Notice To Unregistered Users: By visiting this forum, you are automatically agreeing to the terms and conditions set forth in our Safety Notice & User Agreement. All electrical work shall be completed by a qualified and licensed electrician. Admins, moderators, and members do not accept any liability for the information posted here. Please make sure to read the Safety Notice & User Agreement for the full disclosure. To remove this message, please register for an account.
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
48V 1500W Inverter
#41
Probably means me. By no means am I endorsing pulling 40A from only 12p or 8p as I've done, it is very bad levels of heat produced. I'm amazed that it worked at all really. I was just impatient and really wanted to give my system a try before I'm done adding cells.
Reply
#42
Yea It was to Rev0. I find these cells just do not like much over 1A pull in regards of the Voltage drop. For my lawnmower I run it at worst case load of 16A with 16p cells. During a Cut the pack will get pretty warm but those are also my crappy cells.
Reply
#43
Finally completed the 4th pack, so it now sits at 1.8kWH, 4p(14s4p), with all intermediate cells interconnected to a smart BMS. One of the packs has high drain Sony VTC5 cells (each cell is capable of 25A continuous), but my other experiment showed that once those drain past ~50% SoC the other cells will take a majority of the load. Thankfully, that should be about 30 minutes into a 60 minute discharge, so I should theoretically be able to extract almost all of the pack's energy with this setup, unlike before where I was thermally limited. I also taped on a 120mm low speed fan which I will have running during the discharge. 2 of the packs are build with 3D printed fuse/bus bar holders. All packs have connectors for main power (XT-60) and balancing (9-pin JST-XH with only 8 of the 9 pins populated), so I can swap out any pack if something needs changing.




I will be doing a full discharge test tomorrow or the next day and will try again to get some thermal + regular video to analyze it. The BMS has 2 temperature sensors also, and is set to disconnect the pack if the sensors exceed 65 C.
Korishan and jdeadman like this post
Reply
#44
I can't believe I forgot to post this here! Here's the result of the 4-parallel pack discharge test, worked great:





I got the most interesting stats from the first discharge:

Run #1:
47:54.84 duration
1336 WH In (DC)
1125 WH Out (AC)
67.1% SOC => 4.8% SOC added ~= 888WH to 999WH => Batt to wheels eff. 66.5-74.8%
min cell v at end = 3.172/3.376 (loaded/unloaded) 7,8, max cell v at end = 3.403/3.523 (loaded/unloaded) 1,2,4 33.06A
cell 7 IR at discharged = 6.17mOhm eff. ~= 98.7mOhm/cell
cell 4 IR at discharged = 3.63mOhm eff. ~= 58.1mOhm/cell

Overall pulled just about 1.4kWH from the pack. Unfortunately the BMS current shunt setting is way off, and the power meter on the DC side is also a bit off, but I was able to correct for that offset in the graphs posted in the video at least. The pack has been plugged into my solar panel since last Friday and has put in roughly 1kWH so far (again not too sure because the BMS shunt/current accuracy is questionable, but the charging calibration seems a lot closer than the discharging).
Korishan likes this post
Reply
#45
Minor update, one of the packs developed a "leaker" after charging past ~4.1V/cell. Actually, it has developed 2 leakers, which I just found out after rebuilding it to my newest pack format (using the fuse buddy 3D printed busbar holders). The second one was a much slower leak, but still apparently greater than the 30-50mA of balancing current the smart BMS manages. I am thinking of upgrading the BMS with an external balancing board capable of at least 100mA balance current (still a tiny fraction of the ~37AH the pack sits at now), but it's clear that the current balance current is like spitting in the ocean for getting the cells balanced. Barely makes a dent after a week of balancing.
Reply


