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deegore is offline deegore
2010-09-04 , 19:38
Posts: 34 | Thanked: 9 times | Joined on Apr 2010 @ mn
#1
Hi everybody,
I'm putting together what I hope will charge my n900 from a camp fire. I ordered this thermoelectric generator that puts out about 1 volt, and a lv boost to bring it up to 5 volts.
My plan is just to wire it up to a usb plug to connect to my phone. since I know nothing of electrical engineering, I was hoping someone would tell me if I'm missing anything. thanks
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j.s is offline j.s
2010-09-04 , 20:07
Posts: 486 | Thanked: 251 times | Joined on Oct 2009
#2
Originally Posted by deegore View Post
Hi everybody,
I'm putting together what I hope will charge my n900 from a camp fire. I ordered this thermoelectric generator that puts out about 1 volt, and a lv boost to bring it up to 5 volts.
My plan is just to wire it up to a usb plug to connect to my phone. since I know nothing of electrical engineering, I was hoping someone would tell me if I'm missing anything. thanks
The short answer is no.

Your first link is to a device that gets cold on one side and hot on the other when you pass an electric current through it. It will make some electricity when you heat one side *_AND_* cool the other.
Where do you see that you get 1 volt when you do that? Also, how much current?

Your second link is to a device that requires 3 volts input to produce 5 volts output. 1 volt will not do it.

After you fix all that, it will take hours to charge your n900 a few percent.

You will have better luck using a golf cart motor to push a full cement truck.
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Last edited by j.s; 2010-09-04 at 20:13.
 
deegore is offline deegore
2010-09-05 , 00:49
Posts: 34 | Thanked: 9 times | Joined on Apr 2010 @ mn
#3
Originally Posted by j.s View Post
Your first link is to a device that gets cold on one side and hot on the other when you pass an electric current through it. It will make some electricity when you heat one side *_AND_* cool the other.
Where do you see that you get 1 volt when you do that? Also, how much current?
I think a thermoelectric cooler is the same as a thermoelectric generator. When I heat a griddle to 300 degrees and put it on with a heasink on the other side, my multimeter shows as high as 1.7 volts. As both sides heat up the voltage drops.
I'm not sure how to check the current, but probably not much.

Your second link is to a device that requires 3 volts input to produce 5 volts output. 1 volt will not do it.
The lvboost will output 3.3v - 5v, but the input is listed as 0.5v - 5v.

After you fix all that, it will take hours to charge your n900 a few percent.
Agreed it won't do much. My hope is it will give me enough power to check my gps quick if I get lost while I'm out backpacking.
thanks for the reply.
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hawaii is offline hawaii
2010-09-05 , 01:03
Posts: 1,030 | Thanked: 792 times | Joined on Jun 2009
#4
Your better bet is to buy a solar charger...or a second battery.

Unless you want this as a little project, it might not really be feasible.
 
j.s is offline j.s
2010-09-05 , 01:30
Posts: 486 | Thanked: 251 times | Joined on Oct 2009
#5
Originally Posted by deegore View Post
I think a thermoelectric cooler is the same as a thermoelectric generator.
Yes, that is true.

Originally Posted by deegore View Post
When I heat a griddle to 300 degrees and put it on with a heatsink on the other side, my multimeter shows as high as 1.7 volts. As both sides heat up the voltage drops.
I'm not sure how to check the current, but probably not much.
Your multimeter has a high resistance, and does not put much load on your thermoelectric device. As soon as you attach your boost device, the voltage produced by your thermoelectric device will plummet. Also, as you noticed, the power produced will quickly drop unless you keep the cool side cooled.

Your second link says:
From a 3V input, 500mA @5V out is easily achievable
OK, the 500ma @ 3v gives you some margin. At lower input voltages, the output can be maitained for a while with reduced current. But, even 500ma is not much for charging an n900. People have reported n900s slowly losing charge while connected to a computer by USB.

Originally Posted by deegore View Post
The lvboost will output 3.3v - 5v, but the input is listed as 0.5v - 5v.
You are not only not going to get 3V out of your thermoelectric device, you are not going to get the 1.7 V that you get with an open circuit. You are certainly not going to boost half a volt to 5 V.

Your n900 will not charge without 5V in.

Originally Posted by deegore View Post
Agreed it won't do much. My hope is it will give me enough power to check my gps quick if I get lost while I'm out backpacking.
thanks for the reply.
As mentioned above, you would be better off with a solar panel, and even better off with an extra n900 battery or an external battery pack, maybe with a booster.
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shadowjk is offline shadowjk
2010-09-07 , 14:13
Posts: 1,258 | Thanked: 672 times | Joined on Mar 2009
#6
Solar panel with intgrated Li-Ion battery. then one could try feed extra power from the TEG+lvboost in through the same path as the panel...
 
deegore is offline deegore
2010-09-07 , 21:48
Posts: 34 | Thanked: 9 times | Joined on Apr 2010 @ mn
#7
Originally Posted by shadowjk View Post
Solar panel with intgrated Li-Ion battery. then one could try feed extra power from the TEG+lvboost in through the same path as the panel...
That sounds like a good idea. It's probably safer to charge a battery seperated from the phone.

I'm getting 1.3 amps at 1.5 volts with 300 degrees. According to the lvboost.pdf that should put out 300 ma at 5 volts. I hope to get it put together later this week.
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Wichall is offline Wichall
2010-09-07 , 22:00
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#8
Get one of these https://powertraveller.com/iwantsome...nkey-explorer/

It's what I used when I went travelling, worked amazingly well, you strap the solar panel to your backpack and charge while you walk, you can either charge the separate blue battery or directly charge your phone.
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shadowjk is offline shadowjk
2010-09-08 , 01:12
Posts: 1,258 | Thanked: 672 times | Joined on Mar 2009
#9
Another reason for the reuse of solarpanel+battery -charger devices is that they're designed to charge their internal batteries from low current source, and have built in booster for boosting the battery voltage to 5V..

It's probably not entirely reliable to get N900 to charge from 200-300mA with bme, or atleast I've found it a bit unreliable with the default software. So the external storage battery+panel+teg would also serve to discharge the harnesses energy at a rate N900 is happier with.

Those are some impressive figures for your teg though.. How do you maintain a 300 degree temperature differential I wonder?
Last edited by shadowjk; 2010-09-08 at 01:14.
 
deegore is offline deegore
2010-09-08 , 03:06
Posts: 34 | Thanked: 9 times | Joined on Apr 2010 @ mn
#10
The powermonkey looks nice but a bit pricey.

I've been testing with my griddle set to 300 degrees so it's only about a 200 degree difference. I set a cup of water on the other side.
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