I have gone dark on my solar array for 3 years (pun intended) while I moved and then built a new home. I am just now getting back to rebuilding my system. I have a MSPAE48 inverter with a Classic 150 Charge controller. Since my old FLA batteries are 7 years old and have died (even with a battery maintainer on them) I have purchase a bank of LIFEPO4 batteries.
My question is - I am assuming there has been a firmware update to my classic in the last 3 years that will enable support for LIFEPO4 batteries. Is that assumption correct and if so what are some of the basic settings associated? I have not yet purchased the BMS's that I will be using for these and will be building the bank from discreet LIFEPO4 cells.
It isn't a bad idea to update your Classic Firmware.
Though there isn't anything specific to Lithium batteries - you still need to put in the correct charging parameters and that is going to depend on the type of battery and your bms.
Take a look here
http://midniteftp.com/forum/index.php?board=63.0
also at this
http://www.midniteftp.com/support/kb/faq.php?id=75
Larry
I'm running a Classic-200, 250A-EPanel, Samlex EVO Inverter and with 24V/1190AH/30.4kWh of LFP as my primary bank consisting of 3x 24V/280AH & 1x 24v/350AH, each with a Chargery BMS8T SMart BMS with Solid State Contactors and 1x QNBBM-8S Active Balancer per pack.
I have spent a Great Deal of time doing assorted tests including Hard Thrash testing to push the limits. This is done because I am quite Rural & Remote and being 100% offgrid solar, it must be reliable & dependable.
While LFP does not require FLOAT, I've settled on a profile with Float that keeps the batteries very happy at 90% and never overworks the bank at all.
My Midnite Classic-200 Charge Controller settings
- This is for 24V, X2 for 48V or ÷2 for 12V -
Absorb: 28.2 for 15 minutes
Equalize: OFF
Float 27.9V
MIn Volts: 22.0 Max Volts: 28.7
Rebulk Voltage: 27.7
End Amps: 14A
This get's the bank charged to full with high amps (Constant Current) and then float (Constant Voltage) tops off so the cells are on average between 3.475-3.500. I am running 7/24/365 so float is used up by the Inverter + provides whatever the packs will take to top off.
I built all of my own packs and even wrote a document in use by many on how to assemble your LFP Packs and more. Here are some links to help you along your path.
CLASSIC - LITHIUM Quick Start
http://www.midniteftp.com/support/kb/faq.php?id=121
CLASSIC - LITHIUM - How do I set the Classic to charge Lithium batteries (explained)?
http://www.midniteftp.com/support/kb/faq.php?id=75
How do I set the KID to charge Lithium batteries?
http://www.midniteftp.com/support/kb/faq.php?id=87
Luyuan Tech Basic LiFePo4 Guide: http://midniteftp.com/forum/index.php?action=dlattach;topic=5143.0;attach=8402
Chargery BMS8T-300A : https://www.chargerystore.com/index.php?route=product/product&path=20_26&product_id=86
Chargery DCC 300A Contactor : https://www.chargerystore.com/index.php?route=product/product&path=62&product_id=66
QNBBM-8S Active Balancer: https://deligreen.en.alibaba.com/product/62035896240-806516208/8S_24V_Active_Battery_Balancer_Equalizer_Anti_Short_Camper_Trailer_Battery.html
NOTE: Chargery is about to release a new series of SmartBMS with additional communications like CANbus, better UI and proper Active Balancing for large capacity cells. BTW: There is a certificate error that pops up with some browsers on their store site.
(https://diysolarforum.com/attachments/lfp-voltage-chart-jpg.27632/)
Hope it helps, Good Luck
Steve_S
Steve
What is advantage to using the balancer in addition to the BMS ?
It sounds like my AGM batteries could also use this same balancer device.
Thanks for all your detailed write ups and testing. Wish I had this reference years ago when I bought some Calb cells.
But a lot has changed since then in availability of BMS and general lithium knowledge.
Larry
Quote from: ClassicCrazy on May 28, 2021, 11:29:01 AM
Steve
What is advantage to using the balancer in addition to the BMS ?
