Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Pack Design Question
#1
Thanks to all who readily share their experience and knowledge.  I have a couple of pack design questions.  After reviewing hundreds of video and forum posts, I have decided initially on creating 4 system packs consisting of 7S10P using new Samsung 30Q cells (3000ma @ 3.6v and Max continuous discharge current of 15A).  I will then parallel these system packs together for what I believe to be a 30A at 25.2v. = 756Wh/pack x 4 packs = 3024Wh per entire system.   The system will need to provide 30A max power for short periods but primarily the system will be only supplying <10A continuous for the application I have in mind.
 
First question I have is,  I would like to know if fusing individual cells to nickel strips (.2mm x 8mm) instead of copper wire bus bars will be a problem for the load and size mentioned above.  I realize the IR of nickel and cost is not as good as copper but it’s easier to work with for me.
 
Second question I have is, how to calculate the C rating for the cells in my application defined above.  I believe the C rating of the cells above would be C5.  How do I determine what the amp load each cell is going to be subjected to?  I am thinking this is the way it would work but maybe I’m wrong. 
30A Load / 4 parallel system packs  = 7.5A per system pack / 10 cells in parallel per pack= .75A per cell.  Would this equate to a C .15 rating for each cell?
 
Thanks in advance for any comments and suggestions.
Reply
#2
No individual fusing on new cells on that small pack with that current is needed if you ask me.
Just use a proper BMS

You will have 40 cells in parallel. And if you say you have 10A total thats 10/40 = Your current per cell. Thats rather low Smile
The Ultimate DIY Solar and build place
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
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
Reply
#3
(03-01-2019, 03:37 PM)daromer Wrote: No individual fusing on new cells on that small pack with that current is needed if you ask me.
Just use a proper BMS

You will have 40 cells in parallel. And if you say you have 10A total that's 10/40 = Your current per cell. Thats rather low Smile

Thanks daromer,  can you help me understand how I have 40 cells in parallel?  Is each pack that has 10 cells in parallel considered 1x10 even though it has 70 cells in a pack?  Then I multiply the individual pack times the number in parallel (4).  If that's the case then the C rating would be 30A max / 40 cells = .75. 

Also, I'm a bit confused as to why no fusing is required?  Is it because the amp load across the cells is relatively small?  If I still choose to fuse would it work with the nickel strip I have spec'd out.

Thanks.
Reply
#4
(03-01-2019, 03:29 PM)Ebarnett Wrote: Thanks to all who readily share their experience and knowledge.  I have a couple of pack design questions.  After reviewing hundreds of video and forum posts, I have decided initially on creating 4 system packs consisting of 7S10P using new Samsung 30Q cells (3000ma @ 3.6v and Max continuous discharge current of 15A).  I will then parallel these system packs together for what I believe to be a 30A at 25.2v. = 756Wh/pack x 4 packs = 3024Wh per entire system.   The system will need to provide 30A max power for short periods but primarily the system will be only supplying <10A continuous for the application I have in mind.
Your calculations are correct 
First question I have is,  I would like to know if fusing individual cells to nickel strips (.2mm x 8mm) instead of copper wire bus bars will be a problem for the load and size mentioned above.  I realize the IR of nickel and cost is not as good as copper but it’s easier to work with for me.
 
Second question I have is, how to calculate the C rating for the cells in my application defined above.  I believe the C rating of the cells above would be C5.  How do I determine what the amp load each cell is going to be subjected to?  I am thinking this is the way it would work but maybe I’m wrong. 
30A Load / 4 parallel system packs  = 7.5A per system pack / 10 cells in parallel per pack= .75A per cell.  Would this equate to a C .15 rating for each cell?
 
Thanks in advance for any comments and suggestions.
1. Your calculations are correct  7s10p will give you 0.76kWh

And 7s10p x4 will give you 3.02kWh


2. 30A max requires at least AWG 10 wire no matter what V. You need to treat this as a 7s40p pack as the individual 10p packs just confuse the issue.

