I reviewed the power distribution of the robot and the system of 2 batteries… and finally, I’m not satisfied… Having 2 batteries inside take more space, it’s not good for the weight balance and it’s more complicated for the electronic because I would have have to design a board with 2 chargers (LTC4008 and MCP73861) and 2 power monitors (LTC2945). It’s not that complicated but designing a charger board is not obvious and the Electromagnetic compatibility (EMC) would be a nightmare…
So I searched on the Internet for a new battery, and I found this one : Tenergy Li-Ion 18650 11.1V 7800mAh. I could have assembled the battery by myself by buying each element separately which is much more cheaper, but I have enough work to do… 😉
There are many benefits :
- Battery’s weight better balanced,
- Space better distributed,
- One charger and one power monitor,
- More capacity than with the 2 others,
- The battery case is reinforcing the rigidity of the body.
It looks like this once integrated :
I logically changed the charger and chosen a LTC4006 which fit perfectly to my application. Indeed, the LTC4008 doesn’t have a integrated termination charge like the 4006 and the use case of the robot (charging point of view) will be the same as a laptop, so I needed a charger compatible for this utilization.On the datasheet you can find a good application schema, which I have to modify to fit my expectations in order to handle the average 5-6A consumed by the robot…
However, I’m still keeping my
precious switching regulators :
- 1 PTN78060WAH : 5V power supply of the RasPi, the STM32 and the speaker’s amplifier.
- 1 PTN78060WAH : 3V night vision LED (+ mini fan).
- 3 PTN78020WAH : 7.4V legs power supply : 1 for each pair of leg (front +head, middle, rear).
I replaced the PTN04050C by the PTN78060WAH (boost converter), as I won’t use the 3.7V Li-Po battery anymore.
Here is the new electrical architecture :