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Ched

Solar in UK in Winter?

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Trying to see how feasible it is to be without EHU in winter in the UK with solar. Not yet bought a van but doing the ground work :-)

Thinking of probably no more than 7 days away at a time without EHU on CL/CS type sites but would like to use van all year if possible?

 

I am a gadget freak and think we will use a lot of power. TV is 40watts ( 3.3A) then there is the blown heating fan ?A, LED lights ?A, water Pump ?A, TV antenna amplifier ?A. Not to mention wanting to charge lipo batteries for racing quadcopter, maybe not in winter as fingers too cold to fly properly :-). 

So I was thinking of 2x100w solar panels on roof with mppt controller would be able to maintain almost a full 110Ah leisure battery?

 

Do you think that would be OK in winter in UK or am I being a bit optimistic?

 

Now the tricky one.

If we want to use the microwave and a hairdryer now and again do you think we would need 2 x 110Amp batteries to power a 2000w inverter?

 

My partner is keen on a generator with lpg conversion as she wants to be able to use anything electrical but I am not too keen on a geny as I feel they are a bit antisocial, a fairly expensive, and heavy, not that an additional leisure batter is light :-)

 

Any help would be great, thanks.

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Think the term is oxymoron.....what you are seeking wouldn't work with an array as big as Jodrell Bank!

Sorry

Geoff

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I cannot see how you would sustain your usage of power, especially as you are a self confessed gadget freak, given the British weather and lack of clear skies to recharge your main battery.  It would all be hit and miss and weather dependant and I imagine quite stressful. Having a generator would work but lots of sites simply dont allow them. 

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Can solar panels work in UK winter? Yes

Do you get as much power out of them as in summer? Nowhere near!

Will you get enough for your needs? How long is a piece of string?

Can you use an inverter to power a microwave and/or hairdryer and inverter with solar power? Yes, BUT .you need an impractical number of batteries and huge panels, even in summer. (several previous threads discuss this.)

 

Many CLs and CSs have ehu.

Many people get by for 7 days without either ehu or solar, many need a second battery and to be careful how much they use.

A generator is a more practical option, or as a backup.

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1 hour ago, Ched said:

Trying to see how feasible it is to be without EHU in winter in the UK with solar. Not yet bought a van but doing the ground work :-)

Thinking of probably no more than 7 days away at a time without EHU on CL/CS type sites but would like to use van all year if possible?

 

I am a gadget freak and think we will use a lot of power. TV is 40watts ( 3.3A) then there is the blown heating fan ?A, LED lights ?A, water Pump ?A, TV antenna amplifier ?A. Not to mention wanting to charge lipo batteries for racing quadcopter, maybe not in winter as fingers too cold to fly properly :-). 

So I was thinking of 2x100w solar panels on roof with mppt controller would be able to maintain almost a full 110Ah leisure battery?

 

Do you think that would be OK in winter in UK or am I being a bit optimistic?

 

Now the tricky one.

If we want to use the microwave and a hairdryer now and again do you think we would need 2 x 110Amp batteries to power a 2000w inverter?

 

My partner is keen on a generator with lpg conversion as she wants to be able to use anything electrical but I am not too keen on a geny as I feel they are a bit antisocial, a fairly expensive, and heavy, not that an additional leisure batter is light :-)

 

Any help would be great, thanks.

Hi Ched,

 

You can achieve what you want by various means, I have solar panels on my roof and a 3500w Purse Sine Wave inverter. I have one 110a/h battery installed in the caravan and another in a portable box that I can strap down in the boot of the car or my van. It then plugs in to split charge system for the towbar and as I drive around in the day or evening it charges that battery from the vehicle. Back at the caravan it plugs in and is in parallel to the existing caravan battery. You can find suitable boxes in marine shops for speedboats etc.

 

I do also have a Honda EU20i as a backup, I was going to change it over to LPG and plug it in to the BBQ point but never bothered, I dont have to use it very often, when I do it's quiet anyway.

 

AJG

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Thanks for all the replies. They are all helpful.

We did have a 2001 motorhome that came with an 80 watt solar panel and a pwm controller plus a 12v microwave from the factory! So we were a bit spoilt, plus we used a 2000w inverter from engine battery when engine running. But that was a few years ago. I was hoping things had moved on a bit.

 

I do realise solar panels give out significantly less  power in winter than summer. I was hoping that they might generate about 20% during daylight hrs.  I suppose that's only about 10Ah with 200 watts of solar for 6 hrs!

