Solar panel efficiency in the UK (aka 100w panel vs the 47w fridge - round 2!) (1 Viewer)

[gerry mcg]

Any idea where I can get one (and how much?) or where do you leave your keys

don't know if it would fit but a LT411 control panel but available here at 87 Euro plus delivery.
https://www.campingshopwagner.de/pr...lfeld-Schaudt-LT411--passend-fuer-CSV409.html

 

[Vanman]

Thanks again for all your suggestions. I'm going to take a step back for a few days and try a couple of experiments with what I've got.

Adding monitors that cover Cab/Hab AND solar looks as though it's probably beyond my comfort zone and the cheaper options are a bit limited and still require fitting (if you have no Hab 12v sockets). The new control panel is highly desirable but doesn't make my beer any cooler

I accept what people say about defining and measuring the problem, but without good sunlight it's all a bit academic anyway.

 

[tonyidle]

Your figurers don't add up, 250w from a 150w panel? Yes they can produce more under ideal conditions than the nomial panel rating but not that much. 250 watts is only around 15.6 amps, as I said in an eaierler post no good working your figurers out at 12 v, with only 12 v output you would never be able to charge a battery.

It's less confusing to use the correct units. It's watts x hours = Watt-hours (Wh).

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[two]

Even some of the ‘better’ motorhomes provide very basic information about battery and water levels. It seems that customers appreciate bling rather than function.

A cheap voltmeter might be a solution for checking the state of charge of your battery and should prevent you from draining it. Maybe get a panel mounted one and put that alongside your ‘control’ panel.

 

[gerry mcg]

It's less confusing to use the correct units. It's watts x hours = Watt-hours (Wh).

Yes, apologies. My op should have quoted Wh rather than W. My mistake

 

[Infinity31]

Even some of the ‘better’ motorhomes provide very basic information about battery and water levels. It seems that customers appreciate bling rather than function.

A cheap voltmeter might be a solution for checking the state of charge of your battery and should prevent you from draining it. Maybe get a panel mounted one and put that alongside your ‘control’ panel.

One mans bling is another mans accurate battery management.

A volt meter is a useful tool, but it'll only measure volts, not SoC.

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[two]

Voltmeter is better than nothing for determining SoC. Ah counters are better but cost more. And how many batteries have a stated Peukert constant (you end up guessing)?

 

[Infinity31]

Voltmeter is better than nothing for determining SoC. Ah counters are better but cost more. And how many batteries have a stated Peukert constant (you end up guessing)?

Only just better than nothing in my view.

The BMV-700 is a great aid to battery management but as you say not totally accurate for SoC, for that you need a Merlin Smartgauge.

Many spend £50000+ on their vans and £1000's more on accessories. You can have both of the above for less than £250, not that much. Just a matter of priorities.

 

[Davylambretta]

Thanks for all the replies so far. My MH is small and both roof space and weight need to be considered. Also my pockets are not deep so I can't just throw money at it, hoping it will work well enough on a dull day ... I was trying to be a bit more scientific than that.

@SuperMike that Solar level indicator looks useful for seeing what I am getting from my existing panel. Is it easy to fit? I think my panel has a Sargent unit under the passengers seat. Also, do you have any other figures for dull days and early/late in the day? Thanks.

It's also making me wonder though if there's a limit to what the batteries will take in when charging, presumably the rest is just wasted if you can't use it as fast as it's being generated?

I know where some 250 watt panels are for sale if your prepared to travel for them glass is cracked but working you can fix with an encapsulation resin just got 2 for 70 quid and just measured one 20mins ago and putting out 22volts

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[Vanman]

Well experiment #1 started this morning. I disconnected the EHU at 0810 and we'll see how many hours the 100w panel under the 'broken cloud' conditions that are forecast for the next week or so. The competition ends when the panel shows 12.2v. Feel free to place your bets.

Many spend £50000+ on their vans and £1000's more on accessories. You can have both of the above for less than £250, not that much. Just a matter of priorities.

It's clear that mine is a 'shoe string' project compared to the 'many'. If/when I spend £250 I need to know it will make a significant difference.

if your prepared to travel for them glass is cracked but working you can fix with an encapsulation resin

Thanks for the information but my DIY skills do not extend in that direction.

 

[gerry mcg]

What are you using to measure your battery voltage during your test?
I would recommend you don't rely on the Globecar panel as it is extremely unreliable and suggest you use a multimeter
I use this as a guide to the SOC battery voltage

 

[vwalan]

i use one similar to this ,
but an aldi version . it only gives a guide its not accurate as such . but put on the first screws of a solar reg it gives an idea of charge . the middle or third screws (pos/neg)gives an idea of battery voltage .
after a few trips you soon learn to interpret the flashing lights .
i know a few that have them wired in permanently to give a watch of whats happening . i just connect mine as and when i want to check. .
yes i cant give figures like many but do have an idea of battery condition .
plus the tool is good for use on all vehicles , well 12v .

