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  1. #101
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    Default Re: Camp fridge,105ah battery and solar?

    Quote Originally Posted by Kudus View Post
    Thank you for this! So Iíll be fine with 2x100W panels then.
    Yes, you will be fine!
    Jeep Grand Cherokee 2002 4.7 V8
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  2. #102
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    Default Re: Camp fridge,105ah battery and solar?

    Quote Originally Posted by Kudus View Post
    Thank you for taking the time to write such a detailed experience down. I think Iím getting a good picture now from everybodyís experiences.
    Iíll go through it all again and quantify it.

    So if a 105ah battery only discharges 50% but a 50ah lithium battery almost 100%, would the 50ah lithium battery not be a better option?

    I camp remote, no electricity and so far Iíve been using a mixture of alternator and 100w solar with a normal high cycle battery (donít laugh). It has been working great but Iím always aware and conservative. So I would like to get a battery in a box being able to go with any car and not just with the one with the duel battery system in. Hence my need for info to go completely solar with a deep cycle battery.

    Appreciate all the expert advice here. Thank you
    Simple, get a 100Ah diy kit 60A BMS from Lithium Batteries SA put it into a neat metalbox, slap a WRND DcDc charger on and Bob's your uncle. Portable, runs your fridge for at least 30hrs, charges quickly (160w foldable solar panel) and is light. It works well.
    2002 Discovery td5

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  4. #103
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    Default Re: Camp fridge,105ah battery and solar?

    Quote Originally Posted by Nambro View Post
    Simple, get a 100Ah diy kit 60A BMS from Lithium Batteries SA put it into a neat metalbox, slap a WRND DcDc charger on and Bob's your uncle. Portable, runs your fridge for at least 30hrs, charges quickly (160w foldable solar panel) and is light. It works well.
    Awesome. These guys look affordable when it comes to lithium batteries. Thanks

  5. #104
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    Default Re: Camp fridge,105ah battery and solar?

    The wattage of a solar panel is not really a useful measure of how the panel will perform for your requirement, and you should be wary of advisors who demonstrate their ignorance on this.

    This is because the wattage specifies how much energy, in joules per second, the panel will convert from solar radiation into electrical energy. But it doesn't tell you at what rate it will charge your battery.

    A battery is like a water tank on a tank stand. You push water in intermittently during the daylight hours, and you take water out intermittently both day and night. The tank is not concerned with the power of the water squirt, it is only interested in the quantity of water being pushed in, and how this compares with the quantity of water being released through the load, in this case the fridge.

    The water quantity is measured in litres, and the rate of flow is measured in litres per second. The electrical equivalent for litres is coulombs, which are a specific quantity of electrons, and the rate of flow of coulombs per second, which is measured in amperes. One coulomb per second flowing past a point in the circuit constitutes one ampere.

    In the case of the water tank on its stand, to get water into the tank you need only enough pressure to overcome the gravity-induced pressure of the water wanting to flow the other way. If the stand were 11 metres high, and the tank a further 2 metres tall, and each metre of height represented a single volt then 11.1 volts would be sufficient to get the tank filling, and 13 volts would be sufficient to fill it entirely. Any further pressure would be wasted. The rate the tank filling would be dependent on the water flow rate, and not the water pressure, once the pressure was high enough to overcome gravity.

    The same applies to the solar panel. That the output voltage is going to be more than sufficient to overcome the output voltage of the battery (equivalent to the gravity of the water) is a given. What now becomes important is the rate of current flow into the battery (the amperage) while the sunshine lasts. That figure can be extrapolated from the short-circuit current which is specified on the same sticker as the wattage, and will only be slightly lower than it when the solar panel is made to charge the battery. A full-sized panel will often deliver about 4.5 amperes into a 12 volt battery, but it's easy enough to measure with a cheap multimeter if you have any doubt.(Be sure to use the 10A input on the meter).