 

Maybe a second removable battery would help. I am not sure about connecting a fully charged battery to a partially charged battery as the current flow between the 2 to equalise could be massive! 

Oh just thought my lipo battery chargers are capable of being powered by a lead acid (12v) and charging another lead acid (12v) with regulated current and voltage with low input voltage safety cutoff. So I could use a second battery to top up the charge of the main battery.

That would be fairly easy to do using the 'split charge' cable in the car and a sealed box with vent. 

Think I will need to put more thought in to this.

Cheers

 

 

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46 minutes ago, Ched said:

Thanks for all the replies. They are all helpful.

We did have a 2001 motorhome that came with an 80 watt solar panel and a pwm controller plus a 12v microwave from the factory! So we were a bit spoilt, plus we used a 2000w inverter from engine battery when engine running. But that was a few years ago. I was hoping things had moved on a bit.

 

I do realise solar panels give out significantly less  power in winter than summer. I was hoping that they might generate about 20% during daylight hrs.  I suppose that's only about 10Ah with 200 watts of solar for 6 hrs!

 

Maybe a second removable battery would help. I am not sure about connecting a fully charged battery to a partially charged battery as the current flow between the 2 to equalise could be massive! 

Oh just thought my lipo battery chargers are capable of being powered by a lead acid (12v) and charging another lead acid (12v) with regulated current and voltage with low input voltage safety cutoff. So I could use a second battery to top up the charge of the main battery.

That would be fairly easy to do using the 'split charge' cable in the car and a sealed box with vent. 

Think I will need to put more thought in to this.

Cheers

 

 

A common mistake, in fact its not massive at all.  A fully charged battery will have a terminal voltage around 12.65v a flat battery will have a terminal voltage of 11.89v or thereabouts. A difference of only 0.76v now assuming the terminal voltage of the flat battery doesn't rise (it will) and the fully charged battery doesn't drop (it will too) if we assume the connecting cable has a resistance of 0.05 ohms (very low and would have be good quality connectors) the current flow would be 15 amps maximum, the likelihood is that a) you wont have the flat and full scenario b) the resitance will be greater than 0.05 ohms all of which will reduce the 15 amps. 

Try it with a clamp meter, your will be surprised.

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Last year on a particularly dull December day our 150W SP put a grand total of 3.6 Ah in to the battery. 

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To give you an idea of the difference in solar panel output winter to summer I have a 3.9Kw 15 panel array on the roof of my house where there is no shade at any time of the day and they are angled towards the sun. A solar panel on a caravan roof will be flat. 

On 22nd June this year it was a really sunny day it generated around 27 kilowatt hours, that being the highest single days generation figure for the entire year! 

During Last December the highest daily figure  was 6.73 kilowatt hours  so only about 25% of the June figure. On one (clearly grotty)  day it was ONLY  0.18 kilowatt hours, which by anyone’s standard ain’t much! 

Extrapolate that to the output of your proposed solar array! 

 

So to sum up I think you will not be able to do what you want off grid. Remember If you have two batteries you will still only have the output from one solar panel to charge them both.

 

Sorry to burst your bubble.

 

Andy

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2 hours ago, AJGalaxy2012 said:

A common mistake, in fact its not massive at all.  A fully charged battery will have a terminal voltage around 12.65v a flat battery will have a terminal voltage of 11.89v or thereabouts. A difference of only 0.76v now assuming the terminal voltage of the flat battery doesn't rise (it will) and the fully charged battery doesn't drop (it will too) if we assume the connecting cable has a resistance of 0.05 ohms (very low and would have be good quality connectors) the current flow would be 15 amps maximum, the likelihood is that a) you wont have the flat and full scenario b) the resitance will be greater than 0.05 ohms all of which will reduce the 15 amps. 

Try it with a clamp meter, your will be surprised.

Interesting. I would have thought that both batteries internal resistance would have players a part? ie. A 110ah leisure battery is capable of discharging something like 700amps for very short duration. So v=ixr therefore 12.65/700 =0.02ohms. So looking at the 2 batteries plus the cables as the entire circuit the resistance will be very low and this a high current will flow. If you remember when jump starting a car the negative to the dead car goes to the chassis not the battery as the dead battery will be charged fast and may produce flammable hydrogen and removing the negative from a battery could cause a spark igniting the gas. 

