Powering 4WD Rover

I am currently working on a new rover and I just had a few questions. Lets start off with powering the motors. The chassis and motors haven't shipped yet but here is what I do know about them:

-The Motor Rated Voltage: 12VDC The Motor No-Load Speed: 120 r / Min The Motor Rated Speed: 108 Rpm / Min11 -The Motor Gear Box Length: 19mm The Motor Rated Current: 0.37A The Motor Rated Torque: 26.8mN.M14 -The Maximum Motor Torque: 55.3mN.m

I have no clue what the best option would be to power these 4 motors but I was thinking about these: http://tinyurl.com/ptwk77h

I choose Li-Ion because they are lightweight and not susceptible to memory damage. Also went with the 3.7v compared to the typical 1.5v AA to save space/weight and I believe these will fit into standard AA battery holders. Like I said I'm sure there is a better option. I don't even know if these will work or how long it will power it for. Please let me know what your thoughts are, I would appreciate any insight!

The problem with building your own battery pack, is that you then need to learn how to build your own charger (and build it, of course). Plus testing. Plus potential failures. Filled with fire and explosions (seriously - Lithium chemistry cells have interesting failure modes).

Skip that. Go with something already pre-built.

My suggestion would be to purchase hobby-grade radio-control LiPo packs, for the voltage and current needs you require. For instance, the closest size to the 12 volt motor would be a 3S LiPo (3 cell) - ie, 11.1 volts. Or - go with a 4S pack (14.8v) - then use PWM to keep the average voltage to the motors at 12 volts or below (you'll be using PWM anyhow for speed control most likely).

Split the output the pack to an SBEC (battery eliminator circuit) with a 7-9 volt output - feed that into the Arduino's barrel jack (alternatively - go with a 5V SBEC and bypass the Arduino's voltage regulator via the USB port). Most SBECs output 2 or more amps, so you'll have enough to power the Arduino, plus a couple of servos or such, most likely.

Be sure to purchase a smart LiPo charger for the batteries, too. A well-known name brand in the hobby is Tenergy - for battery packs and chargers.

Finally - when you charge your pack (especially if you roll your own!) - put it inside a fire-proof container (inside a cinder block on a concrete floor - or inside a metal bucket) away from anything flammable, and stay around during the charging. While things have gotten better, there have been in the past incidents where somebody was charging a standard battery pack, left their house, and returned to find it burned down and them homeless. Seriously. Stay safe - monitor your battery charging.

If all of that is too much for you - then stay away from Lithium chemistry battery packs. Stick to SLA or NiMH.

Don't forget that to have control over your motors you will need a motor controller/driver. The batteries sure provide power to your motor, but no control.

You should consider a motor controller based on the goal of your project.

For the rated current of your motors, you wouldn't need anything expensive, a typical motor controller should be able to provide enough current for all your motors.

Good luck!

cr0sh:
snip

Thank you very much for the warnings with LiPo batteries, I had no idea.

I was just quickly browsing amazon for the batteries you recommended. It seems like most of them are rated between 2300-3000 mAh. Now is that x mAh per cell or is the listed mAh for the battery the sum of all the cells? Sorry for the elementary questions, my electronics background only consists of hooking sensors/motors/servos up to a RPI.

Thanks again you were very polite and informative!

sinq: Don't forget that to have control over your motors you will need a motor controller/driver. The batteries sure provide power to your motor, but no control.

You should consider a motor controller based on the goal of your project.

For the rated current of your motors, you wouldn't need anything expensive, a typical motor controller should be able to provide enough current for all your motors.

Good luck!

Thanks for the tip! I currently have a L298N module kicking around, I'm thinking I'm going to need two since my rover will be 4WD. CrOsh was talking about a SBEC, I believe the motor driver module has one built in? Unless I am completely misunderstanding what a SBEC is :). I had a few questions about motor drive modules, we will save that for another thread.

Thanks for the responses, very much appreciated!