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Small Cabin Forum / General Forum / My Final Config for Midnite Classic Solar Controller & JKBMS' w/ Large Bank (works amazingly well)
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# Posted: 29 Jun 2022 17:08

INTRO: I have debated posting this for a while until I got everything tweaked in and working as best as possible. The End Result is Gobsmackingly Good !

I cannot speak for other SCC and such as each is different & unique in their own ways BUT this may likely be a Good Reference.

My FINAL Tweaked out settings, NOTE this is for 24V system, Using a Midnite Classic 200 (not really designed for Lithium Based due to single decimal point accuracy. I am also posting the JKBMS Settings which by the time the packs enter Float Mode they are very nicely Balanced.

Important FYI, Active Balancing Quick Guideline is 1A Balancing per 100AH / 200AH - 2A Balancing / 300AH - 3A and so on.

Midnite Classic Charge Controller Settings (Effective since Finalized build June 2022)

All equipment MUST BE Voltage Corrected & Calibrated (VERY IMPORTANT)
Divide Values X2 for 12V. Multiply X2 for 48V.

Absorb: 27.6 for 45 minutes (3.45vpc) (some call this boost) *I run a Bank of 5 packs, but never actually runs the full 45mins because of EndAmps
Equalize: OFF
Float: 27.5V (3.437vpc)
Min Volts: 21.2 (2.650vpc)
Max Volts: 28.6 (3.575vpc)
Rebulk Voltage: 25.6 (3.200vpc)
End Amps: 8.7A (*1) (** Using WizbangJr Smartshunt to control) (*** Allows for full Saturation at set Float Voltage)

(*1): End Amps is calculated from the LOWEST AH Battery Pack in a Bank. IE: (100AH X 0.05 = 5A 280AH X 0.05 = 14A. My Smallest 174AH is 8.7A)

NB: Victron Forum discussion says EndAmps = TailCurrent

Coulumbic Efficiency / Battery Status Meter Efficiency for LFP = 99%.

This get's the bank charged to full with high amps (Constant Current) and then float (Constant Voltage) tops off so the cells are at 3.47Vpc. I am running 7/24/365 so float is used up by the Inverter + provides whatever the packs will take to top off. (which is minimal)

* Do Not forget to adjust for Voltage Offsets between Actual Voltage @ Battery Terminal & at Solar Controller.

Very Special NOTE: Floating & Saturating to 3.437vpc, accounts for the Voltage Settling post Charge of any kind which actually brings the cells to just below 3.400Vpc.

What is a WizBangJr ?
Description: The Whiz Bang Jr is a current sense module that attaches to the standard 50mv / 500A Shunt (MNSHUNT) and wires into the Classic and KID charge controllers to give Amperage readings from the shunt. To use the Whizbang jr (MNWBjr) with any of the Classic Lites, you will either need the local app or an MNGP.
* Sadly designed for Lead Acid Chemistries and therefore only Single Decimal Point Accuracy. Similar higher Accuracy Smartshuts like Victron (2 decimal point accuracy) can also perform similar functions for various SCC's.

JKBMS SETTINGS (warning, long) BELOW the Main BMS status screens showing the Delta between cells in ALL Packs.
2 BMS STATUS Shown in Attachment 1
BMS Config Screen Attachment 2

ATM that is 2x174AH Used EV Grade LFP & 2x280AH ESS Grade (what many call Bulk or B grade)

Hope it Helps, Good Luck
2 pack delta info (JKBMS)
2 pack delta info (JKBMS)
JKBMS Config Screen
JKBMS Config Screen

# Posted: 29 Jun 2022 18:53

Your numbers are almost identical to the whitepaper I wrote for our boat. I used a lower float number (3.3 per cell), but it was probably too conservative. I didn't really need to eek every Ah out of the cells so I just left it. All my other numbers pretty much matched yours.

Our goal was to judge the power we would make that day and keep the charger in BULK as much as we could. If we knew we were going to make a ton of power we would turn on the water heater, use the immersion cooker, do laundry, ect. If the system went to float, I was wasting power I could be using. We got pretty good at estimating our production and using up power (it actually became an obsession for me).

Man that JKBMS looks interesting. Sigh it wasn't around when I was doing it(or I didn't know about it). Might be fun to build an LFP system again someday.

# Posted: 29 Jun 2022 19:48 - Edited by: Steve_S

I worked through a LOT of combinations. tweaks & hard thrash tests, in the process a few grand was spent doing so as I dumped my fleet of Chargery BMS8T-300's and DCC-300A stuff (NOT CHEAP) (8 full Units). Approx $240 USD + S&H each.

