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lastRites
03-23-2011, 09:17 PM
I have six motors on my battle bot, each of which draw 7A when stalled and a wiper motor of 8A. I tried to power my bot using two pc smpss(450w) but it does not seem to be enough. Moreover the motors seem to run at a lower speed. So I am thinking of purchasing a motorcycle battery(14Ah). Would that be enough and is there any cheaper alternative? Where can I get DPDT switches of 30A rating or above in kolkata??
Thanks:)

vikas
03-24-2011, 01:24 AM
Go for lipo ... they are light and have high C rating. Though expensive ... Look up lipo terminology and ull see how a great source of Amps they can be.

Lead acid is by my definition too heavy for anything fast or anything built for competitive sports.

lastRites
03-24-2011, 06:53 AM
My main restriction is the cost since i have only about Rs 1000 left. Lightness is not required as the battery will be off-board. I need the batteries to last for at least 2 years and bike batteries come with about 15mnths of warranty. do they have the required charge density? i need about 20A continuous current.. Can the battery be used in parallel with the smps?

MohitM
03-24-2011, 05:50 PM
I love your thread title: "Need Power!"...
Well, who doesn't? All humanity is driven by the desire for power! ;-)

lastRites
03-25-2011, 06:58 AM
Thanks:D I am participating in a competition today. I am running each side of the bot(3 motors) with a separate smps. Still if one motor gets stalled, the other 2 barely move. Moreover the stall torque is a fraction of what the motors really deliver.

lastRites
03-26-2011, 09:07 AM
Can I reconfigure those SMPSs in any way such that I get a 12V 60A source??

allbits
03-26-2011, 12:23 PM
Dont use an SMPS for driving a motor like that. Well, Dont.

vikas
03-26-2011, 12:58 PM
I dont know why competitions allow wired battery powered motors with DPDT swithes ... nothing robotic about them. Ive seen people using car battries lying on the side of the arena and wires dangling all over ... the first robot if i were to build to compete will simply aim to chop these wires :) .

Also there is a lot more to it than simply connecting wires , AWG , voltage drops , power transfer capacity etc etc

http://www.powerstream.com/Wire_Size.htm

I still say for a real robot invest in a LiPo with

http://www.nex-robotics.com/products/batteries-and-chargers/lithium-polymer-3cell-11-1v-6000mah-30c-discharge-battery.html

Also PC SMPS will shutdown automatically incase it detects extreme load and requires hard restart , most probably leading the user loosing the match/disqualification. So SMPS is not recommend.

lastRites
03-28-2011, 07:46 PM
I cannot afford lipo now:( BTW chopping of wires is not allowed :P
I started a similar thread on societyofrobots and got some interesting replies:
http://www.societyofrobots.com/robotforum/index.php?topic=13517.0#msg100144