LifePO4 batteries for use with Midnite Classic 150?

[Sunking]

250 sized racing quads typically use 1000mah 4S batteries, and the 50W B6AC V2 works great for those:

Well yes but that is a tiny battery 14.8 volts @ 1 AH or 14.8 watt hours. Your charger is capable of charging them at 3C. But your 4S GBS 100 AH is roughly 100 times larger and best your charger can do is what 3 to 4 amps on a 4S LFP? That is C/33 to C/25 or 100 times slower.

Interestingly enough, I hadn't read this post before I made the purchase, but I did indeed buy a Power Lab 8. Weird that you and I are on the same page for once, eh?

Now you are talking. Do you have a good 12 to 80 VDC 60 amp power supply to use with the Cellpro? It will make short work of balancing the batteries.

When you get your batteries use the busbars and wire all 4 in parallel and walk away for a couple of hours. The decide on Top or Bottom, your choice. If you Bottom discharge them to 2.5 volts, let them rest, repeat until when at rest they are at 2.5 vpc an dlet them rest 12 hours. Your target is anywhere from 2.4 to 2.5 range.

If you decide on Top Balance charge to 3.65 volts and hold until charge current drops to C/33. With all 4 cells in parallel that is 400 AH / 33 Hours = 12 amps. Additionally buy yourself a 4 S JST Balance Plug from any Hobby Shop. When you wire the batteries in series you can do your maintenance and Top Balance checks with your Cellpro 8. You will thank me later for that advice once you realize what it can do. Trick is you will need a good 1500 watt 18 volt DC power Supply to take full advantage of the Cellpro Power Lab 8. If you are not aware it will do bidirectional charging from one battery to another of any chemistry know today and all future types.

Good luck.

[inetdog]

You are definitely acquiring a dangerous thing.

Yeah but he is into a cool hobby. I enjoy flying RC but never got into racing quads.

Mine goes up and has come down hard a couple of times.

I was referring to a little knowledge....
But it applies to the batteries too.

[Sunking]

I was aware of the greater internal resistance of the GBS cells before I made the purchase, though I admit I don't fully understand how it will affect my system in practice yet. .

Well lets fix that for you right now. Short Story it effects how fast you can charge and discharge. Don't concern yourself with Charge because you will never need or be able to go fast enough for it to be a problem if you charge at C/2 (50 amps or less). Even if you did, the batteries just slows it down by physics and self regulates. So don't waste anytime worrying about it.

Where it might become a problem is on discharge in the form of Voltage Sag. We need to talk a little math to understand

Voltage = Current x Resistance.

Simple enough equation if either current or resistance goes up, so does voltage. Resistance is pretty much fixed, so voltage will vary with current. With me so far?

So your battery as Internal Resistance we will call Ri GBS is fairly high. For each cell roughly .005 Ohms. Wire all of them up in seires coupled with connector resistance you have roughly .021 Ohms. So you charge up your battery fully, and are seeing 14 volts Open Circuit voltage. That means no current or 0 amps. You have a 1000 watt Inverter with a 1000 watt light bulb and turn it on. While doing this you are watching the battery voltage right on the battery term post. You observe the voltage of the battery falls from 14 volts to 12 volts. What happened. Th ebattery is rated for 3C or 300 amps.

You had voltage sag from high battery Ri. Use the Equation. 100 amps x .02 Ohms = 2 volts. 14 volts - 2 volts = 12 volts. Keep that light on for 20 minutes or less and the Inverter will trip off from LVD set to 11 volts despite you still having 50 to 70% capacity left in it. When the Inverter trips off you battery voltage jumps back up to 13 volts.

Another catch is the battery wire between battery and Inverter also adds voltage sag compounding the problem. If the wire is too long or too small for the length, the Inverter might very well shut off immediately despite having a fully charged up battery.

Understand now? In an EV that just sucks acceleration way down. That is one reason why I ditched the GBS them. Will it be a problem for you? I cannot say except it might if you have heavy loads left on for any period of time. Good news is it does not hurt the batteries. Your Inverter LVD will trip before it becomes a problem.

