DIY themoelectric cooler

[Flapdoodle_dinghy]

Hello to all. I am new to the group; encouraged to join by one of your members. My interest is more in the area of dinghy cruising, but many of the problems we encounter are similar.

There is a page of my on-going work in TEC devices that may be of interest. You are welcome to follow along as I learn (and unlearn) the secrets of these fascinating cooling devices.

http://www.flapdoodledinghy.com/cooler.html

Comments and input appreciated.

Bill Weller

[Podunkfla]

Bill... It will be intyeresting to see your results... I'm not impressed with the little one I bought.

[Alphacarina]

Curious as to how big your 'enormous' deep cycle battery really is?

As a longtime sailor who always travelled with 'enormous' battery banks (400 to 600 AH's) I never found TEC's efficient enough to use for cooling anything

If you want cool and don't actually have 'enormous' banks of batteries, look into Engel refrigerators - They use little power and will even keep ice cream frozen

Nice selection of them on eBay . . . . a 43 quart one is going in my teardrop

Don

[bdosborn]

Several people on the list have messed around with them but nobody has had any luck with them. They all gave up because of excessive current draw.
Bruce

[Flapdoodle_dinghy]

I am getting as much cooling at 5 volts and 2 amps (including the fan) as I did with 5.5 amps and 12 volts. That works out to 10 watts. The reason is there is not as much waste heat going to the hot side heat sink.

Since this is project is intended for 8' dinghy cruising, 400-600 Ah would be out of the question.

Yes, I could buy a small refrigerator. But then it would not be a DIY project.

Bill

[jmullan99]

I know this an old thread, but perhaps someone is still monitoring.

I have 3 thermoelectric units. 2 larger coolers, and a little 6 can mini fridge. The mini fridge was disappointing, until I swapped out the fan for one with higher CFMs. Now, it will turn my pop to slush in a few hours.

The 2 coolers work alright if you keep them out of the sun, and somewhere that the heat can escape. But don't expect them to cool down nicely if you pack it with warm food first.

Now for my point: Running one of these cooler units, at about 4 amps continuous, versus a small compressor type bar fridge, with intermittent draw via inverter, can net almost the same battery draw.

So given the superior cooling ability of the bar fridge, I will take that over the thermoelectric coolers.

Cooler unit = 96AH = 4A x 24hr )
Fridge = 95AH = 1.2A x 10 (for inverter) x 24hr, based on 33% average duty cycle.

Of course, depending where you keep your fridge and how often you open it, the duty cycle could increase significantly, but at night could drop a lot as well.

Cheers.

[Podunkfla]

jmullan99... Sounds like a good plan. Plus, if you are going to install one of those little dorm/bar fridges built in, you can vastly improve their efficiency by wrapping them with 2 or 3 inches of foam insualtion board. You can get about another R-30 or so in a small space and prolly double the amount of time between compressor cycles. Insulation is cheaper than electricity...
Of course, ya have to vent the condenser coils somehow, preferably to the outside.

[jmullan99]

jmullan99... Sounds like a good plan. Plus, if you are going to install one of those little dorm/bar fridges built in, you can vastly improve their efficiency by wrapping them with 2 or 3 inches of foam insualtion board. You can get about another R-30 or so in a small space and prolly double the amount of time between compressor cycles. Insulation is cheaper than electricity...
Of course, ya have to vent the condenser coils somehow, preferably to the outside.

Yes, but you have to watch. A lot of fridges now have the condesner coils inside the sheet metal sides. Covering those would be a no-no. Look for ones with the coils on the rear.

Cheers.

[Podunkfla]

jmullan99... Sounds like a good plan. Plus, if you are going to install one of those little dorm/bar fridges built in, you can vastly improve their efficiency by wrapping them with 2 or 3 inches of foam insualtion board. You can get about another R-30 or so in a small space and prolly double the amount of time between compressor cycles. Insulation is cheaper than electricity...
Of course, ya have to vent the condenser coils somehow, preferably to the outside.

Yes, but you have to watch. A lot of fridges now have the condesner coils inside the sheet metal sides. Covering those would be a no-no. Look for ones with the coils on the rear.

Cheers.

Hmmm... I haven't run across one of those yet? Sounds like a bad design idea to me?