All the above said I have never measure the current when connecting a partially charged battery to a full one. 

 

What I do know is that my racing quadcopter lipo batteries will blow pcb tracks on a parallel charge board if there is more than 0.5v difference in batt voltage and they are only 1.5AH 16v but can discharge over 120Amps in short bursts. 

 

Don't get me wrong I am not disagreeing with your measurements just trying to understand things in my head. Always better to listen and learn from people with practical real world experience that theory. 

Thanks for your experience and making me think. 

2 hours ago, Mr Plodd said:

To give you an idea of the difference in solar panel output winter to summer I have a 3.9Kw 15 panel array on the roof of my house where there is no shade at any time of the day and they are angled towards the sun. A solar panel on a caravan roof will be flat. 

On 22nd June this year it was a really sunny day it generated around 27 kilowatt hours, that being the highest single days generation figure for the entire year! 

During Last December the highest daily figure  was 6.73 kilowatt hours  so only about 25% of the June figure. On one (clearly grotty)  day it was ONLY  0.18 kilowatt hours, which by anyone’s standard ain’t much! 

Extrapolate that to the output of your proposed solar array! 

 

So to sum up I think you will not be able to do what you want off grid. Remember If you have two batteries you will still only have the output from one solar panel to charge them both.

 

Sorry to burst your bubble.

 

Andy

Thanks very much for the real world figures. Very helpful. I have no problem with getting my bubbles burst :-) 

Basically solar won't really do much at all on dull winters day. Maybe have to use ehu in winter :-) 

Thanks 

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5 hours ago, Ched said:

Interesting. I would have thought that both batteries internal resistance would have players a part? ie. A 110ah leisure battery is capable of discharging something like 700amps for very short duration. So v=ixr therefore 12.65/700 =0.02ohms. So looking at the 2 batteries plus the cables as the entire circuit the resistance will be very low and this a high current will flow. If you remember when jump starting a car the negative to the dead car goes to the chassis not the battery as the dead battery will be charged fast and may produce flammable hydrogen and removing the negative from a battery could cause a spark igniting the gas. 

All the above said I have never measure the current when connecting a partially charged battery to a full one. 

 

What I do know is that my racing quadcopter lipo batteries will blow pcb tracks on a parallel charge board if there is more than 0.5v difference in batt voltage and they are only 1.5AH 16v but can discharge over 120Amps in short bursts. 

 

I fly on a regular basis a heavy lift drone (19.8Kg inspecting wind turbines, that has onboard 2 x 16,000 mAh 6S batteries which are flat in 14 minutes! I understand what youre saying about LiPo's and parallel charging. a 3s LiPo will have a difference of 3.6v between full and flat instead of the 0.75v for a lead acid. LiPo's with a burst rating of 80c do have very low internal resistance for sure, the tracks on the parallel charging board dont compare to some decent sized cables. On my setup Ive never seen anything greater than about 12 amps when taking the battery from the car and connecting to the caravan, try it with a set of jump leads and a clip on ammeter, it works for sure. I use an Anderson connector to  connect the portable battery.

 

image.png.b5576e22c578467b9786944993ddb1aa.png 

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4 hours ago, AJGalaxy2012 said:

I fly on a regular basis a heavy lift drone (19.8Kg inspecting wind turbines, that has onboard 2 x 16,000 mAh 6S batteries which are flat in 14 minutes! I understand what youre saying about LiPo's and parallel charging. a 3s LiPo will have a difference of 3.6v between full and flat instead of the 0.75v for a lead acid. LiPo's with a burst rating of 80c do have very low internal resistance for sure, the tracks on the parallel charging board dont compare to some decent sized cables. On my setup Ive never seen anything greater than about 12 amps when taking the battery from the car and connecting to the caravan, try it with a set of jump leads and a clip on ammeter, it works for sure. I use an Anderson connector to  connect the portable battery.

 

image.png.b5576e22c578467b9786944993ddb1aa.png 

Cheers for the reply. Heavy lift multi rotor, cool. Mine are built just for speed and acrobatics I can drain a battery within 2mins if I go for it :-)

I have never checked the current when connecting  2 lead acids batts when connecting different voltages. I don't doubt your readings at all. I will give it a go and see.  I do like the Anderson connector, I used them on my 2000watt inverter when hooking it up to motorhome starter battery.

Thanks again for the info, very helpful. Happy Flying. 

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