Lithium Iron Phosphate


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Wolf

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So I went on my monthly trip to my recycler to pick up my quota of 200 laptop and medical packs and he hadset these aside for me.
Gota remember to bring a DMM everytime i go from now on. They are K2B24V10EB Looks like there are ~50 of them.
What I can deduce they have an incredibly life cycle (+1000 cycles). BMS included internally? If I get them
does 50s2pfor a nominal V of 51.2 sound OK? 9.6Ah X 25 = 240Ah and that's usable not like my lead acids.
Comments, suggestions?
Wolf


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Church1182

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Wow! That could be a deal depending on what life is left and what they want for them. Spec sheet indicates to me an internal BMS as it says you cannot put them in series (last line under Max Operating Conditions) and it has high and low voltage cutoffs built in.So if you need a 24V solution that pile could be what, 12ishkWh of capacity?

If you can get a couple test, and your supplier gives/sells them to you at a reasonable rate I'd collect them all, test, and resell them if you personally don't need them. Looks like it could be a killer deal for someone building a 24 V system. (Cough cough) :angel:
 

friedpenguin

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How many $$???!!! Those are great batteries. I have 7 and would love more. You can flip those for serious $$ and be a good guy and offer them up here!
 

Wolf

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friedpenguin said:
How many $$???!!! Those are great batteries. I have 7 and would love more. You can flip those for serious $$ and be a good guy and offer them up here!
Church1182 and friedpenguin


I will be going to pick up more laptop cells in a couple of weeks and can check them for V and IR.
The Recycler has agreed to keep them for me tosell. I cannot use them as I am running a 48V system
so my bad fortune is your good luck. I will try to acquire them as reasonable as I can and pass the savings on to whomever is interested.
Anything I should know and check on them from your experience with them?

Shipping should not be a problem I suspect as they are contained in their own case more or less like a laptop battery.

Wolf
 

friedpenguin

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Most of mine I bought as "not working" but they were just too low to take a normal charge. So really, go crazy! I will watch this like a hawk tomorrow and reply ASAP if you get numbers. Where in the US are you?
 

Wolf

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friedpenguin said:
Most of mine I bought as "not working" but they were just too low to take a normal charge. So really, go crazy! I will watch this like a hawk tomorrow and reply ASAP if you get numbers. Where in the US are you?

I am in the Portland Maine area so on the other coast.

As I said it will be a couple of weeks before I know what condition they are in. I will then let everyone know.

Wolf
 

friedpenguin

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Yeah, not the Portland close to me that's for sure. Though I've been through your Portland when I worked outside of Bar Harbor. If you throw together a 7s 18650 you can equalize the K2 batteries a bit. If you get them to 20v they should charge fine. 18v or lower I don't think they'll work with their intended charger. That's all I did to revive all of mine.
 

Wolf

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friedpenguin said:
Yeah, not the Portland close to me that's for sure. Though I've been through your Portland when I worked outside of Bar Harbor. If you throw together a 7s 18650 you can equalize the K2 batteries a bit. If you get them to 20v they should charge fine. 18v or lower I don't think they'll work with their intended charger. That's all I did to revive all of mine.

Ok I went on my trip and checked a bunch of them and they were all at 25V to 26V there are 72 of them.
I took 5 to test and see what transpires. I got 1 on a CC/CV charging at 29.2V at 2A. Am I understanding correctly that they have theirown internal BMS and balancingsystem so I can't really hurt them?
They supposedly came from a hospitals emergency lighting system and where replaced because of time. I cant imagine they have very many cycles on them as they would only be used when the power goes out and how often does that happen in theNew England area?
Besides the generators would kick in after a couple of minutes anyway.

If they pan out let me know who is interested
 

Redpacket

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Wolf, I'm pretty sure you can parallel LA & LiFePo4's in a nominal 48V system your LAs voltages are not 48V they'd be early 50V ish?
You could begin migration to LiFePo4's as well?
 

Wolf

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Redpacket said:
Wolf, I'm pretty sure you can parallel LA & LiFePo4's in a nominal 48V system your LAs voltages are not 48V they'd be early 50V ish?
You could begin migration to LiFePo4's as well?

Yea I thought of that also but according to the spec sheet you can't put them in series. Last line on the max operating conditions.


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Wolf
 

Redpacket

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"Max Modules in Series = 1"
Translation: you'll need a BMS to balance them....
They're just batteries like any other!
 

Wolf

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Redpacket said:
"Max Modules in Series = 1"
Translation: you'll need a BMS to balance them....
They're just batteries like any other!

You may be right.The batteries at 24Vmust be 8s 3.2VLiFePO4 internally I imagine.
They have their own built in BMS according to the spec sheet. So I wonder how that would affect a pack.
I suppose you would need to add a BMS to the whole pack if you would put 2s10p for 48V nominal for a ~200Ah pack
So in essence what you are saying the individual batteries balance themselves, but if in a pack you need to balance the pack of individual 24V cells. Makes sense.