It sounds like my AGM batteries could also use this same balancer device.
Thanks for all your detailed write ups and testing. Wish I had this reference years ago when I bought some Calb cells.
But a lot has changed since then in availability of BMS and general lithium knowledge.
Larry
I know some Active Balancers can work with AGM Batteries but I do not think these are it.
A BMS has ONE TASK, to manage the Cells & Battery Pack to ensure everything is working within spec.
Some offer "Passive Balancing" which is typically in the Millivolt range and is intended to keep cells within 5-30mv. Other BMS' offer Active Balancing (This is recent addition to brands) which can move power from Hi to Lo cells and handle larger cells.
QuoteActive cell balancing redistributes charge during the charging and discharging cycle, unlike passive cell balancing, which simply dissipates charge during the charge cycle. Thus active cell balancing increases system run-time and can increase the charging efficiency.
By the time my System reaches Float after 15 Minutes of ABSORB, the battery packs settle and the Active Balancing brings the cells in all the pack to within 10-15mv difference from each other. Also dring float, as it progresses along, the Packs themselves level up very nicely as well, typically to within 0.02v of each other.
I've run several tests and processes even with measuring the IR of the cells through runs using a Yaorea YR1035+ battery tester, because it is my Type-A Personality with Virgo Handicap at work. But when it comes to something ones life depends upon, is there such a thing as being too cautious ?
Steve_S
I’m sure you have seen my posts about the 200 amp pouch cells, I’m ready to do something with them. I have no use for the Chinese inverter/charger as it does not fit my use well, My main charger is the smaller one A Exeltech XL1100 24 volt 120 ac hard wire. I want to make a 2 ea. 24 volt 8S sets using separate BMS’s I have several reasons for this redundancy, better balancing between cells , least disturbance of the current setup. As mentioned the cells are clamped in plastic frames with bolts at each corner. Each “cell pack†contains 4S cells. It’s very easy to remove some battery jumpers and reconfigure as two banks. Now then BMS’s.....I’ve tinkered there I have several iCharger i208b multi mode charger/discharger/testers. This unit is capable of doing the initial testing of the stacks...it’s rated 20 amps and 8S really made for model airplane buffs, not sure, but anyway a very capable unit.
Specifically which BMS would suggest for my systems, so far I’m impressed with the Chargery and Overkill The separate monitor of the Chargery would be a huge asset but the iCharger can be in monitor mode as well, backup data is very valuable in resolving issues. Active balancing does seem to be a big plus My charge source will be Classic’s with 2S 72 cell panels .
I am a little stumped by no one stating that they have seen any pouch cells like these
Edit....I saw you online and chased you here not realizing this is probably thr wrong place to post this question
Thanks..tecno
Quote from: tecnodave on May 28, 2021, 11:41:24 PM
Steve_S
Edit....I saw you online and chased you here not realizing this is probably thr wrong place to post this question
Thanks..tecno
I wrote a long reply in the lithium thread on your post BUT it got lost while writing it. I'll try one more time.
This thread got a little off topic. LOL but that's all good. I guess what I was really asking was do I need the BMS or would just a active balancer do the trick. Especially since all I have been able to find are common lead BMS's (daly) and I am concerned that if the BMS shuts down the battery the classic will be left with no battery connection especially with power being provided by the panels and then suffer damage. Is that really a concern or am I just being overly cautious.
Quote from: nhsnm on June 17, 2021, 04:39:01 PM
This thread got a little off topic. LOL but that's all good. I guess what I was really asking was do I need the BMS or would just a active balancer do the trick. Especially since all I have been able to find are common lead BMS's (daly) and I am concerned that if the BMS shuts down the battery the classic will be left with no battery connection especially with power being provided by the panels and then suffer damage. Is that really a concern or am I just being overly cautious.
PV to Classic to Batteries.
If the Classic shuts off there is no PV to the batteries.
Larry
A BMS is the Guard dog, watcher & keeper of the Cells and the entire pack. Brakes on your car !
