battery powered water / aquarium heater

Posted on 2013-12-25
Medium Priority
Last Modified: 2014-01-13


Are the above 2 items just water pump or they heat up
the water as well?

I'm looking for water heater (to heat up about 35-39 litres
of water in pail) for shower:

Would the following be under-powered, ie takes more than 20 mins
to heat up from my room temperature of 27 Celcius to 37 Celcius:

I plan to cut the car cigarette input & re-attach to the 12V battery below to power it:

Or anyone know of any aquarium heater that's battery-powered?
I've seen an EHeim model that can go up to 88 F (almost 31 C ?)
but it needs power inputs from wall.

I thought of APC mini UPS but this is too bulky a device (almost
7-8kg) & doubt its batteries have many charging cycles
Question by:sunhux
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Author Comment

ID: 39739162
Or use the Rayovac 12V batteries with the horse drinking
heater below but it only heats up to 55F only (I'll need 97F).
There's no contact at that website too

Heating in an open pail can cause heat escape, so perhaps
the following 12V (need to cut & re-attach to the Rayovac
battery) will prevent heat escape better but I'll need perhaps
6 of them to add into the pail of cold water?
LVL 10

Assisted Solution

Korbus earned 2000 total points
ID: 39739235
"I'm looking for water heater (to heat up about 35-39 litres
of water in pail) for shower"

Dude! That is HARD CORE!

Keep in mind your energy requirements, heating up water takes alot of power.  I'm not sure if you will be able to do it with a battery that is NOT bulky, and it will need a recharge after each use.

1 calorie can heat 1g of water 1deg C
35 L of water heated 10 degrees C=350K calories
1 cal = 0.001163 Wh
350K cal = 407 WH

I'll use my solar cell batteries as an example, each weighs about 100lbs and cost about $350.   They are 6V each, with 360AH total storage.  Thats a total of 2.16KWH,  though you can't really draw all those AH without ruining the battery-  so say you pull 15% before recharging:  thats only 324WH, not quite enough to heat up your water.

Another option:
Use the sun-  paint the outside of your pail black, and put it out in the sun on a sheet of reflective mylar.  You can use more sheets of mylar hung up nearby to reflect more sun onto the bucket.  I have got 100degF water on 70degF days with this (I didn't even paint the 5 gal water jug we used, black).  Of course, if you want a hot shower in the morning, or on cloudly days, this simply wont work.  

One other thought: We live in a remote area and Liquid Propane, rather than electricity is usually our power-source-of-choice for heating.
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Author Comment

ID: 39740092
LVL 10

Expert Comment

ID: 39741263
I was going to help try to compute a best case scenario, but I can't find the specs on the pot or battery.  I'm going to guess though that a small/medium battery like that is NOT going to put out sufficient power for the pot.  Without the ability to draw sufficient current from the battery the pot either wont work, or the heating element will get only so hot, and/or do it really slowly (possibly slower that you will loose heat to the enironment).

Perhaps we can help think of a workaround.  Are you trying to keep things light so you can carry it?  Is the water just for showering?  Are you in an area where a plain-old coleman solar-shower-bag wont work consistently enough?

Author Comment

ID: 39743257
Well, I'm afraid of using gas or fossil fuel to heat up water as
we have a couple of gas escaping & almost caught fire.

Yes, the water is just for showering at night when temperature
drops to 26 Celcius (from 30 C).  Well, the weather is sunny
about 70% of the times but the concern is can coleman solar-
shower bag keep the water warm say for 5 hours (after sunset
at 5.30pm), will only take the shower at 10.30pm.
LVL 10

Assisted Solution

Korbus earned 2000 total points
ID: 39743854
Shower bags are only intended to get warm in the sun- they have no insulation, so I doubt it would stay warm for 4 hours.  I guess it you kept it in your sleeping bag or somthing that would help-  unless you get a leak!

If you are not carrying the stuff around, perhaps a deep cycle car battery would power that hot-pot.  They are really heavy though.

Author Comment

ID: 39744549
What if I have 8 D batteries joined together serially?
Can this power the hotpot?  I'm looking at Tenergy's
10000mAH rechargeable D cells.

Guess I'll have to look for something that could enable
me to easily joined all 8 D cells together: anything in
Amazon you could recommend or I have to DIY it?
LVL 10

Assisted Solution

Korbus earned 2000 total points
ID: 39744962
Ok, so if you hook them up in seriers you will ADD all the voltages up, but the current (amps) will remain the same.

I think those NiCa batts are 1.25V each (http://en.wikipedia.org/wiki/D_battery)
So, 1.25v * 8 = 10V (this is NOT the right voltage for the power connector on that hot-pot - which is 12V)

at 10,000 mAH or 10AH, thats a total Energy of 10V*10AH= 100 Watt hours
(This is not really how much power you can draw efficiently, but rather the max the battery can store. So, expect a less.)

