Making my first project - a bluetooth controlled car with a water gun that can be aimed with 2 servos and I'm not sure if my 8 x AA NiMH 2000 mAh battery pack will be enough to power it. I added a screenshot of a fritzing diagram of my project. The brand of the battaries is amazon basics.
8 AA batteries are not going to last too long. Better to use 18650 lithium-ion.
Roughly depends on the average current your drawing. And you have to careful how
you set them up not to exceed the voltage rating of the components you are using.
Do you plan to hook them up 2 parallel banks of 4 batteries ?
I was going to use 8 aa batteries in series.
That would be about 1.5x8 =12 volts. So you have to check max voltage specificaton for any component your powering direct from the battery to make sure they can handle 12 volts without damage.
To estimate battery lifetime, measure the average current draw of the project. A multimeter will work fine, but you need to do the measurement while the robot is moving around in a typical environment.
(approximate battery lifetime in hours) = (battery capacity in mAh)/(average current draw in mA)
For series packs, pack capacity is the same as for the single cells (2000 mAh for the cells you mention).
Capacity adds with parallel cells.
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NiMh cells don't give 1.5 volts. Charged, with no load, 1.39 volt. With load, less.
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I would connect 4xAA in parallel with other 4xAA, giving only ~5V but with double the current capacity.
Replace the l298 motor driver with a more modern and efficient MOSFET driver such as TB6612FNG which will run the motors directly from the 5V battery supply.
The Uno can be powered directly from the battery through its 5V pin (instead of Vin pin).
The DC-DC buck converter will not be needed.
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Well filtered if it’s on the same supply as the motors !
Agreed. It would be better to separate the supply for all the motors (2x DC, 2x servo, 1x pump) from the supply for the electronics (Uno, sensor, Bluetooth module). To keep the supply to the electronics stable, separate them from the motors with a low value resistor and place a large cap like 1000uF on the electronics side.
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