How much solar?

To run a fridge

 
 
 
 
 
 
Steveontour
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How much solar?

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Posted: 14.10.2018  ·  #1
Hi all. Our 91 Fiat Dukato has the following when we bought it. Two leisure batteries (tested as sound), 100 w solar, a Waeco 26c fridge (working badly), hot water unit and led lighting. We added alternator charging and got the fridge working with Craic help by running cables direct to batteries.. Now, after coming off hook up we can be off grid for two nights before the fridge stops o and the lights flicker. Is this about par for the course or should we be able to last much longer? And, if I want to last much longer, what shall I do? Thanks!! Steve


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Re: How much solar?

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Posted: 14.10.2018  ·  #2
Is your fridge a 3 way Steve?
Does it work on gas?


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Re: How much solar?

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Posted: 14.10.2018  ·  #3
Fridge shouldn’t be connected to leisure batteries at all.
12 volt on fridge should only be active and powered from the main battery and only when the engine is running and wired through a relay. The 12 volt side of it is only designed to be used when travelling and not when stationary.
When on 240v hook up use the mains to power the fridge.
If no mains hook up then gas is used to provide cooling.

Your solar setup won’t be able to charge your leisure batteries if you’ve got the fridge hooked up to them. The light coming on is to tell you that your batteries are becoming flat.
Also, if you’ve dragged the batteries below a certain voltage and it’s been done more than that once the chances are that your leisure batteries will be damaged.

Have it wired properly as powering it on 12 volt continuously isn’t the way it is designed to operate.


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Re: How much solar?

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Posted: 14.10.2018  ·  #4
Quote by JJF

Fridge shouldn’t be connected to leisure batteries at all.
12 volt on fridge should only be active and powered from the main battery and only when the engine is running and wired through a relay. The 12 volt side of it is only designed to be used when travelling and not when stationary.
When on 240v hook up use the mains to power the fridge.
If no mains hook up then gas is used to provide cooling.

Your solar setup won’t be able to charge your leisure batteries if you’ve got the fridge hooked up to them. The light coming on is to tell you that your batteries are becoming flat.
Also, if you’ve dragged the batteries below a certain voltage and it’s been done more than that once the chances are that your leisure batteries will be damaged.

Have it wired properly as powering it on 12 volt continuously isn’t the way it is designed to operate.


Unless it's a 12 volt compressor fridge.


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Re: How much solar?

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Posted: 14.10.2018  ·  #5
Quote by johnnymac

Quote by JJF

Fridge shouldn’t be connected to leisure batteries at all.
12 volt on fridge should only be active and powered from the main battery and only when the engine is running and wired through a relay. The 12 volt side of it is only designed to be used when travelling and not when stationary.
When on 240v hook up use the mains to power the fridge.
If no mains hook up then gas is used to provide cooling.

Your solar setup won’t be able to charge your leisure batteries if you’ve got the fridge hooked up to them. The light coming on is to tell you that your batteries are becoming flat.
Also, if you’ve dragged the batteries below a certain voltage and it’s been done more than that once the chances are that your leisure batteries will be damaged.

Have it wired properly as powering it on 12 volt continuously isn’t the way it is designed to operate.


Unless it's a 12 volt compressor fridge.


True Johnny, maybe it’s a newer fridge.....
In that case I’ve just typed a load of bollox !


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Re: How much solar?

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Posted: 14.10.2018  ·  #6
People do run 12 v compressor fridges successfully off grid. So to add to above comments, I would say it is not so much that your fridge is not designed to run on 12 volts, it is that your 12 volt systems is not designed to run your fridge.

First off , you are overcharging your batteries. You should stop doing that immediately. If you are running your batteries to the point of failure you will shorten battery lifespan at the very least. Lights and other equipment should not be flickering. Don’t discharge below 50% of your battery capacity. A good and trusted battery monitor would help here.

Secondly, if you want to run a compressor fridge and stay off grid, you will have to expect that you will eventually need to hook up so that you can recharge your batteries. Your fridge could be consuming about 20 Ah per day. No amount of solar will replace that in this country.

You can increase the time between charges by increasing battery capacity and solar charging. I know some people are squeezing In severaldays in between charges and running a compressor fridge but you have to be realistic.

So you have a 100W panel, you could easily add another 100W. What’s your current battery capacity?200Ah? Realistically you will have to increase i.e. more or bigger batteries.

