly, even using the automated equalizing, and not using some water, I would guess the bank is not fully charged when equalizing, hence little is happening, how under paneled are you? What size of array do you have?

Vic · September 2015

Hi Dan,

Thanks for the detailed reply.

Little time just now, but ...

Assume that the Canadian Solar 250 W PVs have a Vmp of about 30 V (?), so strings of three have a string Vmp of about 90 V. Fine. But do not know how your use two of the BP 195s, as the ones that I can find have a Vmp of 24.4 V. Perhaps you use an additional CC with those .. else they would have too low a string Vmp to be of much use, unless those BPs are different than the ones that found on the Net.

Quickly, voltage readings can be misleading when trying to infer SOC, as loads at the time or in the previous few hours affect the accuracy of SOC vs voltage. Furthermore, one needs to temperature compensate the voltage reading for the actual (average) battery temperature.

Your handy, high quality Hydrometer is the best tool to measure SGs, and from that, know the actual SOC.

Do you know the model number of the Trojan L-16 batteries that you are using? The target SG and charge setpoints can be affected by the battery model.

Thanks, More Later, Vic

Dan-A-Canuck · September 2015

Hi Vic, thank you: briefly as well -,packin' for camp.
-two 195v panels each on their own small CC, they are only for supplement late in the fall. Each charges at about 8amps at best. Plan to add a second FM 80 to replace the small CC's.
-the 3x250 is one string.
-batteries are Trojan L16EAC
-I am temp. compensating with the therm. pretty close to Trojan specs.
-I checked the SOC with a hygrometer on a full charge after a two hour float with my battery time in the mid 70's, don't remember the number but every cell tested in the middle of "good" or higher.
-the setpoints I quoted in the previous post match the Trojan spec's.

Thanks Again

Off to camp for the weekend, don't plan on opening the laptop - next week... off to camp for 6 weeks or freeze up, what ever comes first

Vic wrote: »

Hi Dan,

Thanks for the detailed reply.

Little time just now, but ...

Assume that the Canadian Solar 250 W PVs have a Vmp of about 30 V (?), so strings of three have a string Vmp of about 90 V. Fine. But do not know how your use two of the BP 195s, as the ones that I can find have a Vmp of 24.4 V. Perhaps you use an additional CC with those .. else they would have too low a string Vmp to be of much use, unless those BPs are different than the ones that found on the Net.

Quickly, voltage readings can be misleading when trying to infer SOC, as loads at the time or in the previous few hours affect the accuracy of SOC vs voltage. Furthermore, one needs to temperature compensate the voltage reading for the actual (average) battery temperature.

Your handy, high quality Hydrometer is the best tool to measure SGs, and from that, know the actual SOC.

Do you know the model number of the Trojan L-16 batteries that you are using? The target SG and charge setpoints can be affected by the battery model.

Thanks, More Later, Vic

Vic · September 2015

Hi Dan,

Thanks again for the added detail. Will study it.

Have Fun! Will look for updates later. Vic

706jim · September 2015

I'm up in the north as well (on an island in Thunder Bay). I ran 12 GC's for 19 seasons using about 430 watts of solar. Too many batteries was never a problem for me as long as I was able to get them to float. I've replaced the GC's with 8 L16's but extra panels will have to wait for at least another year. From what I can see, you are doing things right.

softdown · September 2015

Sorry to change the subject a bit.....

Do Canadians generally get golf cart batteries made in Canada? Because your batteries seem to last a lot longer.

American quality is a gamble. All over the place. I never hear about Canadians making crap.

BB. · September 2015

Usually it is "COLD WINTERS"... The old engineering rule of thumb, for every 10C below ~25C, batteries will last 2x longer.

In the deep freeze area--The batteries almost stop aging during winter (and many of our folks here move back to town during winter).

Everybody does have problems once in a while... There are some older threads with people questioning the Rolls/Surrette batteries (Springhill, Nova Scotia, lots/specific types?) that seem to have cells failing early in life, some problems getting fully charged on solar.

-Bill

706jim · September 2015

softdown wrote: »

Sorry to change the subject a bit.....

