Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Powerwall voltage
#1
hey im gonna make my very first pack, 6s50p 3000wh mini powerwall and i have all the parts ready to buy but, i cant find an inverter which you can select the cutoff voltage in, one i found was for 21 volts cutoff voltage which means it will cutoff the cells at 3.5 volts but they arent near discharged at 3.5 volts, theyre disharged at 2.9 or 3 volts,

now i could just connect the inverter to the load in the solar charge controller but the solar charge controller only out puts 100 amps or so but id rather connect them to the battery itself so no voltage is changed as i dont think the solar charge controller can supply enough wattage, {2400w} is the max it can output but i need 3000 in my inverter. any help?
Reply
#2
(05-29-2019, 12:47 PM)youlasty Wrote: hey im gonna make my very first pack, 6s50p 3000wh mini powerwall and i have all the parts ready to buy but, i cant find an inverter which you can select the cutoff voltage in, one i found was for 21 volts cutoff voltage which means it will cutoff the cells at 3.5 volts but they arent near discharged at 3.5 volts, theyre disharged at 2.9 or 3 volts,

now i could just connect the inverter to the load in the solar charge controller but the solar charge controller only out puts 100 amps or so but id rather connect them to the battery itself so no voltage is changed as i dont think the solar charge controller can supply enough wattage, {2400w} is the max it can output but i need 3000 in my inverter. any help?

You can't run a typical non-grid tied inverter directly off the solar controller. It'll be unstable at best.
Panels > solar controller > batteries > inverter > loads

re the voltages, you need to focus your efforts on the common inverter voltages of nominal 24V or nominal 48V.
24V = 7s with 18650 Li-ion cells, 48V = 14s

100A from the solar is going to stress a 50p battery, that's 2A/cell charge which is steep. 
At 3kW, you want to be looking at a 48V system.
Running off solar, DIY & electronics fan :-)
Reply
#3
(05-29-2019, 12:47 PM)youlasty Wrote: .....  which means it will cutoff the cells at 3.5 volts but they arent near discharged at 3.5 volts, theyre disharged at 2.9 or 3 volts,

If you are able to, measure the capacity between 3.5v and 2.9v (or just look at some typical discharge curve graphs)  - I suspect you'll then be amending your requirements such that your low cell disconnect voltage is nearer to 3.6v than 3v.
Reply
#4
(05-29-2019, 01:05 PM)Redpacket Wrote: You can't run a typical non-grid tied inverter directly off the solar controller. It'll be unstable at best.
Panels > solar controller > batteries > inverter > loads

re the voltages, you need to focus your efforts on the common inverter voltages of nominal 24V or nominal 48V.
24V = 7s with 18650 Li-ion cells, 48V = 14s

100A from the solar is going to stress a 50p battery, that's 2A/cell charge which is steep. 
At 3kW, you want to be looking at a 48V system.
thanks ill do 7s, and ill connect the inverter directly to the battery, turns out, at 7s, batteries discharged are 21V! exactly what the inverter cutoff voltage is! gonna go with a 2000w inverter not 3000w as im not gonna be powering serious stuff
Reply
#5
As my system grew... I eventually took the step up to a Midnite Solar Classic Controller. More sophisticated controllers have auxiliary controls based on things such as battery voltage (or other controller parameters). I use this to turn the inverter on/off based on battery voltage - so I can affirmatively control the battery discharge depth. This lets me draw power in a middle range of battery bank voltage range in an effort to make battery last twice as long.
Reply
#6
(05-29-2019, 06:16 PM)OffGridInTheCity Wrote: As my system grew...  I eventually took the step up to a Midnite Solar Classic Controller.   More sophisticated controllers have auxiliary controls based on things such as battery voltage (or other controller parameters).  I use this to turn the inverter on/off based on battery voltage - so I can affirmatively control the battery discharge depth.  This lets me draw power in a middle range of battery bank voltage range in an effort to make battery last twice as long.

ive decided on a 7s36p, 3016wh battery consisting of 252 18650s, and it will be 430amps of output, if i calculated right. but i dont think a wire that handles 430amps exists unless its a gigantor industrial wire thats negative 10awg.. the dual xt90 connectors would burn off. how do people use little xt60 connectors and 12awg wires for a monster powerwall battery?
Reply
#7
36cells of high Power cells can hand out many 100a but do you need thta? You design the Wire based on ur useage and same goes with the fuse.


And No.. noone uses xt 60 for that Power. Xt60 is max 60a continued.... Wink
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
#8
(05-30-2019, 12:32 PM)daromer Wrote: 36cells of high Power cells can hand out many 100a but do you need thta? You design the Wire based on ur useage and same goes with the fuse.


And No.. noone uses xt 60 for that Power. Xt60 is max 60a continued.... Wink

all cells will have to output 10 amps continious which theyre capable of.
10amps x 36 cells = 360 amps output x 7s = 2520watts output
Reply
#9
(05-30-2019, 11:54 AM)youlasty Wrote: ive decided on a 7s36p, 3016wh battery consisting of 252 18650s, and it will be 430amps of output, if i calculated right. but i dont think a wire that handles 430amps exists unless its a gigantor industrial wire thats negative 10awg.. the dual xt90 connectors would burn off. how do people use little xt60 connectors and 12awg wires for a monster powerwall battery?

