LifePO4 batteries for use with Midnite Classic 150?

[Sunking]

I call them Chinese. Drop the racial slurs.

What racial slurs, they are communist.

[Sunking]

Sunking, how would you initially balance the UltraEnergy 100ah battery I just linked to?

You don't, it has already been done for you at the factory. That is what you are paying 100% to 400% higher price for.

[Sunking]

Sunking, does your LFP balancing logic apply to batteries like the UltraEnergy line? http://store.starkpower.com/12V-100A...tery_p_24.html

Their product documentation just says the charger should not float charge, but instead stop charging at 14.6V. It doesn't mention anything about the need to vary current.

Fine, just do not flirt with 14.6 volts. Lower to 13.6 volts and you can most certainly Float Charge if you cycle daily. But you must use a Float type CC/CV charger. You do not want a 3-stage charger. You would set Midnite Solar controller to Bulk = Absorb = Float = 13.6 volts.

What you are paying for with that battery is factory Balanced cells with a mini-BMS in a box. Instead of paying $500 for a set of 4S 100 AH set of CALB's, this one with 4S 100 AH in a box cost you $1000. Both the Calb's and this one have the same performance, usable capacity, and cycle life of a good quality high end 12 volt 125 AH FLA battery for $250. So ask yourself why you want to spend $1000 on a battery when you can get the same for $250 you don't have to worry about and watch like a infant child?

[createthis]

You still have not answered how you intend to Balance the batteries initially.

Sunking, how would you initially balance the UltraEnergy 100ah battery I just linked to?

[Sunking]

Sunking, does your LFP balancing logic apply to batteries like the UltraEnergy line? http://store.starkpower.com/12V-100A...tery_p_24.html

Their product documentation just says the charger should not float charge, but instead stop charging at 14.6V. It doesn't mention anything about the need to vary current.

If you are foolish enough to charge to 100%, then yes you must shut down or else you will damage the battery , but not if you only charge to 80 to 90%. Set the voltage to 13.6 volts and Fuhgeddaboudit, no need to shut down or worry.


Midnite Solar is going to tell you what you want to hear. You can use Midnite Solar or any manufacture to charge a LFP battery. But you had better know how to work around their incompatibility to work with LFP. What everyone has been trying to tell you and is not sinking in you do not want to fool around or get near the knee's of the charge/discharge curves of the LFP battery. Real bad things happen when you do that. LFP batteries do not tolerate abuse, one mistake and they are boat anchors. You are Hell Bent on destroying it going to 100%.

So go ahead and do it your way. No better teacher than loosing a lot of money. You still have not answered how you intend to Balance the batteries initially.

[createthis]

Sunking, does your LFP balancing logic apply to batteries like the UltraEnergy line? http://store.starkpower.com/12V-100A...tery_p_24.html

Their product documentation just says the charger should not float charge, but instead stop charging at 14.6V. It doesn't mention anything about the need to vary current.

[createthis]

You can set all 3 voltages to equal. thereby making it a CC/CV charger 1 stage charger. Midnite Solar is not made or intended to work with LFP batteries period. All you can try to do if you know how, is work around the incompatibility. You do that by setting the controller voltage well below 100% SOC so you do not gfry your cells. There is only one I know of made by Genasun using their integrated battery. Problem is limited to a 140 watt panel and their battery.

Chargers intended to work with LFP batteries communicate. What you do not know is how Balance Boards Work and that is what the killer is. All they do is turn ON when the cell is fully charged and bypass a small amount of current to be passed onto lower cells. Sounds great huh? It sucks. That can only work if your charger can then cut back current to the limit of the balance boards.

Now stop and think about that a moment. I bet it never occurred to you what is happening or what can happen. So you batteries are charging along at full power, say 25 amps. First Balance Board turns on when it gets fully charged and turns on and bypasses say .3 amps. That leaves 24.7 amps still flowing into a fully charged cell heating it up and causing damage. No Solar Charge Controller except Genasun has the ability to cut back current, they can only regulate VOLTAGE, not CURRENT. A real LFP chargger can do that and you set what that amount of current is to match the balance boards.

Secondly no Balance Board (BMS) can Balance an a out of balance battery bank in any meaningful time frame. Why you ask?. I already told you because they can only bypass a very small amount of current. All they can do is make for very small minor corrections.

Now if you completely understand how LFP works, what destroys them, and how to protect them you can work around all that. So your first challenge is when you receive the cells, HOW ARE YOU GOING TO BALANCE THEM? Can you even answer that? Give you a hint, you need some expensive equipment you do not have.

I am trying to prevent you from making a huge mistake. But it is yo money to loose, I really do not care, have at it. But smart money in you case is FLA batteries, much cheaper and will last longer. In you rcase much longer because you will destroy your first set of LFP batteries. Your choice.

