Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Good Chinese BMS review
#21
(03-07-2019, 06:30 PM)Ebarnett Wrote: Thanks Sean, I've see some other posts recommending 4.0 as the max charge voltage to help with battery life.

SOC vs voltage is not a linear function.
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
Reply
#22
(03-07-2019, 05:21 PM)Ebarnett Wrote: I hate to ask a stupid question but I'm going to.  Ajw22, you mention charging to only 90% of cells max voltage.  On a battery with a Standard charge of .5C of 1500ma and 4.2v wouldn't the max charge voltage need to be .9 x 4.2 = 3.78v per cell.  How did you come up with 4.05v.  That comes to about 98% not 90%.  Please show me where my math is incorrect.

Thanks.


It's not really based on maths.  What one can do is to look at a charge or discharge graph for that chemistry like this one:
https://learn.adafruit.com/assets/979
and look up the Voltage vs DischargeCapacity at your desired C rating.
Temperature, battery model, internal resistance (esp with older cells) all throw this off, so you should expect an accuracy of at best +/- 5%.  

Just to correct your _math_: you need to consider that the usable voltage range is 4.2V ~ 3.0V .  
So the calculation should be 3.0V + (4.2V-3.0V)x90% = 4.08V
But as Cherry67 state above, this would be a very poor approximation because "SOC vs voltage is not a linear function."
Modular PowerShelf using 3D printed packs.  40kWh and growing.
https://secondlifestorage.com/t-AJW22-s-...PowerShelf
Reply
#23
Excellent thanks.
Reply
#24
This china bms together with victron multigrid does it all. Multigrid does cc/cv and can also control Eltek flatpack2 chargers via can bus in order to increase charging current. Therefore bms does not need to control charging process...
Reply
#25
Yes it does. The Victron does not know about individual cell voltages. It only knows about total voltage.
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
#26
(03-16-2019, 07:53 AM)Charly144 Wrote: Multigrid does cc/cv and can also control Eltek flatpack2 chargers via can bus in order to increase charging current.

How ?

Can it request a lower charge rate when cells are in bypass ?
Reply
#27
Yes, multigrid lowers amperage when defined voltage is reached. As well for itself and the flatpack2...
Reply
#28
(03-16-2019, 01:30 PM)Charly144 Wrote: Yes, multigrid lowers amperage when defined voltage is reached. As well for itself and the flatpack2...

Charge current will naturally taper towards terminal voltage - could you explain how the Multi talks to the Eltek via CAN please ?
Reply
#29
I have no details on that but victron confirms integration with flatpack2...
Reply
#30
(03-16-2019, 02:47 PM)Charly144 Wrote: I have no details on that but victron confirms integration with flatpack2...