When you get your Cellpro Power Lab 8 and use the Balance plug, you can measure Ri of each cell. Without the Balance Plug it can only read the total pack RI. RI is your health meter of a battery. To be useful it has to be done at a specific SOC and temperature. Best method is 50% SOC and Room Temp cells. Keep a log. When you see Ri go up, you will know they are aging and loosing capacity. Also keep Capacity logged.

Same thing can be applied to your LiPo's on your Quads.

[createthis]

Now you are talking. Do you have a good 12 to 80 VDC 60 amp power supply to use with the Cellpro? It will make short work of balancing the batteries.

I've got a 12V 33 ah AGM battery. I can cycle it until the job is done. If that gets tedious, maybe I can use my truck's starter battery or something. I saw a guy using the regen capability of the cellpro to bottom balance an LFP cell and charge a lead acid battery on Youtube. Figured I'd read the manual when the cellpro arrives, do the math, and go from there.

[createthis]

Well lets fix that for you right now. Short Story it effects how fast you can charge and discharge. Don't concern yourself with Charge because you will never need or be able to go fast enough for it to be a problem if you charge at C/2 (50 amps or less). Even if you did, the batteries just slows it down by physics and self regulates. So don't waste anytime worrying about it.

Where it might become a problem is on discharge in the form of Voltage Sag. We need to talk a little math to understand

Voltage = Current x Resistance.

Simple enough equation if either current or resistance goes up, so does voltage. Resistance is pretty much fixed, so voltage will vary with current. With me so far?

So your battery as Internal Resistance we will call Ri GBS is fairly high. For each cell roughly .005 Ohms. Wire all of them up in seires coupled with connector resistance you have roughly .021 Ohms. So you charge up your battery fully, and are seeing 14 volts Open Circuit voltage. That means no current or 0 amps. You have a 1000 watt Inverter with a 1000 watt light bulb and turn it on. While doing this you are watching the battery voltage right on the battery term post. You observe the voltage of the battery falls from 14 volts to 12 volts. What happened. Th ebattery is rated for 3C or 300 amps.

You had voltage sag from high battery Ri. Use the Equation. 100 amps x .02 Ohms = 2 volts. 14 volts - 2 volts = 12 volts. Keep that light on for 20 minutes or less and the Inverter will trip off from LVD set to 11 volts despite you still having 50 to 70% capacity left in it. When the Inverter trips off you battery voltage jumps back up to 13 volts.

Another catch is the battery wire between battery and Inverter also adds voltage sag compounding the problem. If the wire is too long or too small for the length, the Inverter might very well shut off immediately despite having a fully charged up battery.

Understand now? In an EV that just sucks acceleration way down. That is one reason why I ditched the GBS them. Will it be a problem for you? I cannot say except it might if you have heavy loads left on for any period of time. Good news is it does not hurt the batteries. Your Inverter LVD will trip before it becomes a problem.

When you get your Cellpro Power Lab 8 and use the Balance plug, you can measure Ri of each cell. Without the Balance Plug it can only read the total pack RI. RI is your health meter of a battery. To be useful it has to be done at a specific SOC and temperature. Best method is 50% SOC and Room Temp cells. Keep a log. When you see Ri go up, you will know they are aging and loosing capacity. Also keep Capacity logged.

Same thing can be applied to your LiPo's on your Quads.

I've read the GBS cells quoted at between 1.5 and 1.8 mohms or 0.0018 ohms. I'll be sure to measure and log it per cell in order to keep an eye on things. This particular battery will mostly be used to charge laptops, small 12V devices, and personal electric vehicles like boosted boards and electric bicycle batteries that charge at under 300 watts, so I'll be surprised if it's a problem in the immediate future. I'm kicking around a few future projects in the back of my head where I'm sure Ri will be an issue, but they're just ideas for now.

What if the voltage does sag below 10 volts for some reason, but then bounces back to 10 volts. Would that damage the battery? Or does it only damage the battery when the voltage bounces back to under 10 volts?