[Alphacarina]

Most all of them I've seen over the past 10 years or so have the condensers incorporated into the case - I think primarily because the little units are so portable and there is less likelyhood of damage than with the ones which had the condensers hanging off the back

Another consideration (and a big one if you're counting energy consumption) is that they are all front loaders - With a front loading box, you dump out all the cold everytime you open the door . . . . even for just a couple seconds, so the cooling process must begin anew everytime you open the door - Stick with toploaders if you don't have 'shore power'

If you're depending on running off batteries, dorm room units are just about as useless as the TEC units are

Don

[jmullan99]

Another consideration (and a big one if you're counting energy consumption) is that they are all front loaders - With a front loading box, you dump out all the cold everytime you open the door . . . . even for just a couple seconds, so the cooling process must begin anew everytime you open the door

Don

I agree, and understand, the inefficiencies of front loader. I would like to mention however, that if you keep it as full as possible with already chilled items, there is little cold air to lose, and less recovery time. It helps a lot. But still doesn't beat a top loader.

Cheers.

[jmullan99]

As a follow-up, my results from most recent camp-out using my bar fridge and inverter/batteries.

I have about 110AH worth of battery (deep cycle marine). I ran the fridge via inverter. Prior to heading out, I froze a 24pack of bottled water 24x500ML. This was stored in the fridge along with frozen meats, some dairy products, etc. and consumed. Removing a bottle to set out for an hour to melt so it was drinkable).

Other than on-board water pump and a couple of wall-wart based items, this was about the only real load on the battery.

I got a little less than 48 hours time before the inverter complained. One hour charge from the (running) tow vehicle topped them back up. But I ran to Canadian Tire to get a second battery, and let that take over while I charged up the other. Now with both, I imagine I will run an entire long weekend on battery without much issue.

After the weekend, there were still mostly frozen water bottles.

I am confident that a TEC would not have done as nice a job. And they have less volume than the bar fridge.

I would like to also point out that unless you are an off-grider, marine hybrid (deep cycle + starting) are an excellent choice of occassional camping. You can charge and discharge them at a faster rate than actual deep-cycle units, and yet they will perform nicely on a longer small draw. Best of both worlds.

I have a longer trip coming up this long weekend (canada). Will put it to an even bigger test. Including a small 1200W generator for other occassional needs, like the microwave.

I will post additional electrical experiences from this trip for the benefit of anyone that is curious as to real life results.

John

PS: Mods (Mike?) should this be a seperate thread?

[Johno]

jmullan99

In your last post you were going on a trip the following weekend, if you did, could you please post your most recent inverter / battery results? Thanks.

- John -

[jmullan99]

Ahhh yes, the second test.



Well, we went on a camp out with my brother and his partner, my sister and her partner, myself, wife and grandson.



My sister had a thermo-electric cooler, with an AC adapter added as a load. There was quite a bit more water pump usage with 7 people. The fridge was opened quite a bit more often. I again had it loaded with 24 frozen bottles of water. They melted quite a bit faster with the increased access to the fridge.



I got less than 24 hours out of the batteries. But I did neglect to ensure they were topped up before we left. They were topped up when we returned from the previous trip, but not since (almost a month). Error number 1.



I attempted to charge them up via our vehicle. Even after 2 hours, they didn't really get topped up. My 3 stage charger at home is more suited to it. I attribute that to leaving it at normal idle, as well as being a total of 3 batteries in the circuit (the tow vehicle battery and the extra I had purchased last trip).



I should have been able to squeeze more time from the batteries, but not being topped up and the extra loads were just too much. The RV style 12V converter (40A) was also tried, via the small generator, but it is only 13.5V and really not enough to push the battery voltage to it's max. They are not designed for true battery charging.



Our next 2 night outing is next week, but we may have hydro hook-up. However, I will bring my home-built 12V generator (see my album) and go without the hookup unless I run into issues again. The 12V genny should do a bit better at adding back the power into the batteries. For one thing I can set the throttle on it higher to get better output from the alternator. And it will only be the two house batteries.

We were foresighted enough to bring an extra empty cooler, and we resorted to putting the important fridge stuff in it with some purchased ice for the last day or so.

Again, with next week's trip (wed noon to fri noon), I will experiment. I will ensure that the batteries are absolutely full before we leave.



Feel free to ask questions if I haven't covered everything.

John

[BrwBier]

My sister had a thermo-electric cooler, with an AC adapter added as a load. There was quite a bit more water pump usage with 7 people. The fridge was opened quite a bit more often. I again had it loaded with 24 frozen bottles of water. They melted quite a bit faster with the increased access to the fridge.



John

Isn't that just wasting the power? Just skip the ac adapter and run off the battery. I'm glad someone (not me) would go through this fruitless effort just to prove that if you haul enough stuff along that... oh well thanks any way.