Advice, please, boondocking on solar, using a DC thermoelectric cooler

Discussion in 'Boondocking' started by JayGoCamper, Jul 5, 2019.

  1. JayGoCamper

    JayGoCamper Member

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    I know that these 12v coolers are less efficient than the 12v refrigerator freezers, but they are also less expensive, and lighter in weight, both of which are important to me. I am looking at this machine, which draws 48 watts (or 4 amps, if A=W/V). I have a countertop ice maker that uses 110 watts AC. I thought I would run the cooler for 10-12 hours during the day (using 40-48 ah, yes?) then run the ice maker for an hour and dump the ice into the cooler for overnight chilling.

    My Solar panel is 150 watts, my group 29 batteries are each rated for 12Oah and I have a 1000 (2000) surge watt inverter. Even though I have a total of 240 ah, I understand that I never want to drain them completely, so I am guestimating that I have 200 ah to work with, exluding solar replenishment. Since the icemaker is on AC, what is the number I should use in the A=W/V equation?

    I am trying to figure out what other small household appliances I might also be able to run and for how long. Any help from those with actual experience or knowledge would be most welcome.

    Thank you.
     
  2. SteveP

    SteveP Well-Known Member

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    Most inverters are only 80% efficient so A=(W*1.2)/V would be close enough. Inverters also have a parasitic draw when powered but not in actual use, it should be included in the spec sheet.
     
  3. tombiasi

    tombiasi Well-Known Member

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    Those coolers cool to a maximum of 40° F below ambient. Yours says 36°F. That means if it over 76° F outside you will just barely be in the safe food zone.
    Don't expect to get out of the solar what the specs say, that's lab conditions.
    IMO: Inverters have no place in this application.
     
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  4. neighbormike

    neighbormike Well-Known Member

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    It sounds like a generator would be a better option for you.
     
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  5. Anthony Hitchings

    Anthony Hitchings Active Member

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    The main thing is to have a good cooler and ice for the main or backup cooling device - so that essential perishables can remain cool all the time in our case, real milk for morning coffee is the key thing) . When you get the fig/freezer /battery/PV etc etc all sorted out then you can decide to ditch the 2nd unit (or not). At the moment, we are using an Engel electric frig (which can freeze if needed, run from PV) and a largish YETI (ice cooled). So we have options - which is nice out on the road.
     
  6. xvz12

    xvz12 Well-Known Member

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    We are currently using a Coleman Powerchill thermoelectric cooler, we cool it down well ahead of time, put a few bottles of ice in it, along with our food, & away we go. I have 200 watts of solar panels on the roof of our pup, with 2 g24 Optima blue top batteries on the hitch. Our pup is an '84, so our power needs are modest, otherwise. We keep the Powerchill in the shade, usually under our awning, & power it during the day, when the panels are producing good power. We shut it down in the early evening, & so far, we've had no issues using it for a long weekend...usually still have frozen bottles of water when we get home. If the weather is cool, we hardly power it at all, as it will freeze things in cooler weather. We try hard to not open it more than absolutely necessary, so we carry a regular ice chest for drinks, etc. Not a perfect method, but works till I can alfford a better solution.
     
  7. JayGoCamper

    JayGoCamper Member

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    [QUOTE="tombiasi] Those coolers cool to a maximum of 40° F below ambient. Yours says 36°F. That means if it over 76° F outside you will just barely be in the safe food zone.[/QUOTE]

    Thanks, Tom. I know about the 36 below ambient temperature. I thought I could keep the cooler in the shade, under an insulated blanket and could use the ice from the ice machine to bring the cooler temperature down during the day, if and when I need to.

    If I understand the formula for figuring out the electricity usage of the ice machine, it gives me a figure of slightly less than 1 amp/hr (110 watts/120 volts) which means I would still have plenty of power left, even if I need to run the ICE machine for 2 or 3 hours a day on a cloudy day.

    [QUOTE="Anthony Hitchings] At the moment, we are using an Engel electric frig (which can freeze if needed, run from PV) and a largish YETI (ice cooled). So we have options - which is nice out on the road.[/QUOTE]

    Thanks, Anthony, I would love to have an Engel, but even if I were willing to pay the price, realistically, I don't think I want to be moving a heavy 26 liter size around, and can't imagine getting much use out of anything smaller.

