Beginners Guide to Processing 18650 Cells | Cell Database


Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
How to calculate pack and charger?
#1
I am looking to build a pack for a 48v cart, it has a 3.3hp 48v electric motor on it (3kw/9kw peak), I have access to a few hundred Li-ion Samsung 18650 2200mah cells. Knowing that I want to be able to run this around lets say 2 hours max per day what would one suggest for a pack size and charger?

I have yet to purchase anything so now is a good time to get ideas / opinions from the group to point me in the right direction. Why re-invent the wheel when we have access to so many experts =o)
Reply


#2
3kW@48V would mean 67Amps flowing, 9kW means 187,5A. Check the data sheet of your cells for rated discharge current. This is sometimes measured in C, which means a multiple of capacity. Example: If the cell's discharge rate is 2C and the cell has 2200mAh, the cell can max. deliver  4.4Amps.

Then devide the amps you think you'll need (anything between 67 and 187,5A) by this value and you'll know the minimum of parallel cells. For 48V, 14s is quite common, so then take the number of cells you calculated and multiply it with 14 for the cell count overall.

The charger also depends on the specs of your cells, resp. max. charge current - and how fast you want to charge. Also keep in mind that you might need balancing, overcharge and overdischarge protection, commonly knows as BMS...
Inverted 18650 likes this post

Cells tested: 4238 (overall: 8077 Ah, average: 1906 mAh)
Cells in production: 2240 (overall: 4704 Ah, average: 2100 mAh)
Powerwall config: 7s320p, 672 Ah, 16 kWh
What's left: my current grid consumption

Reply
#3
I did write an answer here long as an a4 page... But i fucked it up. I dont want to rewrite how to do this today so I leave it for tomorrow or if someone else want to answer.
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
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
Reply
#4
you would need a min of 14s 160p to equal the standard 8 golf cart batteries.

if you go with high amp drain bats like in a cordless drill you could get away with half as many.
Reply
#5
(08-19-2017, 08:53 PM)owitte Wrote: 3kW@48V would mean 67Amps flowing, 9kW means 187,5A. Check the data sheet of your cells for rated discharge current. This is sometimes measured in C, which means a multiple of capacity. Example: If the cell's discharge rate is 2C and the cell has 2200mAh, the cell can max. deliver  4.4Amps.

Then devide the amps you think you'll need (anything between 67 and 187,5A) by this value and you'll know the minimum of parallel cells. For 48V, 14s is quite common, so then take the number of cells you calculated and multiply it with 14 for the cell count overall.

The charger also depends on the specs of your cells, resp. max. charge current - and how fast you want to charge. Also keep in mind that you might need balancing, overcharge and overdischarge protection, commonly knows as BMS...

Excellent, so from what I can determine the max these cells can produce is 10A (continuous discharge) they are - ICR18650-22P (Honestly not sure how to read this chart - http://www.tme.eu/en/Document/cf2b91a946....2P-HV.pdf )

When I measure the cart in motion its drawing 12 amps (I agree the match doesn't add up, so lets assume 67 amps so 67/10c so apx 6.7 rounded down to 6 cells in parallel. This gives us a total of 14 cells in series 6 in parallel or 84 cells per pack?

My goal is safety first (so yes to BMS) followed by cell life second and capacity third. I see a ton of BMS boards on ebay but not sure if I need balancing, etc.. for this project so it makes picking one a chore. Any feedback would be appreciated and a I have no reservations to making a donation via paypal for your help =o)

(08-19-2017, 09:03 PM)daromer Wrote: I did write an answer here long as an a4 page... But i fucked it up. I dont want to rewrite how to do this today so I leave it for tomorrow or if someone else want to answer.

Oh noooooooooo, what happened to your post? I feel your pain I lost a post to a guy on a Freenas project that I spend the better part of an afternoon typing up and wanted to pound my head against the wall for not copying it before I sent it out (just in case).

I hope you day goes better tomorrow and you are willing to share some insight.

(08-19-2017, 09:29 PM)1958 greyhound Wrote: you would need a min of 14s 160p to equal the standard 8 golf cart batteries.

if you go with high amp drain bats like in a cordless drill you could get away with half as many.

Currently the way this cart is setup (right or wrong) as I received it is with 4 12v 150ah batteries. The batteries I have access to are: http://www.tme.eu/en/Document/cf2b91a946....2P-HV.pdf
Reply
#6
to equal USABLE CAPACITY of the 4x 12v 150ah lead acid.

14s 35p
490 cells total.
Reply
#7
(08-20-2017, 07:32 AM)1958 greyhound Wrote: to equal USABLE CAPACITY of the 4x 12v 150ah lead acid.

