I'm in the Australian queue for EV6

Zappi installed, just need to wire into the new breaker sub panel ( which I haven't started yet ! )
Power cable is run.
Comms cable is run
CT cable is run.

Just got to get my act together and get the sub panel done !




"Hmmm that's and interesting way to wire the panels, haven't seen that before ? "

How so ?

This is how it was with the two strings north plus the 2 single strings east and west.
Blocking diodes on the east west to stop one reverse biasing the other at the beginning / end of that day.
Diodes on north because I had morning shade on the north east string, and then afternoon shade on the north west string.

The diodes stop any reversed bias going back into the shaded string.
Because the PV panels are a high impedance current source, the shaded ( or worse aligned string ) voltage can increase to the same voltage as the other string, and thus forward biasing that diode and contributing power to the circuit.

Fascinating to watch the string voltages as the MPPT did its thing !

A few "engineers" told me it wouldn't work, which is why I tried it ! and yes, it definitely does work !!

The breakers are DC type and thus polarity conscious.

Having each leg go thru 2 breakers in series gives much better isolation in case of arcing if the breaker trips under load.
Removing the bottom links and replacing with diodes was an elegant solution for me

AndyM said:

panels built in blocking diodes

Click to expand...

Not really. Those are bypass diodes to allow the current from generating cells to bypass cells that are not generating. The don't stop the panel from reverse biasing.

In fact, in snowing climates, there is a trick that you can reverse bias the panels to heat them up and melt off the snow !

Then once the snow is gone, remove the bias and let the panels produce.

Have to have very careful control over voltage and amps , but works a treat apparently.

Because each solar cell is effectively a diode ( 0.6V ) in a big string to get to say 40 volts, if you apply reverse bias higher that the panels open circuit voltage rating , the cell "diodes" will bias on and conduct.
If paralleled with another string that is producing power, that power gets dumped into the shaded panels and doesn't get to the inverter. Ultimately damaging the shaded panels.

The diodes were standard off the shelf 1000v 20 amp jobbies. a couple of bucks each.

I actually saw some MC4 connector diodes on Allie express. www.aliexpress.com/item/1005003198899356.html

Easy solution !

AndyM said:

Hmmm that's and interesting way to wire the panels, haven't seen that before ?

Click to expand...

Just for clarity

in the quad breaker block. ( one for each string of panels )
breakers numbered 1 - 4 from left to right

positive from 1 string of panels into the top of breaker 1
positive from that string of panels to the inverter out of the top of breaker 2 with a diode forward biased between the bottom of breakers 1 & 2


Negating from the same string of panels into the top of breaker 4
Negative from that string of panels to the inverter out of the top of breaker 3 with a diode forward biased between the bottom of breakers 3 & 4

Blocking diodes on both the positive and negative leads just to be sure ( negatives are normally all common'd at the inverter, so probably not required and are normally grounded as well )