    [QUOTE="SteveP] Most inverters are only 80% efficient so A=(W*1.2)/V would be close enough. Inverters also have a parasitic draw when powered but not in actual use, it should be included in the spec sheet.[/QUOTE]

    Steve, My inverter specs say Xantrex 2000 Inverter Charger Pure Sine Wave 2000w - 55 Amp - 12v. I think, so far my energy usage falls within those specs. Do you see a problem that I am overlooking?

    [QUOTE="neighbormike] sounds like a generator would be a better option for you.[/QUOTE]

    Why do you say that, Mike? The previous owner did a lot of desert camping and he carried a Honda 2000 generator, just to power his air conditioner, but I don't want to use non-renewable energy if I don't have to. Of course, I will be doing 99% of the cooking using propane, but that's unavoidable.. Right now, with the most conservative figures, it appears that even if it rained 4 days in a row, I could still power the lights, the cooler, and the ice maker from the batteries, without draining them.

    [QUOTE="xvz12] .... We keep the Powerchill in the shade, usually under our awning, & power it during the day, when the panels are producing good power. We shut it down in the early evening, & so far, we've had no issues using it for a long weekend...usually still have frozen bottles of water when we get home. If the weather is cool, we hardly power it at all, as it will freeze things in cooler weather. We try hard to not open it more than absolutely necessary, so we carry a regular ice chest for drinks, etc. Not a perfect method, but works till I can alfford a better solution.[/QUOTE]

    Thank you, xvz12] That is very similar to what I want to do. I am so glad to know that it works in practice as well as in theory. It may not be a perfect method for everyone, but it will be perfect for us. The cooler will ride in the car during travel days, so will draw power from the vehicle, but 20 pounds is about the most weight I want to be muscling in and out of the car at the beginning and and end of the trips.

    Mahalo, Muchas gracias and many thanks to all of you lovely folks who have taken time to reply and help this newbie out.
    Jan (j.)
     
  8. roybraddy

    roybraddy Well-Known Member

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    I played some with an ice maker from WALMART... I can make ICE ok but it is not the hard frozen ICE CUBES and melts real quick... We live out of the COLEMAN 5-day ICE CHEST on our off-road trips. Can make three days pretty easy but after that we have to go looking for ice somewhere...

    My salvation is the 2KW Honda generator... We have enough batteries to do what we want to do from 5PM to 11PM and then the next morning when allowed we will run the 2KW generator to re-charge our battery bank backup from the 50% charge state to the 90% charge state. Once I get them back up to the 90% mark then we can do it all over again for the next day/night run...

    If my ICE MAKER would make hard Frozen ICE I would not have to go looking for more ice...

    Been thinking about adding solar but will need to get at least 17-20AMPS of juice per battery to get my battery bank fromits 50% charge to its 90% charge in a three to four period of time usually starting at Breakfast while I have my generator on-line... I suspect the solar panels will only work for me after I run the generator first for about an hour to get the absorption past it highest current draw. When I first hit my battery bank with 14.4VDC I see a good 50AMPS being absorbed by the battery bank... Then after an hour of charge this drops back to around 6-8AMPs. This for me would be the time I would shut down the generator and let the solar panels take over during the high sun day to get my batteries back up to their 90% charge state before the evening hits me... I can get a good 4-5AMPS DC CURRENT per solar panel when in high sun it seems... That is from a 100WATT solar panel I have been playing with...

    I measure all of this with one of those craftsman clamp on current meters on the battery cables... I can see the + and - symbols when the battery is charging or being used for load...

    The heck with all the ohms law math haha... All I need is a good clamp on DC current meter...

    This was my battery bank of three GP24 80AH Interstate batteries in parallel
    [​IMG]
    Roy's image

    My batteries held up good from late 2008 to around 2012... Then I nursed them along to 2014-15... Then I have been shut down for personal reasons and just now finally getting back into the camping thing again. Will have my new battery bank of two groups of 6VDC Duracells in series which will give me a good 430AHs capacity. These will be mounted in a torklift diamond plate box across the tongue area...

    [​IMG]
    Google image

    Roy Ken
    [​IMG]
     
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  9. theseus

    theseus Centerville, OH

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    If I were in the same situation, I would use a good Yeti type cooler, and ditch the thermoelectric cooler. The ammonia based refrigerators work better (when you know how to actually use them) than a thermoelectric cooler in my opinion.
     
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  10. rabird

    rabird Howdy!

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    but that is not 1ah from the battery. its ~10ah @12v. Power in an inverter = power out less inefficiencies.

    12v * 10A = 120w inveted to 120v *1A = 120w less inefficiencies.
     
