Heating shower water with a coffee cup heater?

[CC58]

I'm trying to figure out the easiest way to heat up 2 gallons of water for a shower using a Home Depot pump up sprayer.  I thought about those coffee cup heaters you put in your cup and read up on them.  The 12V models won't work because they are only ~100W.  The 120V models are 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.  I would use a 350W inverter and a deep cycle battery to plug it in.
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?

 

[abnorm]

SOLAR......set the sprayer in the sun filled with water,,,,,,try spraying it Black

Water bottles set on the dashboard in the sun

We use a bucket on the propane stove...………...

 

[barleyguy]

You can just heat about 3 quarts of water to boiling, mix it with 5 quarts of room temperature water, and shake well. I've done this quite a bit, and usually end up in the 110 degree range. If that's too warm, let it sit for a while to cool down. You can use a laser thermometer to check it.

A tea kettle on a propane stove would probably be easiest as far as heating the boiling portion. Or you can use an electric kettle if your inverter is big enough,or a coffee pot with no coffee grounds in it. Or a "jet boil" which is a portable device that tent campers use to boil water.

 

[highdesertranger]

heating anything with electricity is very inefficient. heat the water on your stove.

helpful tip,
a word of caution on a infrared thermometer they cannot accurately measure the temp of liquid. the instructions that came with mine specifically stated this and I have a professional model not a consumer grade. when you try to take a reading on a liquid it is passes through the liquid and measures the temp of the container. which is usually less than the liquid. keep this in mind.

highdesertranger

 

[CC58]

I plan to have a secondary 100AH deep cycle battery with a 20A renogy charger and traveling daily.  Using 20AH daily for heating shower water is no problem as it will be replenished daily.  Storing a little coffee heater is less space than a stove and propane, and electricity will never run out.  If I were stationary then electric wouldn't be efficient without a good amount of solar.  I won't have solar.  Space is my biggest problem in a SUV.

 

[Spaceman Spiff]

It will be interesting to see how long they last; they aren't made for long duty cycles.  The one I used for coffee at work lasted about 6 months heating 8 oz of water.

 

[highdesertranger]

you will not recharge your battery to 100% unless you are driving 5-8 hours a day. unless you are driving that much everyday you will ruin your battery in a short time.

may I suggest you do some more research in charging and discharging batteries.

like I said before it is very inefficient to heat anything with electricity. you don't really notice this in a house because electricity is so cheap but on the road you are the power company and you will soon realize that it is neither cheap or easy.

I have said it a hundred times,
It is always cheaper and easier to conserve power than it is to make it.

highdesertranger

 

[LoupGarou]

I don’t have a sink, but I do use an enamel wash basin placed on a single burner butane stove to heat water for sponge baths and doing dishes.

https://www.amazon.com/s?k=enamel+eash+basin&ref=is_s

 

[DannyB1954]

If you are driving every day, use the heat from your vehicle engine to heat the water. Just put two T fittings in the lines that go to the vehicle compartment heater, and run hoses to a container of water with a loop of hose or copper tube in it. If the container is insulated it will stay hot for hours. Some marine water heaters have a place to hook up the water lines to the engine. The one I had on a boat was 6 gallons. I could heat from shore power, or engine heat. It will heat the water to 180 degrees F, so have cold water handy or let it sit for a while.

One trick that I found for the pump up garden sprayers, (besides painting them black), is to get a clear plastic bag large enough to go over the top of the sprayer. The sun heats the water, but the wind cools it. The plastic bag acts like a green house to keep the wind off. it also helps hold the air temperature around the sprayer at a higher temp.

 

[CC58]

I've researched LiFePo4 batteries with a 20A Renogy charger. I have a cheap used LiFePo4 battery coming soon. LiFoPo4 will pull 20A until it tops off so it would only take one hour drive to restore 20AH needed to heat 2 gallons of water. You are right that lead-acid deep cycle take several hours to top off the last 20% of charge due to it's much slower absorption final stage of charging.

 

[CC58]

If you are driving every day, use the heat from your vehicle engine to heat the water.