FWIW Inetdog and PNJunction are telling you the same thing. You might want to listen to one of us.

I'll ask Midnite Solar about this, since they told me the charge controller was indeed capable of charging LFP. Thanks for the info.

[createthis]

What do you call Chinese Communist? I call them what they are.

I call them Chinese. Drop the racial slurs.

[Mike90250]

OK, related to that useful advice, I have a few questions:

1. If you build a battery bank out of random off the dealer's shelf cells, all the same brand and model and hopefully same or similar manufacturing date, how likely is it that the cells will be reasonably (within the capacity of the BMS to handle) balanced as to SOC when you get them?

Zero chance the balance boards can bring random cells into balance within a couple days. Might take a week or 3, with a very low power charger. The balance boards can only shunt a small amount of power - look at their photos, most don't even have a heat sink.

2. Same question but a group of cells ordered new from the factory or from a large internet dealer as a single order? Better or worse than the first situation?

Might actually happen in a couple days. Cells shipped from factory only about 80% or so full, to enhance lifetime, Changing still has to happen at slow rate to allow boards to bypass cells that fill first (the lower capacity cells)

3. Same question but this time you buy a preassembled battery pack with an integrated BMS?

Depends if the vendor did their work manually, or they hope the BMS does it, and you are stuck with filing a warranty claim. Even mature lead acid tech has limited lifetimes, we don't know yet what the exotic chemistries reaction over time will be, accelerated testing is not 100%, just a best guess,

Regarding Vampire and Monitor boards: Clearly any differences in current consumption of the boards is going to cause a growing imbalance as the cells sit idle or discharging. But if the cells are on almost constant charge at a high enough voltage that current difference is not going to matter. Where between those two extremes do the boards continue to make sense? Clearly not for typical solar PV where charge/float time is limited, and especially if you deliberately never bring the bank to 100% SOC where the cell bypass function kicks in.

Then you need to start factoring in the quality of the design and of the components of the BMS. Add all the reliability factors up for all the wires, components and design, and what the design life is. A BMS with a 5 year design life is not going far with a pack with a 10 year warranty, So who designs, fabs and installs the boards ?? Heck most spacecraft stuff only has a 5-10 year design life. Most last much longer because of the extreme care that goes into the design.

[Sunking]

Let take another pass at this. First read this thread as it may help you understand charging algorithms.

OK assume you want a 12 volt 100 AH LFP battery or 4S. About the size of a large trolling motor or truck battery. So you buy 4 100 AH Chi-Com cells like CALB, best of the Chi-Coms Those will cost you roughly 45-cents per wh. Really good LFP'slike A123 Pouch Cells cost $2/wh or 4 times as much as Chi-Coms

So your cells arrive. You have to Balance them before you can use them. Manufactures do not send them out fully charged because fully charging them is stressful, and storing them fully charged is a recipe for destruction. So take that hint from the manufacture. They will arrive to you from as low as 40%SOC to as high as 70% SOC charged. That means the lowest charged cell is 40 AH,a nd highest at 70 AH a 30 AH spread you have to BALANCE OUT. somehow.

So not knowing any better you use your BMS and it uses 300 ma Balance boards on a 50 amp charger made to work with LFP batteries with a BMS. So you start charging at 50 amps, and 45 minutes later the 70 AH cell is fully charged, and signals the charger to cut back charge current to 300 ma from 50 amps.If the charger cannot cut back keeps right on pushing 50 amps through your fully charged battery So now your low 40 AH cells has charged up to 70 AH with 30 AH more to go to 100% when the charger cuts back to 300 ma. So now you are charging at 300 ma. It will take another 30 AH / .3 A = 100 hours to charge up and Balance if you are using a AC charger running 24 hours a day. That is 5 days. If you tried that with solar on a 4 hour sun day it will take 25 days to Balance. Do you have a problem with that?

Now once Balanced clear sailing because LFP cells do not become unbalanced or drift much. Maybe a few mah each day and your BMS can handle that OK in a short period of time. Say th imbalance is 30 ma only takes 10 minutes to balance at .3 amps.

But guess what? No Solar Charge controller can cut back current to match your BMS charging current.

Here is something else to think about. No Commercial EV manufacture allows the customer to charge their batteries to 100% SOC. It is the only way they can offer a 5 year warranty. They do have a BMS, but their cells are matched at the factory and BALANCED at the factory. There BMS only has to make small corrections from time to time when the computer detects there is a imbalance. 99% of the time, the built in charger works as a 1-Stage CC/CV charger. The computer controlling the BMS allows the charger to charge at full rated current until the PACK Voltage reaches 80 to 905 then shuts off. No Balance is done. They only Balance from time to time when needed which is not often.

