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amberpp1

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Jul 7, 2021
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Hi all,
Could someone look over a system I am trying to put together for an off grid property? I've watched many of 's videos, but I'd feel better if I had some feedback about the compatibility of the components, and I am also struggling to find the correct wire gauges.
I planned on using a Growatt 5000ES with two sets of panels in parallel, where each set is made up of eight 250watt panels in series. I have 4 lithium batteries, each 12V 100AH. I've included the data sheet for the Growatt. I was going to wire the batteries in series to make a 48V battery bank.

Some specs for the 16 panels:

Rated Power: 250W
Open circuit voltage (VOC): 37.6 V
Max power voltage (VMP): 30.3 V
Short circuit current (ISC): 8.85 A
Max power current: 8.27 A

Some specs for the batteries:

Charge Voltage: 14.6V
Max Charge Current: 50 A
Max Discharge Current: 100 A

The end of the array will be 43-45ft away from the Growatt and batteries. To the best of my knowledge I should use 8 gauge wire from the panels to the Growatt, and possibly 4 gauge between batteries? Any help would be appreciated.
 

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The image you attached is unreadable.

Edit: Now it's readable.
 
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The Growatt is single phase 230VAC input and is not suitable for North America.
Is it compatible with mains power for your part of the world?
 
5000 ac watts * 1.5 low frequency inverter factor / 48 volts low cutoff = 156.25 dc amps
156.25 dc amps / .8 fuse headroom = 195.3125 fuse amps
That requires 2 awg minimum between inverter and battery.
Also 156.25 amps far exceeds the continuous discharge rating for your battery.
 
Is there something I can change to bring that amperage down or have I just chosen the wrong parts?
 
amberpp1 said:
Is there something I can change to bring that amperage down or have I just chosen the wrong parts?
Click to expand...
You could double up on the batteries or you could possibly get a smaller all_in_one.
Is the voltage correct for your part of the world?
 
You could wire 8 batteries in 4S2P. That would give you 48V with 200A max discharge current. Or get a smaller inverter. Do you need 5kW?
 
I would prefer the 5kW, and really we should have more batteries with the amount of cloudy days we get here. I had just hoped to squeeze by with 4 for now, but if I need 8 I will just have to work it out
I am a little confused on the compatibility with North America thing, I see on the data sheet it says 230VAC, but signature solar lists it at 240VAC
In David Poz’s video they show it seemed he was using the inverter as a 240VAC with an auto transformer to split the 240VAC into two phases of 120vac?
 

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amberpp1 said:
Hi all,
Could someone look over a system I am trying to put together for an off grid property? I've watched many of Will's videos, but I'd feel better if I had some feedback about the compatibility of the components, and I am also struggling to find the correct wire gauges.
I planned on using a Growatt 5000ES with two sets of panels in parallel, where each set is made up of eight 250watt panels in series. I have 4 lithium batteries, each 12V 100AH. I've included the data sheet for the Growatt. I was going to wire the batteries in series to make a 48V battery bank.

Some specs for the 16 panels:

Rated Power: 250W
Open circuit voltage (VOC): 37.6 V
Max power voltage (VMP): 30.3 V
Short circuit current (ISC): 8.85 A
Max power current: 8.27 A

Some specs for the batteries:

Charge Voltage: 14.6V
Max Charge Current: 50 A
Max Discharge Current: 100 A

The end of the array will be 43-45ft away from the Growatt and batteries. To the best of my knowledge I should use 8 gauge wire from the panels to the Growatt, and possibly 4 gauge between batteries? Any help would be appreciated.
Click to expand...
 
amberpp1 said:
I would prefer the 5kW, and really we should have more batteries with the amount of cloudy days we get here. I had just hoped to squeeze by with 4 for now, but if I need 8 I will just have to work it out
I am a little confused on the compatibility with North America thing, I see on the data sheet it says 230VAC, but signature solar lists it at 240VAC
In David Poz’s video they show it seemed he was using the inverter as a 240VAC with an auto transformer to split the 240VAC into two phases of 120vac?
Click to expand...
I'm not sure what David Poz did but for the North American market its typical to either run a single leg of 120VAC or 2 legs of 120VAC that can be combined to make 240VAC.
I guess you could add a transformer after the inverter but that is going to be an added expense.
I'm not understanding whatever the attachment is meant to convey.
 
