Level of battery charge

#1

Hello,

Is ther a way to know the level of the battery charge ?

There is a topic /battery but echoing it I can’t see anything …

Eric

#2

The /battery topic should echo the battery voltage.

#3

no echo, but it is there a publisher that should run too ?

#4

The voltage is mesured in the firmware and it’s published using ros_serial.

#5

Try the /firmware/battery topic

#6

/firmware/battery work!

But this is the voltage, but what about the % of charge ?
(maybe it’s a stupid question)

#7

The battery supplied with the LeoRover isn’t equipped with a BMS. Therefore, the only information available is the voltage. (There’s no stupid question, we’re all at a different stage of learning :wink: )

#8

OK, indeed I’m not a battery specialist, and I’m sure I don’t one to become one :slightly_smiling_face:

Having a quick look to Battery Management System (BMS): Effective Ways to Measure State-of-Charge and State-of-Health | by Anastasia Ponomareva | Integra Sources | Medium I rapdily confirm that I’ll not dive into that.

So the question is quite interresting : how to know the percentage of battery charge, but it seems the answer is not simply. Anyway someone has a trick for that ?

In other words, how do you do, when working with your Leo, to know that’s time to charge ?

#9

That’s not true. The batteries supplied with Leo Rover include a BMS circuit that does at least these things:

  • Over-current protection - If I remeber correctly its rated 10 A
  • Under-voltage protection - when one of the cells discharges to a certain voltage level, the BMS will cut the power off until the cell is charged.
  • Cell balancing during charging
#10

We did not implement any Voltage to percentage of battery charge converter as it varies depending on the battery. For the batteries we are currently supplying with the rover, you can assume the following:

  • A fully charged battery will have 12.6 V - the voltage reported by the firmware will be slightly lower due to voltage drop when under load.
  • A voltage o 10 V is considered low and we highly recommend recharging the batteries at this point.
  • The BMS will allow lower voltages (until one of the cells reaches 2.5 V), but the wheels may not have enough power to properly skid steer and it might not be healthy for the batteries to store them at this voltage level.