Bulk/Absorb is only supposed to get you to Max trigger point (Constant Current) before switching to Float (Variable Current). During Float if all of a sudden you draw say 50A, it will increase to cover it and then return to trickle & top the battery packs and continue to feed whatever demand is required by the loads.

Remember that LFP will immediately settle Post Charge and this ensures you remain high on the "Working Voltage Curve" (3.000-3.400) which is NOT the Full "Allowable" voltage of (2.500-3.650) It is perfectly fine to hit 99-100% of the Working Voltage Curve which is what is expected. So MANY trip over that it is insane, no matter how much they are told, shown the proof etc...

I just dragged off the Rolls Surette S-550's to Recycle for Scrap lead weight value ($35 a pop). Ouch that was $3500 when I bought them...I kept them as a secondary bank and never needed them but still maintained & equalized with occasional Heavy Discharge... wasted time.

I can VERY Highly Recommend the JKBMS with Active Balancers. I am presently assisting them with a few things and will review/edit manuals to ensure proper English for them.

The Lead Vendor who is maintaining the Firmware & APPS is here (contracted by JiKong Corporate):

Hope it helps, Good Luck.

# Posted: 29 Jun 2022 20:28 - Edited by: gcrank1

Just want to say a big thanx to you, Steve, for the solid charge info for my 12v 100Ah LFP's.
Ive run both bats through a couple of cycles (took some time as our usage is pretty light) and recharge at 14.0/20ish A until the Amps fall off to about 3-4 (on my simple meter), 15 min or so there and I pull 'em off the power supply. Both have been giving me a Huge increase in available amp hours; about 3x what my old, tired FLA provided.
Havent even hooked up the solar this year (yet), wanted to get a feel for how they worked. I just swap 'em out and bring the low one home when it drops to about 12.9v resting. We run whatever we want whenever we want.

# Posted: 30 Jun 2022 03:16 - Edited by: Steve_S

You are most welcome gcrank1, it's always a pleasure to help good folk;

It's a Shame there isn't a subforum for Cabineer Solar, it would be great to populate it with info for everyone's benefit forward. I have so much over @ diysolarforum over the years and I've got a lot of fairly good & recent ones I could cherry-pick out for here. Oriented more for "Our" kinds of places.

# Posted: 5 Jul 2022 22:22

WOW - Cannot edit my post to add important supporting info. :

Ohhh well, that's that then.
I will POST it Here and I am done.

EDIT - July 7 2022.
❗Voltage Corrected & Calibrated (VERY IMPORTANT)
- Midnite Solar Classics SCC's can be programmed for OFFSETS.
- Not all are capable so to adjust values it will have to be in charging values AS WELL as your Inverter/Charger.
- Even 0.1 Volt offset Can & Will affect operations
The simplest Way
Use 2 or 3 Decimal Accurate DVOM/DMM.

While SCC is Charging, Measure the Real Voltage coming out of the SCC and write it down, Same for the Inverter/Charger @ its BATT Terminal.
When Batts are in a + Charge (NOT when Discharging) measure the Voltage @ its/their Battery Terminal Lugs.
There WILL be some variances but there is always some Line Loss between these devices, Most important is what is going into the BATT.
Check your notes from each test. That Differential in Voltage must be Compensated for !

Take that Voltage Offset and apply it to the SCC, either an Offset Function or by the Charge Settings
IE, Assume SCC to Batt Terminal is 0.1V and you are Charging, Bulk/Absorb/Float Adjust the values UP. IE If Absorbing @ 27.6V increase that to 27.7V to compensate and the other Values as well. DO NOT FORGET to do the same for Low Voltage Disconnect !
The Inverter Needs two values;
The Charging Voltage offset applied as Above You got that value in your tests above. With SCC Charging.
Low Voltage Disconnect. MUST BE Measured when No SCC Charging is happening and the inverter is drawing from BATT only. It will be different than when SCC is charging the batts. Use that to adjust for Low Volt Disconnect ! Or you may get a Late Disconnect @ Low Volts making the disconnect lower than you set. NOT A GOOD THING !

Lastly, be aware that every Fuse/Breaker, Lug & Batt terminal adds to Voltage Drop collectively due to resistance.
---- End of Edit ----

# Posted: 6 Jul 2022 09:54

All good info, Steve. And this last isnt 'too far away' from the one you wanted to edit
Sadly, we seem to have a 'time-out' for making edits; I agree that it can make it difficult when a post needs correction or improvement. I prefer to keep info comprehensive and cohesive rather than strung out through a thread but it is what it is.
All that to say nobody here is picking on you, we are glad to have your inputs

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