Solar panel size

[cosmo68]

Currently have a 90 watt panel, but not enough to keep us powered up. Looking to buy another panel, fully understand difference of connecting in parallel or series. Would like to hear from people with different size panels to see if it’s better getting another 90 watt or bigger.

 

[Jev88]

I believe the rule of thumb is the max solar you can fit/afford combined with the max battery capacity you can fit/afford and have payload for. I happen to have an old 90watt panel and added a new 100 watt alongside it.

 

[Raul]

If this is not enough, I would go new large 300-340w panel and decent mppt controler. New panels are miles better in performance compared to old degraded panels.

 

[cosmo68]

we have 2 85ah batteries and a solar panel is 14 years old, I tested the other week and is 98% of what it should be on paper so pleased with that!

 

[The Wino]

Depends in what way you run out. If the battery is full in the afternoon and runs out in the evening it could be an extra battery you need and maybe more solar. When I fitted a panel last year the bigger capacity ones weren't much more than the smaller ones. I just went for 100w as we had no solar before and never ran out it was an in case panel!

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[CamperJack]

I have 340 watts of solar and 220 ah of battery.

 

[Richard n Ann]

I fitted 150w of solar, mppt controller and an 80ah gel battery. Plenty for us, the solar has the battery recharged by lunchtime, I use the excess then for the small PSW inverter and mains fan if it's hot.

 

[cosmo68]

We are not far off because it’s after 5 or 6 days that the batteries are low

 

[Richard n Ann]

We are not far off because it’s after 5 or 6 days that the batteries are low

First thing I'd do is find out what the current drain is with the van's control panel switched on but everything else off. What equipment do you use? 90w would be ok for us, our main uses are phones, led lighting, water pump and evening TV.

 

[The Wino]

We are not far off because it’s after 5 or 6 days that the batteries are low

Sounds like you don't need a huge extra panel then. How big is your battery?. If it is say 100ah so 50 usable and low after 5 or 6 days I'm sure someone could calculate the shortfall at 10 ah a day in terms of the panel needed to supplement the existing one my guess would be 100w extra would be plenty. It's always easy to buy stuff you don't need!

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[The Wino]

Just looked it up its a very straightforward calculation 10ah at 12v 120wh. So a 100w panel should cover that easily most of the year. By the way I'm an amateur don't treat it as gospel!!. When people say their batteries are fully charged again by breakfast doesn't that mean they've wasted a lot of cash on excess solar and batteries?

 

[Mr mrs tupcox]

We have 450 w of solar keeps us happy all year round ..

 

[Two on Tour]

Just looked it up its a very straightforward calculation 10ah at 12v 120wh. So a 100w panel should cover that easily most of the year. By the way I'm an amateur don't treat it as gospel!!. When people say their batteries are fully charged again by breakfast doesn't that mean they've wasted a lot of cash on excess solar and batteries?

I put together our system to cover us for the winter months when the sun is low and weak and days with little and no sun to speak of when we are off grid.
As a consequence we have way more than we need in the summer months and at low latitudes when abroad, so is it money wasted or money well spent ?

I now harvest more of the power of the sun that would have gone to waste by switching to heating water when our battery is fully charged, which in turn is saving us on propane.

 

[cosmo68]

We have two 85 ah batteries and live in south of France so don’t need much more. The original thread was to get feed back about mismatched panels

 

[Two on Tour]

We have two 85 ah batteries and live in south of France so don’t need much more. The original thread was to get feed back about mismatched panels

Matching the panel voltages is the most important thing if your going to connect different panels in parallel.

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[The Wino]

I put together our system to cover us for the winter months when the sun is low and weak and days with little and no sun to speak of when we are off grid.
As a consequence we have way more than we need in the summer months and at low latitudes when abroad, so is it money wasted or money well spent ?

I now harvest more of the power of the sun that would have gone to waste by switching to heating water when our battery is fully charged, which in turn is saving us on propane.

In your case if it's getting lowish in winter no not wasted at all. But I do think quite a few just spend without thinking what's needed to acheive what they want.