# Boost converter current calculation

Discussion in 'General Electronics Discussion' started by BlackMelon, Aug 21, 2014.

1. ### BlackMelon

188
5
Aug 7, 2012
Hello there!

I'm designing a boost converter by using this book:

http://www.mediafire.com/view/00awc...tronics_-_D._Hart_(McGraw-Hill,_2010)_BBS.pdf

From Example 6-4 of page 216, I want to calculate an inductor current but my load resistance is only 1 ohms (since I want the circuit to be able to supply 12V 12A dc motor from a 1.5V battery). The result that I've got is 123.45A of inductor current. My questions are..

1) Did I make any mistakes?
2) If not, do I need a very very large wire to withstand the current?

Thank you
BlackMelon

2. ### OLIVE2222

690
25
Oct 2, 2011
for the inductor Inom = (Uout/Uin)* Iout, so rawly 100A
do yo really expect to supply the motor from a 1.5v cell?

3. ### BlackMelon

188
5
Aug 7, 2012
Yeah, I think may be 2-3 cells in parallel might be lighter than a 12V battery...

So how to deal with the current? It's kind of massive >_<

4. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,505
2,849
Jan 21, 2010
Get a large 2V lead acid battery.

It will need to be somewhat larger than a 12V battery used to power the same load due to the inefficiencies of the boost converter and higher I²R losses.

5. ### OLIVE2222

690
25
Oct 2, 2011
definitively the better way to drive a 12V motor is a 12V battery , you must have very good reason to don't do it so.

6. ### BobK

7,682
1,689
Jan 5, 2010
For the same chemistry, the same weight of battery will provide roughly the same amount of power no matter what the voltage is. So adding a boost converter (which, in this case would be heavy because of the massive inductor you would need), does not help at all. Use a 12V battery.

Bob

7. ### KrisBlueNZSadly passed away in 2015

8,393
1,272
Nov 28, 2011
Of course he does! Why not?

BlackMelon and OLIVE2222 like this.
8. ### OLIVE2222

690
25
Oct 2, 2011
That's cool thank you Kris, may I ask you the battery Digi-key part number?

9. ### BobK

7,682
1,689
Jan 5, 2010
Damn, I just looked it up in Digikey and they only sell in QTY 1000.

Bob

Arouse1973 likes this.
10. ### BlackMelon

188
5
Aug 7, 2012
My idea just collapsed!!! lol, 14.8V or 11.1V LiPO might be the best solution

PS: If I want to drive 12V DC Motor with 14.8V, can I just control the maximum duty cycle of a motor driver board to be less than 12/14.8?

Thank you everyone

5,170
1,092
Dec 18, 2013
Oh Kris you do make me laugh PSML
Love it

12. ### KrisBlueNZSadly passed away in 2015

8,393
1,272
Nov 28, 2011
You get the battery free when you buy the truck!

Arouse1973 likes this.
13. ### OLIVE2222

690
25
Oct 2, 2011
14.8 for a 12V motor will probably not be a problem, but yes if you have a driver board you can adapt the duty cycle accordingly.