Solar panel wiring for maximum efficiency.

[PaddyHaig]

Indervidual solar panel specs:
Voc: 18.88V (Voltage Open Circuit)
Vpm: 16V (Voltage Power Maximum)
Isc: 7.58A (Amps Short Circuit)
Imp: 6.88A (Amps Maximum Power)
Max system voltage 500V

My question is.
I have 4 x 110w solar panels.
I have wired 2, pair, in series (= 32V @ 8.88A)
and then wired both the pairs, in parallel.
(= 32V @ 17.76A) my MPPT Solar controller

Each indervidual panel creates more than adequate voltage for my needs, as I use a 12V LifePo4 battery system and any one panel will give me 16 Volts.


They are all wired in close proximity to one another, and wired a very short distance to the MPPT controller.

What I'm not sure about. Is should I have wired them all, in parallel, so as to increase the current (Amps) or will the increased Voltage in my mixed configuration, be reduced by the MPPT controller, and converted into Amps?

Please can anyone advise?

 

[FilterGuy]

Indervidual solar panel specs:
Voc: 18.88V (Voltage Open Circuit)
Vpm: 16V (Voltage Power Maximum)
Isc: 7.58A (Amps Short Circuit)
Imp: 6.88A (Amps Maximum Power)
Max system voltage 500V

My question is.
I have 4 x 110w solar panels.
I have wired 2, pair, in series (= 32V @ 8.88A)
and then wired both the pairs, in parallel.
(= 32V @ 17.76A) my MPPT Solar controller

Each indervidual panel creates more than adequate voltage for my needs, as I use a 12V LifePo4 battery system and any one panel will give me 16 Volts.


They are all wired in close proximity to one another, and wired a very short distance to the MPPT controller.

What I'm not sure about. Is should I have wired them all, in parallel, so as to increase the current (Amps) or will the increased Voltage in my mixed configuration, be reduced by the MPPT controller, and converted into Amps?

Please can anyone advise?

You are fine with your configuration. The MPPT controller will convert the energy appropriately.

 

[Whinny]

The best configuration may depend on the brand of your "MPPT" controller-a link or photo would be helpful.

 

[fafrd]

Indervidual solar panel specs:
Voc: 18.88V (Voltage Open Circuit)
Vpm: 16V (Voltage Power Maximum)
Isc: 7.58A (Amps Short Circuit)
Imp: 6.88A (Amps Maximum Power)
Max system voltage 500V

My question is.
I have 4 x 110w solar panels.
I have wired 2, pair, in series (= 32V @ 8.88A)
and then wired both the pairs, in parallel.
(= 32V @ 17.76A) my MPPT Solar controller

Each indervidual panel creates more than adequate voltage for my needs, as I use a 12V LifePo4 battery system and any one panel will give me 16 Volts.


They are all wired in close proximity to one another, and wired a very short distance to the MPPT controller.

What I'm not sure about. Is should I have wired them all, in parallel, so as to increase the current (Amps) or will the increased Voltage in my mixed configuration, be reduced by the MPPT controller, and converted into Amps?

Please can anyone advise?

In general, the closer the string voltage is to your charge voltage (but at least ~2V higher), the better for efficiency (check the manual of your MPPT).

On the other hand, lower string voltage = higher string current = greater wiring losses (I^2R).

You can determine charge efficiency by calculating Pcharge / Psolar (where Pcharge = Vcharge x Icharge and Psolar = Vsolar x Isolar),

If your current 2S2P array is already getting you charge efficiency of over 95%, changing to 1S4P is probably not worth the effort.

But if you are measuring actual charge efficiency well below spec’s values, you may want to try disconnecting 2 panels to make a 1S2P array to see whether charge efficiency is significantly better with lower string voltage.

If so, and your home run wiring is already beefy enough, you’ll need to add 2 more pairs of Y connnectors as well as an inline MC4 fuse to each panel to switch from 2S2P to 1S4P (so probably not worth the trouble and expense unless your gaining at least another ~10% production…).

 

[PaddyHaig]

I am so very grateful of your reply's however I am still a little confused (Not understanding the shorthand algorithms). However, I've been caught up, in an 'in person' debate. With some vanlife friends. Who are adamant, that I have wired my panels up foolishly. They claim, I should of wired all the panels up in parallel, maximising the amperage being delivered to the Votronic Solar controller. However, my method was (This being mainly due to a neater wiring layout for the solar panels) to use the method of wiring as described in my original post. Two panels in series, then the two pairs wired in parallel.

I was counting on my Votronic MPPT controller reducing the excess voltage and converting it into current. However my associates are telling me that this is not possible as MPPT Solar controllers do not convert excess voltage into current. Apparently I should of just maxed out the Amperage by wiring all the panels in parallel. The voltage for such a short run of wiring (Less than a yard or less than a metre) was not an issue.
So the was no need to increase the voltage by wiring in the manner that I chose. All thoughts and feedback on this matter are greatly appreciated.

 

[Quattrohead]

Your Votronic manual will tell you everything you need to know.
MPPT chargers take the available voltage and current, massage it to get the most out of it to charge the battery as quick and hard as it can. BUT, they do need a certain voltage to start this process so obviously the more voltage you can get from the panels as soon as they get light, the sooner the MPPT can start. However, you must respect the maximum voltage input it can take including Voc in cold conditions. Current/watts you can go over some, it will only use what it can process.
You have wired your panels the best way.

 

[fafrd]

I am so very grateful of your reply's however I am still a little confused (Not understanding the shorthand algorithms). However, I've been caught up, in an 'in person' debate. With some vanlife friends. Who are adamant, that I have wired my panels up foolishly. They claim, I should of wired all the panels up in parallel, maximising the amperage being delivered to the Votronic Solar controller. However, my method was (This being mainly due to a neater wiring layout for the solar panels) to use the method of wiring as described in my original post. Two panels in series, then the two pairs wired in parallel.

I was counting on my Votronic MPPT controller reducing the excess voltage and converting it into current. However my associates are telling me that this is not possible as MPPT Solar controllers do not convert excess voltage into current. Apparently I should of just maxed out the Amperage by wiring all the panels in parallel. The voltage for such a short run of wiring (Less than a yard or less than a metre) was not an issue.
So the was no need to increase the voltage by wiring in the manner that I chose. All thoughts and feedback on this matter are greatly appreciated.

Your friends do not know what they are talking about (as long as you truly have an MPPT and not a PWM solar charge controller.

The only reason to prefer all-parallel wiring (1Series4Parallel) over the 2Series1Parallel configuration you have chosen is because you are getting poor charge efficiency when charging a 12V battery from a 32V string.

I’ve already suggested a simple way to check how much better efficieny you would get with an all-parallel array by temporarily disconnecting 2 panels to form a 1S2P array.

 

[SupraSPL]

I like 4 in parallel, more resistant to shading, which might net you a decent amount more power each day. But in your case 4 in parallel would be a max of 35+ amps, so I think your 2s2p 18 amp max is a good way to go.