Can you mimic what they do? Yes. Question is do you know how,a nd what the consequences are if you get it wrong. A Midnite Solar Controller cannot do any of that. To make it work you have to force to act as a 1-stage CC/CV charge which is easy to do. You set Bulk = Absorb = Float and disable EQ. You set the voltage less than 100% so the Balance Boards never turns on. and no reason to shut down the Controller if you set the voltage to lower than 100% pack voltage. When the batteries reach the voltage SET POINT charge current stops all by itself. So if that happens at say 2 in the afternoon with good sun hitting the panels, load current comes from the panels, not the batteries unless load demand current exceeds what the panels can produce. You cannot do that with a BMS set up to charge to 100%, nor can your charge controller support a BMS.

Lastly if you use a LFP battery you have to protect them from Over Discharge. To do that you must have a Low Voltage Cut Off (aka LVC) circuit between the batteries and Load. That consist of a Heavy Contactor and a Voltage detection circuit Again your controller will be of no use to do that.

Do you see any problems with any of that? How are you going to do that?

[Sunking]

You realize just about everything is made by the Chinese these days, right? Were you in Vietnam? We don't really call them Chi-Coms anymore.

What do you call Chinese Communist? I call them what they are.

[Sunking]

You can set all 3 voltages to equal. thereby making it a CC/CV charger 1 stage charger. Midnite Solar is not made or intended to work with LFP batteries period. All you can try to do if you know how, is work around the incompatibility. You do that by setting the controller voltage well below 100% SOC so you do not gfry your cells. There is only one I know of made by Genasun using their integrated battery. Problem is limited to a 140 watt panel and their battery.

Chargers intended to work with LFP batteries communicate. What you do not know is how Balance Boards Work and that is what the killer is. All they do is turn ON when the cell is fully charged and bypass a small amount of current to be passed onto lower cells. Sounds great huh? It sucks. That can only work if your charger can then cut back current to the limit of the balance boards.

Now stop and think about that a moment. I bet it never occurred to you what is happening or what can happen. So you batteries are charging along at full power, say 25 amps. First Balance Board turns on when it gets fully charged and turns on and bypasses say .3 amps. That leaves 24.7 amps still flowing into a fully charged cell heating it up and causing damage. No Solar Charge Controller except Genasun has the ability to cut back current, they can only regulate VOLTAGE, not CURRENT. A real LFP chargger can do that and you set what that amount of current is to match the balance boards.

Secondly no Balance Board (BMS) can Balance an a out of balance battery bank in any meaningful time frame. Why you ask?. I already told you because they can only bypass a very small amount of current. All they can do is make for very small minor corrections.

Now if you completely understand how LFP works, what destroys them, and how to protect them you can work around all that. So your first challenge is when you receive the cells, HOW ARE YOU GOING TO BALANCE THEM? Can you even answer that? Give you a hint, you need some expensive equipment you do not have.

I am trying to prevent you from making a huge mistake. But it is yo money to loose, I really do not care, have at it. But smart money in you case is FLA batteries, much cheaper and will last longer. In you rcase much longer because you will destroy your first set of LFP batteries. Your choice.

FWIW Inetdog and PNJunction are telling you the same thing. You might want to listen to one of us.

[inetdog]

I could be wrong but I believe the problem is that the Midnite Classic does not have the logic to perform "balance charging" of each cell which is required for Li chemistry batteries.

You are in part wrong, but mainly you are not relating to the problem and the terminology.

No CC which does not have connections to each of the individual cell terminals (i.e. six cells requires seven wires) can actually balance a bank of cells.
You do not balance individual cells, you balance a set of cells. That balancing may involve charging each cell individually to a known SOC (top balancing) and then connecting them.
Once the battery bank (or string) is balanced the Classic can be set with Bulk = Absorb = Float with the voltage being the 80% or 90% SOC voltage of that particular cell type.
That setting, along with neither Vampire nor Monitor boards on individual batteries, should allow the bank to stay balanced for a long time. The one remaining component that is absolutely essential is a low voltage detector that both disconnects loads AND inhibits normal high current charging when the voltage drops below a set limit.
That function is not, AFAIK, part of the repertoire of the Classic.

Continuous balancing is NOT required for Li chemistry, but at least periodic monitoring IS. Then rebalancing can be done manually if necessary.

[createthis]

I could be wrong but I believe the problem is that the Midnite Classic does not have the logic to perform "balance charging" of each cell which is required for Li chemistry batteries.

Correct. It needs a BMS for that. I'm just trying to find one to buy. I think that's pretty obvious if you read the thread.

[createthis]

PN I think you would agree the CALB's are the best of the Chi-Coms. Would you not agree with that?

You realize just about everything is made by the Chinese these days, right? Were you in Vietnam? We don't really call them Chi-Coms anymore.