Who read this thread?
100 User(s) read this thread:
AZ_Tekkie (01-14-2018, 06:24 AM), daromer (02-05-2018, 07:08 PM), mike (04-06-2018, 06:10 PM), PaulKennett (01-30-2018, 04:59 AM), miwall (12-27-2017, 08:17 AM), Majorphill (01-21-2018, 10:38 AM), Korishan (04-06-2018, 08:51 PM), A + A (04-06-2018, 06:16 PM), PAF (03-24-2018, 09:15 AM), FERCSA (12-19-2017, 04:27 PM), Franky Beuselinck (04-08-2018, 07:44 PM), Darmok (03-25-2018, 01:46 AM), Wattsup (01-20-2018, 08:46 PM), Frnandu Martiński (02-02-2018, 08:58 AM), jdeadman (04-06-2018, 06:15 PM), wim (04-06-2018, 06:13 PM), Brian Drury (01-02-2018, 12:49 PM), typ49 (04-09-2018, 07:32 AM), watts-on (04-07-2018, 09:50 AM), jesusangel (12-19-2017, 04:22 AM), Hanssing (02-06-2018, 06:49 AM), Dietmar Rheeder-Kleist (01-11-2018, 01:15 PM), IronSky (04-09-2018, 04:47 PM), Mark Daniel Olsen (01-13-2018, 10:05 PM), tamkov (12-24-2017, 09:03 PM), kazbach (01-02-2018, 01:54 AM), Stefaan De Ridder (04-07-2018, 07:47 AM), Chiptosser (02-02-2018, 07:19 AM), systemtm (03-30-2018, 08:56 AM), BlueSwordM (01-26-2018, 06:24 PM), Travis Watson (03-02-2018, 05:01 PM), Mazlem (04-06-2018, 06:39 PM), ivnz (03-02-2018, 04:13 AM), Geek (04-09-2018, 05:20 AM), Rad (03-10-2018, 09:08 AM), Jon (01-02-2018, 10:10 PM), mr_hypno (03-01-2018, 09:57 PM), floydR (04-07-2018, 01:15 AM), grgdgreek (01-13-2018, 03:57 PM), DarkRaven (02-02-2018, 12:37 AM), Grumplestiltskin (03-26-2018, 09:25 PM), burtyb (12-22-2017, 09:06 AM), Lucian Macota (01-30-2018, 02:20 PM), howiegrapek (12-22-2017, 12:44 AM), dougm352 (12-26-2017, 04:20 PM), cristof (12-20-2017, 08:32 AM), Oderus420 (01-21-2018, 02:50 PM), neurocis (01-19-2018, 08:35 AM), rev0 (05-17-2018, 06:07 AM), joel0v3sgames (04-17-2018, 07:52 AM), wycito (02-13-2018, 06:19 AM), CarelHassink (02-02-2018, 03:46 PM), sedorikku (12-19-2017, 08:03 PM), kennl (01-30-2018, 02:14 AM), Dave Adams (12-24-2017, 11:39 PM), cmg_george (03-12-2018, 09:53 AM), macallazack (02-01-2018, 10:04 AM), Pavel Razzorenov (01-30-2018, 10:40 AM), garolittle (03-10-2018, 07:20 PM), kronultimate (02-06-2018, 09:57 PM), Spkerking (12-22-2017, 12:30 AM), PowerLio (03-12-2018, 11:45 PM), vlmendezjr (02-08-2018, 03:45 AM), Filip (12-19-2017, 04:33 PM), BGrillo (03-13-2018, 10:16 PM), putter32 (01-04-2018, 08:09 AM), Solexx X (03-01-2018, 06:10 AM), br0l (03-05-2018, 06:23 PM), Ste Collister (12-19-2017, 03:34 AM), Brent Brown (02-03-2018, 01:00 AM), rdh824 (03-01-2018, 01:11 PM), djuro (06-21-2018, 01:50 PM), Detritalgeo (01-16-2018, 04:59 PM), SecondHandPower (01-24-2018, 06:05 AM), ClardiPower (03-07-2018, 10:28 AM), BaronVonChickenPants (01-30-2018, 09:52 AM), CFProject (12-27-2017, 01:21 PM), Matthew Hunter (12-23-2017, 01:45 AM), spinningmagnets (01-12-2018, 04:17 PM), Geoffo (12-19-2017, 02:29 PM), earlYnot (12-20-2017, 10:53 AM), jm1 (04-18-2018, 03:19 AM), lennoxlewis (12-22-2017, 01:31 PM), thefixer06 (03-07-2018, 12:05 AM), dwarflundgren (12-21-2017, 11:00 AM), Jason Morris (04-06-2018, 11:56 PM), Markuss (01-02-2018, 04:20 PM), marcin (01-15-2018, 01:50 PM), julianmh (01-03-2018, 11:07 PM), kiriku (03-31-2018, 08:25 PM), Brian Wilson (01-14-2018, 11:19 PM), atiko (12-28-2017, 06:24 PM), Silver (12-30-2017, 12:06 PM), brwainer (04-06-2018, 07:31 PM), Alperx (12-30-2017, 11:54 PM), drchips (01-21-2018, 02:58 PM), Brent (01-21-2018, 09:54 PM), HughF (01-02-2018, 12:14 PM), Micka76550 (01-01-2018, 10:18 PM), Roland Domke (01-30-2018, 07:19 AM)

Forum Jump:


Users browsing this thread: 1 Guest(s)