Parallel or Series connections on Solar panels

[Frans Ackermann]

With a 5kw 48v Inverter and 6 panels, is it best to connect all panels in series, or parallel?

[georgelza]

it's a combination of how big the panels are, they max V and X output, your Charge controller capability (might be part of your Inverter or seperate) and the direction/roof space.

for the 48V input to inverter, ye you will require 4 x 12V batteries.

The panels feed the Charge controller, which feeds the batteries, which feed the inverter.

I'm guessing you will end with 2 strings of 3 panels in series, that also allow you to easily go to a 3rd and a 4th string later, just adding more parallel streams, as much as your charge controller can handle, as much as your roof can handle and as much inverter can handle (if it is a Voltronic design, that switches between input, no use in having more capability / panels than your Charge controller or inverter can handle, as in installed capacity).

G

[Jaws]

I would guess that Frans has an Axpert inverter with a built in MPPT  

 

And  guess number two would be that his panels has an open circuit voltage of 40 V and operating votage of 32 V

2 parallel strings of 3 panels = 120 V < 145 Vdc        60 Vdc < (3x32 V) < 115 Vdc

 

 

 

[Coulomb]

We need to know is the inverter a PWM or MPPT model? 

If the latter, is it a 145 V PV max model, or a 450 V PV Max? It should say on the sticker on the side.

Edit: I'm assuming an Axpert inverter. The full model number is always a big help.

Edited April 9, 2019 by Coulomb

[Frans Ackermann]

[Coulomb]

Ok, @Frans Ackermann, that's a genuine Axpert 5 kVA 5 kW with 80 A (at battery side) MPPT solar charge controller. It seems to be a 64 V model (max battery voltage 64 V under charge). It presumably comes with 72.XX firmware, and if so can use patched firmware version 72.20e if you wish.

If you have 60-cell panels (usually the ones around 250-260 W), then you can definitely use strings of three (3) in series. Parallel as many strings as you want until you just exceed a total of 4000 Wp; up to 4800 Wp should be Ok. If you have 1 or two panels left over, you can't use them (get one or two more when you can afford it, to make another string of three).

If you have 72-cell panels (usually the ones around 190-220 W or 300+ W), then you'll be OK with strings of three in series, provided that you don't regularly get cold nights (say less than -2°C). If you do, you'll need strings of two (2), and as many strings of 2 up to the 4800 Wp limit. If you have one panel left over, you can't use it; get another one panel to make another string of two in series.

To answer your original question, neither pure series connection or pure parallel connection will work. All series (of 4+ panels) will end up too high a voltage, damaging your solar controller. All parallel will be too low a voltage, and won't do anything.

[Frans Ackermann]

Thanx Coulomb. The installation is basically to cover the house in case of load shedding, its got 4 x 200ah batterys. When there is load shedding everyday, the batterys dont get charged fully by the solar panels. There is 3 fridges, 2 computers and the lights of the whole house connected. Is it better to get more batterys or solar panels?

 

[Coulomb]

6 hours ago, Frans Ackermann said:

Is it better to get more batterys or solar panels?

200 Ah is probably just adequate. You didn't say what nominal power your 6 panels are, but even if they are 300 W, that's only 1800 W at the very best of times. You could probably use more panels, especially if they really aren't enough to recharge the battery.

You might be running into the premature float bug, however.

[SilverNodashi]

13 hours ago, Frans Ackermann said:

Thanx Coulomb. The installation is basically to cover the house in case of load shedding, its got 4 x 200ah batterys. When there is load shedding everyday, the batterys dont get charged fully by the solar panels. There is 3 fridges, 2 computers and the lights of the whole house connected. Is it better to get more batterys or solar panels?

 

solar panels are cheap and it always help to have a bit more, especially in winter. The 200ah battery bank is on the lower end, as you only have 100ah to work with if you limit it to 50% DOD. So I would incresse this as well if you can.

[Frans Ackermann]

Can I mix panels? Say line 1 is 3 x 60 cell 150w panels in series, and line 2 is 3 x 72 cell 380w panels in series, The 2 lines is then connected in parallel.

[Dex_]

42 minutes ago, Frans Ackermann said:

Can I mix panels? Say line 1 is 3 x 60 cell 150w panels in series, and line 2 is 3 x 72 cell 380w panels in series, The 2 lines is then connected in parallel.

I am no expert but no... your strings at least need to be close enough to each other that is a massive difference

I would be interested to hear differently.

 

you could however put the other string on a seperate charge controller potentially i beleive would be the easiest

Edited October 8, 2019 by Dex_

[Coulomb]

21 hours ago, Frans Ackermann said:

Can I mix panels?

Basically, no, not 60 cell and 72 cell. One set or the other will be far from their optimal operating point. You also risk pushing power from one string to another, and I believe that this could even be a fire risk.

[wehanvdw]

270w panels 

open v 38.3

open 9.20

max 31.1v

8.68amp 

axpert inverter should 6 pX2 s or keep it 3pX4s

 

400AH oliter battery bank gel