Do Canadians generally get golf cart batteries made in Canada? Because your batteries seem to last a lot longer.

American quality is a gamble. All over the place. I never hear about Canadians making crap.

Hard to say. The GC's that I mentioned were Dunlop branded and were purchased from Sam's club in 1996 for $44 each (!)
Too much time has passed since then for me to guess as to the relative quality of newer batteries.
And as previously mentioned, my batteries spent every winter in a fully charged, but very cold state.

softdown · September 2015

Well....do Canadians make crap? Sometimes we do. There was nothing wrong with USA made goods in the 50's. Dunno what happened...

BB. · September 2015

We are getting spoiled here... I like to listen to Old Time Radio Shows. The car battery ads talk about "only" needing to add water ~3 times a year. And batteries that last 3 years.

And I remember cars from then that usually lasted 99,999 miles between overhauls.

These days, much longer between adding water to maintenance free batteries... And expect almost 2x the mileage between overhauls.

Things are getting better (on average, if you are willing to pay for it).

-Bill

Mountain Don · September 2015

BB. wrote: »

And I remember cars from then that usually lasted 99,999 miles between overhauls.

I can recall when you started thinking about a new car when the one you had hit 60,000 miles.

Remember the annual change of ignition points and spark plugs? Annual or biannual fan belt replacements? Coolant hoses rupturing every second or third year? Manually adjusting the brake shoes for wear? Greasing 20+ fittings on near everything that moved in the steering / suspension and still having to replace parts? A new muffler every few years, especially for those in snow country? Car bodies rusting through? Yeah... those were the good old days!

As for car batteries I regularly get 4 to 5 years out of an flooded maintenance free style automotive battery (high end) even here in the hot SW.

Bucho · September 2015

Dan-A-Canuck wrote: »

I'm typically fully charged and floating by noon. For a lot of the days, my battery voltage does not drop below 12.7 (just burning surface charge I assume). The system has been in service for about 2 years, I've been at the camp about 150 days in that time (so it gets used). I have not had to add 1 drop of water although I noticed that there has been a slight drop in the level.... still well above the pates. I equalize them about once a month May to November then once or twice in the winter.

Voltage isn't a great way of determining how your batteries are doing and considering the temperature you've listed it seems like those voltages shouldn't correspond to anything real. The reliable way to check on your batteries is to use a hydrometer

http://s936.photobucket.com/user/m69800/media/soc7.jpg.html

Dan-A-Canuck · September 2015

Hey guys: finally up at camp for my 6 week fall sabbatical (and finally some time to myself - No such thing as time off work, just time compression)

Again, thanks for all of the insight, it's appreciated. To answer a couple of points from above.
- Bucho, yes - every cell tested good or better on the hygrometer.
-706jim: good to hear from someone in a similar clime, you're further north than I am but our winters about the same. Camp is half way between Timmins and Sudbury (suburban Gogama). The local Trojan retailer says he frequently hears of battery banks lasting 20 years... if you treat time well.
-Softdown: I don't think there is such a thing as a Canadian battery manufacturer (could be wrong) and I think??? that there are only 3 "real" manufactures in the States (Delphi, Exide and Johnson Controls - maybe that's just automotive, I'm not sure) - everything is just branded, but probably built to different specs depending on how much you want to pay.
-Mountain Don: thanks for the defense but I have a handle on gels and AGM. This is actually my second system, I ran a bank of 8x group 31 12v Gels for several years (only because I got them for 8 x $35 each

friend - long story bla bla bla.... till a forest fire put our camp and 100,000 acres of land around us into "restart mode". That was simpler system with lighter demands but I did like the gels. Put them to bed at 12.3 or 12.4v on my way out the door in November, no problem - up and running just fine in the spring - year in year out for 6 seasons without any sign of fade on performance. I still have two of them in my boat for the trolling motor that are probably 10 years old... and running great (boat happened to be hooked up to my truck when the fire broke out). I'm also running a "cheap" Chinese group 27 AGM in my boat for starting (yea, I know... wrong battery but I already had it and I do run a few accessories from it as well). It's hanging in there pretty well but it's only 3 years old).