You mention you have hot water. Is that gas powered? I certainly wouldn’t be trying to run hot water from 12 volts, that would be a battery killer.

I’ve been doing the math myself to see what it would take to run a compressor fridge. They are so much more efficient than absorption fridges, and run cooler. But there is the challenge of replacing that 20 Ah/ days. I’ll stick with my 3-way while it still works and they do have some good points.

Some back of the envelope calculations here; fridge @ 20Ah/day for 5 days = 100Ah. Add another 100Ah for lights, appliances. 400Ah battery capacity will cover this in between charges. And that’s before adding solar. So you can see how it is possible to go longer if factoring in solar and alternator charging.

So good luck


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Re: How much solar?

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Posted: 14.10.2018  ·  #7
Quote by The Rambler


I’ve been doing the math myself to see what it would take to run a compressor fridge. They are so much more efficient than absorption fridges, and run cooler. But there is the challenge of replacing that 20 Ah/ days. I’ll stick with my 3-way while it still works and they do have some good points.



You and me both, but I'm not much good at the maths :)

There is a new compressor fridge on the market, Kevin (Blag) sent me the link, it uses 40 watts.

https://www.donedeal.ie/camper…s/17378354


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Re: How much solar?

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Posted: 14.10.2018  ·  #8
Quote by JJF

Quote by johnnymac

Quote by JJF

Fridge shouldn’t be connected to leisure batteries at all.
12 volt on fridge should only be active and powered from the main battery and only when the engine is running and wired through a relay. The 12 volt side of it is only designed to be used when travelling and not when stationary.
When on 240v hook up use the mains to power the fridge.
If no mains hook up then gas is used to provide cooling.

Your solar setup won’t be able to charge your leisure batteries if you’ve got the fridge hooked up to them. The light coming on is to tell you that your batteries are becoming flat.
Also, if you’ve dragged the batteries below a certain voltage and it’s been done more than that once the chances are that your leisure batteries will be damaged.

Have it wired properly as powering it on 12 volt continuously isn’t the way it is designed to operate.


Unless it's a 12 volt compressor fridge.


True Johnny, maybe it’s a newer fridge.....
In that case I’ve just typed a load of bollox !


Not at all, it's good advice.


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Re: How much solar?

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Posted: 14.10.2018  ·  #9
Quote by Ally

Quote by The Rambler


I’ve been doing the math myself to see what it would take to run a compressor fridge. They are so much more efficient than absorption fridges, and run cooler. But there is the challenge of replacing that 20 Ah/ days. I’ll stick with my 3-way while it still works and they do have some good points.



You and me both, but I'm not much good at the maths :)

There is a new compressor fridge on the market, Kevin (Blag) sent me the link, it uses 40 watts.

https://www.donedeal.ie/camper…s/17378354


The spec sheet says nominal 40watts. What does that mean? If that is the average consumption then over 24 hours it will absorb 80Ah from the battery. (40 Watts x 24 hours)/12 volts.

Before going that way suggest you get the manufacturer to advise the typical Ah consumption over a day in an ambient temperature of 25C to 35C which may be encountered in Spain say.


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Re: How much solar?

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Posted: 14.10.2018  ·  #10
Quote by kabundi

Quote by Ally

Quote by The Rambler


I’ve been doing the math myself to see what it would take to run a compressor fridge. They are so much more efficient than absorption fridges, and run cooler. But there is the challenge of replacing that 20 Ah/ days. I’ll stick with my 3-way while it still works and they do have some good points.



You and me both, but I'm not much good at the maths :)

There is a new compressor fridge on the market, Kevin (Blag) sent me the link, it uses 40 watts.

https://www.donedeal.ie/camper…s/17378354


The spec sheet says nominal 40watts. What does that mean? If that is the average consumption then over 24 hours it will absorb 80Ah from the battery. (40 Watts x 24 hours)/12 volts.

Before going that way suggest you get the manufacturer to advise the typical Ah consumption over a day in an ambient temperature of 25C to 35C which may be encountered in Spain say.


You have to factor in the duty cycle Kabundi. It will be in the region of 25%. So the compressor is only running for about a quarter of the time, hence the 20Ah per day. The manufacturers spec might quote something slightly different but it will be in that region.


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Re: How much solar?

