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I have 5 of these TEC1-12706 peltier coolers. I don't want to use them at max capacity. My question is to cool water (about 40F or 5C). What voltage can I do this with? If you have prior knowledge or know the math behind it or can give and advice in general all help is appreciated.
Depends on how much water and what kind of container the water is in.
Maybe some experimenting is in order.
Look at a constant current source to supply the power.
If you have a 12 volt PS (or battery) that can supply 6-8 amps use this to power the CCsource/peltier cct..
Adjust the CC to 4.5 amps and see if you get the results you want.
An adequate heat sink will be needed.
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You will need to be able to dissipate 100W just from the power input to the module. Add to this the heat removed from the water. This is for each module.
Peltier devices are interesting to play with but are not a practical source for cooling due to their high inefficiency.
Weedpharma
What is your suggestion for cooling water (about 1L)? Thanks
Room temperature would be the starting temperature
I realize I can use a TEC1-xxx01 to drop to a 1 amp draw (the 06 are what I have on hand).
Refrigeration would bw ideal but I suspect you are looking for something a lot cheaper.
Tell us more of what and why.
You may be able to locate an old office water cooler. These have relatively low volume and do not consume a lot of power.
Weedpharma
What is your suggestion for cooling water (about 1L)?
Obviously, you could put it on ice, or in the refrigerator.
Perhaps you could tell us why the water needs to be actively cooled.
I think you need ~4.2watt for 1second to cool 1cc of water by 1 degree.
If you know the efficiency of a pletier, you can work it out.
Leo..
PrescottJoule:
What is your suggestion for cooling water (about 1L)? Thanks
If budget is important, consider using an electric cool box, example:
http://www.argos.co.uk/static/Product/partNumber/1717103.htm
or an electric mini-fridge, example:
http://www.argos.co.uk/static/Product/partNumber/1395013.htm.
The cool box has a cooling fan and the mini-fridge may have a cooling fan; the fan noise could be annoying. Note these will probably not cool to near +5C on a hot day and will take a few hours to cool 1 litre of water.
weedpharma:
Peltier devices are interesting to play with but are not a practical source for cooling due to their high inefficiency.
My electric coolbox is quite practical for keeping drinks cool on a boat but it will certainly not be practical to try to reach 5 °C, it might cool by 5 C° though 
Russell.
russellz:
My electric coolbox is quite practical for keeping drinks cool on a boat but it will certainly not be practical to try to reach 5 °C, it might cool by 5 C° though
According to the Q&A for that cool box: "At an outside temperature of approximately 25°C the inside of the box will have an ideal cooling temperature of 5°-8° after about 2 hours of operation."
My project is to cool a water bottle (1L or less) to 5C/40F during a 1 hour or more bike ride/practice/workout etc.
Peltier efficiency is indeed very poor, but it is solid state which makes things a whole lot simpler
in some situations. Your main issue will be getting rid of all the heat, which means something like
a CPU heatsink and fan per peltier device. The cooler the "hot" side of the peltier the more
efficient it will be. Adding 5W of cooling fan may well give you more than 5W more effective
cooling from the device due to the lower temperature difference across it - don't skimp on
the fans!
Also a powered-down peltier is a very good conductor of heat, so you cannot simply stop
the power when you've reached the target temperature, or you'll simply warm it up again
fast. The only way round this is to physically separate the device from the cool chamber
somehow, such as a servo. This could well be a more effcient way to control the temperature
than continuously driving the peltier.
The only way round this is to physically separate the device from the cool chamber
somehow, such as a servo.
Or when the temperature is reached, PWM the peltier to maintain the temp.
PID controller?
PrescottJoule:
My project is to cool a water bottle (1L or less) to 5C/40F during a 1 hour or more bike ride/practice/workout etc.
Cool your water in home fridge, then put it in a vacuum flask with some crushed ice.
On your bike, where are you thinking of getting 14.4 volts at 6.4 amps from for each of your five Peltier coolers? . . . . . or is this a student project?
By the way, if you pedal fast enough you won't need a fan!
By the way, if you pedal fast enough you won't need a fan!
You can pedal quite slow and get it to freeze in Canada (a few months from now).
Clarification: I am using 1 of the five and I will use TEC1-12701s instead of TEC1-12706s due to the far they only require 1 amp and can be run on a smaller power supply.
PrescottJoule:
My project is to cool a water bottle (1L or less) to 5C/40F during a 1 hour or more bike ride/practice/workout etc.
Chill the bottle in a fridge first.
Then keep it insulated.
Chilling water on a bike gets you the weight penalty of the battery required.
Insulation is much lighter.
You can roughly figure out how much cooling you will need to do this, and a peltier solution isnt great.
The specific heat of water is 4.186 j/g/c, so to cool 1 litre of water (1000g) from 25C to 5C will need
4.186 X 1000 x 20 = 83720 j which is 23 WH.
The typical efficiency of a peltier cooler is around 30% assuming you have a good heatsink and can get rid of the heat from the hot side so that means you need 23 X 100/30 = 77WH, so you need a 77W peltier as a minimum requirement, if you want to cool the water in an hour.
This calc assumes zero heat loss from the container thats holding the water being cooled,zero thermal resistance between the peltier and both sides of the heatsink and ignores also the power needed to run the fan to keep the peltiers hot side cool, so to be sure you are really looking at a 100W peltier.
Much easier and cheaper to just fill a thermos flask with iced water.