mBot Ranger Lithium Ion Batteries

#1

We have purchased over 100 mBot Ranger robots and have them in multiple schools in our district. We are using them for an extensive robotics unit in our introductory computer science courses.

That being said, we need to solve our battery problem. We planned to use 9V that we were going to get donated to us. However, we are finding that the 9V batteries drain quickly and they can’t provide long enough power to keep the motors moving. They’ll provide enough power to light the LEDs and play sounds, but not run the motors.

We are looking into lithium batteries. We’d like to save as much money as possible, while still providing a good battery that lasts at least 3 hours without needing to be charged.

Many of the posts I saw were for the mBot robots and not the Rangers.

  1. What are the lithium charging specs for the Auriga board?
  2. Should we get 3.7v or 7.4v?
  3. What mAh should we consider?
  4. Do you see any concerns about plugging all of the mBots into a USB charging station like this one from Amazon?

Any help or feedback anyone can provide would be super helpful!!

#2

As a general rule, the larger the mAh (milliamp hours) value, the longer the battery will continue to provide the stated voltage. :slight_smile:

With regard to the USB charging station, check with the battery manufacturer’s specs to see what charging amperage is recommended, especially with lithium ion batteries, to avoid damaging the battery.

Get the 7.4v (or larger). The Ranger operates on 6-12VDC and a 3.7VDC battery will not provide adequate power for the motors.

#3

I’ve looked at the Ranger closer, including the schematic. Is the only way to power the Ranger through the barrel plug? That’s what it looks like to me.

If so, that narrows down our options.

We are debating between the DF Robot 7.4V Lipo 2500mAh Battery (Arduino Power Jack) with the corresponding DF Robot 7.4V Lipo Battery Charger for around $40 per robot or getting rechargeable 9V batteries and chargers from Amazon for around $6 per robot. (We already own the 9V barrel plugs.)

It’s likely we can’t swing an additional $40 per robot at this time. Even if we shared chargers, it’s a bit more than we were hoping to spend.

Just thought I’d provide this information for anyone who searches the forums in the future looking for battery solutions like I did.

#4

The power jack is the only way to power the Auriga board as far as I know. You might give eBay a spin to check into 7.4v lipo chargers that can charge more than one battery at a time but you would likely need to construct adapter plugs to accommodate the barrel plugs. Not too difficult to do but it does require some soldering. Just a thought. :slight_smile:

#5

I wanted to give an update to let everyone know what we settled on to solve our problem.

We now have almost 250 mBot Rangers in our school district and are using them in our introductory computer science course. We had to find a solution for rechargeable batteries, or this just was not going to be cost-effective in the long run.

We decided to get Sony NP-750 Camcorder batteries with 2.1 DC Jack adaptors (from Adafruit). I’ve been using a Ranger running on a camcorder batteries for three days straight now. No problems at all.

#6

That’s great news, and thanks for sharing! :slight_smile:

#7

Dear rosemarybianchi,

we are planning to use the makerbot ranger in school as well. I bought one for me in advance to prepare the lessons and wondered how fast the batterie is low.
When I searched the internet I found your information of using camcorder batteries.Could you please tell me how you fixed the cables to the batterie? Do you use the “DC Jack adaptor to alligator clips”?
Thank you very much in advance!

Best regards
Markus

#8

Hi Markus,
According to our test and research, it is suggested to use rechargeable Li-ion battery or rechargeable nickel-metal hydride, nickel-cadmium which can be bought from amazon or local shop. Or Alkaline battery with good quality like Energizer, DURACELL.
As for how fast? It depends on the capacity of battery you bought.
“Fixed cables to battery”, are you referring to fix the battery to robot? Try adhesive tape?

#9

Hello!

I want to start by saying this solution is for the mBot Rangers only. Not for the regular mBots.

We purchased this product from Adafruit to connect the camcorder batteries to the robot.

You can get the batteries cheap from Amazon. Lots of options. Just search NP-750.

Here are a few photos of how it looks when connected to the Rover and Raptor builds:
2 new photos by Rosemary Bianchi

My teachers are reporting great success with the batteries. In my testing, I’ve gotten a full day of use without recharging.

We bought these charging towers which fit multiple battery chargers (they won’t fit in a regular strip without skipping slots because they are too wide):

We are very happy with this solution so far. If you have any additional questions, please let me know.

#10

Hello rosemarybianchi,

thank you for taking time to help me.
I´ve never seen these type of adapters - your link helped me a lot!
In between I found a dealer selling similar adapters in germany and already ordered one for testing.

For sure I will have some more questions after bringing it to school - thanks!
But there´s still some work to be finished first.

#11

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