Feels like there is a problem... but

Rngr275 · September 2012

I am so new to this and my system is so new I am not sure if there is a problem.

I have 2 PV array's(4Kw total) each array goes to a classic200 controller. When they were bringing up my system He showed me on controller that the readout was saying we had made 2.2KwH so far that day (In side of read out bottom line). The when the other bank came on line that controller was showing me how much had come into it. My FNDC would shown Kw in for the day @ say 2-4Kw with just one array going and when both were fired up and running I had days ranging from 5-10Kw). I noticed a day ago that the FNDC showed only 3.2Kw for the day and yet it was quite sunny all day. I went to the cellar and looked at the contollers and the one read Some number of KwH had come in and the batteries were at Float, while the other controller showed 0Kwh in and batteries were in absorb. There was a voltage in readout (top line on screen) for both controllers. Feels like the one array is making voltage but it isn't going into the batteries, or something as I am not sure... it just doesn't seem right. Also, the controller that is acting weird has reset it's date to 2000 and gives me a invalid date flashing when I try to look at the logs.

My installer will be back on Tuesday and my battery voltage seems ok 50.8v(but I have been extra conservative). Should I be concerned... what is going on?

Cariboocoot · September 2012

Re: Feels like there is a problem... but

Two things: first the two controllers need to agree on the charge stage. If they don't it's due to some lack of communication; they either have different Voltage levels set or one does not have a RTS and the other does. Second, the kW hours produced reading on an off-grid charge controller is irrelevant, because it depends on how much power the batteries actually need. Once they are fully charged the harvest drops to near zero unless some load is drawing. To that end, if one array & controller gets the batteries charged first the other will do nothing and may skip to Float because the Voltage is high enough for that level and it has not had to go through Bulk/Absorb due to the other controller's having provided the needed power.

A grid-tie system would be different because it is suppose to sell any and all 'surplus' power to the grid. On the whole it sort of sounds like your system is not balanced properly; perhaps too much capacity for the average usage? 4kW of array would support 640 Amp hours of battery @ 48 Volts - and would only need one MidNite Classic controller (64 Amps peak current) unless the arrays are pointed in two different directions. That size battery bank could supply roughly 7.6 kW hours which would match with the array's minimum 8 kW hour AC output potential.

I wonder why you have two controllers, and what else may be out of balance.

Photowhit · September 2012

Re: Feels like there is a problem... but

Likely your not seeing as much, since the batteries are topped off, the controller not showwing the correct date is a bit disturbing if originally setup correctly. Midnite has a very active forum Here.

'boB' pops in over here pretty often, an Engineer at Midnite, who will fix this problem completely at some point when he has software setup for one controller to be master over the other controllers.

I'm not sure why it shows absorb, but it's acting correctly, it doesn't take much to maintain the float state. You could run the A/C or some heavy draw appliance and take a look after 15-20 minutes and see if they both have 'kicked' in. This might give them a little more information. If the one showwing the wrong date was setup correctly and has dumped it's setup something might well be wrong.

Photowhit · September 2012

Re: Feels like there is a problem... but

Cariboocoot wrote: »

Two things: first the two controllers need to agree on the charge stage. If they don't it's due to some lack of communication; they either have different Voltage levels set or one does not have a RTS and the other does.

Not sure what RTS stands for, but They don't have the ability to talk to each other, yet. They act independently, boB is working on the Master>Slave software.

For the Classic 200 4KW array is just over what it can handle, 83 Amp potential at 48 volts. I think it can handle up to 74 Amps.

TheBackRoads · September 2012

Re: Feels like there is a problem... but

Remote Temp Sensor? Are these 2 separate systems/ battery banks?

Cariboocoot · September 2012

Re: Feels like there is a problem... but

Photowhit wrote: »

Not sure what RTS stands for, but They don't have the ability to talk to each other, yet. They act independently, boB is working on the Master>Slave software.

For the Classic 200 4KW array is just over what it can handle, 83 Amp potential at 48 volts. I think it can handle up to 74 Amps.

Remote Temperature Sensor.
I know the Classics can't actually 'talk' to each other yet, but the communication can also lie in agreed settings - and temp compensation.

My calc for the array potential:
4000 Watts @ 77% efficiency = 3080 / 48 Volts minimum = 64 Amps. No place near the 83 it can handle. Oddly, if you divide 4000 by 48 you get ... 83.

Rngr275 · September 2012

Re: Feels like there is a problem... but

They are not 2 seperate systems, 1 battery bank (740AH). Added the second controller with expansion of array size I think. What bothers me is that the FNDC is showing half the KW generated as it was prior to this hic-cup... but the same as it was when there was only 1 array online.
The date being wrong is another thing that adds to the mystery. Febuary 26 2000 on the one I am concerned about the correct date on the other.

As far as why 2 controllers... well one was just a little on the light side of what it could handle and I wanted the to be able to expand the system next summer if it turns out the 4Kw is not enough.