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  11. roybraddy

    roybraddy Well-Known Member

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    After looking at the thermoelectric cooler here I think I might have a good use for one of those as well... Would be a good PLAN B item perhaps... One of my back half seats folds up and has a nice flat platform there. That would sit there just perfect and be in hands reach from the front seats. I see you can add a lot of items in there to keep cool when in travel mode...

    Be kinda neat to have all that cold stuff in arms reach in the Truck back seat when in travel mode

    Roy Ken
    [​IMG]
     
  12. JayGoCamper

    JayGoCamper Member

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    Thank you Rabird. A couple of stupid questions, but I have to ask because I really want to understand.

    Where did you get !0A? Is that based on my figures from my ice maker calculations or is it some given that all Solar geeks know?

    So, even though this cooler uses a DC connection, I have to calculate the inverter effect, just because it is between the batteries and the cooler? To avoid this, I would have to make a direct connection from cooler to battery, yes?

    Should I get an AC adapter for the cooler> That seems even less efficient than using the DC plug.

    What difference does it make to the calculation if I run my batteries in parallel? Or should I do that on general principle for some reason or another?
     
  13. rabird

    rabird Howdy!

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    solve the equation if 1A x 120v = 120w = XA x 12v.

    to get 1A @ 120v from an inverter, you feed it 10A @ 12v + a little extra
    watts is power and can be compared, 1A X 120v = 120watts = 10A x 12v
    1A @ 120v is 120w, 1A @ 12v is 12w!

    if the ice maker is 120v then you need a inverter to operate it via battery.

    12v batts are paralleled to make a bigger 12v 'battery'.
    2 x 6v in series is one 12v 'battery'.

    hook parralled batts in a balanced fashion, both load and charge.
    Pianotuna12V.png
     
    Last edited: Jul 6, 2019
  14. BillyMc

    BillyMc Well-Known Member

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    I wouldn't drain mine that low.
     
    Last edited: Jul 9, 2019
  15. JayGoCamper

    JayGoCamper Member

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    Thank you, Rabird. It's much more clear now. I don't know this for sure, but have been told by someone who has the same inverter that if I only want DC power, I just flip the switch on the inverter to battery 1, battery 2, or both.. I will check this out once I open up to set up the beds and pack the essentials. Tomorrow will be devoted to hooking up, and pulling forward in the driveway, then trying to back into the same parking place. I imagine I will be exhausted after a few rounds of that.
     
  16. JayGoCamper

    JayGoCamper Member

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    Thank you Billy. Just to be make sure I understand what you are saying is that would or would not?
     
  17. BillyMc

    BillyMc Well-Known Member

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    Oops! Wouldn't, not good for the battery to be drained below 50%. Not to mention low voltage can damage some things and some will stop working.
     
  18. 8lugnutz

    8lugnutz Member

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    We used our power chill cooler on a 17 day road trip, kept it in our car with the A/C going and it worked very well until the fan failed on day 5 and left us with a spoiled bunch of food that we found on day 6. I repaired it after finding a fan (7 Radio Shacks later), but learned a valuable lesson: have a backup plan. I would not recommend using this as your only method to keep food cool.

    We now have a Cabelas Polar Cap cooler and use Salt Ice Blocks. See here. This kept our frozen stuff cold throughout our entire trip to the Grand Canyon. Here is one of the ice blocks after 4 days.


    We have a 12v/propane fridge in our camper, and because of the above lesson learned, I now have a road pro temp alarm on it to warn me when temps rise or fall outside of the upper or lower thresholds. I don’t even use the fridge as the primary cooling source.

    Propane runs out. Batteries die. Ice melts. But ice makes very cold water, and keeps things cold longer.
     
    Last edited: Jul 15, 2019
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  19. JayGoCamper

    JayGoCamper Member

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    I LOVE the salt ice block idea! Thank you.
     
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  20. Arlyn Aronson

    Arlyn Aronson Well-Known Member

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    We ran thermo-electric coolers for years and years. Of course they were on all the time while on the road, then daily we'd plug it in again while at camp to cool it down. That worked reasonably well and we don't normally camp in hot weather anyway. The cooler crapped out and we bought a new one built in Canada off of Amazon (ask if you care to hear the name brand) and it never worked right. It had a lose electrical connection within it that would occasionally break free and we could not locate the poor connection. This problem was wasn't found until its warrantee was over with. After finding this problem, I noted other folks had the same grief among the reviewers. We started using ice coolers with lots of insulation and found that worked well with less parts to break down...
     
    Last edited: Jul 15, 2019
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