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28-05-2017, 20:00   #1
Anchises
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Batteries for robot

We've built obstacle avoiding robots .

Simple spec: 2 DC motors (6V-10V), HC-04 Sonar sensor, 1 servo - based on Arduino Uno with L298N motor controller. Doing this as part of a CoderDojo group project for beginners.

Powered by two PP3 9v batteries, one for the uno, one for the motors.

Clearly the PP3s are not up to the job. The start/stop demand is too great. After a while the motors will not start , or one only will start and generally it becomes erratic. Particularly bad if using PWM to control speed. I need a better solution.

I've been reading about possible battery configurations. I've seen it suggested that LiPo rechargeables are the way to go. They seem a tad expensive and require expensive chargers too. ( and as an aside - dire warnings exist about how hazardous they are.

I could run from a single 11 volt maybe and supply 5volts, for the Arduino, off it, by regulation.

I would welcome suggestions as to what batteries/ battery configuration might be suitable.
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29-05-2017, 05:21   #2
zg3409
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Rechargeable PP3 may be much better, in particular nicad versions. While the total capacity is not that high, they can give out high power for short periods, are cheap and easy to recharge. For relatively high consumption projects they might be the way to go and would not require any changes.

In Dublin we built these kits. No software needed, just very basic soldering skills:
https://www.tog.ie/2017/05/electroni...it-workshop-3/

https://www.youtube.com/watch?v=fxr_rktYpqk

Let us know how you get on.
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29-05-2017, 06:09   #3
ED E
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Two 18650s would be a little bigger but could provide 8.4v and 6A+. With protected cells there really is no risk.
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29-05-2017, 14:50   #4
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Thanks to both of you.

Will try the pp3 rechargeable first.

The other, 18650, I've no experience of and would need two to get the Volt up to 8.4.
Are they really over Euro 20.00 each ?
And what kind of charger would I need ?
Since they are bigger than AA batteries, I would need a battery holder too.

And links to Irish suppliers ? I'm in Cork.
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29-05-2017, 14:57   #5
Anchises
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> 18650s would be a little bigger but could provide 8.4v
Should that be 7.4V ?

This looks like the one you suggest ... Is it ?

http://ie.farnell.com/ansmann/1307-0...mah/dp/2723326
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02-06-2017, 23:11   #6
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Depends on the voltage you look at. Empty its 3.7v/cell, full 4.2v.
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03-06-2017, 17:59   #7
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Good

That clarifies that.

From what I was reading it looked like there were two different batteries
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12-06-2017, 08:40   #8
aido79
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Quote:
Originally Posted by ED E View Post
Two 18650s would be a little bigger but could provide 8.4v and 6A+. With protected cells there really is no risk.
I'm building an arduino smartcar with collision detection at the minute which specifies that unprotected 18650 batteries should be used. It uses a Uno board and apparently the difference in voltage between the unprotected and the protected batteries can affect the board. It's just something to be aware of.
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