Author Topic: If my cat sat on a Seebeck effect module, could she charge my phone?  (Read 565 times)

Porkins

  • Formerly Nick H. And a long time ago etc, Eurostar
Serious question. Cats run very hot. Shame to waste all that heat.

Kim

  • Timelord
Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #1 on: June 29, 2020, 01:06:22 pm »
IIRC, cats run a couple of degrees hotter than humans.  Maybe 20C above ambient.  Plug that into the specs for the module and see how much power you'll get.

Obvious problems:

- Phones need >500mA at 5V.  You'll probably have to store up energy slowly and then release it into the phone in one go.  Which is fine, because you'll need some electronics to do voltage conversion and regulation anyway.  It's not going to be plug and play.
-Cats are furry, you won't get very good thermal coupling.
-If there's a decent heat flow through the device, it will feel cold to the touch.  The cat will promptly wander off in search of something warmer to sit on.  (AIUI this is one of the main barriers to using them to power devices like watches or hearing aids).
-Cats are contrary fuckers at the best of times, and will sit on anything except that which is intended as a cat bed.


In summary:  I think you'd get better results from a treadmill.

Careful, Kim. Your sarcasm's showing...

Porkins

  • Formerly Nick H. And a long time ago etc, Eurostar
Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #2 on: June 29, 2020, 01:14:20 pm »
Dammit, the cooling issue knocks it on the head. 

I want to take her cycle-camping. She's a 3kg hairy lump which needs special fuel daily. Probably the least useful bicycle accessory ever. But I can't leave her at home.

Tim Hall

  • I want to eat the fleeting shade of your lashes
Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #3 on: June 29, 2020, 01:20:05 pm »
IIRC, cats run a couple of degrees hotter than humans.  Maybe 20C above ambient.  Plug that into the specs for the module and see how much power you'll get.

Obvious problems:

- Phones need >500mA at 5V.  You'll probably have to store up energy slowly and then release it into the phone in one go.  Which is fine, because you'll need some electronics to do voltage conversion and regulation anyway.  It's not going to be plug and play.
-Cats are furry, you won't get very good thermal coupling.
-If there's a decent heat flow through the device, it will feel cold to the touch.  The cat will promptly wander off in search of something warmer to sit on.  (AAIU this is one of the main barriers to using them to power devices like watches or hearing aids).
-Cats are contrary fuckers at the best of times, and will sit on anything except that which is intended as a cat bed.


In summary:  I think you'd get better results from a treadmill.
Cover the charger thing with newspaper and try to read it. Cat will then sit on the newspaper. They read through their bums.
There are two ways you can get exercise out of a bicycle: you can
"overhaul" it, or you can ride it.  (Jerome K Jerome)

Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #4 on: June 29, 2020, 02:33:25 pm »

Cats are heatsinks, not sources

Feanor

  • It's mostly downhill from here.
Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #5 on: June 29, 2020, 06:51:28 pm »
Obvious problems:
-Cats are furry, you won't get very good thermal coupling.

Shaved patch and heatsink thermal paste?

Kim

  • Timelord
Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #6 on: June 29, 2020, 07:14:33 pm »
Obvious problems:
-Cats are furry, you won't get very good thermal coupling.

Shaved patch and heatsink thermal paste?

Now you have two problems.
Careful, Kim. Your sarcasm's showing...

Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #7 on: June 29, 2020, 08:05:03 pm »
A charger with sharp claws :o. I think this might turn out painful  :)
the slower you go the more you see

Porkins

  • Formerly Nick H. And a long time ago etc, Eurostar
Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #8 on: June 29, 2020, 09:03:40 pm »

- Phones need >500mA at 5V.  You'll probably have to store up energy slowly and then release it into the phone in one go.  Which is fine, because you'll need some electronics to do voltage conversion and regulation anyway.  It's not going to be plug and play.


What if I wanted to get the heat from a fire? I've seen people making something on youtube to do this...what kind of electronics for the conversion/regulation do I need?

Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #9 on: June 30, 2020, 12:11:23 pm »
Other significant issue. Cats sit on anything not intended as a cat bed (see Kim's post). They will therefore sit on the tent and to get there will climb up said tent using said sharp claws (see Cyclemans post).

Claws go through tent fabric. I know this because we garden camped the other week and one of our cats delighted in climbing on our Hilleberg and when that didn't get us moving (I'd apparently not left enough food down for her to ignore) she stabbed my feet through the inner from the air vent at that end of the tent.
Duct tape is magic and should be worshipped

Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #10 on: June 30, 2020, 12:13:30 pm »

- Phones need >500mA at 5V.  You'll probably have to store up energy slowly and then release it into the phone in one go.  Which is fine, because you'll need some electronics to do voltage conversion and regulation anyway.  It's not going to be plug and play.


What if I wanted to get the heat from a fire? I've seen people making something on youtube to do this...what kind of electronics for the conversion/regulation do I need?

This doesn't solve the 'leaving the cat at home' issue.

To actually charge your phone book into camp sites with charging points or use a dynamo wheel.
Duct tape is magic and should be worshipped

Porkins

  • Formerly Nick H. And a long time ago etc, Eurostar
Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #11 on: June 30, 2020, 10:41:29 pm »
This looks good. https://www.amazon.com/Ajirangi-Portable-Thermoelectric-Generator-Camping/dp/B00YPKY1ZQ

It weighs 350 grams. With a pocket wood stove you can charge your phone with twigs.


Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #12 on: July 01, 2020, 08:14:04 am »
This looks good. https://www.amazon.com/Ajirangi-Portable-Thermoelectric-Generator-Camping/dp/B00YPKY1ZQ

It weighs 350 grams. With a pocket wood stove you can charge your phone with twigs.

The temperature difference between the hot and cold sides is a lot larger than you will get with a cat, so it's an approach that has a lot more promise. (AKA could actually work)
Quote from: Kim
Paging Diver300.  Diver300 to the GSM Trimphone, please...

Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #13 on: July 01, 2020, 08:35:48 am »
This looks good. https://www.amazon.com/Ajirangi-Portable-Thermoelectric-Generator-Camping/dp/B00YPKY1ZQ

It weighs 350 grams. With a pocket wood stove you can charge your phone with twigs.

You need to fill it with water and the reviews say it only charges properly when at a rolling boil, which requires lots of fuel and water to maintain.

I don't think there are any portable non-mains-powered phone charging approaches that aren't a huge disappointment in practice, at least outside limited circumstances.

(solar if you live/travel somewhere very sunny; dynamo if your riding-hours-to-use ratio is very low; etc)

Re: If my cat sat on a Seebeck effect module, could she charge my phone?
« Reply #14 on: July 03, 2020, 07:53:42 am »
Serious question. Cats run very hot. Shame to waste all that heat.

Fundamentally cats use about 250kcal a day. If my maths is correct that means that, at best, a cat is a ~12W heat source.   I think that cats feel warm because they are well insulated, not because they are pushing out loads of heat. In any event it is unreasonable to expect to do any better than you might if you 'burned' ~100g of cat food, which is pretty much what the cat is doing.

To put it in perspective if you imagine a 'miracle hot water bottle' that contains ~2L of water and somehow manages only to cool by ~20C in about four hours, that would be pushing out about 12W of heat too.

Of the 12W of heat you would only be able to capture a small fraction, and furthermore that small fraction would not be converted to electricity with any great efficiency.  That electricity will be in turn not be stored with perfect efficiency in the battery.  If you ended up with 100mA charging current into a ~5V battery (charging at 6-7V input voltage) I'd be amazed. Probably it would be a lot less than that.

Practical issues include that anything that is sucking heat out of a cat at any great rate will feel cold to the cat, and even the most rational  cat won't want to stay put for long, any more than (say) it might like to sit on a cold tiled floor.

cheers