[Sunking]

What if the voltage does sag below 10 volts for some reason, but then bounces back to 10 volts. Would that damage the battery? Or does it only damage the battery when the voltage bounces back to under 10 volts?

That cannot happen as it is physically impossible. Think of it like a sling shot, You put your marble in, draw it back, and let it go.

However if you draw to high of a C-Rate for too long, then yes you can and will have thermal damage. Short the cell out and it can explode. Note on your battery specs. If i remember correctly maximum continuous rate is 3C (300 amps), and Pulse is 10C (1000 amps for 10 seconds)

[createthis]

That cannot happen as it is physically impossible. Think of it like a sling shot, You put your marble in, draw it back, and let it go.

However if you draw to high of a C-Rate for too long, then yes you can and will have thermal damage. Short the cell out and it can explode. Note on your battery specs. If i remember correctly maximum continuous rate is 3C (300 amps), and Pulse is 10C (1000 amps for 10 seconds)

I see how that would be annoying if you are trying to design an EV. Below the threshold, the only way to drain the battery completely is to use fewer and fewer amps.

Every battery has some Ri, and I know I can 100% drain the 400wh lithium battery in my electric bicycle. So what did they do? Design the battery so the max amp draw is lower than the threshold? Is there a proper name for the "threshold"?

[karrak]

Lithium batteries do not go out of balance. The only metric that throws them out of balance is differencand e in leakage current which takes months to accumulate.

Yes, it takes months to accumulate but it does accumulate. At present my battery goes out of balance by at least 1% per year. I am sure it was more when it was newer but have only started keeping data on the imbalance recently.

Karrak you came here for one purpose and one purpose only. To harass me. You even conspired on another forum to bring others here to help you. You found one poor soul. At least he had enough common sense to give up and leave.

If trying to counter some of the misinformation, incorrect information and what I see as bad advice that you sometimes post is deemed as harassment, then yes I am here to harass you. I have not conspired on any other forum and did not ask for anyone to come on this forum to counter your misinformation. If you mean wb9k, who runs the warranty lab at A123 Systems as the poor soul, I am sure he has better things to do with his time than put up with your rudeness and abuse. Shame for the rest of us that he is not around this forum anymore. He probably has far more knowledge and experience with LFP batteries than anyone posting on this forum. It is worth reading what he had to say, his first post is here https://www.solarpaneltalk.com/forum...629#post247629 My post three post before this is what he had to say on the other forum, if anyone has the time it is worth reading all the other posts that he wrote in that thread.

[Sunking]

I see how that would be annoying if you are trying to design an EV. Below the threshold, the only way to drain the battery completely is to use fewer and fewer amps.

Every battery has some Ri, and I know I can 100% drain the 400wh lithium battery in my electric bicycle. So what did they do? Design the battery so the max amp draw is lower than the threshold? Is there a proper name for the "threshold"?

I am not real familiar with the E-Bike crowd bu tI have looked at the equipment you guys use so I have a clue. When I look @ online E-Bike supplies in batteries, I am seeing the same LiPo's we use in RC airplanes. Yes I fly RC 3D Planes. Here is what I am driving at Any Lithium battery you buy has C-Rates listed. One for Continuous, and one for Burst (maybe be called Pulse, Intermittent .....)

There is no defined method for the C-Ratings crazy as that sounds. It is an arbitrary number the manufacture feels comfortable with. It is related to Ri, however it is not a performance specification, it is a THERMAL specification one in which the Manufacture is comfortable with.

Back to E-Bike Batteries. LiPo's used in RC Hobby are extremely low Ri and thus have very high C-rates. Smallest out there is 20/40 and many as high as 100/200. For RC planes, heli's, quads it is extremely important to keep them light in weight as possible and they require very high power to weight ration motor to get them off the ground. A 2.5 pound airplane or heli will use a 500 to 700 watt motor @ 3S or 4S. That requires an operating current of 50 to 65 amps. Well if you were to use LiFePo4 would mean a 3S 30 AH 10 pound battery in a plane with a gross max flying weight of 2.5 pounds. Does not compute. However LiPo's have much higher energy density and much higher C-Rates. So that plane of heli can use a 1/2-pound 3S 2200 mah 30/60 C-rate battery. Not much fly time of roughly 5 to 6 minutes, but does work.