C rating is basically the multiplier of the rated capacity so charging at 1C would be charging a 3000mAh battery at 3000mA 0.5C would be 1500mA and 0.2C would be 600mA.
Same goes with a 2600mAh battery 1C is 2600mA 0.5C 1300mA and so on 2C would be 5200mA etc.

3 30A load on 10 cells in p would be 3A per cell.
If I understand you correctly you will have 10p X 4 X 7s than that would be 30A on 40 cells = 1.333A per cell 0.44C per cell.




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 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
Reply
#5
Thanks. Wolf, that's very helpful. Since you recommend 10GA wire for 30A, I need to figure out if the nickel strip defined above will work in stead of 10G copper wire. I am planning to used XT90 connectors with 8ga wire to parallel the system packs together.
Reply
#6
(03-01-2019, 04:48 PM)Ebarnett Wrote: Thanks. Wolf, that's very helpful.  Since you recommend 10GA wire for 30A, I need to figure out if the nickel strip defined above will work in stead of 10G copper wire.  I am planning to used XT90 connectors with 8ga wire to parallel the system packs together.

I think the nickel strips (.2mm x 8mm) are adequate for your project depending on how you want to put your packs together.
Obviously the 10 in 1 line is not a good idea. If you go with 5 in a row you are pushing the strips to their limit. I don't know what cross spot welding would do but it probably won't hurt. The other 2 methods put the least amount of stress on the strip with number 1 being the least.
I have included a nickel strip amperage chart with some reference to amps per strip size. Your size was not included but close enough for reference.
The XT90 with AWG 8 is definitely adequate and should work perfect.
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 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
Reply
#7
Thanks again Wolf.  I have seen that chart and was concerned, that's what led me to post this message.  I'll have to evaluate the nickel in my design as I was planning on using them as internal bus bars and fusing the cells to them.  I liked it as it seemed easier to work with, but performance is my first priority.
Reply
#8
(03-01-2019, 03:29 PM)Ebarnett Wrote: Thanks to all who readily share their experience and knowledge.  I have a couple of pack design questions.  After reviewing hundreds of video and forum posts, I have decided initially on creating 4 system packs consisting of 7S10P using new Samsung 30Q cells (3000ma @ 3.6v and Max continuous discharge current of 15A).  I will then parallel these system packs together for what I believe to be a 30A at 25.2v. = 756Wh/pack x 4 packs = 3024Wh per entire system.   The system will need to provide 30A max power for short periods but primarily the system will be only supplying <10A continuous for the application I have in mind.
 
First question I have is,  I would like to know if fusing individual cells to nickel strips (.2mm x 8mm) instead of copper wire bus bars will be a problem for the load and size mentioned above.  I realize the IR of nickel and cost is not as good as copper but it’s easier to work with for me.
 
Second question I have is, how to calculate the C rating for the cells in my application defined above.  I believe the C rating of the cells above would be C5.  How do I determine what the amp load each cell is going to be subjected to?  I am thinking this is the way it would work but maybe I’m wrong. 
30A Load / 4 parallel system packs  = 7.5A per system pack / 10 cells in parallel per pack= .75A per cell.  Would this equate to a C .15 rating for each cell?
 
Thanks in advance for any comments and suggestions.

I have come out a design which maybe close to what you want... just need some DIY.
You can use 2 OFPPK kit to combine to become 8S 16P or 7S 16P configuration. 
http://bit.ly/416OFPPK
Reply
#9
Wolf I was wondering why you were dividing the parallel cell count by the amps as opposed to dividing the amps by cell count to get the cell c rating? Included is a diagram of my pack design based off your suggestions.
Reply
#10
(03-03-2019, 03:00 PM)Ebarnett Wrote: Wolf I was wondering why you were dividing the parallel cell count by the amps as opposed to dividing the amps by cell count to get the cell c rating?  Included is a diagram of my pack design based off your suggestions.

