### Author Topic: 7.2 volts battery pack with the \$50 robot  (Read 636 times)

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#### TheStone

• Beginner
• Posts: 6
##### 7.2 volts battery pack with the \$50 robot
« on: January 31, 2010, 11:41:42 AM »
Hi

Reading from other posts I have concluded that you should be able to use a 7.2 volt battery pack instead of a 6 volt one for the \$50 robot using a resistor to lower the voltage to 6 volts? Right, I haven't missed something?

So I have three battery packs, one at 1400mAh one at 3000mAh and one at 1500mAh, which one would be best to use, and which resistor should I use?

Aron

#### Soeren

• Supreme Robot
• Posts: 4,672
##### Re: 7.2 volts battery pack with the \$50 robot
« Reply #1 on: January 31, 2010, 01:40:58 PM »
Hi,

[...] use a 7.2 volt battery pack instead of a 6 volt one for the \$50 robot using a resistor to lower the voltage to 6 volts? Right, I haven't missed something?
Wrong!
You want a steady voltage, not one controlled by the current draw.
If you use a voltage regulator in the circuit, you don't need to lower the voltage ahead of it, as the extra cell won't be a problem for the regulator, but unless you use a switching regulator, the extra cell won't give you any advantage over a 5 cell battery (but a bit more weight to drag around).

So I have three battery packs, one at 1400mAh one at 3000mAh and one at 1500mAh, which one would be best to use, and which resistor should I use?
The larger capacity, the longer the runtime, but the more weight as well.
If your motors/servos can drag it, go for the 3Ah battery.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Engineering is based on numbers - not adjectives

#### TheStone

• Beginner
• Posts: 6
##### Re: 7.2 volts battery pack with the \$50 robot
« Reply #2 on: January 31, 2010, 03:02:33 PM »
Great, so then I can just plug my 7.2 volt battery right in to the circuit (there is a 5 volt regulator in the circuit).

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