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Posted: 14.10.2018  ·  #11
And if you compare that to a 3-way on 12 volts, mine will consume about 120Ah 240Ah per day! So absorption fridges are far less efficient on 12 volts than compressors. And they will only cool to about 20 below ambient. In the south of Spain, hmmm not great. There is a reason why people in the Outback or Mojave don’t run 3-way fridges.

I’d like a compressor fridge. But that said, I don’t live in the south of Spain, I have a working 3-way, and so can’t quite justify the initial investment to switch to a compressor. And they are darn convenient on gas.


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Re: How much solar?

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Posted: 15.10.2018  ·  #12
Hi folks. Thanks for the info. The fridge is a Waeco CR65, so it is a compressor fridge and it is only two way. The hot water is gas when off grid. I am trying to attach a pic of the fridge spec. Does this help?
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Re: How much solar?

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Posted: 15.10.2018  ·  #13
This type of fridge is compatible with a battery system unlike an absorption fridge. Providing there is adequate capacity and suitable recharging that is. The spec is saying average consumption is 1.6Ah to maintain 5c when ambient is 25c. That’s still a hungry enough appliance when operated 24/7.

You didn’t mention what your battery capacity is. And we don’t know if your batteries can deliver their stated capacity. Do you have a battery monitor that shows state of charge? Measuring real world parameters will help to determine how long you can stay off grid. Ideally, measuring how many Amp-hours your fridge consumed over 24 hours and how much your battery discharged, would help to give you realistic figures.

But let’s take the figures in the spec. And say your fridge consumes 1.6Ah on average. Over 24 hours that 38 Ah. Without knowing how much beer food is in your fridge, outside ambient temperature, how often you open and close the fridge door etc. I’m going to say you are consuming 40Ah over 24 hours. This could be higher but I’m betting it won’t usually be a 25c day. And say you have 200Ah battery capacity. Well you could run the fridge for 2 days on battery. This would leave 20Ah to spare for other appliances. Now you have discharged your batteries to 50%. Time to recharge.

That’s a rough example. Maybe 20Ah for appliances is not enough for you. Perhaps your solar and alternator charging has offset this to give you 3 days. If I was running this fridge I would be looking to run about 400Ah of battery capacity with 200 watts of solar. And I would be sure to start every journey with full charged batteries and a cooled down fridge i.e. plugged in at home for at least 24 hours.

On a practical point, can this fridge’s freezer zone be switched off? If so, it will be a lot less hungry for battery, assuming you don’t need the freezer on every trip.

So what’s you battery capacity? And do you have a battery monitor showing a reliable state of charge?

Charles Sterling does a good 24 hour test here comparing fridges. Notice how the compressor fridge without freezer performs.


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Re: How much solar?

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Posted: 15.10.2018  ·  #14
I don’t know why my YouTube video didn’t seem to imbed properly in my last post

Fixed it


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Re: How much solar?

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Posted: 15.10.2018  ·  #15
Jason. You are a mine of information! Right, we have two batteries. A Hankook DC 31, 125 MHA which has everything connected to it, and a Halfords 115 AH sort of attached to it. (Sorry for the lack of technical language!). There is a digital voltmeter linked in but I don’t think I would call it reliable. (At best after hook up it reads 12.9, after night one about 12.2 and after a second night about 11.8, by which time we have switched everything off. I don’t think I can turn the freezer compartment off. So, would you recommend another 2 batteries and double our solar? Thanks again. Steve


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Re: How much solar?

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Posted: 15.10.2018  ·  #16
I think the mismatched batteries are your problem, batteries need to be matched same brand model and capacity.
Think of electricity as like water if you have two drums with a hose connecting them at the bottom and fill one, the other will fill to the same level.
Likewise batteries that are different ages and amp/hrs will equalise out with the weaker battery pulling the stronger one down to its level.


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Re: How much solar?

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Posted: 15.10.2018  ·  #17
Steve, your batteries are mismatched alright. They will be connected in parallel, positive to positive and negative to negative, and should be seen to act like one big battery. But they should be matched i.e. same brand, type and age. Your system will kind of work but it won’t be optimal. And your batteries will reach end of life prematurely. Sounds like someone added the Halfords battery as an afterthought some time after the Hankook was already in service.