It stops Over/Undercharge situations, Over/Under Temp functions (can be nasty if not) and prevents cells from going too far out of balance (large differentials).
An Active Balancer will only operate above 3.200 some higher. They only transfer Hi Voltages from High Cells to Low voltage cells within the pack. That's it, That's all. Balancers have no safety systems, that is not their job.
Some' BMS have Passive Balancing, not much goof for cells above 15AH really & passive only burns off High Voltages from cells and is extremely slow. Recently (this year) some companies are producing BMS' with Active Balancing built-in, as well as a "Bonus Feature / Function" of course costs, reflect that.
There are many good quality BMS' as well as some real trash out there. Some can support different Lithium Chemistries while some are very specific.
I use Chargery BMS' which uses External Relays/Contactors to control the ON/OFF switching *this method is used for high performance systems like EV's or where loads can be high as Relays / Contactors can be sized according to Amp Draw limits. These are SmartBMS that are programmable (passive balancing only).
JBD FET Based BMS' are good. QUCC with BYD PowerSaver Relays are also quite good (have Bluetooth management module as well) there is also HelTec which has an assortment of smart/dumb BMS' with many options.
Known Good Active Balancers are QNBBM by DeliGreen as well as various versions from Heltec (tricky to choose, careful spec reading is required, choose the wrong one and it won't make you happy). I use a QNBBM-8S on each of my packs (24V/8S config).
REFS:
Chargery BMS w/ Passive Balancer: http://chargery.com/balancer.asp
QNBBM Active Balancers: https://deligreen.en.alibaba.com/productgrouplist-806516208/QNBBM_Balancer.html
HelTec Active Balancers (all varieties/types): https://cncdheltec.en.alibaba.com/productgrouplist-814905857/Active_Equalizer.html?
HelTec SmartBMS (All chemistries,): https://cncdheltec.en.alibaba.com/productgrouplist-821326332/Smart_BMS.html
QUCC SmartBMS & Active Balancers (I do not know about their balancers): https://www.aliexpress.com/store/all-wholesale-products/5777447.html
JBD SmartBMS: https://dgjbd.en.alibaba.com/productgrouplist-813065523/smart_BMS.html
BTW: I did not mention Daly as I have not much good to say about them. They do Promo a LOT but their quality is inconsistent.
Hope it helps, Good Luck.
Steve
Thank you. Very informative answer and I appreciate it.
My only concern was that if I am using a common port BMS and it shuts down the Battery the Charge controller is left with no load or reference voltage. However the more I think about it... If I program the CC correctly and have its TOP voltage a little below the top voltage cutoff setting for the BMS and program my Inverter to cut off above the low voltage cutoff of the BMS I will really limit the potential of that happening.
I did purchase a DALY but only because that seemed to be the only brand I could get my hands on (that alone concerns me lol). But my thought is that I will just use it for a little while until I can get a better device and then this will either become spare or used in a different solution not my production House power.
With all of that said. Thank you for you input it is very helpful.
Quote from: nhsnm on June 18, 2021, 02:18:22 PM
My only concern was that if I am using a common port BMS and it shuts down the Battery the Charge controller is left with no load or reference voltage. However the more I think about it... If I program the CC correctly and have its TOP voltage a little below the top voltage cutoff setting for the BMS and program my Inverter to cut off above the low voltage cutoff of the BMS I will really limit the potential of that happening.
I did purchase a DALY but only because that seemed to be the only brand I could get my hands on (that alone concerns me lol). But my thought is that I will just use it for a little while until I can get a better device and then this will either become spare or used in a different solution not my production House power.
My Classic settings profile for my LFP bank is posted above (Samlex EVO-4024 similar (different wording)) and that setup gives me no trouble with my Bulk Commodity 280AH cell Packs, nor the Matched & Batched one (they behave Soooo much better) and even my recycled EV-LFP 175AH cell pack (those cells are persnickety).
BTW, I have TWO Classic Profiles stored because I have 2 banks, one 30kWh LFP and 1 22kWh FLA (Heavy Rolls Surette's), I flip the battery bank switch & load the appropriate profile and continue... That is a nice capability thanks to the Midnite PC Sofware.