Long and the short, I guess the only thing that will answer my original question about the harm in not cycling my batteries deep enough will be time. I'm tempted to run them down to 12.4 or so, 4 or 5 times a year just to make them work. Based on what I'm reading above, it is likely our winters where everything is in suspended animation for 40% of the year and summers that only hit the high 80's a few times.

Simpler times before the fire.

Image: https://us.v-cdn.net/6024911/uploads/editor/ys/uu8miiqyv6ik.jpg

Not so much a camp anymore.... but when you're looking at retiring in a few years and spending summers... you start to think comfortable... and way more solar. But I'd trade it in a second to have the old one and the trees back!

Bucho · September 2015

You want every cell to test 1.260 after you've compensated for temperature and if there's more than a .050 difference you need to equalize.

Mountain Don · September 2015

Too bad about the fire, we've had 3 close calls since 2009. Now with the thinning that we and the forest service have done we are in better shape. (Cross fingers)

jcheil · September 2015

Bucho said:

You want every cell to test 1.260 after you've compensated for temperature and if there's more than a .050 difference you need to equalize.

Trojan changed the electrolyte sometime in March 2012 from 1.260 to 1.280 for most lines of their batteries.
You would need to check with them on your model and check the date codes on your batteries to see for sure. usually on one of the POSTS there is a Letter (which is the month) and a digit (which is the year). So B3 would be Feb 2013.
If you have the newer 1.280 (March 2012+), then bringing it up to 1.260 is not getting them a full charge (if your batteries are one of the lines they changed to 1.280 - I know my L16RE-B's are).

I have the Trojan L16RE-B (370ah) batteries and I can tell you that they need a LOT more voltage/current and LONG absorb times to properly charge them vs GC2 batteries because they are TALL and you need the gassing to prevent stratification. If you are not visually seeing bubbles when charging, then they are not charging properly and will stratify. That is what concerns me when you say you are not consuming any water. if you are not consuming water, that means you are not gassing them (like you need to).

Note: Trojan says to EQ if there is a difference of more than .030 actually.

Photowhit · September 2015

https://youtu.be/jCl5klSF4tE

Note: Trojan says to EQ if there is a difference of more than .030 actually.

Note, Trojan says a lot of things;

https://youtu.be/jCl5klSF4tE

jcheil · September 2015

Photowhit said:

https://youtu.be/jCl5klSF4tE

Note: Trojan says to EQ if there is a difference of more than .030 actually.

Note, Trojan says a lot of things;
https://youtu.be/jCl5klSF4tE

Yeah I have to agree that sometimes you can find conflicting information at different points on their website.

Dan-A-Canuck · September 2015

Thanks for the good hints Jcheil, nice sunny day... I'm going to go out and keep an eye on them. I don't get the smell of gassing off like when I equalize. A longer absorb may be in order; I'll start bumping it up till I get some gassing off. In the meantime, hopefully they're OK because of the regular EQ'ing.

Regards from the North: Dan

Johann · September 2015

BB. said:

Usually it is "COLD WINTERS"... The old engineering rule of thumb, for every 10C below ~25C, batteries will last 2x longer.

In the deep freeze area--The batteries almost stop aging during winter (and many of our folks here move back to town during winter).

Everybody does have problems once in a while... There are some older threads with people questioning the Rolls/Surrette batteries (Springhill, Nova Scotia, lots/specific types?) that seem to have cells failing early in life, some problems getting fully charged on solar.

-Bill

Will this kind of environment have problems to charge batteries and keep the charge or does the charging take longer/shorter and still slows the aging? Does the cold slow down the self discharge?

BB. · September 2015

Yes, lead acid batteries have lower self discharge when cold... How much, probably the rule of 10C and 2x -- 1/2 rule is a good estimate (for every 10C drop, self discharge reduces by 1/2 times).

In general, lead acid batteries really like a lot of time on charge (a few hours under bulk--depending on rate of charge, and another 2-6 hours on absorb--depending on how deeply discharged/type of battery/etc.). That adds up to more hours of "sun" for many northerly locations during winter. Trackers (real and virtual) can help--Generators are usually needed at times for systems used during winter.

-Bill

Oversized Battery Bank - Is that a Problem?????

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