Continuous running robot (while charging)

Community General Discussions
1

Hi,

I know this topic has already been addressed, yet I could not find a complete answer.

Untill now, I have always built robots that needed to be turned on when I wanted to use them. So the charging has never really been an issue.

Now I'm thinking of a "sentinel robot" which would always be turned on so I can take control anytime without being on site.

So the idea is to have a base where the robot sits most of the time, his batteries get always charged. At anytime, it can leave its base, make a little walk and return to its base to recharge its batteries.

What would be the best kind of batteries to achieve this behaviour ?

I have always used Ni-Mh batteries, untill now. Safier and easier to use than LiPos (especially if the robot is always On, eaven when no one is around at home). I have never used lead acid batteries, mainly because of their weight.

I could not find much information how to do that with Ni-Mh. Most of the time, it seems the robot has to be turned off (am I right ?). I have found some modules like this one :
http://www.microchip.com/Developmenttools/ProductDetails.aspx?PartNO=MCP1630RD-NMC1
but it can only charge 2-3 cells.

So nothing convincing. What I do know, is that I have a radio that takes rechargeable Ni-Mm batteries, and it can operate while charging.

I've found many modules that helps handling LiPos charging. So maybe it is the way to go. I have also read that lead acid batteries maybe the easiest way to do what I want. It is a bit heavy, but a small one (eg. 6V, 2A, 500g) could be sufficient.

To summarize, 2 questions :

  • Is there a way to have my robot running while charging with Ni-Mh batteries ?
  • Do you think LiPos or Acid Lead batteries are better suited for that scenario ?

Sorry, too much words for a 2-lines question ;)

Thanks for reading !

2

LiPo can come with minimal

LiPo can come with minimal protections or even with built in safe charging circuit, to find these batteries search “lipo battery pack”. Bare LiPo cells are the ones that must be treated carefully. Packs also do cell balancing.

3

Thanks

Hi,

First of all, thank you for your answers and ideas :slight_smile:

This kind of behaviour sounded so widely used, I thought I could find an easy way to deal with it, using common patterns (or existing hardware). I was probably dreaming :wink:

I’ll do some reading, following bdk6’s link to batteryuniversity.

Thanks !

4

**Charging battery separately while on robot. **

When the robot is on his charging station, he actually can get all of his power from the base he needs. In fact he is already wired up  then. This ables you to disconnect the entire battery completely, while robot still up and running. I’m imaging something like a relay that will break this circuit and connects the battery to a charger directly. This can be a smart charger that stops automatically when full. 

 

5

@Lordgg:Continuous charging

@Lordgg:

Continuous charging while running is easy, do you have a geared dc motor where you can spin it with your hand ?

Try to connect it with your avometer, After it connects to avometer, try to spin it ! Suppose you use a 12 volt dc geared motor .

You’ll see on your avometer, each time you spin it with your hand it can produce approximetly the same 12 volt as your motor needed.

Actually this trick is what I used on Julia as long as she’s running, she can charge her battery.

Another alternative is solar charging, unfortunetly it’s definitely pretty slow, unless your solar panel is big enough and your robot has to be run outdoor.

 

btw for the first one here’s the schema that I used :

hack_0.jpg

dammit my drawing skills are bad

6

Hey sw0rdm4n,What I had in

Hey sw0rdm4n,

What I had in mind was having a robot always turned on, but which could go to a base station to charge its batteries when needed (while staying on).

In the end, I have chosen an easier approach : when the robot is connected to its station, it gets its energy from the station. When it moves away from its station, it switches automatically to its batteries (which act as an emergency power source). It is not perfect, because I will have to charge the batteries myself, but it is acceptable (the robot is always On). Charging (properly) a Nimh battery is not that easy, and I don’t want to use LiPos for a robot that should be turned on all the time (event when no one is at home).

I understand a DC motor can return current to the power source, but I didn’t get how you did implement it in your robot. Does DC1 make the wheel spinning AND also make DC2 spinning which returns current to the power bank ? So DC1 needs more power to make DC2 spin, but this supplement of power is returned to the battery. I am missing somethin here :wink:

Sadly, I have no sun in my living room (ok, a little bit, but not enough :smiley: )

 

 

7

@Lordgg : Yes, I connect it

@Lordgg : Yes, I connect it parralel.actually this is the cause of why the torquee reduces on my dc that runs the wheel. I think what you have already pretty perfect.