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Old 19-04-2020, 11:19   #1
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Solar Capacity

Hi all,

I have a Victron Solar MPPT Charger 75/15 that has a Vmax of 75v and 15A charge capacity. I take it that according to this data sheet (here) that the max solar array I can have is 220W on a 12V system. Am I reading it correctly?

Many thanks.
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Old 19-04-2020, 11:39   #2
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Re: Solar Capacity

Yes.

There is a spreadsheet 3/4 of the way down this page which you can use to check the cable sizes you are using. Worth 10 minutes effort:

https://www.victronenergy.com/suppor...loads/software
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Old 19-04-2020, 12:00   #3
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Re: Solar Capacity

Ah yes, that's a good sheet, thank you.
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Old 19-04-2020, 12:28   #4
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Re: Solar Capacity

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Originally Posted by lawrence_craig View Post
Hi all,

I have a Victron Solar MPPT Charger 75/15 that has a Vmax of 75v and 15A charge capacity. I take it that according to this data sheet (here) that the max solar array I can have is 220W on a 12V system. Am I reading it correctly?

Many thanks.

Just to be clear, the maximum sized solar array you should use with one 75/15 charger is 220 watts.

You can use multiple 75/15 chargers & array configurations to expand the total amount of energy going into the 12 volt system.

I personally have 1 charger for each panel to isolate the effects of shading that degrade array output.
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Old 19-04-2020, 13:07   #5
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Re: Solar Capacity

To be a bit clearer, you CAN connect more than a 220W panel to this controller, but the controller would still not output more than 15 amps of charge current. Not sure why you might want to, but you could...

Higher power availability from the panel will not hurt the controller as long as you are within the allowed PV Open circuit voltage and PV short circuit amperage specifications
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Old 19-04-2020, 14:04   #6
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Re: Solar Capacity

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Originally Posted by SVHarmonie View Post
To be a bit clearer, you CAN connect more than a 220W panel to this controller, but the controller would still not output more than 15 amps of charge current. Not sure why you might want to, but you could...

Higher power availability from the panel will not hurt the controller as long as you are within the allowed PV Open circuit voltage and PV short circuit amperage specifications

Itís really not that uncommon to not get rated power from panels on a boat due to shading etc. So I can see the logic in overrating the controller, plus you would get a lot more hours of the day at the 15 amp limit.
As 250W panels are so common it might be that you can get a deal on them.
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Old 19-04-2020, 14:26   #7
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Re: Solar Capacity

You can connect more than 220w if you want to accommodate shading. You will never get 220w out of a 220w or two 110w panels anyway.
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Old 20-04-2020, 01:34   #8
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Re: Solar Capacity

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Originally Posted by mikedefieslife View Post
You will never get 220w out of a 220w or two 110w panels anyway.
If you are cruising areas with reasonable solar insolation, you should find the maximum power output of each solar panel matches the rated output or at least very close to this number. It is not unusual to slightly exceed the rating with good installation and quality panels.

These outputs will be seen occasionally and briefly, but they do confirm that the installation and panels are performing as they should be. If you are not seeing these results then some troubleshooting should be undertaken.

Nearly all solar regulators can limit their current and therefore prevent damage if the panels deliver excessive current (but not voltage), but as well as throwing away power, relying on this self protection mechanism to avoid disaster is not a great policy in my view. MPPT regulators are not the most reliable devices and the popular Victron controllers use passive cooling and run reasonably hot even when sized correctly.

Victron suggest limiting the 75/15 to a maximum of 220w for a 12v system.
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