Safety first (1 Viewer)

[Vikdikdok]

Can I safely connect 3 12v solar panels 1x120w, 1x115w& 1x100w (total 335w) together through my Victron 75/15 MPPT controller ?

 

[RogerIvy]

Assuming you plan to connect in series:
You may exceed the maximum voltage (75v) which, according to Victron may damage the controller. Depends on the VOC of the panels. You could also exceed the max amps of 15 which will just cause your controller to reset for a few seconds and try again.

If you connect in parallel:
Voltage-wise you will be fine. You will probably exceed the max amps from time to time and the controller will simply reset and retry.

TBH you’d be better off with a 100/20 and they’re reasonably inexpensive.

 

[Vikdikdok]

I'll go with parallel, cheers

 

[Tombola]

max wattage for the 75/15 = 220 of course its a question of how often are you gong to get the max out of them = hardly ever if you do put 220 up there

 

[Googlebot]

You will be pulling the power down of the 120 and 110 panels if you pair them with the lower one. You also need to check the voltage is the same on the panels.

It’s only in the summer my panels make near their quoted output so I would go for it.

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[Lenny HB]

Wiring different panels in parallel you will get some loss but probably not enough to worry about. A rough rule of thumb, if the difference in output voltage is less than ½v it's not enough to worry about.

The output will be limited by the panel with the lowest voltage.
To work out your power output take note of the onload voltage and current of each panel. add up the current and multiply the total current by the lowest panel voltage.

You will get far higher losses connected in series as you will be limited by the panel with the lowest current.
To work it out take the sum of the voltages and multiply by the current of the lowest panel.

I would always go for parallel on a Motorhome roof as if one panel is in shade you will still have the output from the other panels, in series you would lose the lot.

 

[Vikdikdok]

these are the odd wattage panel’s that were sitting in my shed & decided to fit them over the south facing bay window in our house which gets all the sun (when it shines), these via a 200A lithium battery power all the 12v LED
lights in our house - (of which there are 12 (as Sylvia likes ‘mood’ table & side lights) in both the dining & front rooms) ho hum - and of course it drastically reduces mains electricity & saves money so it’s a win win keeping her happy & saving me money!

 

[Guigsy]

Assuming you plan to connect in series:
You may exceed the maximum voltage (75v) which, according to Victron may damage the controller. Depends on the VOC of the panels. You could also exceed the max amps of 15 which will just cause your controller to reset for a few seconds and try again.

If you connect in parallel:
Voltage-wise you will be fine. You will probably exceed the max amps from time to time and the controller will simply reset and retry.

TBH you’d be better off with a 100/20 and they’re reasonably inexpensive.

I know you shouldn't exceed the voltage. But I think having the panels capable of supplying more current than the controller can take is fine. It'll just max out at 15 amps output and the rest goes unused. Like when you plug a low power device into a beefy battery. So when it's really sunny, you won't be getting the maximum benefit.

 

[Vikdikdok]

- at least the ‘power’ is free regardless of any wastage

 

[Lenny HB]

these are the odd wattage panel’s that were sitting in my shed & decided to fit them over the south facing bay window in our house which gets all the sun (when it shines), these via a 200A lithium battery power all the 12v LED
lights in our house - (of which there are 12 (as Sylvia likes ‘mood’ table & side lights) in both the dining & front rooms) ho hum - and of course it drastically reduces mains electricity & saves money so it’s a win win keeping her happy & saving me money!

View attachment 844036

Interesting I thought it was for the van.
I assume you are going to disconnect a lighting circuit from the consumer unit and make it a 12v circuit.

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[Vikdikdok]

No, I’ve no plans to isolate or intergrate the 240v house power, I’ll keep the 12v system totally separate.

 

[Lenny HB]

No, I’ve no plans to isolate or intergrate the 240v house power, I’ll keep the 12v system totally separate.

What I was thinking it would still be isolated just using the existing cabling.

 

[RogerIvy]

I know you shouldn't exceed the voltage. But I think having the panels capable of supplying more current than the controller can take is fine. It'll just max out at 15 amps output and the rest goes unused. Like when you plug a low power device into a beefy battery. So when it's really sunny, you won't be getting the maximum benefit.

The extra power (exceeding the amps) doesn’t go unused, instead the controller stops charging for a short time (as I recall about 10-20 seconds) as the controller resets and tries again. Our experience is that it is not a problem and no damage to the controller. It just means that under ideal conditions (very good overhead sun on a cool day) it spends more time resetting than charging.

 

[Guigsy]

The extra power (exceeding the amps) doesn’t go unused, instead the controller stops charging for a short time (as I recall about 10-20 seconds) as the controller resets and tries again. Our experience is that it is not a problem and no damage to the controller. It just means that under ideal conditions (very good overhead sun on a cool day) it spends more time resetting than charging.

My brother had a 400w panel on a 30a Victron charger in July sunshine. Ok, not much over, but it just seemed to peg at 30a output.

 

[Raul]

You can set the solar charger in the settings by one amp less than what is rated, and will throttle back as soon as it gets there. No more blips from transient sun. If you over panel a controller, normally the mppt will modulate to its max output. It can overshoot on load disconnect, or cloud lensing, hence the protection kicks in; just set max charging amp to one less than the charger is, giving it a chance to catch up to modulate soon enough.

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[Lenny HB]

My brother had a 400w panel on a 30a Victron charger in July sunshine. Ok, not much over, but it just seemed to peg at 30a output.

I thought the 30 amp was speced for 440 watt input.

 

[Raul]

I thought the 30 amp was speced for 440 watt input.

You know how Victron rates them? 14.4v times max output amps, (multiply for 24-48v), this is the max theoretical output. In reality you can over panel by quite a bit, as long as you stay bellow rated VOC , and below max amps in. Anything within these parameters the converter is capable to modulate the power down, and take in only what the charger is set to. By default is set to max amps out. You can change that to keep the controller cool if it’s over panelled.