Back to E-Bike again. Unlike a EV you are very restricted in space and weight and LiFePo4 is just not a good option. So they tend to use LiPo's for the same reasons RC aircraft use them. LiPo's have two huge negatives Very Expensive and Very short Cycle Life. . A LiPo with 150 cycles is a very tired old fat puffy battery. Sound familiar?

[createthis]

There are a ton of e-bike systems out there, but mine is the Bosch Powerpack Performance line: http://www.bosch-ebike.de/en/kompone.../powerpack.php
It uses 18650 cells: https://endless-sphere.com/forums/vi...p?f=14&t=75748
They're either Samsung 29E cells or LG 11865, from what I can tell: https://endless-sphere.com/forums/vi...p?f=14&t=66277
Far as I can tell the 29E cells are NCO chemistry: http://batterybro.com/blogs/18650-wh...ally-explained
I don't know what the LG 11865 chemistry is.

This page seems to indicate the internal resistance is 0.06 ohms for a 29E cell: http://lygte-info.dk/review/batterie...lue)%20UK.html

That's weird, because that would mean it has a higher internal resistance than GBS LifePO4.

[Sunking]

This page seems to indicate the internal resistance is 0.06 ohms for a 29E cell: http://lygte-info.dk/review/batterie...lue)%20UK.html

That's weird, because that would mean it has a higher internal resistance than GBS LifePO4.

No Sir that is not what it means. You are not comparing Apples to Apples leading you to the wrong conclusion. Stop and think what is different.




Did you figure it out?







Hint: Amp Hours








You are comparing a GBS 100 AH cell to what size E-Bike cell? 2.9 AH maybe? To equal you have to compare 100 AH to 100 AH. Those cells are what 2.9 AH? It would take 34 of them in parallel to = 100 AH. 34 cells in parallel is:

.006 Ohms / 34 cells = ..00017 Ohms. A hell of a lot lower than the GBS like 1/10th as much. Not even close. If the GBS sag 2.0 volts, the other sags 0.2 volts

[PNjunction]

That was my logic, yeah, but I ended up buying a PowerLab 8 v2 to aid in automatically pulling the battery voltage down to 2.5V. Didn't feel like babysitting it, and I figure I'll probably make more battery systems in the future, so why the hell not?

Great! Now you can decide for yourself if bottom balance, or top balance is your thing. Yawn.

AND, you can also try the 3rd KISS method (still top-balance per se), of using the PowerLab 8 in a single-cell charge mode (1S), charge each cell individually to 3.60v until current drops to 5A (for your 100ah cells, aka .05C). Try to use more than .05C for charge - if you can at least 10A to 30A - it will depend on your supply capability...)

Let them sit fully charged for a few days. They should eventually settle to near 3.38 3.40v. If any cell is drastically lower, then it has a high level of self discharge and should be inspected / replaced under warranty.

Discharge normally as a pack now, no faster than 0.5C, (who even DOES that with properly sized lead acid anyway??), and stop when any cell reaches 2.7v under load - preferably sooner. Me, I go no further than 3v under load - ie loads no larger than about 0.1 to 0.2C. Easy to remember - 12v on your 4S bank is the lowest I'd ever go, and 10.8v *under load* would be a dead-man kind of thing. Lo and behold!

SHHH .. Don't tell this to anyone .. WHAT?? My LVD's on my inverters kick off at 10.8v under load, and some even 11.7v. Sure, designed for Pb, BUT that's a total dead-man lvd, but at least you'll save the bank from going to zero. Obviously, better to not hit this at all, but it is there right? I don't rely on these but use my own external LVD with higher voltages, but for dead-man failures, at least *something* lvd is there.

Reset your Powerlab to charge as a pack to no more than 3.40v (13.6v for your bank) and you can let current taper to near nothing - it won't be fully charged anyway.

