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Powerwall voltage
#11
(05-30-2019, 12:49 PM)youlasty Wrote: all cells will have to output 10 amps continious which theyre capable of.
10amps x 36 cells = 360 amps output x 7s = 2520watts output

10A per cell is 16.62 minutes of power from this 7s36p battery. Now that's what I call a power wall Tongue

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
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#12
So the OP mentioned 2kW draw & a 7s, "24V" system.
So at 2kW with say 90% inverter efficiency, that's 2000W/24V/0.9 = ~92.6A at full load.
So to keep the cell draw reasonable, say 0.5A/cell, that means 92.6A/0.5A/cell = a 7s/186p battery.
With this, under best conditions, you'd get approx 6hrs at full load for good 3000mAhr cells.

With the above, the cable sizing for the battery to inverter & DC breaker/fusing would need to be rated 100A or so continuous.
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#13
(05-30-2019, 01:06 PM)Korishan Wrote: @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?

an edecoa 3000w inverter, with all my batteries at 10a continious it will be 10amps x 45 cells in paralell x 7s = 3150watts so it will power the inverter continious and it will shut off auto when batteries are at 21v {3v each cell}

so it will be 450 amps by 1s, 45p
my cells will be rated to do 10amps continious per individual cell
unless im seriously bad at maths, 3000w can power a heater, microwave and fridge
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#14
(05-30-2019, 02:29 PM)youlasty Wrote: an edecoa 3000w inverter, with all my batteries at 10a continious it will be 10amps x 45 cells in paralell x 7s = 3150watts so it will power the inverter continious and it will shut off auto when batteries are at 21v {3v each cell}

so it will be 450 amps by 1s, 45p
my cells will be rated to do 10amps continious per individual cell
unless im seriously bad at maths, 3000w can power a heater, microwave and fridge

A 3000W inverter at 24V will draw 125A.

You moved from 7s36p to 1s45p? I think you mean 7s45p? Right?

Your 3000W inverter even at surge ( excerpt from spec sheet )
  • POWER:Output Continuous Power: 3000w. Output Peak Power (<10ms): 6000w. DC working voltage: 21-28V. Modified Wave Type.
6000W for less than 10ms (that's not good) draws a max of 250 amps.

So in essence your now upgraded to a 7s45p battery (with 3000mah cells I am guessing) 
3Ah per cell  X 45 =135Ah.  Which would last at max output of 3000W continuous for about 1.08hrs in a perfect world.
I personally don't think you will be using the fridge ,microwave, heater (well maybe the heater if you are at the north pole, but then why the refrigerator??) 100% of the time so your battery should last longer.

Just because you have 450A available does not mean you are going to use it If you are using 450 Amps at 24 volts that is 10800W.
If you need that much wattage you need a bigger inverter.

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
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#15
yeah i moved to 7s45p for a total of 315 2250mah cells, resulting in 2.976kwh --> 3kwh

so that means, this battery outputs 3000w for an hour to the inverter which changes that 3000w to ac so it can power 3000w worth of appliances for an hour in a perfect world? or if a ps4 uses up 300wh then this mini powerwall of mine can keep a ps4 turned on for 10 hours?

when i make this first build then how do i add capacity to my profile
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#16
(05-30-2019, 03:07 PM)youlasty Wrote: yeah i moved to 7s45p for a total of 315 2250mah cells, resulting in 3kwh

so that means, this battery outputs 3000w for an hour to the inverter which changes that 3000w to ac so it can power 3000w worth of appliances for an hour in a perfect world? or if a ps4 uses up 300wh then this mini powerwall of mine can keep a ps4 turned on for 10 hours?

OK the dynamics have changed again.
Will you make up your mind or mine. Tongue

7s45p with 2250mAh cells is 101.25Ah Calculation goes as follows 45 cells in parallel times 2.25Ah = 101.25Ah.
101.25Ah at 24V = 2430Wh (2.43kWh) not 3kWh
Not including your Inverter loss you can play your 300W PS4 for 8.1hrs 300W X8.1hrs =2430Whs.