You sent me a PM but you have PM revive turned off so I cannot answer.
Here is may answer to your PM
I don't mind at all just a little busy today.
Will post stuff soon.
Location Portland, Maine area USA East Coast.
Getting another snow storm tonight.
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 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
Reply


Who read this thread?
64 User(s) read this thread:
foamovercast (04-22-2019, 06:58 PM), CU17 (03-04-2019, 03:33 AM), Greenbatt (03-09-2019, 11:51 PM), strat24v (03-01-2019, 08:16 PM), Havskum (04-05-2019, 06:18 PM), mxboy27s (04-01-2019, 07:54 PM), kophi (03-07-2019, 04:21 PM), beserker786 (03-01-2019, 09:54 PM), mskip (03-05-2019, 11:29 AM), Richard (03-01-2019, 05:54 PM), kurt13r (03-24-2019, 06:08 PM), Powersaver (03-13-2019, 03:34 PM), 1Lukas1 (03-17-2019, 09:10 PM), zoookii (03-03-2019, 07:40 PM), LEDSchlucker (03-03-2019, 08:32 PM), Ebarnett (03-06-2019, 09:59 AM), allend83 (03-01-2019, 03:52 PM), Ada_Lithium (04-09-2019, 07:15 PM), ben teker (04-27-2019, 07:09 PM), Zaziki (06-03-2019, 06:19 AM), ocorrea73 (04-05-2019, 02:03 AM), agungprm (03-22-2019, 02:30 PM), sgrevskott (03-26-2019, 06:44 PM), elettri (03-30-2019, 06:35 AM), zoneblue (03-13-2019, 05:11 AM), MonkeyThink (03-22-2019, 10:53 AM), GeneralDJ (03-15-2019, 12:41 PM), Kenjutsu (03-11-2019, 08:42 PM), Bilabob (03-18-2019, 05:39 AM), 100kwh-hunter (05-05-2019, 08:15 AM), piedranet (03-01-2019, 05:32 PM), kevinjaye (09-09-2019, 09:17 PM), BmoreThor (05-02-2019, 01:31 AM), sturgeo (08-10-2019, 08:57 AM), Oz18650 (06-25-2019, 10:04 AM), ChrisD5710 (03-02-2019, 12:29 PM), Grumplestiltskin (03-04-2019, 09:42 AM), Geek (03-03-2019, 11:27 PM), Mazlem (03-04-2019, 01:28 AM), BlueSwordM (03-04-2019, 12:44 AM), Stefaan De Ridder (03-03-2019, 06:31 PM), Dan Lim (03-24-2019, 01:59 AM), watts-on (03-04-2019, 10:18 PM), wim (03-02-2019, 06:40 AM), PAF (03-03-2019, 04:24 PM), Korishan (03-03-2019, 11:21 PM), Sean (03-03-2019, 05:35 PM), rodagaster (03-01-2019, 10:38 PM), Ibiza (03-04-2019, 06:53 AM), PaulDane (03-05-2019, 08:18 PM), Manju18 (03-16-2019, 03:32 PM), Speicher (03-03-2019, 06:32 AM), Generic (03-03-2019, 07:55 PM), camthecam (03-03-2019, 10:00 PM), Wolf (03-04-2019, 12:28 PM), risoman (04-05-2019, 07:14 PM), Shawndoe (03-02-2019, 09:39 PM), clupton (03-09-2019, 04:08 PM), Mikethezipper (03-08-2019, 05:45 AM), Riplash (03-02-2019, 09:56 PM), choncy12 (03-04-2019, 12:08 PM), cadric (03-25-2019, 09:06 AM), Zvonko000 (04-28-2019, 06:38 PM), daromer (03-03-2019, 09:59 PM)

Forum Jump:


Users browsing this thread: 1 Guest(s)