Recent loss in charge input

[BlackwaterPark]

Oh thank god, lol. Whew... I've had this system up for 13 months now and its been beautiful (modest though it's daily task is). At least according to the wbjr, and I've not let the batteries slip below 65%, and generally they nearly never go below 75%... Except these last 6 or 7 days. Yup, I've read that before... I must have spent over a year combing that forum and asking countless questions, devouring past posts and articles/ guides, etc, before putting this system together. It's a good remedial though... I'm sure I forgot more than I remembered, heh.

[boB]

BWP, yes, trees growing and shading might also be the problem.  Darn infestation of plants and foliage !

You should see 100% SOC once in a while as your Classic SHOULD complete an Absorb cycle
now and then to de-sulfate the batteries.  When it completes the Absorb cycle naturally,
(usually after a couple of hours time), then it goes to Float and at that time it should
reset to 100% State Of Charge.

Doesn't need to do this every day but once every week or two at least...  Otherwise your
batteries will be no good after so many months or so.

If partial shading, that's good you found that !

boB

[BlackwaterPark]

Yup, I generally get to float a few times a week. The only thing I've yet to do is equalize the batteries.  I checked the waters levels periodically and have only had to add a little water to each cell once, after about 9 months... These are the T-105REs
I'm guessing because my discharge is very light and steady in general, an avg of 3.5 amp (per hour)draw. Should I be doing a regular equalization?

[mike90045]

only had to add a little water to each cell once, after about 9 months

You are undercharging your batteries !!
either
get more solar PV
run a generator in the morning to Bulk the batteries, and let PV Absorb
reduce your loads
 
If you are not using much water in 9 months, you are undercharging.  Every other month should require watering.  And without a vigorous Absorb, the electrolyte will stratify into different layers and eventually ruin the batteries.  When my batteries are in Absorb, the room sounds like it's full of hissing snakes !  Lead acid batteries will not gas nearly as much as my NiFe cells do, but they should gas and bubble some to stay healthy.

[BlackwaterPark]

I'm not sure what I could do different about that... Normally, those panels keep the bank 85% and up, absorb happens at least 4 times a week for a couple hours a day, and they do make that sound.  Then they typically go into float. What would more panels do, if the two I already have are keeping the back charged up?  Should I change the absorb setting to longer periods?  It was my understanding that those RE Trojans used a lot less water than the normal 105s.
This last week and a half, however, has been virtually sunless and there's no end in sight. Never seen such a stretch like this ever. Currently, the batteries are sitting at 66% and I have been using the generator exclusively for the last five days, inverter off.  I don't have a charger, and I find myself at an impasse... If I spend the 500 or so to set up a charger, then I won't be able to get the bigger inverter/charger I need anyway anytime soon. I want a vfx3524 to run the pump and have charging ability.  If I don't do something relativly soon though, I suspect the batteries will suffer. The inverter upgrade could happen within a month, but if I end up getting having to get a charger out of necessity, then the opportunity to get the inverter will be lost for a good long while.

[BlackwaterPark]

BTW, it bears mentioning that my typical load is about 3.5 amps.   During the weekdays, from 7a-5p, there is no load aside from whatever the classic is using, as the inverter goes off, and then off again from around 11p till 6a.  We probably use somewhere in the vicinity of 400 watts daily.

[Westbranch]

absorb happens at least 4 times a week for a couple hours a day, and they do make that sound.  Then they typically go into float.

Should I change the absorb setting to longer periods? 

If I don't do something relatively soon though, I suspect the batteries will suffer.

Absorb V is the first target, the second one is Absorb V for X amount of time..  that is when you truly finish the main part of a 'full charge'. 

You need too Absorb for a longer period..Period!

Otherwise you will soon have a lot of scrap lead...

Start by adding an hour to the timer, if it's not enough add more time.

Lots of discussion over on NAWS forum on this topic...http://forum.solar-electric.com/discussions

hth

[BlackwaterPark]

"Absorb V is the first target, the second one is Absorb V for X amount of time..  that is when you truly finish the main part of a 'full charge' "

I don't understand this. What is absorb V? The voltage that absorb triggers at? Second, how do I determine when the batteries have absorbed enough?

I'm guessing at this point that the best thing I can do is add a charger and two more panels which I could do much sooner than adding a big inverter charger.  If I'm following this correctly, the idea is to get past bulk and into absorb as quickly as possible to ensure that the absorb phase has adequate time to do it's thing as thoroughly as possible?  So.... Charger recommendations for a bank my size?

[BlackwaterPark]

"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?

[Westbranch]

I don't understand this. What is absorb V? The voltage that absorb triggers at? Second, how do I determine when the batteries have absorbed enough?

There are 3 stages to daily charging,  BULK , ABSORB and FLOAT

See page 91 of the current manual
http://www.midnitesolar.com/pdfs/Classic_manual_REV_2056.pdf

Bulk MPPT-

Maximum current charge stage, the Classic is trying to bring the batteries to the Absorb voltage set point. We are basically putting all available power into the batteries.

