Solar ?

[headlight]

For those of you with experience of solar roughly how many amps per day would a 115 watt panel through a Victron MPPT controller produce on a clear sunny UK summer's day ?

 

[headlight]

I know that it should produce about 8 amps an hour peak but am just wondering roughly what it would produce over a day in total if it was bright sunshine all day.

 

[Offagain]

If it’s at the optimum angle to the sun all the time with no shade at all, and the sun shines for 8 hours you might get 40amps
According to my auto electrician

 

[Boringfrog]

Where you getting the 8amps figure from?

 

[Phill D]

More like 6amps in peak conditions and that will be very lucky.

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[funflair]

In ideal conditions it will make 115 watts or even a touch more then it depends how flat your battery is to how many amps that makes but 8 would be around maximum. We are out in sunny Germany and making between 2000 and 2400 watt hours in a day out of 520 watts of panel, you could work that back to just under 40ah per day for your 115 panel, we might get more if we needed it but are fully charged mid afternoon.

 

[headlight]

Where you getting the 8amps figure from?

From Vanbitz who fitted the system yesterday.
Initially they were going to fit a 175 watt panel which was the size I was after but after looking at my roof yesterday morning they said there was only room for a 115 watt panel.
I'm just a bit concerned that 115 watts won't produce enough amps.

 

[funflair]

From Vanbitz who fitted the system yesterday.
Initially they were going to fit a 175 watt panel which was the size I was after but after looking at my roof yesterday morning they said there was only room for a 115 watt panel.
I'm just a bit concerned that 115 watts won't produce enough amps.

It all depends on what you take out, 520watts is enough for us when the sun is average and more than on a good day, the more you have the more you use

 

[Boringfrog]

From Vanbitz who fitted the system yesterday.
Initially they were going to fit a 175 watt panel which was the size I was after but after looking at my roof yesterday morning they said there was only room for a 115 watt panel.
I'm just a bit concerned that 115 watts won't produce enough amps.

How to calculate Amps

 

[headlight]

How to calculate Amps

So are you saying that it won't produce what Vanbitz said ?

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[funflair]

How to calculate Amps

Amps are simply a product of watts and volts, the unit of power is watts, on a good day and a tail wind the panel will produce its rated power in watts, how many amps your battery sees is down to the voltage W=VA therefore A=W/V.

 

[Phill D]

So are you saying that it won't produce what Vanbitz said ?

Vanbitz will gave quoted what the panel specified at.

It will depend on the type of solar cells in the panel and the operating voltage.

Personally I trust Vanbitz.

 

[Boringfrog]

Amps are simply a product of watts and volts, the unit of power is watts, on a good day and a tail wind the panel will produce its rated power in watts, how many amps your battery sees is down to the voltage W=VA therefore A=W/V.

I know that, the link was for people who didn't. Some people think with a 12V panel you will divide say 115W/12V which will give you 9.5 amps, but you should divide the Watts by the Maximum power Voltage figure. So say it's a Victron panel as in the following Link it will be 115W/19V = 6.05 Amps.

 

[autorouter]

I'm not convinced by the link in Boringfrog's post. Even if that method works with MPPT controllers (I'm sure it won't) it is only giving you the amps from the solar panel, not the amps output from the MPPT controller. They might be similar, but they might be quite different.

I know that it should produce about 8 amps an hour peak but am just wondering roughly what it would produce over a day in total if it was bright sunshine all day.

I think the 40 amp-hour yield per day that funflair calculated is a good ballpark figure. Day length will vary, depending on the time of year and also the latitude, big difference between Norway and Morocco.

 

[WillH]

As above, how much you need is solely governed by how much you use. Our 100w panel is more than adequate for us in the summer with direct sunshine. In winter however, it's not enough to keep both batteries charged.

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[autorouter]

Some people think with a 12V panel you will divide say 115W/12V which will give you 9.5 amps, but you should divide the Watts by the Maximum power Voltage figure. So say it's a Victron panel as in the following Link it will be 115W/19V = 6.05 Amps.

But if you want the solar controller output, the voltage when actively charging will be about 14.4V, so the amps will be 115/14.4 = 8 amps.