The reason I keep mentioning this over and over is that your solar controller as far as I know has no way of incorporating individual cell monitoring, and this solution of fully charging to 3.60v first individually, and then charging to no more than 3.40v as a pack thereafter, can at least get you in the ballpark without endangering the cells. You are relying on the manufacturer to be providing reasonably close cell characteristics, and in *our low current application* as far as the cells are concerned, fretting over internal resistance and minute voltage differences and the like is fun, but not a deal breaker. If you feel like it, repeat the individual cell charge to 3.60v / 0.05C end current on a regular basis - maybe once a year or whatever floats your boat.

Essentially, YOU are the bms, without any vampire boards, or in this case not even individual cell monitoring / balancing. But go ahead and do the individual cell thing if you feel like it. You aren't putting these things into an EV, or a remote cell tower. Perhaps you'll do just fine being the bms. Again, the emphasis here is that at some point, your Midnite controller comes into play without the individual cell stuff.

You'll see. These things aren't made of glass. Go forth and experiment and find YOUR level of comfort. I wish more would do the same.

[createthis]

No Sir that is not what it means. You are not comparing Apples to Apples leading you to the wrong conclusion. Stop and think what is different.




Did you figure it out?







Hint: Amp Hours








You are comparing a GBS 100 AH cell to what size E-Bike cell? 2.9 AH maybe? To equal you have to compare 100 AH to 100 AH. Those cells are what 2.9 AH? It would take 34 of them in parallel to = 100 AH. 34 cells in parallel is:

.006 Ohms / 34 cells = ..00017 Ohms. A hell of a lot lower than the GBS like 1/10th as much. Not even close. If the GBS sag 2.0 volts, the other sags 0.2 volts

Now I understand why everyone uses 18650 cells. That's kind of like magic.

[Sunking]

Now I understand why everyone uses 18650 cells. That's kind of like magic.

Well yes and no. Application and economics dictate what needs to be used. If you make battery operated power tools that demand 10C batteries, you can justify the cost of using clylindrical cells.

This is why I was pounding on you so much You can buy a CALB 100 AH cell all day long for $130. Works great for applications using 3C or less applications. Do the math and the Cost is $130/ [3.2 volts x 100 AH] = $0.4065/ watt hour. Want to do that with 3.2 volt 1.1 AH 18650 cells with 10C discharge rate for a 3C application? That will cost you $4.05 / [3.2 volts x 1.1 AH] = $1.15 watt hour. You are paying over 100% more almost 200% more for something you have no use for. Not to mention a lot heavier and bulkier.

[PNjunction]

Note too that "18650" refers ONLY to size, and not specifically the chemical makeup inside.

Most consumers think of laptops, flashlights and so forth that do not use LFP, but a different li-ion chemistry. Yet if you look closely at many hobby-type chargers like Nitecore, Xtar etc and others used by flashlight fanatics, most have an option specifically designed to put them into the LiFeP04 mode. Very important. See Candlepower forums for that type of application.

For instance, and this is VERY important, you can get "18650's" with either LiFeP04, or any other li-ion chemistry, such as LiCo02. LFP is a nominal 3.2v cell, whereas all the rest are nominal 3.7v cell, which are REALLY fussy about charge termination and so forth.

For example, had you not purchased the GBS cells, you could have also gotten some hands-on with smaller LFP 26650 cells detailed here:

https://www.solarpaneltalk.com/forum/off-grid-solar/batteries-energy-storage/lithium-ion/300609-low-cost-lifep04-learner-bank

What we find here is that in the case of either the large prismatic GBS or the cylindrical 26650 LFP's used in that project, the overall characteristics, other than capacity, are nearly the same. In this case, both cells, whether prismatic or cylindrical are mostly "energy cells", aka "3C" cells, rather than others like Headway cylindricals, which are "power cells", aka "10C" cells.

You CAN use "power cells" for a low-current solar storage product, but that would be mostly a waste of money since you'll never use that capability - unless you are designing an improperly small solar storage bank to begin with.