1 watt hour = 860 calories
total Calories in btteries 86,000 Calories =
The hot pot holds 20oz (or 591g of water)

So, if 1 calorie can heat 1 gram of water 1 deg Celcius:

86,000 Calories / 591grams = 145deg C
You will be able to increase the tempurature of the water in the pot by a total of 145degC, using ALL the energy in the batteries.  

Even though this is a "best case" scenario, thats actully alot more heat than I thought you would get!  

If you use two more batteries you will have a 12.5V output, which will work with the pot (and provide more total heating power).
One other thing to consider-  as the load(hot-pot) is connected, and the batteries drain, thier voltage WILL go down, so starting over 12V is generally a good idea.

Regarding connectors: check out digikey.com  they probably have somthing.

Author Comment

ID: 39746348
> those NiCa batts are 1.25V
At amazon site, those D cells are published as 1.5V each
so guess 8-9 cells would suffice.  At 10000mAH ie 10Amp
each, isn't this enough?

Would the following help join together the D batteries
serially or I'll still need to get crocodile clips?



Author Comment

ID: 39746374
On reviewing most of amazon's D cells ratings, looks like the
D cells give 1.2 to 1.25 Volts only, so you're right.

I've noticed that D cells are rather costly at around US$6.2 per cell
(from dx.com's
 to US$7.35 for Tenergy's).

Would AA cells at 3000mAH each be enough to boil the water per charge?
I don't mind recharging the AA cells daily as it costs only US$1.05 per cell
& if four of it were to be joined in parallel to give 12000mAH, it costs only
US$4.2 for 4 D-cells

Author Comment

ID: 39746412
Typo correction:
>  ... it costs only US$4.2 for 4 D-cells
   should have been
... it costs only US$4.2 for 4 pcs of AA cells

The water temperature at night here is around 26-27 C,
so I'll need to heat them up by 73 C, so 10pcs of D-cells
can be used twice : correct me if I'm wrong

Author Comment

ID: 39746467

I think the above Li-Ion battery is a better deal, delivery 3.7V
& 3000mAH.  Is the size of this battery the same as AA & can
a AA charger be used to charge it?
LVL 10

Expert Comment

ID: 39746472
"Can be used twice"-  I doubt it, keep in mind that was a best case scenario computation, we used 100% efficiency for the batteries and hot pot, and assumed no loss of heat to the air.
LVL 10

Assisted Solution

Korbus earned 2000 total points
ID: 39748885
I realized last night while going to sleep:

"The water temperature at night here is around 26-27 C,
so I'll need to heat them up by 73 C"

only if you want to make tea:  I strongly advise against showering in nearly boiling water, LOL.
40degC  is what I see on google for hot showers.  
You'll probabaly need a thermometer to see when it gets that hot.

So at 40-26 = 14degC change:  looks like you can indeed get much more than one 20oz heating out of those batteries.

Author Comment

ID: 39754053
So Korbus, is it feasible for me to heat up 60 ounces (ie 3x hotpots)
of water from 26 to say 95 Celcius & mix this 60oz into a pail of
26 C water, volume 40litres for the purpose of taking a bath?

I'm comfortable with 34 Celcius water for a bath, don't need to go
up to 40 Celcius
LVL 10

Accepted Solution

Korbus earned 2000 total points
ID: 39755699
26 to 95, that's lets say 70 degrees per hotpot.  For three pots thats a total change of 210deg, more energy than those batteries can store (145degC total change per 20oz pot)

regarding mixing the hot and cold water, here's how I would compute the final temp of the water..
60oz = 1.7 liters @ 95C
40L -1.7L = 38.3L @ 26C
(1.7*95 + 38.3*26 ) / 40= 28C  

This looks so low because your pail is 40 liters, compared to the mere 1.7 liters of hot water.  

The idea I metioned previously about using a solar shower is starting to look a bit better now.  If you keep it insulated, maybe in a foam "cooler" after the sun gets low it can stay warm enough.  If you can increase your starting temp by say 5 deg C...

60oz = 1.7 liters @ 95C
40L -1.7L = 38.3L @ 31C
(1.7*95 + 38.3*31 ) / 40=  (161 + 1187)/40=33.7C

How many people are showering?  The two of us can both shower on 5 gal (19 liters), just gotta keep it short.  If you can reduce the water to half a bucket, without the solar heating...

60oz = 1.7 liters @ 95C
20L -1.7L = 18.3L @ 26C
(1.7*95 + 18.3*26 ) / 20 = 31.8C

You get a much larger increase in temp.
LVL 10

Expert Comment

ID: 39778376
Thanks sunhux,  I somhow missed your questions about which batteries to get..
The total POWER(watts) is Voltage(volts) * Current(Amps)

So look at what type of battery is going to give you the most POWER per dollar (and possibly also look at POWER per pound- if lugging them around)

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