14s 35p
490 cells total.

Okay yeah I think with that many cells I'll build two separate packs and put them in parallel 2 of 14s18p
Reply
#8
Just beware of how you interconnect the paralelled packs. Perhaps easier to build 7s35p and then hook 2 of those together to 14s instead?
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
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
Reply
#9
(08-20-2017, 06:35 PM)daromer Wrote: Just beware of how you interconnect the paralelled packs. Perhaps easier to build 7s35p and then hook 2 of those together to 14s instead?

Good to know, I figured it was easier to parallel to packs (like you parallel 2 car batteries) than to put 2 in series, that not the case?

I did actually get some accurate current measurements today, the cart draws close to 200 amps at 48v when you first floor it, then maintains about 100amps, Most of the time I am at about 75% throttle and see 60amps as average.
Reply
#10
(08-20-2017, 06:35 PM)daromer Wrote: Just beware of how you interconnect the paralelled packs. Perhaps easier to build 7s35p and then hook 2 of those together to 14s instead?


Why do you say that Daromer? "Beware of how you interconnect the parallel packs." I'm curious as I was planning a future parallel interconnected system. I'm not challenging I'm honestly trying to learn. Thanks, Alec
Reply


Who read this thread?
59 User(s) read this thread:
Cody2o0 (11-10-2017, 12:54 PM), 江冠穎 (08-24-2017, 05:59 AM), floydR (10-01-2017, 07:13 PM), Dan Clark (08-23-2017, 07:00 PM), costasc68 (08-24-2017, 05:27 AM), jamesk9 (10-29-2017, 07:01 PM), jrandomb (09-06-2017, 12:05 AM), Kenneth Bonanno (08-23-2017, 10:33 PM), electricJolt (08-24-2017, 04:01 AM), mike98 (08-24-2017, 01:38 AM), Geek (09-01-2017, 06:19 AM), nokiasixteth (09-18-2017, 10:57 PM), Gary DW (09-26-2017, 03:10 PM), SimonW (09-19-2017, 03:01 AM), ryaner (09-19-2017, 10:41 PM), sebjustin (08-28-2017, 11:34 AM), randy4me (11-22-2017, 10:47 PM), revbryce (10-29-2017, 12:08 PM), Panda (11-02-2017, 12:42 PM), accoelho (10-05-2017, 04:41 PM), Shinken_Otacon (09-19-2017, 02:25 AM), ICEMAN (10-04-2017, 10:34 AM), Reuse energy (09-08-2017, 11:25 AM), aarn (09-01-2017, 08:55 AM), ps915 (08-31-2017, 09:19 PM), jrobida (08-30-2017, 10:12 PM), hookemdevils22 (09-14-2017, 07:53 PM), Matthew Nagy (08-30-2017, 12:55 AM), Mazlem (08-24-2017, 03:04 PM), rememberthemagic (08-29-2017, 04:38 AM), Robert Crawley (08-30-2017, 04:11 PM), Jeremy Choy (08-21-2017, 05:18 AM), Robert Baumer (08-21-2017, 03:07 AM), typ49 (08-22-2017, 07:54 AM), frnandu (08-29-2017, 01:36 PM), wim (08-29-2017, 06:17 AM), jdeadman (08-29-2017, 12:29 PM), Alec_J (08-21-2017, 02:56 AM), Wattsup (08-29-2017, 10:52 AM), Majorphill (08-21-2017, 07:21 AM), owitte (08-29-2017, 12:24 PM), mike (08-24-2017, 12:25 AM), daromer (08-29-2017, 06:37 AM), 1958 greyhound (09-06-2017, 06:26 AM), Kaspars Krumins (09-30-2017, 07:50 PM), rebelrider.mike (08-23-2017, 12:21 PM), Eric Snyder (09-10-2017, 06:03 PM), colishere (08-24-2017, 05:26 AM), BlueSwordM (08-20-2017, 04:32 PM), Chris Evans (08-19-2017, 10:02 PM), Inverted 18650 (08-21-2017, 06:47 PM), Chiptosser (08-20-2017, 10:54 PM), Stefaan De Ridder (08-23-2017, 07:34 PM), MetalFang (08-23-2017, 05:59 AM), Hanssing (08-29-2017, 04:50 AM), Daggerzz (08-20-2017, 07:46 AM), jesusangel (08-23-2017, 07:30 AM), watts-on (08-29-2017, 09:34 AM), hbpowerwall (08-29-2017, 09:51 AM)

Forum Jump:


Users browsing this thread: 1 Guest(s)