 

[headlight]

I was told that the max amps from the 115 watt panel was a little over 9 amps in full direct sunshine and that the batteries would see about 8 amps.
I realize that max amps will only be produced maybe an hour either side of noon so I was just trying to find out how many amps in total per day the system would deliver in good sunny weather.
I think my usage will be around 40 amps and I am a little concerned as to whether this system will deliver 40 amps a day.
Unfortunately I am stuck with it as Vanbitz said they couldn't fit a bigger panel

 

[funflair]

I know that, the link was for people who didn't. Some people think with a 12V panel you will divide say 115W/12V which will give you 9.5 amps, but you should divide the Watts by the Maximum power Voltage figure. So say it's a Victron panel as in the following Link it will be 115W/19V = 6.05 Amps.

Doesn't it depend whether you want to know how many amps the panel is producing or how many amps are going into your battery ?

 

[headlight]

Well panic over.
Iv"e just done 4 nights not on EHU and my power consumption and solar were fine.
First day was sunny and the solar had the batteries fully charged by 11.30am after the nights usage.
Second day, even though it was very cloudy and overcast, batteries were fully charged late afternoon.
Third day it rained on and off and was very gloomy and batteries weren"t recharged fully, maybe 4-5 amps produced all day.
Fourth day batteries were fully charged by 1.00pm.
I think I overestimated my expected usage by quite a bit and rather than using 40 amps a day I actually used around 15 amps a day.
Fridge worked fine on gas as did the hot water which was the first time either had been used on gas as previously I"d always been on EHU.
Second toilet cassette got used for the first time also

 

[funflair]

God result, you can't beet a real world test to put your mind at rest, now start using more power and you can have more solar and more batteries

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[headlight]

God result, you can't beet a real world test to put your mind at rest, now start using more power and you can have more solar and more batteries

Unfortunately the single 115 watt panel was all Vanbitz had room to fit.

 

[The Wino]

Unfortunately the single 115 watt panel was all Vanbitz had room to fit.

As you say it's providing enough to cover what you use so why would you want to pay for more?. I think it's like everything to do with motorhoming you can pay for ever on self leveling lots of solar tons of payload then of course it will need a new huge motorhome that drinks like a fish etc etc. If your set-up does what you want I'd say on the basis of stick or twist....... stick!
You will get a lot of solar and battery evangelists suggesting ways of adding stuff but if you don't need it what's the benefit

 

[headlight]

Yes my usage was pretty constant at about 15 amps per day.
The last day the solar replaced 2 days use by 1.00pm
I could probably double my usage to 30 amps a day and the solar would replace it, provided the weather was ok.
I've got 2 X 100AH lead acid leisure batteries so 100 amp usable, although personally I'd err on the side of caution so 80 amps usable power.
At 15 amps use per day that would theoretically give me about 5 days even without any solar.

 

[Raul]

I know that, the link was for people who didn't. Some people think with a 12V panel you will divide say 115W/12V which will give you 9.5 amps, but you should divide the Watts by the Maximum power Voltage figure. So say it's a Victron panel as in the following Link it will be 115W/19V = 6.05 Amps.

That’s the panel amps. The controller will push 9-9,5A in bulk.
A mppt controller it’s power in-power out
A PWM controller it’s amps in - amps out no conversion, so it will be the max amps the panel can give. The mppt will convert the extra voltage into amps, down to the battery voltage.

 

[Raul]

But if you want the solar controller output, the voltage when actively charging will be about 14.4V, so the amps will be 115/14.4 = 8 amps.

That’s only true, when the charging hit the CV absorb. Before that, in bulk the battery voltage it’s lower, and specially when under load the voltage will sag allowing max power in if available from the panel.

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[Raul]

Here is a snapshot of my two 115’s portable panels. They are the victron polycrystalline panels on a 100/20 controller. Divide by two for a single panel. Under load, I got 19,2A so about 9,6A for a single under load in good sun.

 

[headlight]

Yes Vanbitz told me that my single 115 watt panel could produce about 9.5 amps in ideal conditions but the batteries would probably get about 8-8.5amps max.

 

[BouncyBoatFolk]

Unfortunately the single 115 watt panel was all Vanbitz had room to fit.

You could have a folding panel as a reserve. The photo shows a snapshot taken of the panel in action recently in France. You could wire it direct to the hab batteries via an Anderson plug, so easy to connect and disconnect.
Mike.

 

[The Wino]

Yes my usage was pretty constant at about 15 amps per day.
The last day the solar replaced 2 days use by 1.00pm
I could probably double my usage to 30 amps a day and the solar would replace it, provided the weather was ok.
I've got 2 X 100AH lead acid leisure batteries so 100 amp usable, although personally I'd err on the side of caution so 80 amps usable power.
At 15 amps use per day that would theoretically give me about 5 days even without any solar.

Sounds like you need more wine more than more solar!