    A figure often thrown around, but not always fully understood is ampere/hours or A/h. If an ampere defines a flow rate of 1 coulomb per second, then an ampere/hour is one coulomb per second for 3600 seconds, or 3600 coulombs. If your battery has a capacity of 105A/h then that works out to 105 x 3600 = 2099 coulombs, (not all of which are available for discharge since you should never fully discharge any lead acid battery).

    The fridge on the other hand will intermittently switch its compressor on and off in accordance with internal gas pressure demands. When the compressor is running it will ask for about 3 amperes, and when not it will only want enough to keep the control electronics running, probably about 300mA.

    To arrive at a plausible consumption figure you can guess the fridge's duty cycle at about 50%, or 12 hours out of 24. At 12 hours of running time at 3 amperes you will need to supply about 130,000 coulombs. If your solar panel in full sunshine supplies 4.5 amperes then it will produce 16,200 coulombs per hour. To replenish the 130,000 C used by the fridge in any 24 hour period you need the 4.5A solar panel to function 130,000/16,200 = 8 hours out of 24.

    So, if you have a single 4.5A panel and less than 8 hours per day of full sunshine then the battery will gradually discharge. If you have more than 8 hours per day the battery will overcharge. Unlike the water tank on the 11 metre stand, which will simply overflow if it is overfilled, the battery will likely suffer some damage if you do not shut off most or all of the charging current once it is full. To avoid overcharging the battery you need a regulator. Either a simple series regulator, which comes with some attendant losses, or a switching 'intelligent' regulator which comes with a higher price tag.

    As you can see, a single panel that produces a short-circuit current of 5 - 5,5A will be quite adequate for driving your fridge under most (say 80%) of conditions. Giving it a switching regulator instead of a series regulator will pay some dividends in efficiency and extent the effectiveness of the single panel. Most fridges come with a built-in under-voltage detector that will shut the load off when the battery voltage drops to the point where the battery can be damaged (about 11,5V). If you find the fridge doing this a lot you'll need to add a second panel (connected in parallel obviously, + to +, - to -), a series connection would serve absolutely no purpose.

    The combined output from these 2 panels will now be 9 amperes, which may be more than some smaller batteries can handle. The max charge current for deep cycle batteries is about one tenth of the ampere/hour specification in amps. In other words a 50A/h battery cannot be charged at a higher rate than 5 amperes. Also the regulator may now be out of spec in terms of its current carrying capacity, especially if it is a series regulator.

    For me the biggest hassle with a solar panel is keeping it facing the sun, every hour or 2 it needs to be moved. During the years that I relied almost exclusively on solar power I often toyed with the idea of making a rotating mounting for my panels that would follow the sun automatically. It involves mounting the panel a rotating shaft that is parallel to the earth's axis (the south end lifting 26 degrees above the horizon, for Jhb), and letting this shaft turn at the same rate as the earth's rotation. Seasons are adjusted by the angle the plane of the panel makes with the shaft. The efficiency of this mounting would be worth at least another panel, and at a fraction of its cost, and it could easily be made collapsible and portable.

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  7. #105
    Join Date
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    Default Re: Camp fridge,105ah battery and solar?

    Quote Originally Posted by Fyko View Post
    The wattage of a solar panel is not really a useful measure of how the panel will perform for your requirement, and you should be wary of advisors who demonstrate their ignorance on this.

    This is because the wattage specifies how much energy, in joules per second, the panel will convert from solar radiation into electrical energy. But it doesn't tell you at what rate it will charge your battery.

    A battery is like a water tank on a tank stand. You push water in intermittently during the daylight hours, and you take water out intermittently both day and night. The tank is not concerned with the power of the water squirt, it is only interested in the quantity of water being pushed in, and how this compares with the quantity of water being released through the load, in this case the fridge.

