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Lithium Iron Phosphate
#11
"Max Modules in Series = 1"
Translation: you'll need a BMS to balance them....
They're just batteries like any other!
Running off solar, DIY & electronics fan :-)
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#12
(04-27-2019, 11:33 AM)Redpacket Wrote: "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 24V must be 8s 3.2V LiFePO4 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 pack in parallel with my lead acids though as these LiFePO4 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 Big Grin

Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 5/23/2019
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#13
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.
Running off solar, DIY & electronics fan :-)
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#14
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.
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#15
(04-30-2019, 12:36 AM)friedpenguin Wrote: 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  Big Grin . 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 varying IR. The first 2 didn't seem to go very well the 3rd and 4th ones seem better and I'm testing the 5th one now.
You can check out the sheet on my google drive it is called K2B24V10EB.xlsx with the progress. I can't charge them right now do 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
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 5/23/2019
Total Number of Cells                          5354
Cells  >80% of Capacity                      3801
Cells <80% of Capacity                       1553
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2645 (155) to go
For Info Google Drive
Not your average Wolf       
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#16
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 Smile
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#17
(04-30-2019, 12:07 PM)daromer Wrote: 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  Smile

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 let the internal BMS to do the rest of the work in the sealed battery.

Is that right? Dodgy

Wolf
friedpenguin likes this post
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 5/23/2019
Total Number of Cells                          5354
Cells  >80% of Capacity                      3801
Cells <80% of Capacity                       1553
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2645 (155) to go
For Info Google Drive
Not your average Wolf       
            Cool



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#18
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.
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#19
(04-30-2019, 04:43 PM)friedpenguin Wrote: 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 just an interface to distribute the power (and charging) from/to the battery.

Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 5/23/2019
Total Number of Cells                          5354
Cells  >80% of Capacity                      3801
Cells <80% of Capacity                       1553
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2645 (155) to go
For Info Google Drive
Not your average Wolf       
            Cool



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#20
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).
Running off solar, DIY & electronics fan :-)
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