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
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#17
(05-30-2019, 03:30 PM)Wolf Wrote:
(05-30-2019, 03:07 PM)youlasty Wrote: yeah i moved to 7s45p for a total of 315 2250mah cells, resulting in 3kwh

so that means, this battery outputs 3000w for an hour to the inverter which changes that 3000w to ac so it can power 3000w worth of appliances for an hour in a perfect world? or if a ps4 uses up 300wh then this mini powerwall of mine can keep a ps4 turned on for 10 hours?

OK the dynamics have changed again.
Will you make up your mind or mine. Tongue

7s45p with 2250mAh cells is 101.25Ah Calculation goes as follows 45 cells in parallel times 2.25Ah = 101.25Ah.
101.25Ah at 24V = 2430Wh (2.43kWh) not 3kWh
Not including your Inverter loss you can play your 300W PS4 for 8.1hrs 300W X8.1hrs =2430Whs.


Wolf

wait but 2.25 x 4.2 x 315 = 3000watts, enough to power the inverter

2.25= battery Ah, 4.2 is the max volts and 315 is the number of cells resulting in 3000w?

oh i think i get it, the batteries must supply 3000w of power even right when theyre gonna die. so 3000w+ at 3.1 volts or something. i guess ill just buy more cells.. this project is gonna cost alot. still worth it

wait mabye ill just use a 2000w inverter because even when the cells are about to die they output 2100watts and 3000w fully charged but would that not blow up the inverter

2000w isnt enough for my air heater tho :{, ugh not like it matters anyway
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#18
No. Total capacity is based on nominal voltage. To be fair use 3.65v. then add 20% losses and you get ur total available energy and time it can run. This though Will be a 100% dod (depth of discharge) bad in real world this isnt usefulle. Perhaps 60% is better Smile

Also the load on the cells isnt larger than the device hooked in. IF you have a tv using 100w then att the battery perhaps 150w. 100+20 +30 where 20 is. The losses and 30 is the Idle draw in the inverter
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#19
(05-30-2019, 03:32 PM)youlasty Wrote:
Quote:wait but 2.25 x 4.2 x 315 = 3000watts, enough to power the inverter
2.25= battery Ah, 4.2 is the max volts and 315 is the number of cells resulting in 3000w?

Yes at full load but are you running the Inverter at full load all the time? It may only need to supply 300W if all you are doing is playing on your PS4.

Quote:oh i think i get it, the batteries must supply 3000w of power even right when theyre gonna die. so 3000w+ at 3.1 volts or something. i guess ill just buy more cells.. this project is gonna cost alot. still worth it


wait mabye ill just use a 2000w inverter because even when the cells are about to die they output 2100watts and 3000w fully charged but would that not blow up the inverter
2000w isnt enough for my air heater tho :{, ugh not like it matters anyway

LOL you got way too many gears whirring in your head.

A 18650 cell will yes charge to 4.2v and usually the low V cutout is ~3V. Once you put a load on a cell the V will drop to ~4.05V and will supply whatever amperage you demand of it till ~3V. So the cell will supply 2250mAh whether you draw 500mA or 2250mA. If you draw 500mA from the cell it will discharge in about 4.5 hrs if you draw 1000mA (or 1A ) it will discharge in 2.25 hrs. Your usable voltage range is really ~4V to ~3V were the battery will supply your amperage requests.
Once the cell hits its cutoff voltage the current supplied drops off rapidly. See chart below.
This is just an example of a cell which happens to be a LG 18650HE2 but all Li-ion 18650 cells work the same. Just different cutoff voltages depending on manufacturer and cell chemistries.
 

Another thought is a BMS for your 7s45p pack. You will have to find a BMS that will handle the amperage you are requesting and also have a shunt trip or some cut off when the pack voltage is ~21V. Also when recharging you will need to be able to balance the pack and have an upper limit cutoff so you don't overcharge the battery.

Wolf
Korishan likes this post
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
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#20
(05-30-2019, 03:32 PM)youlasty Wrote: 2000w isnt enough for my air heater tho :{, ugh not like it matters anyway

What type of air heater is it ?
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