    The water quantity is measured in litres, and the rate of flow is measured in litres per second. The electrical equivalent for litres is coulombs, which are a specific quantity of electrons, and the rate of flow of coulombs per second, which is measured in amperes. One coulomb per second flowing past a point in the circuit constitutes one ampere.

    In the case of the water tank on its stand, to get water into the tank you need only enough pressure to overcome the gravity-induced pressure of the water wanting to flow the other way. If the stand were 11 metres high, and the tank a further 2 metres tall, and each metre of height represented a single volt then 11.1 volts would be sufficient to get the tank filling, and 13 volts would be sufficient to fill it entirely. Any further pressure would be wasted. The rate the tank filling would be dependent on the water flow rate, and not the water pressure, once the pressure was high enough to overcome gravity.

    The same applies to the solar panel. That the output voltage is going to be more than sufficient to overcome the output voltage of the battery (equivalent to the gravity of the water) is a given. What now becomes important is the rate of current flow into the battery (the amperage) while the sunshine lasts. That figure can be extrapolated from the short-circuit current which is specified on the same sticker as the wattage, and will only be slightly lower than it when the solar panel is made to charge the battery. A full-sized panel will often deliver about 4.5 amperes into a 12 volt battery, but it's easy enough to measure with a cheap multimeter if you have any doubt.(Be sure to use the 10A input on the meter).

    A figure often thrown around, but not always fully understood is ampere/hours or A/h. If an ampere defines a flow rate of 1 coulomb per second, then an ampere/hour is one coulomb per second for 3600 seconds, or 3600 coulombs. If your battery has a capacity of 105A/h then that works out to 105 x 3600 = 2099 coulombs, (not all of which are available for discharge since you should never fully discharge any lead acid battery).

    The fridge on the other hand will intermittently switch its compressor on and off in accordance with internal gas pressure demands. When the compressor is running it will ask for about 3 amperes, and when not it will only want enough to keep the control electronics running, probably about 300mA.

    To arrive at a plausible consumption figure you can guess the fridge's duty cycle at about 50%, or 12 hours out of 24. At 12 hours of running time at 3 amperes you will need to supply about 130,000 coulombs. If your solar panel in full sunshine supplies 4.5 amperes then it will produce 16,200 coulombs per hour. To replenish the 130,000 C used by the fridge in any 24 hour period you need the 4.5A solar panel to function 130,000/16,200 = 8 hours out of 24.

    So, if you have a single 4.5A panel and less than 8 hours per day of full sunshine then the battery will gradually discharge. If you have more than 8 hours per day the battery will overcharge. Unlike the water tank on the 11 metre stand, which will simply overflow if it is overfilled, the battery will likely suffer some damage if you do not shut off most or all of the charging current once it is full. To avoid overcharging the battery you need a regulator. Either a simple series regulator, which comes with some attendant losses, or a switching 'intelligent' regulator which comes with a higher price tag.

    As you can see, a single panel that produces a short-circuit current of 5 - 5,5A will be quite adequate for driving your fridge under most (say 80%) of conditions. Giving it a switching regulator instead of a series regulator will pay some dividends in efficiency and extent the effectiveness of the single panel. Most fridges come with a built-in under-voltage detector that will shut the load off when the battery voltage drops to the point where the battery can be damaged (about 11,5V). If you find the fridge doing this a lot you'll need to add a second panel (connected in parallel obviously, + to +, - to -), a series connection would serve absolutely no purpose.

    The combined output from these 2 panels will now be 9 amperes, which may be more than some smaller batteries can handle. The max charge current for deep cycle batteries is about one tenth of the ampere/hour specification in amps. In other words a 50A/h battery cannot be charged at a higher rate than 5 amperes. Also the regulator may now be out of spec in terms of its current carrying capacity, especially if it is a series regulator.

