Heating shower water with a coffee cup heater?

[CC58]

Here are a couple of videos on how to make a water heater using a 12V DC heating elements.

Uses a 5 gallon bucket but uses inappropriate element for battery (he is using solar panels). Should use 12V 300W, IMO.


Uses plastic bucket and 12V 700W element. This would pull 58A so a bit much for batteries only.


I have not tried the below two parts so try at your own risk, however I think they are correct.

Here is a 12V 300W element on ebay. It would pull 25A. Would heat 2 gallons to 105 degrees in 45 minutes. Could jumper it to any idling vehicles battery.
https://www.ebay.com/itm/12-Volt-30...Submersible-Water-Heater-Element/371098092495

Here is bulkhead on ebay.
https://www.ebay.com/itm/Bulkhead-T...-Dual-Threaded-Black-EPDM-Gasket/324138722773

 

[abnorm]

^^^^^""Uses a 5 gallon bucket but uses inappropriate element for battery (he is using solar panels). Should use 12V 300W.""

Residential panels output "high" voltage (more than 12 volt) so if you're direct off the solar panel you must use a higher rated element !

 

[bagabum]

I'm trying to figure out the easiest way to heat up 2 gallons of water for a shower  300W and can boil 10 oz. of water in 2 minutes!

I calculated the 120V 300W model can heat 2 gallons to 105 degrees in 37 minutes.  
Only problem I can think of is this heater might not do well running for 37 minutes instead of it's intended 2 minutes.
Has anybody tried this?   Is there a simpler way?

CC58, to answer your question above. The service factor for the heating element will not be affected by running longer than 2 minutes, it will reach a temperature and equalize, no problem. However, although due to more use it may not last as long in the long run. Maybe use your system  to  "topoff"  off your water. If your like me, I dont want to take a shower at noon, I shower before going to bed. So perhaps you could heat your water in the sun as others had suggested, put the water in an empty insulated cooler (cant be that big of problem  and you could use it for food runs) and then top off later at night.   Lets say you start at 90 to 105 = 15x16.66/3.42/300*60=14.6 minutes

 

[barleyguy]

Got my $7 coffee cup heater from ebay and did an experiment. Put 2 gallons of 72 degree water in a plastic bucket and heated it up with coffee cup heater. It pulled 2.65A @ 125Vac (330W). It took 44 minutes to heat up to 105.6 degrees. That calculates to 20.7AH out of a 12V battery using an inverter.

Using an induction cooktop and a 2 quart tea kettle, I can heat 2 quarts of water to boiling in about 5 minutes. Then mix that 2 quarts of boiling water with 1.5 gallons of room temperature water, and it yields 2 gallons of shower water. I've done this many times.

That comes out to 700 watts times 1/12 of an hour is about 60 watt hours. Or 5 AH, rather than 20. Based on that, the coffee cup heater is 4 times less efficient than an induction cooktop for heating water.

(The induction cooktop I have is currently $53 on Amazon. The power can be scaled from 200 to 1800 watts.) https://www.amazon.com/gp/product/B07HRPGBNH

 

[VanFan]

Thanks for the information and link.  I've been looking for a variable power cooktop in furtherance of my independence from propane.

 

[highdesertranger]

what's room temperature water? around here water from the creek is in the 40's at the moment. water in 5 gallon containers outside is in the fifties. highdesertranger

 

[bullfrog]

We turned the hot water heater off and open the cabinet door so water in the tank is cooled by the AC so we don’t scald ourselves when we turn on the cold water that comes out well over 100 degrees. Was 104 degrees today! Lol!!!

 

[barleyguy]

what's room temperature water? around here water from the creek is in the 40's at the moment. water in 5 gallon containers outside is in the fifties. highdesertranger

That's actually a really good point. If the water is really cold, you might need to do 4 quarts of boiling water rather than 2.

(I'm in an RV with a 42 gallon fresh water tank that has a furnace vent pointed at it. For that matter, I have a propane water heater, but it eats propane like crazy. If I turn it on for 15 minutes and remember to turn it off it's not too bad, but if I leave it on, it will burn through a couple pounds of propane a day. Also, I didn't even have any propane this summer. I ran out and decided I could do everything with electricity until next time I need my furnace.)

 

[Happy Camper]

If you have a roof rack to can do black PVC pipe with a tap on the bottom and a fill on top. Since you don't have solar you can even do several smaller diameter pipes for weight distribution and extra warm water storage.

When it's colder you might be able to put some reflective material to focus heat into the pipes.

I've seen some people that had larger pipes on top, but I always wondered about that much weight on one side so high throwing things off a bit.