Interesting read on Midnights forum Thanks Vic... starts around post 9... might be something!
http://midnitesolar.com/smf_forum/index.php?topic=720.0

Photowhit · September 2012

Re: Feels like there is a problem... but

Cariboocoot wrote: »

Oddly, if you divide 4000 by 48 you get ... 83.

No Oddly about it, that is the potential...

Just so we're talking about real numbers the Classic 200 is OK for 65 Amps - 70 Amps in situations where you need the 200 (it will do 78Amps at 70 Volts, but why would you have a 200 over a 150) Taken from the manual.

Vic · September 2012

Re: Feels like there is a problem... but

There IS a converstion also on the MN Forum:
http://midnitesolar.com/smf_forum/index.php?topic=735.0

The Date Reversion is a known issue. The "Vulcan Mind Meld" -- Rebooting the Classics, and forcing all the registers to be initialized with correct values (some of which were not used in the earlier FW, and therefore possibly loaded with errant random values), as well as resetting the factory Default charger settings, may help the date issue, and some undesired Resting periods.

I've seen both of these issues, here. Updated the FW on each Classic, and did the VMM, and now, all seems fine.
FWIW, Vic

Cariboocoot · September 2012

Re: Feels like there is a problem... but

Well you'd need the 200 if the Vmp/Voc on the panels was particularly high due to configuration needs. But since we don't have that info it's a bit hard to figure out.

740 Amp hours @ 48 Volts (parallel strings of L16 370's?) would give you 8.8 kW hours but should ideally have 4.6 kW of array.

Rngr275; could you give us the full system specifications? Like Photowhit said, a 150 would handle 83 Amps max on a 48 Volt system so there again one of those should do it even for 740 Amp hours @ 48 Volts on a 4.6 kW array. Something must have made the need for a 200, possibly even a mistake.

Rngr275 · September 2012

Re: Feels like there is a problem... but

I don't have or remember the specifics of everything with me. Still trying to become better versed. I will provide the specifics Monday when I get back to work. I do know that the second controller was added when a deal on 255w panels came along and I decided to go with them instead of the 240W originally specified (and a single Classic 200). Currently using an Outback VFX3648 inverter, Midnight 175 STS-L E-panel, 16 370AH Trojan L16-RE batteries, 48V system. I don't have the specifics of the panels with me or know them off hand other than they are 255w (16 of them, 8 to a rack). The second classic 200 was added when the decision was made to go with the 255w panels, and I added the FNDC instead of the Trimetric monitor.

Cariboocoot · September 2012

Re: Feels like there is a problem... but

All the same panel, then.

Example: SolarWorld 255 Vmp 31.4, Imp 8.15, Voc 37.8
Sixteen of them would be 4080 Watts. A string of four would have Vmp 125.6 Voc 151.2 so there's the reason for the Classic 200 right there. The current potential with those extra 80 Watts also bumps up over 65 Amps, so that probably explains the two controllers.

One mystery solved.

Rngr275 · September 2012

Re: Feels like there is a problem... but

I might have the mystery solved for why I thought there was a problem in the first place. (Except for the wrong date part). I kept an eye on both controllers over the weekend from morning till night. Both controllers appeared to be working correctly. Lots of voltage in/ and reading KwH in. As the batteries went from absorb into float the A and KwH in went down. Still showed the panels making Voltage (a good thing). What I think I was seeing is that the batteries are full and there is no need to "Bring In" juice to the system. The FNDC actually confirms this since when the panels first came online the batteries were down and we were using a lot of Watts in construction which was captured in the FNDC page "DC In Today" which showed 6-10 KwH coming in for a few days and then tapering down to 2-4KwH depending. Now last week when I thought there was a problem I went into "Super Saver" mode, which got me into a catch 22. The more I conserved the less A that came in which made me think there was a problem, etc.

Question: Is having a new off grid system linke bringing home your first child? You have read everything you can and feel like you know enough to be ready for anything, but what happens is every cough, grunt, puke up makes you think something bad is going on. I might have the new system jitters!

Did I mention I love not being on the grid.

One other update: Yesterday I was able to install our indoor toilet and break it in! Whooo...Whooooo Things are looking up!

Cariboocoot · September 2012

Re: Feels like there is a problem... but

Rngr275 wrote: »

Question: Is having a new off grid system linke bringing home your first child?

Well there's a question I can't answer; it's been so long since either that I don't remember!

niel · September 2012

Re: Feels like there is a problem... but

"Question: Is having a new off grid system linke bringing home your first child? You have read everything you can and feel like you know enough to be ready for anything, but what happens is every cough, grunt, puke up makes you think something bad is going on. I might have the new system jitters!

"

now there's an analogy i hadn't thought of. this might be accurate too as it's not only expensive at the start, but costs along the way surprise you just as the surprise doctor/hospital visits would and both you would need to maintain. i think the solar would be a little less troublesome and you'd love both in your own way, but there is one major difference though as one day you want the kid to leave home.:roll::p

Feels like there is a problem... but

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