I am building a rover and would like to power the Raspberry Pi and the Motor HAT with the same power source.
I want to use a 2500 mAh LiPo battery for a long play time. My DC motors work at 6V-9V.
How can I do this?
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Can you add some more details to your question? For example, which Pi? Which hat? Which motors? What other electronics will be drawing power from this battery? – YetAnotherRandomUser Nov 2 '17 at 2:48
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You will quickly face 2 problems : voltage and current.
Voltage You battery produce 3.7V, the Raspberry use 5V, your motor 6-9V. You will basically needs two DC-DC step-up voltage converter to produce 5V and 9V from 3.7V.
Current Now let's look if your supply provide enough current : The raspberry pi3 needs 2.5A at 5V and the converter is said to have a 95% efficiency.
0.95*(Ubat*Ibat)=Upi*Ipi
0.95*(3.7*2.5)=5*Ipi
Ipi=1.7575 A
We can see that one battery is already not powerful enough for the raspberry (1.75A instead of 2.5A), so powering a motor on the same battery won't just work.
I don't know how other people solve this case, but you can look for lighter hardware that would limit the need of power (arduino ? rpi zero w?), or for bigger batteries.
Personally I would just use a UBEC and drive the Pi and the motors from the same 5V supply. A UBEC converts a voltage in the range 6V to 26V to typically 5V and is what a lot of model airplane and quadcopter enthusiasts use. Your motors should work from 5V.
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1Union of Banana Exporting Countries (UBEC) FTW. That was DuckDuckGo's Wikipedia first result. Maybe a brief explanation of what you mean by UBEC, what it is, and how you might use it in this case? – YetAnotherRandomUser Nov 2 '17 at 2:47
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@YetAnotherRandomUser I understand your reasoning but am not minded to make a change. Anyone who does not find the intended definition should not be using electricity! – joan Nov 2 '17 at 6:32