Voltage is a poor measure of state of charge. If you measure your battery terminal voltage at say 13.1 V, you really can’t say if your battery is 100% charged, 80% charged etc. But if that is all we have to go with, a chart will usually tell you that at 12.2 V, your battery is at 50% capacity. Which means you are 50% capacity after one night. So you really don’t want to go any lower.

My guess here is that your batteries are not performing, possible reasons; they are damaged, old, and not charged properly. I think your Hankook is a calcium type that needs a higher charging voltage than the Halfords. It could be that they never reach a full state of charge.

Unless money is no object and you are willing to go get a couple of new batteries, I wouldn’t like to tell you get rid of your batteries. At least not without investigating their condition. If they can be recovered they might still have some use. But I don’t recommend keeping them connected together.

First thing first, what kind of charger do you have ( hoping it’s a decent multi-stage Charger) ?


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Re: How much solar?

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Posted: 15.10.2018  ·  #18
It’s a Genius G7200. We are on hook up tonight, and the charge level is yellow flashing 75%.


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Re: How much solar?

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Posted: 15.10.2018  ·  #19
That looks like a decent multistage charger. However, I don’t believe it can do a great job charging two mismatched batteries in parallel. How could it? But I’ll come back to that in a minute.

Question to ask yourself. How many days would you like to go off-grid at a time? Multiply that number by 40 ( amp-hours used by fridge per day ), and multiply that by 2. The result will be the required amount of battery capacity needed and means you do not discharge your batteries below 50%.

For example: 4 days off-grid. 4 x 40 x 2 = 320 Ah. So 2 x 160Ah batteries.

This didn’t factor in energy requirements for other appliances. Could be worth toting up what expected power requirements needed here. Example, 24 watt tv, used 3 hours a day. Work it out in how many amp-hours of use. 24W/12V = 2 amps. 2 (amps) x 3 (hours) x 4 (days) = 24Ah. You can repeat for all other appliances but if it is only intermittent use of things like water pumps this is too hard to do. This will ever only be guesstimating. Real world useage will determine the outcome. Plan on paper but trial and error at the end of the day. Solar is not worth much this time of the year so I would park upgrading that for the time being.

I would think in the example above that you could resign yourself to expect 3 days off-grid. This would allow you to run other appliances comfortably. But a decent battery monitor, that shows you the state of charge in percentage terms is almost indispensable. Then you can better guage how much battery you can use before needing to hook up. A battery monitor let’s you know how many amp-hours you are using every day and what percentage capacity your battery is at.

But back to your existing configuration. I hate to tell you but if it was me I would disconnect the Halfords. I would then charge the two batteries separately. Each one overnight. If the charger reports that the batteries have reached 100% that’s a good sign. If you know anyone who can load test them for you, even better. Then what? Unless you are going to upgrade to new batteries, I don’t know. I would probably keep the batteries isolated from each other, hook the fridge up to the Halfords, and keep all other loads on the Hankook. You could probably get away with running the fridge for a couple of days on the Halfords ( will be deep discharging though ) but you will be doing a juggling act trying to keep two systems charged.


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Re: How much solar?

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Posted: 16.10.2018  ·  #20
This is a great thread folks...


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Re: How much solar?

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Posted: 16.10.2018  ·  #21
That sounds like great advice, but probably beyond my technical ability especially as we are currently (no pun intended) in Portugal. I guess we will have to just keep plugging in every two days and try and sort this out properly when we get home! We did get the batteries looked at by a battery salesman and he said they were sound, and didn’t try to sell us new ones. Thanks all for your time and effort.


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Re: How much solar?

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Posted: 16.10.2018  ·  #22
That is fair enough Steve. I don’t think you are in any panic and you know the limitations. We all have future projects that can wait. Enjoy your holidays!

Oh, and feel free to add an extra solar panel anytime you feel like it. It will never hurt, especially in sunny Portugal.

😎


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Re: How much solar?

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Posted: 16.10.2018  ·  #23
Thanks. We are actually only about an hour away from a solar shop, so I will go and see what they have to say. I think it will cost more than back home, but we might save the difference in campsites over the next few weeks.


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Re: How much solar?

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Posted: 16.10.2018  ·  #24
Below is a good chart.


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Re: How much solar?

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Posted: 16.10.2018  ·  #25
Quote by baguette

Below is a good chart.


Did you mean to attach a chart Colin?