    For me the biggest hassle with a solar panel is keeping it facing the sun, every hour or 2 it needs to be moved. During the years that I relied almost exclusively on solar power I often toyed with the idea of making a rotating mounting for my panels that would follow the sun automatically. It involves mounting the panel a rotating shaft that is parallel to the earth's axis (the south end lifting 26 degrees above the horizon, for Jhb), and letting this shaft turn at the same rate as the earth's rotation. Seasons are adjusted by the angle the plane of the panel makes with the shaft. The efficiency of this mounting would be worth at least another panel, and at a fraction of its cost, and it could easily be made collapsible and portable.
    Very well and thoroughly explained thank you. Some more things to consider

  8. #106
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    Default Re: Camp fridge,105ah battery and solar?

    Quote Originally Posted by Fyko View Post

    So, if you have a single 4.5A panel and less than 8 hours per day of full sunshine then the battery will gradually discharge.
    Thanks for that, well written post

    If you stick to lead acids, then this why I believe High Cycle, or semi deep cycle batteries is a better choice than AGM for camping. After three days of cloudy weather, my AGM's at home take two days of full sun to get back to fully charged.
    Robert van den Berg...(fully vaccinated with two Pfizer jabs & certified)

    '98 Daihatsu Rocky 'The Kitty' (jabbed with 50ppm)
    '02 Daihatsu Rocky 'The Bully' (jabbed with 50ppm)

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  10. #107
    Join Date
    Jan 2021
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    Default Re: Camp fridge,105ah battery and solar?

    Quote Originally Posted by Kudus View Post
    Thank you for taking the time to write such a detailed experience down. I think Iím getting a good picture now from everybodyís experiences.
    Iíll go through it all again and quantify it.

    So if a 105ah battery only discharges 50% but a 50ah lithium battery almost 100%, would the 50ah lithium battery not be a better option?

    I camp remote, no electricity and so far Iíve been using a mixture of alternator and 100w solar with a normal high cycle battery (donít laugh). It has been working great but Iím always aware and conservative. So I would like to get a battery in a box being able to go with any car and not just with the one with the duel battery system in. Hence my need for info to go completely solar with a deep cycle battery.

    Appreciate all the expert advice here. Thank you

    If you draw your 105ah Lead acid to 50%, then the 50ah Lithium will give you ~ the same capacity.
    So then aside from higher purchase price, the difference /advantages will be
    a) that you can charge the Li so much faster - higher Amp input and straight line charge so no slow charging phase
    b) its much lighter
    c) longevity

    For me the 108ah Lithium giving roughly same useable power as 2 std LA batteries, and outlasting them is the answer.

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  12. #108
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    Aug 2014
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    Default Re: Camp fridge,105ah battery and solar?

    I have a 120Ah lithium battery with a WRND charge controller. At home a 270watt panel keeps two camping freezers, some lights and my computer going without fail. I would imagine a 120watt solar panel should keep one fridge happy most of the time (if it is a Snowmaster like mine). Combined with the WRND which also charges from you alternator when the car is running, you should really have no problem keeping the meat frozen. But if you go through a lot of beer and the unit gets opened and closed and new stock is added regularly then you may want to double that up.

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  14. #109
    Join Date
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    Default Re: Camp fridge,105ah battery and solar?

    Quote Originally Posted by omkeerpunt View Post
    I have a 120Ah lithium battery with a WRND charge controller. At home a 270watt panel keeps two camping freezers, some lights and my computer going without fail. I would imagine a 120watt solar panel should keep one fridge happy most of the time (if it is a Snowmaster like mine). Combined with the WRND which also charges from you alternator when the car is running, you should really have no problem keeping the meat frozen. But if you go through a lot of beer and the unit gets opened and closed and new stock is added regularly then you may want to double that up.
    Mm. I run the same setup, 2 fridges 60l NL + 45L Engel 2005 model.
    On my normal trips I do not need Solar as the battery runs my fridges for 2 days without charge.
    Normal trip= camping with daily gamedrives
    Other trips = stationary for 2+ days I use a 200W Solar blanket. In full sun I get about 11A.
    2002 Discovery td5

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