Solar Fridge

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My logic was in my 24 volt truck (with 2 x 105 amp-hr. marine batteries) -- the solar panels eliminate the need for a heavy 55 lb. 3rd 12 volt RV battery, because the starting batteries are fully charged each day (starting when the sun comes up) and with the capacity to operate the fridge, even when the truck sits for extended periods. That saves me weight, space and 3rd battery replacement costs down the line.

Also I have a Morningstar Sunsaver (US made) MPPT (maximum power point tracking) charge controller which is different from PWM (pulse width modulation) controller, which is the standard technology.

A MPPT controller adjusts voltage to ensure maximum power extraction from the solar panels as the voltage fluctuates through the day. A PWM controller can only use the panel voltage when it’s within the battery voltage range – I think up to 15 volts (30 volts if in series). I have measured my panels (2x 12 v series panels) at over 40 volts during the middle of the day, so that excess voltage is captured, whereas with a PWM charge controller that wouldn't be.
The result is the MPPT controllers give 10 to 30% more power from a given panel over the course of a day, because they account for changes in the panel voltage due to temperature and other factors.

A couple of things to consider before you decide on making an investment.
 
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I have a 12V devise - my CPAP machine - which needs a dedicated 12V battery supply. That is my main reason for picking a dual voltage charge controller that does two banks at the same time of different voltage.

Interior space and adding another battery are not an issue for me. I also stopped worrying about weight when I saw all the extras Mat had added inside his rig. :D The biggest performance drag is not a few hundred pounds extra weight but if I have the rack on or not.

I also still have the little 12V Tercel alternator which i am still thinking of adding to the engine. It depends if I go endless air or an electric onboard air.
 
You can't use a 24 v-12v converter? Had this 20 amp unit 6 years -

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Glenn-BJ74 said:
My logic was in my 24 volt truck (with 2 x 105 amp-hr. marine batteries) -- the solar panels eliminate the need for a heavy 55 lb. 3rd 12 volt RV battery, because the starting batteries are fully charged each day (starting when the sun comes up) and with the capacity to operate the fridge, even when the truck sits for extended periods. That saves me weight, space and 3rd battery replacement costs down the line.

Also I have a Morningstar Sunsaver (US made) MPPT (maximum power point tracking) charge controller which is different from PWM (pulse width modulation) controller, which is the standard technology.

A MPPT controller adjusts voltage to ensure maximum power extraction from the solar panels as the voltage fluctuates through the day. A PWM controller can only use the panel voltage when it’s within the battery voltage range – I think up to 17 volts (34 volts if in series). I have measured my panels (2x 12 v series panels) at over 40 volts during the middle of the day, so that excess voltage is captured, whereas with a PWM charge controller that wouldn't be.
The result is the MPPT controllers give 10 to 30% more power from a given panel over the course of a day, because they account for changes in the panel voltage due to temperature and other factors.

A couple of things to consider before you decide on making an investment.
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This is all very good information! Thanks Glenn!
 
Glenn-BJ74 said:
You can't use a 24 v-12v converter? Had this 20 amp unit 6 years -

Home
Click to expand...

I have the same converter in my truck. It will not fully charge the AGM battery. My solution is to just to put it my digital charger on the AGM battery every month or so to give it a full charge. My CPAP machine by itself will probably deplete the battery within a night if I use the humidifier. I think I might get 2-3 nights without running the humidifier. That makes it a problem if I want to stay some place for a couple days without taking the truck for a long enough run to allow the converter to recharge the battery. I think my best solution is the Solar panels - not just for wheeling but also if we have a power outage at home. I need a power back-up that doesn't require fuel. Now I am getting into HAM I also will need a reliable off grid power supply.

I am going to talk to Trevor about the MPPT Epsolar controlers he sells. They are at least double the cost of the standard controllers. I just have to find out if one can meet my vehicle use and emergency home use needs and still not be too expensive.
 
canucksafari said:
I have the same converter in my truck. It will not fully charge the AGM battery. My solution is to just to put it my digital charger on the AGM battery every month or so to give it a full charge. My CPAP machine by itself will probably deplete the battery within a night if I use the humidifier. I think I might get 2-3 nights without running the humidifier. That makes it a problem if I want to stay some place for a couple days without taking the truck for a long enough run to allow the converter to recharge the battery. I think my best solution is the Solar panels - not just for wheeling but also if we have a power outage at home. I need a power back-up that doesn't require fuel. Now I am getting into HAM I also will need a reliable off grid power supply.

I am going to talk to Trevor about the MPPT Epsolar controlers he sells. They are at least double the cost of the standard controllers. I just have to find out if one can meet my vehicle use and emergency home use needs and still not be too expensive.
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Honestly in your case were it means possibly not waking up in the morning I would spare no expense on the system that keeps my life support functional.
 
Its not so much a case of me not waking up (although that could be a possibility) but of me being so damn tired after waking up I can't safely drive.

Trevor has done quite a few home solar systems for CPAP users becuase in a disaster situation gas and diesel generators are only good for the fuel you have to run them. Mine expected/desired uses are just a bit more demanding than only running the CPAP machine offline and i want to be able to move it easily to and from vehicle to home use. Looks like I might have to sell the boat if I want to fund this.
 
I bought Morningstar MPPT charge controller because
- we live in a sunlight deprived area (need every watt)
- it will have a higher resale value than a PWM
- it has a small mounting footprint (very important)
- there are fake MPPT out there (e.g Wellsee)
- it is made by a reputable mfg
- a CSC friend has one for his 160 w setup
- it has been independently tested and verified
 
I just ordered a single 80 watt (I think) panel (supposed to do 5.7 amps 12vdc ideal conditions) and MPPT controller/meter from Polar, where i buy all the stuff for the boats so I am treated pretty well.. I intend to install 2 new 6 volt golf cart AGM batteries that I have in the garage into the trailer on a removable skid with an older Trace 1500 watt inverter/charger and a shore power connector. Maybe I'll put my little Webasto air heater (AT2000) in there as well with a hose up to the RTT? Now looking for a deal on an Engel or ARB fridge...
 
$5 raffle ticket next week gets you a chance at an ARB fridge.... just sayin'
 
AJAEbj42 said:
$5 raffle ticket next week gets you a chance at an ARB fridge.... just sayin'
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Where?

-Daniel

Sent from deep in the mountains of Honduras using only sticks and rocks.
 
And you can't become a member at your first meeting. ;)
 
Yes, you bet! AND would you know it, we're raffling another ARB fridge there too!
 
Enigma said:
But he could make it up for Cruiser Days in July and buy some raffle tickets for that, no membership required :)
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That sounds fun, but it's a bit far to drive. :D

-Daniel

Sent from deep in the mountains of Honduras using only sticks and rocks.
 
I'd rather save it for the Christmas party and keep that kind of prize in the club. Just my $.02.
 
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