Verify This Midnight Calculator

Started by vesserik, August 14, 2017, 10:34:16 AM

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vesserik

This midnight charge controller calculator says I need two charge controllers. Could someone verify this information, and instruct me on how to wire my setup.

12x 295 watt rec twinpeak 2 solar panels
24v 500ah Ni-Fe batteries. 20 batteries in total.

Pole mounted and about 4 sun hours a day.

Was planning on doing 4 series of 3.

Ni-Fe batteries are 1.2v that charge at 1.7v

let me know what other information is needed. I appreciate any help I can get.

Vic

Hi vesserik,   Welcome to the Fourm.

In general,  would suggest following the recommendations that come from the MN String calculator.   It is generally recommended that a second Charge Controller (CC) be added when the calculator notes that 1.2  CCs are required.

Sometimes when one wants to over-PV a CC,  or perhaps if the PVs have differing Azimuths,   it might be OK to exceed this 1.2 suggested limit.

As you probably know,  charging batteries often requires the CC to work near its peak capability for hour,  after hour.   This causes increased heating when one has excessive PV (or other Renewable Energy sources)  available.

When over-PVing MPPT CCs,   during Absorb,   and EQ,  the excessive available PV power will cause the input voltage to the CC to rise,   causing added heating in the CC.   This effect is moderated to a certain extent  with Opportunity Loads on the system,   but,  this too will cause some heating increase.

Personally,   have been in a similar situation to you,   and have chosen to add CCs to handle the excess PVs,   adding redundancy,   and being more gentle on the CCs.

FWIW,  my opinions.(and,  you might try Removing the very similar Post in the Classic FAQ Topic,  IMO).   Vic
Off Grid - Sys 1: 2ea SW+ 5548, Surrette 4KS25 1280 AH, 5.25 KW PV, Classic 150,WB, Beta Barcelona, Beta KID
Sys 2: SW+ 5548s, 4KS25s, 5.88 KW PV, 2 ea. Classic 150, WB, HB CC-needs remote Monitoring/Control, site=remote.
 MN Bkrs/Bxs/Combiners. Thanks MN for Great Products/Svc/Support&This Forum!!

vesserik

Ok so then for my wiring, Would I have to do 2 separate arrays, or can I wire the CC's together and they split the load?

Vic

Hi vesserik,

MPPT  CCs (with very few exceptions)  need to have their own separate array to work at all properly.   f course there is no problem at all in using multiple CCs on a single battery bank.

Will this be your first battery based power system?

Am certain that you have read about all of the tradeoffs in using NiFe batteries.  Often it can be a bit difficult to find  an Inverter/charger that can handle the exceedingly wide range of battery voltage with those batteries,   and so on ...

Have not run NiFe  batteries here,  so the above "attitude"  is just based on reading about NiFe behavior from the few folks that appear to be using them ...

FWIW,   Good Luck,  Vic
Off Grid - Sys 1: 2ea SW+ 5548, Surrette 4KS25 1280 AH, 5.25 KW PV, Classic 150,WB, Beta Barcelona, Beta KID
Sys 2: SW+ 5548s, 4KS25s, 5.88 KW PV, 2 ea. Classic 150, WB, HB CC-needs remote Monitoring/Control, site=remote.
 MN Bkrs/Bxs/Combiners. Thanks MN for Great Products/Svc/Support&This Forum!!

vesserik

Yes, this will be my first battery based setup, and I am very excited about it. I am looking at Midnight MPPT CC's because I was told they have a setting for NI-Cd, which has a very similar charging style to Ni-Fe. I was also under the impression that the midnight classic is able to be fine tuned to my needs.

Im very excited to try Ni-Fe, and got a quote for TN500: USD212.68/pcs. Living in a yurt, I dont have room for batteries, and will be putting them in a root cellar. The Ni-Fe will do better in the temperatures that I will experience in Wisconsin. I like the life expectancy of them, and I like that they are environmentally safer. Personally I would have gone with Aquion’s Salt Water Battery if they didn't go belly up so fast.

I really appreciate your help.

Thank you very much.

Vic

Hi vesserik,

Thanks for the added info on your environment.

There are a few Members here who do run NiFe batteries.   They do consume considerable amounts of Distilled Water,   so it would be a good idea to allow easy access to the batteries for watering them.

YES,   the Classics are very configurable,   and have a wide range of custom settings.

One Member Mike,  at the Link below has been running NiFes for four or five years,  IIRC:
http://midniteftp.com/forum/index.php?action=profile;u=15

OK   Good Luck with your project.    Just be very careful with the Inverter/Charger selection --  check very carefully the EXACT  Hi voltage and Low voltage disconnect setability ranges.   This might be one of the largest issues with NiFes (IMO).    Vic
Off Grid - Sys 1: 2ea SW+ 5548, Surrette 4KS25 1280 AH, 5.25 KW PV, Classic 150,WB, Beta Barcelona, Beta KID
Sys 2: SW+ 5548s, 4KS25s, 5.88 KW PV, 2 ea. Classic 150, WB, HB CC-needs remote Monitoring/Control, site=remote.
 MN Bkrs/Bxs/Combiners. Thanks MN for Great Products/Svc/Support&This Forum!!

ClassicCrazy

#6
I got some lead crystal batteries this past winter and the specs show they perform very well in cold weather and I have the in unheated shed.  . I will let you know in 10 to 15 years if they have the longevity claimed - I am trying to only use 20% of their capacity to make them last  many cycles. In Wisconsin that means you need to have a generator - unless you really oversize your system there isn't anyway to get by without generator.

So I took a risk with these sealed batteries but I have to say it is really nice not having to mess around with watering them. And moving them around for installation was great too - no worries about sploshing around acid.

Not sure what part of Wisconsin you are in but check with Remis battery - he has been in the business for a long time.

http://soneil.com/advance-technology-battery/performance/
there are different capacity cells available
http://php.worldindia.in/soneil_dotcom/wp-content/uploads/2-EFSN-540-1.pdf
https://www.remispowersystems.com/

Larry

system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

mike90045

Another alternative if you have not already bought your inverter, is go to a 48V system and might only need 1 controller.

In addition to special voltage setpoints for the controller, your other gear DC gear & inverter, need to be able to handle the higher charge voltage 34Vdc they will see from the batteries in daytime  ,  And when the batteries are low, the inverter built in LVD may kick off too early, while there is still ample charge in the batteries.
http://tinyurl.com/LMR-Solar

Classic 200| 2Kw PV, 160Voc | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph )| Listeroid 6/1, st5 gen head | XW6048 inverter/chgr | midnight ePanel & 4 SPDs | 48V, 800A NiFe battery bank | MS-TS-MPPT60 w/3Kw PV