how many panels do i need to max the powerwall plus mppts?

[ahreno]

I'm a bit confused by the numbers and how they stack together.

originally i was getting two powerwall 2 but its been changed and i'm getting a powerwall plus and a powerwall 2 for free and am looking to add on some panels. the powerwall plus has its own inverter.

i'm not too worried about blackouts, the grid is quite stable recently. i'd like to just get my pge bill down or erased.

I bought 26 Longi Hi-Mo-5 panels. 411w with up to another 140w bifacial gain. I can get more at $135 each

https://imgur.com/a/A4auvCs

the inverter on the powerwall plus is:

https://imgur.com/a/tFvmCem

am i looking at the "maximum input voltage" of 600 / 48 = 12.5 panels per mppt?

or

operating input range 550 / 48 = 11.45 panels per mppt

or PV mppt voltage range of 480 / 48 = 10 panels per mppt?

i feel like i should max out 3 mppts. probably do a run facing west or at least south west and two facing south. how many more panels do i need to buy?

 

[sunshine_eggo]

You use Voc, so 600/49.8Voc = 12.05 panels

But you must provide some buffer for low temperature voltage effects. 11S would be good down to a little above freezing. I would simply limit them to 10S for extra margin.

The MPPT range is based on Vmp. In most cases, where you don't violate the peak voltage limit, you will satisfy the MPPT range. This is true for your panels in any 2S to 11S string.

13A is the maximum each MPPT can draw from the array. Your panels are 13.12A Imp. good.

19A is the maximum short circuit current each MPPT can be subjected to. Your panels are 13.99 Isc. Good.

For the selected panels, I would limit each MPPT to a single string of 10 panels. If you want to max out three MPPT, 30 panels total.

All panels in a single string must be facing the same direction.

Note that bifacials benefit most when at a notable tilt with 1m of clearance behind the panel - like a steep angle one would expect at Northern latitudes. Flush with a roof means you're probably not going to get much from the backside.

 

[ahreno]

You use Voc, so 600/49.8Voc = 12.05 panels

But you must provide some buffer for low temperature voltage effects. 11S would be good down to a little above freezing. I would simply limit them to 10S for extra margin.

The MPPT range is based on Vmp. In most cases, where you don't violate the peak voltage limit, you will satisfy the MPPT range. This is true for your panels in any 2S to 11S string.

13A is the maximum each MPPT can draw from the array. Your panels are 13.12A Imp. good.

19A is the maximum short circuit current each MPPT can be subjected to. Your panels are 13.99 Isc. Good.

For the selected panels, I would limit each MPPT to a single string of 10 panels. If you want to max out three MPPT, 30 panels total.

All panels in a single string must be facing the same direction.

Note that bifacials benefit most when at a notable tilt with 1m of clearance behind the panel - like a steep angle one would expect at Northern latitudes. Flush with a roof means you're probably not going to get much from the backside.

Thank you! I don't know what 11S or 2S means but the 10 panel answer is what I was looking for.

Would you mind giving me some knowledge on running my wire?

The panels will end up a max of 100' from my batteries and the inverter. What size wire am I running? Can it all go in the same conduit? I assume each string runs on its own wire and not using a combiner box.

My trench is dug and I have 1.25" conduit but I'm thinking that may not be big enough.

 

[ahreno]

You use Voc, so 600/49.8Voc = 12.05 panels

But you must provide some buffer for low temperature voltage effects. 11S would be good down to a little above freezing. I would simply limit them to 10S for extra margin.

The MPPT range is based on Vmp. In most cases, where you don't violate the peak voltage limit, you will satisfy the MPPT range. This is true for your panels in any 2S to 11S string.

13A is the maximum each MPPT can draw from the array. Your panels are 13.12A Imp. good.

19A is the maximum short circuit current each MPPT can be subjected to. Your panels are 13.99 Isc. Good.

For the selected panels, I would limit each MPPT to a single string of 10 panels. If you want to max out three MPPT, 30 panels total.

All panels in a single string must be facing the same direction.

Note that bifacials benefit most when at a notable tilt with 1m of clearance behind the panel - like a steep angle one would expect at Northern latitudes. Flush with a roof means you're probably not going to get much from the backside.

and yes, i'm doing ground mount so the panels should get some gain from bifacial. i dont expect to hit anywhere near max of course. i'll put down some white rock, maybe some white plastic from my greenhouses i have laying around.

 

[hwy17]

Have you figured out if you can get these into the Tesla app successfully? Are you getting them from an Tesla installer?

I got a used Tesla grid tied inverter and was never able to register it, and couldn't access most of the functions I needed because of it.

 

[ahreno]

Have you figured out if you can get these into the Tesla app successfully? Are you getting them from an Tesla installer?

I got a used Tesla grid tied inverter and was never able to register it, and couldn't access most of the functions I needed because of it.

I assume so. I'm getting the batteries (and inverter with the plus battery) thru a power company rebate and they are installing them.

I'm just trying to tie some solar into them diy style.

 

[ahreno]

Thank you! I don't know what 11S or 2S means but the 10 panel answer is what I was looking for.

Would you mind giving me some knowledge on running my wire?

The panels will end up a max of 100' from my batteries and the inverter. What size wire am I running? Can it all go in the same conduit? I assume each string runs on its own wire and not using a combiner box.

My trench is dug and I have 1.25" conduit but I'm thinking that may not be big enough.

Found a calculator that lets me do 500v. is my thinking here correct?
10 panels, 50volts each 13.xx amps.

wired in series.

500 volts 13.xx amps

100ft run

14awg wire minimum

 

[sunshine_eggo]

Thank you! I don't know what 11S or 2S means but the 10 panel answer is what I was looking for.

S indicates series, i.e., 11S = 11 panels in series.

Would you mind giving me some knowledge on running my wire?

The panels will end up a max of 100' from my batteries and the inverter.

Given that you're operating on very high voltage, your wiring losses will be very low.

What size wire am I running?

14awg is likely fine, but you should check the voltage drop:

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

10S, 14awg @ 100 ft, 410Vmp and 14A, you'd get 1.72% voltage drop per MPPT. That's a 1.72% loss in output. It's typical and acceptable. It comes down to $ spent vs. % lost. Your call, but 14awg is the minimum size. I would personally go to 12awg.

Can it all go in the same conduit?

If they fit.

I assume each string runs on its own wire and not using a combiner box.

Yes. Since each string is going to a different MPPT.

My trench is dug and I have 1.25" conduit but I'm thinking that may not be big enough.

3X 12-14awg wires + a ground wire for the array would likely fit.

Your array frames should be connected to each other via a single ground wire. That ground wire should run back through the conduit to the dwelling and be bonded to your earth rod.