Recent loss in charge input

[Westbranch]

The pv array consists of a pair of Canadian solar 250w modules, vmp of 30.1, wired in series through 60' 6awg to the classic.  As Bob had mentioned earlier, perhaps they are too low voltage for my 24v bank? 

If you have them in SERIES they are adequate for charging a 24V bank...
If you add 2 more in SERIES you will have  a  much better charge capacity.

But that hasn't happened in a good 10 days now, as we have been pretty sunless and I'm now encountering shade that wasn't nearly as big a problem last year at this time.

Yup, that darned low sun and short hours will get you.  For my system and loads in the summer if I just wanted to replace my use (fridge, lights, internet)I could get away with just 8 of my panels, ~ 1100W.  We get > 12 hrs of sun   
But right now due to the winter conditions etc., etc., I can only leave the Net on for monitoring and very light use when out there, AND have 1680W and have also used the genset for 3 hrs + each visit 

It is a race you don't want to lose... PV is cheap right now!

[zoneblue]

My bank isn't big, but my usage of confined to very small draws in general. Led lights and TV, and charging misc electronics.  The reason my SOC stays high is because normally it only has to recover about 8-12% to get back to 100%, or so I thought...at least by the wbjr, which I guess is no real indication of the real SOC. 

To reiterate, keeping charge levels high is one thing, but ensuring that 100% is what is really essential.

So, the panels are probably not enough for the bank, even considering my low usage.  Perhaps it would be good to start with the basics again...
The pv array consists of a pair of Canadian solar 250w modules...

Well by the time you add 150Wh for the CC idle, then theres your inverter idle, not sure what your using there, but that can eaily add up to 500Wh or even more. With 500Wp of solar in maine winter even without shading, youd be doing well to get 2 sun hours a day average over a month, so thats = 500W * 2 * 0.77= 770Wh. As you can see after your gears idle there isnt a whole lot left over.

..., vmp of 30.1, wired in series through 60' 6awg to the classic.  As Bob had mentioned earlier, perhaps they are too low voltage for my 24v bank? 

Would another pair of the same in series and paralleled to the other two help here, or should Iook for higher voltage panels? What are ideal panels for my system?  I had thought that one of the major benefits to mppt was flexibility with what panels one could use.

2S 60 cells is fine, i agree with WB. Thats 60-70V total Vmp, which is just dandy. 1S would definately be too low as Bob said.

The reason for the classic was because at some point I had planned for between 6 and 8 panels total. When I had originally designed the system, my thought was to use a kid and not a classic, but a lady from midnight ( also from Maine apparently) had told me,via a phone call, that the kid wouldn't handle 4 of those 250w modules very well, and more or less talked me into getting the classic.

Well 6 or 8 you will find things get easier. The kid is good for 30A, which is about 720Wp into 24V. It would clip a chunk off of 1000Wp on sunny days thats for sure. But for 2 panels, youre good to go.

So far as where I'm located, it is in the western Maine foothills.  Normally, I would hit an absorb cycle every day for a few hours... But that hasn't happened in a good 10 days now, as we have been pretty sunless and I'm now encountering shade that wasn't nearly as big a problem last year at this time.  Hence my questions about a charger ( which Im still pretty unclear about). 

Sounds like you are close, just need to get that hydometer, and get those absorbs a bit longer.

What angle do you have the panels at? In the winter a lot of folk in your neck of the woods tilt the array up real tall to shed snow and get help from snow reflection.

[BlackwaterPark]

The panels are positioned at about 30° .  so my plan is to keep the classic and add 2 more panels very soon, and another two by summer.  The inverter is just a samlex 600sa, which has a tare of .43a, and is off for around 15 hours a day typically, so it's a pretty miniscule loss really.  If not for wanting to eventually pump water, without using the genset,  I could do with this inverter indefinitely. But that's another issue for another time.

My more immediate concern is the charger.  What I'm wondering is is the Iota 25-27, which is stated to provide a steady 27.2 vdc, able to bring the bank voltage up to the higher voltage recommended for absorb?

[BlackwaterPark]

Just spoke to an Iota tech and he set me straight on how the charger works, recommending the DSL 27-25 with an external IQ4. Those guys seem to know their stuff!

[zoneblue]

The panels are positioned at about 30° .  so my plan is to keep the classic and add 2 more panels very soon, and another two by summer. 

30 degrees from the horozontal? That is pretty shallow for your latitude, and will effect your winter performance.
Presumably thats the roof pitch.  Something to think about.

The inverter is just a samlex 600sa, which has a tare of .43a, and is off for around 15 hours a day typically, so it's a pretty miniscule loss really.

