LifePO4 batteries for use with Midnite Classic 150?

[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.

[createthis]

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

I call them Chinese. Drop the racial slurs.

[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]

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.

[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]

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.

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?

[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]

I call them Chinese. Drop the racial slurs.

What racial slurs, they are communist.

[createthis]

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?

Sigh. Your statement above is just plain incorrect, Sunking. The Stark Energy battery I linked above has a cycle life of 2000 cycles at 80% DOD. Flooded lead acid (FLA) has a cycle life of 1200 cycles at 30% DOD. I'd need a 300ah FLA battery for the same capacity with just 60% the cycle life of the Stark LifePO4 battery. FLA is five times the weight, so the FLA equivalent of the 28 pound 100ah stark power battery I linked above would weigh 28 * 5 * 3 = 420 lbs. This is a portable solar setup. FLA doesn't make sense.

More reading: https://www.victronenergy.com/blog/2...um-ion-vs-agm/

[createthis]

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.

I'll investigate this strategy, however, I still want to implement an over voltage protection circuit to shut the Midnight Classic down at 14.6 volts via the AUX2 port. I'm starting to think I'm just going to have to get out the bench top power supply and design my own. I'm not an EE by trade, so this is distasteful to me, but it's looking like no off the shelf device exists to do the job, unless I go with the GBS batteries with the EMS BMS, which I suspect are both lower quality as well as more expensive than the Ultra Energy battery I linked above.

[Sunking]

I still want to implement an over voltage protection circuit to shut the Midnight Classic down at 14.6 volts via the AUX2 port.

OK why? You do not want to flirt with 14.6 volts or 10.5 volts. Stay far away from those two points. There is no reason to go above 14. The only time you would ever flirt with 14.6 volts is to Balance the batteries you cannot see or control. You only need to balance roughly once every 6 months to a year. The issue with a battery in a box is you cannot measure cell voltages to know when they need balanced if ever.

it's looking like no off the shelf device exists to do the job, unless I go with the GBS batteries with the EMS BMS,

What do you think Mike, PN, Inetdog and myself have trying to tell you for 2 days? You have to work around Solar Charge Controllers incompatibility.

[createthis]

OK why? You do not want to flirt with 14.6 volts or 10.5 volts. Stay far away from those two points. There is no reason to go above 14.

I believe you put it best when you said so you "don't have to worry about and watch like a infant child". It's an automated failsafe.

[J.P.M.]

We don't really call them Chi-Coms anymore.

Which is to imply you once did ? If so, when did you get religion and a high horse and join the P.C. mounted police ? Even hear of abbreviations like, for example dot com ? Ruskies ? YANKS ??

[createthis]

What do you think Mike, PN, Inetdog and myself have trying to tell you for 2 days?

There is a lot of misinformation and assumption in this thread by all, myself included. It's been incredibly difficult for me to separate signal from noise. This would go away if charge controller manufacturers like Midnite Solar would just start supporting LFP directly, so I'm not mad about it. It's just been difficult sifting through the noise for the information I need.

I think I have a plan at this point, thanks to you all. I just have a few more things to verify with third parties, then I'll be ready to make a purchase.