First of if you are only using 36 cells in parallel to get 430A you need to pull 12A from each cell.
A 3016Wh battery at 24V has 125.66 Ah available.
That would still mean you are pulling 3.42 Amps from each cell.

So I am confused here. I mean the average standard discharge of a 18650 is ~1A with potential busts into the 5 to 10 Amp range.
at a standard discharge of 1A a 3000mAh battery would last you 3hrs and a 7s36p pack would deliver 36A for 3 hrs.
A mind blistering draw of 5 amps per cell would give you 180 Amps for 0.6 hrs.
So I'm not sure where you get the 430Amps from.
Even if so 430A X 24V = 10320W WOW Exclamation

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
#10
@youlasty: What inverter are you looking at using?

Even if a battery is "capable" of delivering 480A, you won't be drawing that continuously, unless you're welding or something extreme like that. Even an inverter rated 5000W with 10,000W surge @ 24VDC is going to pull 208A with 416A surge, and that's under full load. Running a 15000BTU window A/C unit or 4000W water heater off this thing?
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
Reply


Who read this thread?
69 User(s) read this thread:
Androfire (06-20-2019, 02:14 PM), Powersaver (06-19-2019, 12:59 PM), bchur83 (05-31-2019, 03:57 AM), OffGridInTheCity (06-01-2019, 12:32 AM), oloyeadeniran (06-01-2019, 07:35 PM), kevinjaye (05-30-2019, 10:44 PM), RikH (05-30-2019, 11:51 PM), ajw22 (05-31-2019, 10:00 PM), stevelectric (06-01-2019, 05:37 AM), Solardad (05-31-2019, 01:39 AM), Generic (06-04-2019, 04:36 AM), Scottietheyoung (06-01-2019, 07:28 AM), Bastler_Ro (05-30-2019, 06:35 PM), Wolf (05-31-2019, 05:11 PM), OhmGrown (05-31-2019, 08:05 PM), sl1me (06-17-2019, 08:29 AM), Dutchman (05-30-2019, 01:25 AM), mskip (05-31-2019, 10:08 PM), titi1960 (06-14-2019, 09:22 AM), Saiya (06-15-2019, 03:01 PM), xahmedxsa (06-21-2019, 03:46 AM), Reception (06-10-2019, 04:55 PM), jal (06-02-2019, 09:10 PM), fpv1812 (06-02-2019, 12:04 PM), Timbira (06-03-2019, 07:48 AM), youlasty (06-06-2019, 06:03 PM), Nemo (06-10-2019, 09:54 PM), dalibor.kozak@post.cz (07-05-2019, 02:54 PM), gpearce52 (05-30-2019, 09:13 PM), juanjo57 (05-29-2019, 04:21 PM), energy_man (06-17-2019, 07:08 AM), Rubert (06-19-2019, 07:05 AM), Omalik (05-31-2019, 05:47 PM), jaeger-audiodesign (05-30-2019, 02:34 PM), Truth (05-31-2019, 02:27 AM), emuland-metroman (05-29-2019, 08:00 PM), Oz18650 (05-31-2019, 08:26 PM), ChrisD5710 (05-30-2019, 09:26 AM), Geek (06-03-2019, 05:08 AM), BlueSwordM (05-30-2019, 10:24 PM), Stefaan De Ridder (06-01-2019, 08:01 AM), Hanssing (05-29-2019, 04:00 PM), jesusangel (05-29-2019, 08:07 PM), Jack Daniels (08-17-2019, 06:58 AM), watts-on (06-01-2019, 09:29 AM), wim (05-31-2019, 02:27 PM), jdeadman (05-31-2019, 07:57 PM), Frnandu Martiński (06-05-2019, 09:37 AM), Korishan (06-01-2019, 12:07 AM), Majorphill (05-29-2019, 09:19 PM), Sean (05-31-2019, 05:31 PM), djuro (05-31-2019, 03:01 PM), sturgeo (08-10-2019, 09:01 AM), chuckp (05-29-2019, 09:23 PM), neowolf (08-30-2019, 09:20 AM), michaell (05-31-2019, 06:10 AM), HikingGuy42 (05-30-2019, 11:31 PM), w0067814 (06-02-2019, 12:12 PM), 100fuegos (06-02-2019, 01:37 PM), CBlack (06-16-2019, 02:55 AM), oilskov (07-08-2019, 12:29 PM), Oliman (05-30-2019, 11:07 PM), Jonas Vanbeveren (06-06-2019, 08:51 PM), Zvonko000 (05-30-2019, 08:19 PM), Redpacket (05-31-2019, 11:52 PM), jonyjoe505 (05-31-2019, 03:44 AM), Crimp Daddy (05-29-2019, 07:10 PM), Headrc (06-07-2019, 05:44 PM), daromer (05-31-2019, 05:22 AM)

Forum Jump:


Users browsing this thread: 2 Guest(s)