Ok, so that takes the inverter tare to =0.43*24* (24-15)= 93Wh/d.
So total gear tare in the 250Wh/d range. What did i say your production was... 750Wh/d. Take off 10% for shading and 10% for off angle, and that leaves you with around 450Wh/d on average.

If not for wanting to eventually pump water, without using the genset,  I could do with this inverter indefinitely. But that's another issue for another time.

Inverters are problematic like that. We keep asking midnite for a stackable small inverter with low tare, and hopefully we will see something one day.

My more immediate concern is the charger.  What I'm wondering is is the Iota 25-27, which is stated to provide a steady 27.2 vdc, able to bring the bank voltage up to the higher voltage recommended for absorb?

A charger will help with your present production shortfall thats for sure. On the setpoints issue, well, does it really matter. You can use even the crudest of chargers to do the bulk in the early morning, and let the solar do the absorb. and eq.

Good luck with your system upgrade. Feel free to holler if you have more questions.

[BlackwaterPark]

Heh, I knew that didn't sound right when I have the angle... Was using my clinometer app, being too lazy to forage for the angle finder.  This is what smartphones have done to me.  They are 68°... Should have remembered that from when I set them up a year ago.

[BlackwaterPark]

Alrighty, so I've obtained some proper equipment and have been able to take some readings on those batteries.  The Iota charger (25a), and a hydrovolt to test the SGs.

At present, after leaving the charger running for many hours ( with the IQ4 module plugged in...I got it externally on the Iota techs recommendation), the charger is showing float status, the classic is showing 100% SOC, and everything is turned off.  the voltage under no load is 26.5v...( from 27.1 while the charger was doing its thing).

The readings on the four batteries: (taken under no load and disconnected from rest of system)

Battery 1:               Battery 2:           Battery3:         
6.68v.                      6.66v.                 6.64v.                 
Cell 1: 1233.          Cell 1: 1210.      Cell 1:1216       
Cell 2: 1205.           Cell 2: 1215.      Cell 2: 1216.     
Cell 3: 1215.           Cell 3: 1218.      Cell 3: 1230.     

Battery 4:
6.65v
Cell 1: 1222
Cell 2: 1225
Cell 3: 1210

So, from what I've been reading, the cells seem to be in a SoC of between ~60-80%?  What can I do here?  The charger has dropped the current down to about 4amps or so.  Is it alright to run the charger AND the classic at the same time?  Not that there's much sun to be had up here during this time of year.

[tecnodave]

Blackwaterpark,

If I had those readings I would do an equalization charge more often, you should not have more than about .010 difference between the cells......    .050 difference and you are headed for replacing the set

Your max deviation is .027  does not indicate good maintaince.  I would cycle these a bit harder than you are doing then eq. To get a better balance

I recovered a set of 4 Rolls-Surette S-530 L-16's headed for the scrap pile for $20.00 and recovered them to 100% capacity using my methods.

Set your  absorb to a much longer time , if you have a Whizbang , set it up for end amps at a reasonable value for your batteries and do an equalization several times....you want to see all the cells gassing freely. If you are using water recycling caps such as water savers....open or remove them,

Notes on distilled waters... They are not all the same!   I make colloidal silver for health reasons and I have discovered that a lot of distilled water is not as pure as claimed!  Some has enough metallic particles that my .999 pure silver electrodes are coated with impurities from the distilled water!
Batteries do not like non-pure water!    Unsolicited advertisement for Arrowhead Puritas Water, I don't have to clean my electrodes using Arrowhead Puritas Water like I do when I use off branded water! I only use Arrowhead Puritas Water in my batteries and for my colloidal silver process. Maybe my bias, works for me.

I use approx 1.8 gallons/ month distilled water in 8 ea L-16 batts, 2 sets, 1 rolls-Suretts and 1 Interstate

Hope this helps, Tecno

[BlackwaterPark]

Thanks Tecno, the info helps.  Equalization will be tricky for me, because I'm away from house from sun up till sun down, the sun being very scarce this time of year where I am, and bring somewhat under paneled as I am.  I wish there was some way to force the Iota charger to equalize, but it only appears to initiate that function after seven consecutive days of float... Which isn't going to happen here. 

I'm guessing that you can't run a charger through the classic and do it that way?  Worst case scenario, I'll just have to replace the bank come spring, when I double my array and get more proactive about doing regular EQs (I've only done a manual one hour EQ once in the 14 months I've had the batteries)

Is there some other piece of equipment anyone knows about that can equalize manually? 

[Westbranch]

BwP, I can't remember if it was mentioned above but the way to do an EQ is to start your Bulk in the early AM (pre dawn?) and when the charger gets well into Absorb ( Amps decreasing), switch to Solar power and let the solar do the long slow work of Absorb and Float and then EQ if possible...  hth

[BlackwaterPark]

Yes, I do believe that was brought up.