I researched that method and found a really interesting heat exchanger for $40 on ebay by dudadiesel that several have used successfully. You can find him on ebay by searching for "Stainless Steel Copper Brazed Heat Exchanger".  The 10 plate 8"x3" is really small and transfers a lot of heat.  I decided all the plumbing, wires, and pumps was alot of work, but still interesting solution.  Thanks!

 

[highdesertranger]

get a used transmission or engine oil cooler. tee it into the heater hoses and place it in a bucket of water. cheap and easy. that was a great suggestion Danny. highdesertranger

 

[bullfrog]

My old motorhome had two heater hoses that ran to a coil in my water heater tank to save propane and one of my jeeps had a rather expensive pressurized shower that had a heat exchanger in the heater hoses I imagine they still are available.

 

[chris84]

If you are driving every day, use the heat from your vehicle engine to heat the water. Just put two T fittings in the lines that go to the vehicle compartment heater, and run hoses to a container of water with a loop of hose or copper tube in it. If the container is insulated it will stay hot for hours. Some marine water heaters have a place to hook up the water lines to the engine. The one I had on a boat was 6 gallons. I could heat from shore power, or engine heat. It will heat the water to 180 degrees F, so have cold water handy or let it sit for a while.

This is what I had in my old Class B and in my new conversion I built. The old class b was just a traditional RV water heater with an added heat exchanger. The new conversion is an Isotherm designed for a boat, but it heats 4 gallons of water with either the engine heat or 110V AC 750W. When using the engine heat it gets very hot!. I have a tempering valve on the heater to mix in cold water.

I have never used it with AC power. I drive at least once every two days. If I am in a place with hookups I also have access to a shower for the most part (and not one with a gallon tank). I could easily use the AC part as I have a 3000 watt inverter and 600 AH battery bank, but I have not as of yet had the need.

Using engine heat is going to be the best way to heat water if you run the engine, it is otherwise waste heat. Nothing more efficient than capturing waste heat.

 

[Trebor English]

Drive the WWII Jeep up the hill and back down.  Drain a half a helmet full of hot water from the radiator.

 

[crofter]

Cold water is much more refreshing.  -crofter

 

[Dingfelder]

SOLAR......set the sprayer in the sun filled with water,,,,,,try spraying it Black

Water bottles set on the dashboard in the sun

 Good ideas.

I have had great success using five-gallon black buckets I got from Home Depot.  I've seen them in, I think, two- or three-gallon sizes too.  They sell the lids separately, but I think it came out to about six bucks total.  And buckets are useful for other things too, like storage, so they aren't necessarily wasted space.

I put them out in the sun and the water can get very warm.  I have a sprayer, but prefer to use a battery-operated shower hose that drops into the bottom of the bucket and brings the water up.  I can close off the water flow as needed.  That cost me about 30 bucks I think.  There are lots of them on Amazon.  Five gallons of shower water is really a pleasure.

 

[maki2]

I'm trying to figure out the easiest way to heat up 2 gallons of water for a shower using a Home Depot pump up sprayer.  I thought about those coffee cup heaters you put in your cup and read up on them.  The 12V models won't work because they are only ~100W.  The 120V models are 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.  I would use a 350W inverter and a deep cycle battery to plug it in.
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?

Coleman and other companies make propane powered hot water heaters for camping showers.

 

[abnorm]

Yes but they require a pressurized water supply to operate...…at least 1 gallon per minute or "no ignition".

We used a ShuFlo 12 volt pump and a 55 gallon barrel of water to supply a Camp Chef water heater at YARC camp at the LTVA in Quartzsite...…

 

[CC58]

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.

I was surprised the coffe cup heater worked. The handle barely got warm and the bucket didn't melt. However, I had to stir it ever couple of minutes because the cold water on bottom did not mix with the top hot water. Guess that is why they put heating elements at the bottom of water heaters.

Dingfelder's idea of using 5 gallon black buckets in the sun sounds great, and if not warm enough I could use coffee cup heater to heat it the rest of the way. I appreciate everyone's responses!

I don't think the coffee cup heater is the right solution as it is a bit dangerous running 120Vac and instructions say "danger if handle in water". They do make 12V 300Watt heating elements. I'll post some links after my newbie status is upgraded and I'm allowed to do that.