Absorbâ€"

Constant voltage charge stage to fill the batteries. The controller is regulating so maximum power will not be seen at this time. The Absorb timer is also counting down to the switch to Float

Floatâ€"

Constant voltage charge stage with a lower voltage than the Absorb charge point. The controller is regulating so maximum power will not be seen at this time

there is one more stage and that is Equalize BUT IT IS NOT DONE DAILY, RATHER AS NEEDED. Before an EQ is done the bank must be fully through the Absorb phase.

Equalize-

Constant voltage charge stage to equalize the batteries. The controller is regulating so maximum power will not be seen at this time. The Equalize timer is also counting down to the switch to Float

as well there is a full description on page 32 of your manual, called  Battery Charge Stages and Meanings

hth

[Vic]

Hi B w P,

What IS your Absorption voltage setting in the Classic Charge menu?

What is your Temperature Compensation setting?

Are you using the Battery Temperature Sensor (BTS)  with the Classic?

Check the Limits in the Charge menu  --  make sure that you have set the Limit of temp compensated charge voltage to something appropriate for Flooded batteries.

Also,  use your Hydrometer to MEASURE the Specific Gravity of EACH battery cell,  and record those readings in your battery Logbook,  and please let us know,  at least,  the range in SGs.

Thanks,  More later,      Vic

[BlackwaterPark]

Absorption V: 28.6, f loat: 26.4  eq:31. The absorb was set for two hours, reset it to 3.5.

T-comp: -5.0 mv

BTS: yes

Limits menu: min 26.4 max 31.0... If that's what you are referring to.  When I initially set the system up, I set all the values according to Trojan recommendations for my specific batteries, and nominal voltage. 

Hydrometer: don't have one. I suppose I should order one when I place my charger order today.  Concerning that, I do have one question: It looks like the charger I should be getting is a 25amp Iota, seeing as no one anywhere has recommended any other brand.  Seeing as this unit is for bulk and absorb, is there a reason that I should get the IQ4 add on module?
I'm also curious, looking at the Iota 27-25 specs, that it's voltage is 27.2. If my batteries call for absorption voltage of 28.6, how does that work if this unit can't get to that voltage?
  I'm also uncertain of what additional equipment I will need to hook up the charger... Just a 30a breaker? I want to be able to charge while drawing power from the bank ( as I suppose most people would, heh).  Thank you guys for your input so far... Really appreciated.

[zoneblue]

I dont fully understand your use scenario, on the one hand you reach float a couple times a week, but on the other hand your SOCs stay at higher levels generally. Do you have a big bank, small PV setup? The ideal ratio of PV to battery is one where your peak charge rate is about 0.1C for example:

225Ah bank,  0.1C = 22.5A,
which needs PV (at 24V) = 22.5A *24V *1/0.77=  700Wp

So if you have less than that you might want to consider bumping it up a bit. People who run systems on that rule can easily complete a charge cycle on each sunny day.

Also note that the classic is a big charge controller, capable of managing 4kW of panels. For this reason is has a concomittment level of tare. This means in practical terms that the lowest amount of PV you should use a full classic on relates to keeping the tare under say 5% of production which  is something like (its complicated because the tare varys by time of day):

Tare 6W = 144Wh/d
Required production= 144Wh/d *1/ 0.05 = 2880Wh/d
Min PV= 2880/3= 960Wp  (assuming production of 3Wh/d per Wp)

So again either bump the PV (and battery) up some more, or get a smaller controller like the Kid which has a much lower tare.

Lastly, seems like your missing a few basic concepts on the charge termination. Others have explained pretty well.  I understand that you have a WBJr. The purpose of WBJr is to manage absorb termination (think of SOC estimation as a side benefit). To set this up properly:

- turn on 'use WbJr' for absorb termination
- set absorb time high, maybe 4 or 5 hours 
- set end amps intially to 2% of your bank AH, = 0.02 * 225Ah= 4.5A.
- what this means is that the bank will go to float when either the absorb time is reached or the EA is reached which ever comes first.
- monitor a couple of cycles and at the point where float is triggered confirm that its EA thats triggering it, and that your SGs are at your 100% full target as specified by the battery maker.  Adjust the EA up or down to suit.

If you are doing anything less that this, you are just guessing that your bank is ever fully charged. And murphy will happily step in and guarantee that it is NOT. You cant rely on the SOC from any kind of battery monitor as they are just models and depend heavily on correct parameters, temperature, and lots of real world complexities.

[Vic]

Hi B w P,

Thanks for the detailed reply.

I would guess that your Absorb voltage is a bit low,  but we do not know just where you are located.   But,  would guess that your target SG is about 1.277 - 1.280,  which would imply you would want somewhat higher Vabs.

31 V is probably the recommendation from Trojan,  but,  to me this is a bit too low  --  AND,  IMO,  your EQ voltage should be Temperature Compensated,  there is a setting in the T Comp menu  (is that it ??).

Also,  you should set the high voltage ABOVE the recommended EQ voltage to accommodate cool/cold batteries,  and a possible desire in the future to increase the EQ voltage due to a specific need (but possibly forgetting that the Limit is set to 31 V,  also IMO).

More later,  Thanks,   Vic

[BlackwaterPark]

Yowzers. So, to try and answer some of the questions:

Zone,
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.  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, 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.

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.

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). 

So, I guess the next step is a charger, and hydrometer to assess where my bank is really at, which I am ordering tomorrow.