Can the EQ cycle be programmed to occur that day when it has the opportunity?  The problem in general is that I'm never there during the period of time where an EQ would take place. 

I did some reading up in various places about doing an EQ, and most say to monitor the progress by periodically checking the SGs every hour or so to determine how long the cycle should take. If one is not around to do this, what might be the best approach?

Also, concerning the end amps setting... I used to have it on a value of 4 (on a 24v 225ah bank).  After hearing from everyone that the absorb cycle wasn't likely lasting long enough, I changed the parameters of absorb time from 2 to 4 hours and reset the end amps to 0, figuring that the timer alone would ensure a longer cycle.  Should I reset the end amps value?

Another question... Should I never run both the pv input AND the charger at the same time?

[Westbranch]

In reverse order, yes you can run the charger and Inverter simultaneously.  Best that you are there to shut off the charger once your target state is achieved.  The two units will self regulate based on their individual settings.  ie 2 Classics may 'read' the voltage differently, slightly, and change from Bulk to Absorb ,relatively , in unison but not exactly together.  If the settings are the same the change over is not too significant...

I have my WBjr setting for EA to 0.1A, to max out the absorb over the winter due to minimal hours of sun interception right now, in summer I set it to 1%

I would want to be around for the EQ as the process stresses the battery by doing an overcharge...  I am cautious....  your call.

I have EQ set to OFF on my system... however I have my Absorb rate set to the max V right now and EQ is only a tad higher and , if done is for 16 to 24 hours... AGMs not FLA type.

[Vic]

"Iota DLS-27-40: 24 Volt 40 Amp Regulated Battery Charger", would this be a good choice for a charger on a 225ah bank? There's also a samlex 40a model, which is a fair bit more expensive, but NAWS seems to only recommend the Iota. Thoughts?

SO,  we see that B w P has a 24 V inverter which has NO charger built-in,  and is looking for an external Charger to supplement the PV.

As has been noted previously,  the IOTAs as supplied,  will only do an EQ every seven days,  which does not work for PV-charged off-grid system.

There have been those on another forum (Wind-Sun),  who have opened IOTA chargers and tweaked a Voltage-Setting potentiometer to increase the nominal charge voltage.  It is not clear that this ability is available in all Iotas,  and there could have been a design change in those that previously had this ability.

And,  B w P asked about connecting a Charger,  like the Iota,  to the input of the Classic.  In general,  this approach is not a good idea,  and specifically,  these battery chargers really do not have a sufficiently high voltage to allow almost any Buck-Converting MPPT CC to function well (IMO).

B w P,  you really DO need to fully charge,  and then EQ your battery,  soon.

I do not know of a relatively inexpensive stand-alone charger that has the ability to EQ a 24 V battery on command.  AND,  a candidate charger should really have the ability to vary the EQ (and Absorb) voltage,  and allow these voltage settings to be Temperature-Compensated.

An Inverter-Charger,  like the OB you mentioned  is,  by far your best bet,  for programmable capability  --  and you would need a Mate to do this custom programming.

FWIW,  More Later,  Good Luck,  Vic

[Vic]

The Xantrex TrueCharge line of chargers may have enough capability,  with the Optional Battery Temp Sensor (BTS)  and the Optional Control Panel.

They are not inexpensive, ...   but:
http://www.bassdistributing.com/Marine/xantrex-truecharge-2-24v-30a-battery-charger-8042430

Just as an example.   There may have been some reliability issues with some of these chargers,  so look at the reviews.

FWIW,  more later,   Vic

[zoneblue]

after leaving the charger running for many hours..., the charger is showing float status, the classic is showing 100% SOC, and everything is turned off.  the voltage under no load is 26.5v...( from 27.1 while the charger was doing its thing).
The [SG] readings on the four batteries: (taken under no load and disconnected from rest of system)

Battery 1:                 
6.68v.                               
Cell 1: 1233.               
Cell 2: 1205.         
Cell 3: 1215.         

Under your present circumstances you need to pretty much ignore the battery monitor SOC. To take a proper rest voltage you need to allow about 4 hours after its come off charge with no loads. Now as for your SGs they are low. Given the banks history no suprises there. What happens with a sulphated battery is that it presents as charged too early to the charger, and the charger throttles back. In order to try to break that cycle you need to EQ. As WB said if you use the IOTA early in the day slash overnight, then the classic will be able to do an EQ in just about any weather. EQ doesnt take much current at all, if its done after an absorb. I would try 2 or three good long EQs, keep the water level up as needed, then try to cycle them a bit and see if the SGs come up. If they dont, then, yes, new cells are in your future.