Rover 5 + 4 Motor Driver. Problem

Hi

I have a Chassis Rover 5 https://www.sparkfun.com/products/10336 with two motors 4 Motor Driver https://www.sparkfun.com/products/11593

After using it with some arduinos and controlling the robot using a 433 Mhz link Kit(see a tutorial on my blog: controlrobotics.blogspot.com) I notice that the autonomy is only a of the theoretical autonomy

The setup have two batteries, one for the electronic and other for the motors.

The battery of the robots is 7,2 volts an 5A/h (12 NI-MH batteries). The motors consumes with out charge about 400mah(measured with the driver current pin ). So making some numbers and knowing that the electronic have another battery: 5000/(2*400) = about 6,25 hours.

Making some test I realize that working with out charge until the robots run out of battery , I have 45 minutes of autonomy.

Anyone can help me, with some information for learning what is happening and try to resolve it? Any help will be useful, I hope to resolve it before starting my degree next year.

Please ask for all the information that you will may need.

Thanks very much

PD: I have been searching for information without any success

I would first question the batteries, myself; while you will never get what you think you will get run-time wise (because of temperature de-rating and other factors like internal resistance and such), you should be getting way more output on those batteries than you are, unless you are pulling a ton more current than they are rated for (10-20C is typical).

That doesn't seem to be the case here; you are in the ballpark, I think - at least with the numbers you are giving.

I would be questioning the batteries - where did you get them? Are they manufactured by a reputable company? Did you pay an amount for them that wasn't ridiculously lower than what you would ordinarily pay?

What I am getting at here is that you may have bought fake batteries - that is, batteries rated at one mAH level, when in reality they are much smaller. You see this on a ton of different electronic products and components, and batteries are certainly no different. Sometimes, you can even get hosed by a supposed "reputable manufacturer".

If you can post more details (again - your circuit/schematic might help - but you might also post information about the motors, parts, batteries, etc - links to manufacturer datasheets, perhaps even pictures of the components - especially the batteries, and where/how you bought everything).

I mean - if they can sell large quantities of fake 328 chips, batteries would be no different...

The battery that I normally use for the robot are fake ones (very very cheap like 3 dollar 4 batteries). I also test it with energizer batteries and the difference it’s just about 10 minutes. So It’s cheaper 12 fake batteries than 4 brand name batteries and the difference it’s no critical(I have 4 packs of 12 batteries for long day’s) .

I know that 6 hours of use it’s the ideal situation and I won’t be 6 hours with the same batteries but I think 2 or 3 hours of autonomy it’s a reasonable target with this battery’s.

About data sheet I posted two links. One with the robot base that includes the motors datasheet and another with the motor controller data sheet. I will make an update with some pictures of the robot. About the schematic y just plug the motors in their holes, control circuit is connected to a 5 volts and the 7.2 volts battery to the VCC. I haven’t connected the encoders to the motors board yet. The control circuit haven’t got any problem. Using the function analogWrite(pwmpin,255), I control the speed (maximum speed in this case). another pin (I/0 pin) controls the direction.

An in my opinion buying really cheep components, it’s good option for learning about electronics. The main reason it’s because this cheep components are more difficult to connect and always worst than expensive ones. So at certain level you can learn a lot burning 8) 8) some jejejejeje. I bought an fake arduino nano with not bootloader ( very cheep about 9 dollars more or less) and then I learn how to burn bootloader with no fear of crashing my real arduinos :slight_smile: :slight_smile: :slight_smile:

UPDATE: After studding philosophic ( I want to be an engineer why I have to study it. Spain it’s different =( =( =( =( ) I realise that some H bridges need a Vcc between 4 and 2 volts higher of the working voltage. My motor works at (5-7,5) 7.2 nominal(You can see it at the datasheet). So I measure the voltage that the motors are receiving. Apparently, they are working at 3,5 volt. Could the problem be there?

Thanks very much cr0sh. If we resolve it I will upload a new tutorial in my blog for all people who are working with this setup’s

The robot need a lot of work. The range will be about 300 meters (800 meters theoretically). It have pant/tilt for the camera and a laser point calibrated for the canon. You have 6 bullets and about 3 meters of range (Far enough for play a bit). I hope to made big improves ( Gps, Raspebery Pi on board may be) after starting my degree next year in telecommunication engineering.

Here are some photos ( I have to improve the style too).

roter45: The battery of the robots is 7,2 volts an 5A/h (12 NI-MH batteries). The motors consumes with out charge about 400mah(measured with the driver current pin ). So making some numbers and knowing that the electronic have another battery: 5000/(2*400) = about 6,25 hours.

Firstly lets get these units straight, current is measured in amps (more correctly amperes), symbol A (always capital A).

Charge is measured either in coulombs (symbol C) or in Ah (ampere-hours).

Charge is current times time, 1 coulomb = 1 amp x 1 second 1 Ah = 3600C = 1 amp x 1 hour = 1Ah (1 amp x 3600 seconds = 3600C)

"A/h" is nonsense, amps per hour is meaningless here.

So you claim the batteries are 5Ah NiMH (are they D or C cells?). You also claim the current under load is 400mA (not mah!) per motor and two motors?

That gives an endurance of 5 / 0.8 = 6.25 hours, but its not that simple:

Battery capacity is measured usually at the 10-hour rate - discharging them faster gives less capacity.

Manufacturers give capacity for new cells, charged to the absolute maximum, and tested at the best temperature... Older cells will have a lot less capacity especially if they have been abused (over-discharged, over-charged).

Are you sure the 45 minutes endurance is due to the motor battery and not the other battery?

[ oh, also have you checked you don't have some rogue cells in the pack that are much less healthy than the others - once the pack's voltage is starting to drop test the voltage of each cell - they should be similar, any cell with a markedly lower voltage is suspect ]

Thanks for the replay.

The batteries say to have 2500 mah. About the type, think of the worst type, this will be the type of battery. I can't give you more detail about them.

Also I'm sure that it's the motor battery because all the hardware it's still working perfectly after motor battery ends.

I made some researches and I found that the motor driver needs 4 volts more than the nominal output of the motor. So I test it with 12 volts battery. I see that motor are working better. I will made another test for knowing with 12 volts battery how many time it will we ruining.

I will post the results as soon as possible.

Also I break one of the gearwheels. I need to replace it and i haven't got any extra pieces. Do you know anyone how prints 3d pieces?

Thanks very much.

I test it usign 12 volts of battery and 2500 mah (by the fabricant).

The robot was running about 1 hour without charge = equals a 2 hours with 5000 amh, the last batery.

So I think now I having a reasonable use of the battery

If I want to have better batterys (lipo maybe) what should I use? I need 12 volts and at least 2500mah.

I use a three cell 11.1 LiPo battery for my Arduino/Rover 5. I built a small circuit board to give me 9V, 6V and 5V supplies using simple 3 pin voltage regulators, i.e. 7809, 7806 and 7805. I use the 11.1 V for the motor power, the 9V for the Arduino power, the 6V for an RC receiver and the 5V to power motor controller board. It all works quite nicely.

The trick was finding a LiPo battery that we thin enough to jam into the Rover body length ways and fit between the aluminum L brackets holding the motor legs on.

I hope that helps.

Cheers, John

I forgot to say, I think my LiPo is 3600mAH.

Cheers, John

I think it's time to take my neighborhood crashed RC cars and take some batteries,tires and components.

My battery setup will be dual:

One battery 5 volts 12 Amps ( A Christmas gift for the mobile phone :D :D :D) Another battery between 12 and 11 volts about 3000mah only or rover 5 motors (Li-po)

How many time does your robot move with your battery johnboy888?