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Re: How much solar?

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Posted: 16.10.2018  ·  #26
Quote by The Rambler

Quote by baguette

Below is a good chart.


Did you mean to attach a chart Colin?




Got this message You have no memory left. Please delete some old attachments first.
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Re: How much solar?

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Posted: 16.10.2018  ·  #27
Great thread. Anyone an example of a good battery monitor to display Ah usage and current battery capacity remaining? I could do with one, especially if I get new batteries which may be soon!


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Re: How much solar?

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Posted: 16.10.2018  ·  #28
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Re: How much solar?

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Posted: 16.10.2018  ·  #29
I hear lots of praise for the Trimetric 2030 and the Victron BV700. But you pay for these. I myself use a cheap Chinese job. It’s fiddley but I’ve got it working to the point of being useful.

A couple of things to bear in mind. A good battery monitor needs to know the current in and out of the battery, and needs to log this i.e. counting the Coulombs. So it will need a shunt wired into the circuit. The shunt ( high precision resister in the milli Ohm range ) is usually wired between battery negative terminal and vehicle chassis. The voltage drop developed across the shunt is proportional to the current draw and this is what the monitor measures and counts. It will be in the millivolt range so the power dissipation of the shunt itself is negligible.

Cheap monitors that try to use magnetic induction to measure current flow are not reliable. The shunt is tried and tested. Also, you might see solar controllers that neatly display Amp-hours in and out of your battery but this is unlikely to tell you all you need to know. If your solar controller was the only charging source, and if all your loads were wired off the solar controller, then it might be useful. But that is rarely the case. It will likely be blind to alternator and mains charging, as well as any loads not wired of the controller.


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Re: How much solar?

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Posted: 17.10.2018  ·  #30
Quote by baguette



Got this message You have no memory left. Please delete some old attachments first.
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I'll increase your quota.

Although the following method is better: forum/topic.php?t=15202


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Re: How much solar?

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Posted: 19.10.2018  ·  #31
By way of a follow up I went mad in the solar shop and got a new solar panel and a new battery fitted. It hasn’t stopped raining since! But, the fridge is working and the lights are on. I was going to add a link for a map of our journey, but I don’t know how!


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Re: How much solar?

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Posted: 19.10.2018  ·  #32
Great stuff! So 2 solar panels installed now? And have you got all 3 batteries wired up?


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Re: How much solar?

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Posted: 19.10.2018  ·  #33
Quote by Steveontour

By way of a follow up I went mad in the solar shop and got a new solar panel and a new battery fitted. It hasn’t stopped raining since! But, the fridge is working and the lights are on. I was going to add a link for a map of our journey, but I don’t know how!


Where did you get it done


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Re: How much solar?

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Posted: 19.10.2018  ·  #34
Got it done at FF Solar outside Aljezur. It is a 240 W extra panel on a single 230 MAH battery. We have ice! As I said I went mad. The night before we spent €20 for a night in an awful site just for the hook up which was the final straw. 😂


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Re: How much solar?

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Posted: 19.10.2018  ·  #35
StrandCampingDoonbeg
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Re: How much solar?

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Posted: 19.10.2018  ·  #36
Quote by Steveontour

Got it done at FF Solar outside Aljezur. It is a 240 W extra panel on a single 230 MAH battery. We have ice! As I said I went mad. The night before we spent €20 for a night in an awful site just for the hook up which was the final straw. 😂

The link worked looks like a great trip


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Re: How much solar?

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Posted: 19.10.2018  ·  #37
Quote by Steveontour


Works great. I’ll have to start using that myself. Keep us posted on how many days you can keep the fridge going. I’ll bet you see a big improvement


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Re: How much solar?

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Posted: 19.10.2018  ·  #38
Looks like a super adventure. Mad jealous. Enjoy!


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Re: How much solar?

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Posted: 19.10.2018  ·  #39
Toolio (not sure that’s the spelling) who fitted it says it will run the fridge pretty much week in, week out. Perhaps one or two very grey days a year we might need to switch it off to let the solar catch up. We will see!


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Solar

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Posted: 19.10.2018  ·  #40
Well folks using Ebay and amazon I bought all the equipment and installed it myself 2 100w solar panels + 20amp mppt system +2 fitting corner kits glan for the cable to be routed into the living quarters it was simple enough


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