Beginners Guide to Processing 18650 Cells | Cell Database


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Batrium BMS Questions
On checking the battery this morning I was a bit surprised by this

 

There are two cells that are weaker than the rest ie. (have lower voltage, discharge quicker than others). The two with duct tape on them. I'll  call them runts  Big Grin

When I set up the 16s pack I considered positioning these 2  runt cells as positive and negative feed cells
(Cell 1 & 16). I had the thought that it might force them to perform better. Not sure if there is any merit to this thinking?

 Instead I placed them one cell back ( 2 & 15).

The lowest cell in the above screen is 2.89. This is the lowest any of these cells have been so far. 2.65 being empty.
The remaining 14 cells were betwee 3.14 -3.17v

With regard to my previous post about SOC, it seems the pack was a fair bit lower than I thought.
I have since reset the SOC to 15%.

I'd appreciate any thoughts on above and question below.

1. Would you position runts as cell 1 & 16, will it make any difference, or is this a bad idea?

Reply


Its LiFe Smile You need to top them off good so you get them all level. Top them up so all of them actually go to 3.5V so you know they are level. It can take some time and you might need to help the longmons drain the other packs Smile
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
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(09-13-2017, 04:20 AM)daromer Wrote: Its LiFe Smile You need to top them off good so you get them all level.  Top them up so all of them actually go to 3.5V so you know they are level. It can take some time and you might need to help the longmons drain the other packs Smile

Such is LiFe  Smile 

I'll push the amps into them and see how they balance at the top.
Thanks
Reply
What is the maximum cells in series for the batrium system?
Reply
250 in terms of number of monitors. I have heard numbers of above 700V in series voltage.

https://www.batrium.com/pages/how-many-l...e-watchmon
hbpowerwall likes this post
Follow me! >> YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcomming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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(09-13-2017, 01:08 AM)Wattsup Wrote: There are two cells that are weaker than the rest ie. (have lower voltage, discharge quicker than others)...

1. Would you position runts as cell 1 & 16, will it make any difference, or is this a bad idea?

The only two aspects that occur to me are 
- they may run hotter than the others, which would then tend to (slightly) magnify any difference. An end position would have more cooling exposure, reducing the temperature difference and consequent effects. But this is unlikely to be of great practical significance. 
- and they would be more accessible when you replace them!
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(09-20-2017, 10:03 AM)dougal Wrote:
(09-13-2017, 01:08 AM)Wattsup Wrote: There are two cells that are weaker than the rest ie. (have lower voltage, discharge quicker than others)...

1. Would you position runts as cell 1 & 16, will it make any difference, or is this a bad idea?

The only two aspects that occur to me are 
- they may run hotter than the others, which would then tend to (slightly) magnify any difference. An end position would have more cooling exposure, reducing the temperature difference and consequent effects. But this is unlikely to be of great practical significance. 
- and they would be more accessible when you replace them!

Good point, they probably would run hotter! 
Thanks for 
I think i'll  leave them where they are. Thanks
Reply
Hi All
I am Gabriel.
I brought two module 9 S Tesla one module has 24v /250AH Lition Panasonic."The modules consist of 444 Panasonic 18650 cells of about 3400 mAh nominal capacity. The cells are configured 6s74p, Voltage range for the whole module is about:18.6V soc 0%;23.1V soc 70%;24.9V soc 100%;capacity ~250Ah, ~5.3kWh

They has a Can Bus BMS and I want to monitoring battery parameters .
What is a solution ?

Thanks a lot.
Electrical Engineer 
Reply
Hey everyone! I've been doing extensive research and watched pretty much every youtube video you guys have posted. 
All great stuff! 

I was considering building my own BMS system and came across Batrium. 

Here is my question.

I'm going to be running a mixed chemistry environment using 18650 Li-Ion cells that I acquire over time in a 40p 14s string to net me 51.8v nominal.
As well I'm going to have another battery bank that will consist of 32650 LiFePo4 cells arranged in a 20p 16s string to net me 51.2v nominal. 

The idea is I would just run the Li-Ion bank at 51.2v nominal as well to keep the banks someone in sync with each other feeding a Sigineer 12kw split phase inverter (US)
I can imagine if I don't line the overall capacity with each other I'll need to somehow diode these banks from each other so one doesn't back feed to other after some extensive load. 

I suppose that is for another topic.

But using Batrium can I individually specify the voltage of each cell? Or is it global?
I'd prefer not to have two individual Batrium systems. 

Hopefully I'm making sense here, and look forward to me showcasing my project as I go.  Blush

Attached is my initial rough draft for a 14s Li-Ion battery
Reply
Check out my install. I run LiIon and LiFePo4 connected to each other. What you are doing are exactly what i have been running for quite some time now.

I run 1 batrium for each system. The reason for this is that its actually 2 banks and i want easily to be able to controll them booth on each own terms.

Batrium only have support to set 1 set of longmons at a time even though you could potentially have different configs. Also 1 watchmon can only handle 1 shunt.


[Image: dV4aso.jpg]

No worries about current going back and forth. They will balance as they want. 

Also note that you never will be able to utilize full DOD on the Liion bank due to the longer voltage range compare to the rather short voltage range on the LiFePo4 bank.


LifePo4 goes between 20-100% meanwhile the LiIon goes between 30 and 70 at most.
Follow me! >> YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcomming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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