Could you provide a link please - specifically the CAN control.
Reply


Who read this thread?
100 User(s) read this thread:
hbpowerwall (08-08-2019, 01:38 AM), AZ_Tekkie (04-16-2019, 05:09 AM), daromer (11-02-2019, 04:52 AM), Sean (10-07-2019, 09:02 PM), mike (09-03-2019, 11:34 AM), station240 (03-19-2019, 07:09 AM), yenzand (09-10-2019, 06:06 AM), Majorphill (10-19-2019, 02:47 AM), Korishan (10-19-2019, 12:18 PM), A + A (10-23-2019, 04:49 PM), PAF (10-24-2019, 11:17 AM), Franky Beuselinck (05-09-2019, 09:20 AM), Batrium (09-13-2019, 07:29 AM), BobinTN (05-16-2019, 03:00 PM), Frnandu Martiński (06-05-2019, 09:27 AM), Droid126 (03-13-2019, 01:01 PM), jdeadman (11-02-2019, 02:16 AM), wim (08-28-2019, 05:14 AM), melsom (03-29-2019, 11:17 AM), watts-on (10-23-2019, 04:03 PM), Dan Lim (03-31-2019, 07:14 AM), jesusangel (10-18-2019, 05:37 PM), Hanssing (11-02-2019, 03:33 PM), Fredd (10-03-2019, 08:38 AM), tamkov (10-18-2019, 07:00 PM), Stefaan De Ridder (06-17-2019, 07:56 AM), Igor Maliszewski (03-11-2019, 08:17 PM), Chiptosser (08-30-2019, 12:03 PM), Terry (10-07-2019, 01:18 PM), KtB (10-18-2019, 01:41 PM), Geek (11-05-2019, 04:00 AM), Bigfillly (07-27-2019, 09:16 PM), Jon (04-05-2019, 07:48 AM), Ivo Staelens (08-30-2019, 01:19 PM), floydR (04-16-2019, 01:25 AM), Herbi (07-01-2019, 06:22 AM), stiplanet (10-19-2019, 08:34 PM), Grumplestiltskin (11-05-2019, 09:47 PM), SemaJG (03-18-2019, 03:01 PM), DCkiwi (07-02-2019, 08:13 PM), ChrisD5710 (09-24-2019, 01:25 PM), mattclar (03-18-2019, 11:17 AM), Tentious (10-23-2019, 07:50 PM), cristof (05-09-2019, 02:19 PM), Oz18650 (11-03-2019, 11:26 PM), tocool24 (04-11-2019, 03:58 AM), setite (06-23-2019, 08:30 AM), not2bme (11-05-2019, 11:51 PM), dmallia (07-11-2019, 08:27 AM), CarelHassink (09-01-2019, 07:50 PM), bogptrsn (03-08-2019, 02:52 AM), Jensk (03-07-2019, 10:09 AM), bigblue (04-04-2019, 06:51 PM), Ste Collister (03-07-2019, 12:17 AM), Charly144 (06-03-2019, 10:24 AM), djuro (08-29-2019, 08:09 PM), BaronVonChickenPants (07-17-2019, 05:37 AM), spinningmagnets (03-07-2019, 01:10 AM), Lindsaymac1 (04-29-2019, 07:07 AM), drchips (04-15-2019, 11:24 AM), HughF (09-03-2019, 07:31 PM), Issac (09-04-2019, 02:08 PM), txurdi (05-13-2019, 05:12 PM), Dicklinn (09-30-2019, 12:05 AM), gpn (03-07-2019, 05:11 PM), NGPowerwall (10-21-2019, 09:35 AM), Jimbob01 (10-05-2019, 10:01 PM), Chablis_m (08-27-2019, 09:38 AM), Headrc (10-18-2019, 05:53 PM), kanchana (06-04-2019, 01:09 PM), mbrunton (04-10-2019, 04:58 AM), thanar (05-09-2019, 08:33 AM), rogales141 (09-01-2019, 07:50 AM), Crimp Daddy (10-07-2019, 08:02 PM), jonyjoe505 (05-09-2019, 07:46 PM), Redpacket (09-06-2019, 02:27 PM), completelycharged (09-30-2019, 03:20 AM), Ibiza (11-01-2019, 11:41 PM), Christian Schneider (04-26-2019, 01:12 PM), iomagico (06-17-2019, 07:18 AM), Pyromancy5 (03-28-2019, 06:23 PM), Oliman (08-27-2019, 08:35 PM), SilverNodashi (03-29-2019, 06:03 AM), hyzersauce (03-24-2019, 01:50 PM), dezinger (03-20-2019, 04:18 AM), oilskov (10-25-2019, 12:35 PM), YAW (10-26-2019, 04:48 PM), cadric (07-10-2019, 11:49 AM), philsocal (08-22-2019, 09:51 PM), choncy12 (03-06-2019, 03:51 PM), Bubba (10-24-2019, 10:15 AM), Leo_C (04-15-2019, 02:27 PM), JayRock (11-03-2019, 08:53 PM), Cherry67 (11-11-2019, 07:30 AM), Walde (10-23-2019, 04:53 PM), Riplash (11-02-2019, 10:06 PM), Gaudi (05-16-2019, 03:53 PM), 100fuegos (06-05-2019, 09:14 PM), tecu81 (03-19-2019, 09:06 PM), edd021 (04-22-2019, 05:13 AM)

Forum Jump:


Users browsing this thread: 1 Guest(s)