I went and checked David Poz's video.
This is the auto-transformer.
Price seems good and looks like a decent solution.
shop.signaturesolar.us

5kW Midpoint Transformer by Solar Edge

This is a listing for: (1) SolarEdge SEAUTO-TX-5000 midpoint transformer Designed to be paired with a 240V international inverter, like the Growatt 5000 ES stackable inverter. You can also use this unit to balance the loads on an Outback FXR series or a Sunny Island inverter stack. Features...
shop.signaturesolar.us
 
I appreciate your help
So say I manage to get 4 more batteries so I can have 8 in 4S2P, and I get one of these transformers, wire-wise you think I would need 2 awg between the batteries and inverter?
I was trying to figure out the awg for the wire coming from the panels to the charge controller by using (panels amperage x systems voltage)/(VDI x distance between panels and charge controller), but I am struggling with determining the VDI
I wasn’t even sure if this was the correct equation to be using so I had hoped to find some guidance on that front
 
Hypothetically, would it work if I were to use 4 of the larger SOK Batteries that run on 24V 206amp hour, set up in 2S2P? These still have a max discharge current of 100 amps, but I thought it would mean less room needed for storage and would give me a little over twice the amount of stored kwh that 8 of the smaller batteries would
 
amberpp1 said:
Hypothetically, would it work if I were to use 4 of the larger SOK Batteries that run on 24V 206amp hour, set up in 2S2P? These still have a max discharge current of 100 amps, but I thought it would mean less room needed for storage and would give me a little over twice the amount of stored kwh that 8 of the smaller batteries would
Click to expand...
Assuming the SOK batteries have a continuous discharge rate of 1c which is 206ah, should be fine.
And assuming that SOK supports having their batteries configure serially.
Please verify that they do.
 
smoothJoey said:
And assuming that SOK supports having their batteries configure serially.
Please verify that they do.
Click to expand...
SOK batteries support up to 4 in series for up to 48V. I have two SOK 206Ah in series for my 24V setup.

amberpp1 said:
Hypothetically, would it work if I were to use 4 of the larger SOK Batteries that run on 24V 206amp hour, set up in 2S2P? These still have a max discharge current of 100 amps, but I thought it would mean less room needed for storage and would give me a little over twice the amount of stored kwh that 8 of the smaller batteries would
Click to expand...
4 SOK 206Ah in 2S2P would give you 24V with 412Ah capacity with a total max discharge of 200A. But you still can't run a 5kW inverter with that since at 24V it would be over 200A.

You would still want a 48V system for a 5kW inverter. So whether you use SOK 100Ah or SOK 206Ah, you would need 8 batteries in 4S2P to get 48V and a max discharge current of 200A. Using the 206Ah over 100Ah just gives you double the capacity (more run time).
 
rmaddy said:
SOK batteries support up to 4 in series for up to 48V. I have two SOK 206Ah in series for my 24V setup.


4 SOK 206Ah in 2S2P would give you 24V with 412Ah capacity with a total max discharge of 200A. But you still can't run a 5kW inverter with that since at 24V it would be over 200A.

You would still want a 48V system for a 5kW inverter. So whether you use SOK 100Ah or SOK 206Ah, you would need 8 batteries in 4S2P to get 48V and a max discharge current of 200A. Using the 206Ah over 100Ah just gives you double the capacity (more run time).
Click to expand...
If I had 8 of the 206AH batteries in 4S2P, wouldn't the 4 in series give me 96V?
My thought process was that 2 in series would provide 24V x 2, giving me the 48V I need for the 5kw system. Then if I had 2 parallel sets of these, each set having a max discharge current of 100A, the max discharge would become 200A, which would be more than the 156.25A smoothjoey found would be being pulled from the batteries...if that makes sense?
 
amberpp1 said:
If I had 8 of the 206AH batteries in 4S2P, wouldn't the 4 in series give me 96V?
Click to expand...
No. The SOK 206Ah is a 12V battery. SOK has a 24V 100Ah battery coming out soon, according to their website.
 
16 panels x 250W = 4000W

4 batteries x 12V x 100 Ah = 4800 Wh

4000W/4800Wh = 0.8C, exceeds 0.5C max charge rate of battery.

You may be able to program inverter/charger to limit to a lower maximum charge current.
If you orient half your panels at 10:00 AM sun and half at 4:00 PM sun, the 90 degree angle between them means 0.7x the area presented to the sun at any moment. 4000W x 0.7 = 2800W peak. You get more hours of charging, closer to 2400W max. With PTC vs. STC, probably just about 0.5C

The lithium battery can take 0.5C only at around nominal 25 degrees C. Max current is reduced at lower temperature, perhaps 0.05C near freezing. With 0.5C available from system, change low-temperature charge disconnect in BMS. I would suggest 15 degrees C minimum, 50 degrees C maximum.

diysolarforum.com

Why you cannot charge LiFePO4 below 0 degrees Celsius

...I glazed over...Soooo far past me...... but, does this mean that the claims of the -20F chargeable LiFePO4 cells could be true? Based on what i’ve read in this forum, not for any practical use. I’m no expert on the matter, though.
diysolarforum.com diysolarforum.com

"I was going to wire the batteries in series to make a 48V battery bank."

Confirm the battery is compatible with that series configuration. When the BMS disconnects, its FETs will need to withstand the 48V to 60V it will see. Some brands can, some brands can't.

Use a class T fuse on battery. Lithium cells have specs like 0.25 milliohm max, 0.17 milliohm typical measured. Divide 3.5V/0.00017 = 20,600A short circuit capability. Class T is a perfect fit. If these 100 Ah batteries have higher IR, a somewhat lower current might be calculated and a lesser fuse could be OK.
 
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