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[Vanman]

What are you using to measure your battery voltage during your test?
I would recommend you don't rely on the Globecar panel as it is extremely unreliable and suggest you use a multimeter
I use this as a guide to the SOC battery voltage
View attachment 169658

Thanks Gerry. Unfortunately I have no 12v sockets in the van so I'm watching the panel ... I've tried sticking a hand held multi meter (a good one) into the lighting track and it's currently (no pun intended) showing 15.2v

 

[gerry mcg]

I can only urge caution on using the factory panel then.
When we picked up our van, our panel was only illuminated to the 12.2v LED, but subsequent monitoring with the BMV 700 shows the factory panel significant under reads, therefore you may have significantly more power available that the panel displays and you think.

Fwiw, with heating on overnight in Feb /March, lights and fridge running, we only used 20A, and the SOC dropped to 88%, and this was replaced before noon with 150w solar... In summer, with early sunrise, I would expect full charge by 10am or so

 

[Vanman]

Just been out there to swap out a couple of cold bottles for warm. The sun is beating down so I think the 6a charge and 4a use will come into play all day and the batteries will still be fully charged when the sun goes down. I'll then have to try and get up as early as possible (eek) to see what it has dropped to overnight, hopefully before the sun is exceeding the 4a draw.

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[Chris+Tracy]

All this is great as I have just bought the A**I cooler box for £39.99.
A friend of mine has one and it has a fan control so you can turn it down overnight and leave it in the van and it runs pretty quiet.
They consume ~4 Amps, have not measured the power consumption on lower fan speeds yet but I will and post results here.
Watching this post with interest as we are off wild camping soon and want to run this chiller off leisure batteries (x2) when parked up. My only worry is we are off to bonny Scotland and you don't get a full 14 hours of sun up there

 

[TheCaller]

Thanks Gerry. Unfortunately I have no 12v sockets in the van so I'm watching the panel ... I've tried sticking a hand held multi meter (a good one) into the lighting track and it's currently (no pun intended) showing 15.2v

I would try & check that reading at the battery if you can. If that's a genuine reading & it continues for any length of time, something isn't right - fried batteries will follow. Unless in an equalisation phase of charging (which is for wet batteries only, not AGM or Gel), the voltage shouldn't ever get to 15v.

It's not just the batteries that will suffer. Most 12v kit is fairly tolerant of some under or over voltage, but 15v is 25% over. LED lights can be very sensitive, especially the cheaper ones without their own voltage regulation. I had a solar controller that failed to regulate & the voltage went to nearly 17v on a sunny day. I'm almost certain that's what killed my inverter & it won't have done the batteries any good either.

 

[gerry mcg]

Unfortunately I have no 12v sockets in the van so I'm watching the panel ... I've tried sticking a hand held multi meter (a good one) into the lighting track and it's currently (no pun intended) showing 15.2v

I'd second That that doesn't sound right
I've just checked my lighting track and it is showing 12.7v- 12.85v
my panel shows 12.7v when the Victron BMV 600 showing 12.91v,
And when the compressor pump is running, the display only shows 12.2v with the BMV 600 showing 12.75v (when under load)

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[two]

Potentially, 15V is too high (my pun intended). I suspect it’s coming from your solar panel. The solar controller ought to be keeping it lower than that but that’s not the purpose of my response.

I had suggested that you measure the voltage of your battery before the sun is up. You could otherwise throw a towel over the panel temporarily and see what the voltage has reduced to after a while. I was also hoping that you’d have a multimeter to measure the battery with. If not, stick with what you have and just wait until the 12.2V lamp shines (while it’s dark outside). Maybe you could borrow a meter when your control panel shows 12.2V and compare that with what the meter says. You’ll only get a true measure of voltage for the purpose of SoC while no charge is being provided from other sources, which is why I had suggested doing it first thing in the morning. If early mornings are not your scene, after dark is all you need. You could just as well check it before retiring to bed.

 

[Bartyfixedit]

The best way to make an efficient 12v fridge is this....

Buy the most Energy efficient fridge you can. A++
Replace the compressor with a Danfoss 12v compressor.

Nice idea, have you done it?
I looked into it and all the A++ fridges were using R600a refrigerant which is no good for the Danfos R134 12V compressor. The capillary is different for R600 compared to R134 and is usually buried in the insulation of the fridge so is not easily changed. There is a 12V R600 compressor but no one could supply me one unless I bought a pallet of them.The number of fridge engineers licensed for R600 are very few.
I ended up running the 230V A++ fridge freezer off a 1600 VA Pure Sine Victron inverter and all has been fine for a couple of years.