During my extended Thrash Test cycle I did have all packs disconnect while taking charge from the Classic 200, it did not blink at all just stopped charging and kept all settings. Now I did NOT powercycle the Classic, had I done so it may not have been "pleasant" as it would not have had a Battery Voltage sense. Some SCC's can be firmware programmed for the voltage which get's stored in NVRam so they can powercycle without a battery. Again, I did not try this with my Classic 200.
I have not updated my diagrams as I am not 100% complete with the final revisions to my system but here is the version I've been running that also went through the Hard Thrash Testing. But these may help. They are from my "About my System Page" at DIYSolarForum.com .
GEEZ, can't link images from my page... That Sucks ! Click the links and pictures appear.
https://diysolarforum.com/attachments/our-solar-diagram-v4-dec-2020-jpg.30338/
https://diysolarforum.com/attachments/lfp-4-pack-bank-dec-2020-interim-jpg.30544
Hope it helps fill in some blanks.
Steve
OK, it is time now for... "Ask me what time it is and I will tell you how a watch works" :)
You can think of the battery, when it is connected by the BMS or even a breaker/switch as a LOAD when the PV input is actively charging.....
When the Classic first is turned on, the battery is powering the Classic a tiny bit and then, before the Classic "wakes up", the CLASSIC is the load.
A very small load of course due to the tare/idle loss. When the classic is idling at that time, the battery voltage is slightly higher than the Classic, but it is so little above the voltage at the Classic that you would have a hard time measuring it.
When the PV is active and Classis is charging, the Classic is the source and the Classic's battery voltage should measure slightly higher than the battery terminal. Not a lot though. The higher the charging current, the higher the difference between battery terminals and controller terminals because of the battery cable resistance: Vdrop = I * R
The reason you won't see much voltage drop across the battery cable when it is connected is that the resistance of the cable is so low that the I * R voltage drop is a low. Resistance goes UP ? Then the voltage drop will also rise more at the Classic end when charging.
You can think of this difference in voltage to get a certain amount of current into the battery as kind of a tug-of-war with rope....
The battery side voltage is tugging DOWN on the Classic's output voltage which is trying to pull that wire/rope UP.
So, if you just let go of the rope that the battery is pulling down on, then the Classic is trying to pull that lower voltage UP but ll of a sudden, the rope tries to yank away UPwards because the resistance/connection of the wire/rope is "open". The Classic will quickly try to pull the voltage up real high to get all that current back that just went away because the battery disconnected. BUT, we can't have that happen so the Classic "catches" itself so that doesn't happen. Instead, the Classic' would stop the voltage rise as soon as it gets maybe 3 volts higher. THIS is IF the Classic even stays on for more than a second or maybe a fraction of a second.
A lot (or most ?) of the time , the Classic will not power itself from the still connected PV/Solar in this open circuit case for more than a fraction of a second. If that happens then the Classic will go to sleeping and disconnect the PV input and the whole Classic will turn off.... No display or sound... as soon as the Classic's internal energy storage capacitors discharge.
That's kind of how it works but what that means is that your batteries will be fine and won't experience ANY over-voltage if that is what you are worried about.
I have no concerns about the battery but more for the Classic. If the battery disconnects while the Classic has PV input could the Classic be damaged? That's the real concern.
Quote from: nhsnm on June 23, 2021, 11:33:26 AM
I have no concerns about the battery but more for the Classic. If the battery disconnects while the Classic has PV input could the Classic be damaged? That's the real concern.
Nothing bad should happen. This situation was taken into account when designing the Classic.
What you are talking about here is called overshoot. It can certainly happen if not taken care of.
I remember testing for this a lot and it sure seemed fine after making it work well.
It's not necessarily an easy thing to control either ! But that overshoot was mitigated to be as minimum amount as possible.
So, I would not worry about it.
Very cool. I have really enjoyed this conversation even though it just led me right back to what I was thinking. Thank you for your help.