As you say its just a battery so why would it be any different.
I don't think I would run the packin parallel with my lead acids though as theseLiFePO4 can be discharged to 20V. that would equate to 10V per 12V lead acid which would be pretty bad for the deep cycle.
Gears are turning in my head :D

Wolf
 

Redpacket

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You could always open them & take full control?
I wouldn't be discharging a LiFePo4 cell below ~2.9V (= 23.2V for 8s, OK for LA?) & charging max 3.4 or 3.45/cell (=27.2, again OK for LA)
Even if you didn't run the "full range" of the LiFePo4's you'd still get a good capacity boost.
 

friedpenguin

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72?!?!? Hold on, let me go change my shorts. Holy crap! So what are you willing to do for cost plus shipping? I'd likely have to Paypal with a CC as I'm always cash strapped with two kids.
 

Wolf

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friedpenguin said:
72?!?!? Hold on, let me go change my shorts. Holy crap! So what are you willing to do for cost plus shipping? I'd likely have to Paypal with a CC as I'm always cash strapped with two kids.

LOL Hold onto your shorts :D . I took a sample of 5 of them and started to run some tests. They all seem to be in the 25 to 26 Volt range and varyingIR. The first 2 didn't seem to go very well the 3rd and 4thones seem better and I'm testing the 5th one now.
You can check out the sheet on my google drive it is calledK2B24V10EB.xlsx with the progress. I can't charge them right nowdo to an error :angel: my CC/CV BUCK/BOOST let some smoke out and I cant get it back into it. So I had to order 2 portions of smoke. 1 to use and one to have as a backup lost smoke refiller.I hope to have the smoke (OK enough about smoke) the 2 CC/CV BUCK/BOOST this weekend so I can charge them up and give them a proper test.
Once I feel confident that they are good then we can talk.
In the meantime you can PM me with how many you want and I will see if I can strike a deal with the recycler.

Wolf
 

daromer

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They are not more suited in Parallel compare to LiIon either.

The reason you cannot have them in Series is because the BMS have no idea of how the rest of the cells in series act. This is the same as any setup where you run a BMS. Putting them in Series will only ensure that each one of them have their cells in balance but not that each battery it self that are in series are in balance. For overall protection you need the system to know the overal voltage and individual voltage.

With that said its possible to run them in series but its like lacking bms :)
 

Wolf

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daromer said:
They are not more suited in Parallel compare to LiIon either.

The reason you cannot have them in Series is because the BMS have no idea of how the rest of the cells in series act. This is the same as any setup where you run a BMS. Putting them in Series will only ensure that each one of them have their cells in balance but not that each battery it self that are in series are in balance. For overall protection you need the system to know the overal voltage and individual voltage.

With that said its possible to run them in series but its like lacking bms :)

OK Daromer now I am really confused. :huh: This may be due to translation or something else.
Lets start with what I know.
I understand that the K2 24 volt battery has its own BMS built in. It manages what I perceive to be 8 cells within this battery enclosure and keeps these cells in balance.

Now the question.
If I wanted a ~24V 200Ah battery pack could I put 20 of them in parallel and not have a BMS as each battery is responsible for its own balancing.

If I wanted a ~48V 200Ah battery pack could I put 2s10p and add a BMS such as a batrium system to balance the whole pack.
Basicly the BMS would have to make sure that each individual ~24V battery is the same voltage as the other 19 batteries.The internal BMS of the batteries would make sure the individual cells (8) within the battery are balanced.
So balance the 20 batteries with an external BMS and letthe internal BMS to do the rest of the work in the sealed battery.

Is that right? :dodgy:

Wolf
 

friedpenguin

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I don't see a reason that wouldn't work. Double BMS. Just needs a BMS that is willing to balance a single cell at 25 to 29v instead of a bunch of smaller cells at ~4v each.

FWIW, I noticed your pic had some with a PCB on top. Is that just a charger interface? I thought the BMS itself was in the battery, at least I hope it is.
 

Wolf

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friedpenguin said:
I don't see a reason that wouldn't work. Double BMS. Just needs a BMS that is willing to balance a single cell at 25 to 29v instead of a bunch of smaller cells at ~4v each.

FWIW, I noticed your pic had some with a PCB on top. Is that just a charger interface? I thought the BMS itself was in the battery, at least I hope it is.

Yes the PCB is justaninterface to distribute the power (and charging) from/to the battery.

Wolf
 

Redpacket

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For BMS, you'd have to open each pack & install a new BMS across all the cells, eg batrium.

Or with some engineering you *might* be able to make a circuit to balance with two 24V packs in series (each with original internal BMS).
 
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