 

[Vanman]

Losing the will to live a bit here lol. My fancy digital hand held meter seems to be counting up to some sort of total rather than just displaying a voltage. It's not helped that I can't get at the battery terminals under the seat so am trying to take a measurement from the lighting track.

My other meter is not accurate enough in the 12v range, so I'll be borrowing another tomorrow. I'll be sure to have a training course on it first

I'm beggining to think that my little experiment may be too simple. When away in the van there would be a light or two on during darkness/drinking hours, there would be the odd flush of the loo, there might be the Truma on gas through the night (but presumably using some leccy to circulate) and possibly other bits and pieces (water pump) too. Maybe the fridge is getting a bad press.

I'll check again about 11pm anyway

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[Neckender]

Hi again @Vanman in the overhead lockers over the bed both sides there is a square plastic white box with 12 volts on the box.
Remove the covers and you will see 12 volt connectors you can measure your voltage there, but take note continental wiring is reversed from ours, brown negative and blue is positive.

John.

 

[Vanman]

Minor heart attack as the display was showing 12.2 already. Until I realised the fridge was running ... it returned to 12.7 when it stopped.

I opened the 12v box but there were 8 or 10 wires in there so have left that bit for now.

Just need to drink the last of the tonight's cold beer before bed

Hi again @Vanman in the overhead lockers over the bed both sides there is a square plastic white box with 12 volts on the box.
Remove the covers and you will see 12 volt connectors you can measure your voltage there, but take note continental wiring is reversed from ours, brown negative and blue is positive.

John.

 

[EuroTrotters]

Nice idea, have you done it?
I looked into it and all the A++ fridges were using R600a refrigerant which is no good for the Danfos R134 12V compressor. The capillary is different for R600 compared to R134 and is usually buried in the insulation of the fridge so is not easily changed. There is a 12V R600 compressor but no one could supply me one unless I bought a pallet of them.The number of fridge engineers licensed for R600 are very few.
I ended up running the 230V A++ fridge freezer off a 1600 VA Pure Sine Victron inverter and all has been fine for a couple of years.

I have an old Danfoss R12 12V Compressor that I used with Care30 which is R600a/R290.
I have used R600a in R134a Systems (there are varying opinions on that one).

You Do not have to be licensed to use R600a
You Do have to be for everything else (F-Gas)

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[Richard n Ann]

I have an old Danfoss R12 12V Compressor that I used with Care30 which is R600a/R290.
I have used R600a in R134a Systems (there are varying opinions on that one).

You Do not have to be licensed to use R600a
You Do have to be for everything else (F-Gas)

I've put R134a in a R600 bottle cooler and it worked ok oh, and a chest freezer. And those are just the 2 I remember. You wouldn't believe the sh1t we used to do to keep the coop fridges running

 

[gerry mcg]

Minor heart attack as the display was showing 12.2 already. Until I realised the fridge was running ... it returned to 12.7 when it stopped.

It sounds like your factory panel is under reporting the battery voltage in a similar fashion to mine as per the photos in #78.

 

[Vanman]

This mornings edition of the saga.

Went out, bleary eyed, 0820. Panel was showing 12.2 and 12v circuit showing 15.8 Thankfully by the time I'd measured the circuit the fridge had stopped drawing power and 12.7 had been restored on the panel.

It sounds like your factory panel is under reporting the battery voltage in a similar fashion to mine as per the photos in #78.

@gerry mcg Thanks. As my board only has 12.7v and 12.2v to choose from, it will always dip to 12.2 when anything substantial is drawing power.

Anyway, I went to borrow another test meter and to cut a long story short the 9v battery in mine was down to 6v and that is why it was working incorrectly (you'd thing it would just shut down or wink at me lol).

Got back to the van and at 10am and it's now saying 12.75v

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[Vanman]

Well for most of today the gauge said 12.85v, but now that the sun has gone down we're down to 12.6v and so my very limited control panel is showing 12.2v, as it would because it's no longer 12.7v

I'll check again just before bed tonight and probably let it run as is for tonight, hopefully it will have enough to greet the morning light, from whence it should be OK for tomorrow. Maybe.

 

[Vanman]

The result.

Well after 72 hours the battery level reads 12.4v (which equates, using @gerry mcg chart) to 75% remaining, so I declare the solar panel the winner.

Epilogue

Sticking a hand held meter into an overhead locker x4 a day isn't great fun, so I really do need to fit some sort of digital display.

I'm going to leave the experiment running for today as it's really cloudy and I want to see how that affects things. I'll put it back on EHU tonight. @magicsurfbus or any others with the tech, it would be good to know what your panels are generating any time (Panel size, watts or amps, Country).

Thanks again to all who have helped me understand the complexities, and got me doing something about it!

 

[Stretto Boy]

[QUOTE And it would be a big help if you could tilt the panels up towards the sun when parked.[/QUOTE]

Like this:

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