This question is not about building legal VRC robots. It is about light industrial use of VEX equipment.
I have built an inexpensive, mobile test-fixture/robot that needs to run over night (>=16 Hrs). With one new Vex 3000 mAh battery, it runs 2 hours.
By using a power expander for every motor, and using hobby shop 5000 mAh batteries, I hope to extend the device’s run-time to 10-12 hrs.
Because of the complicated and long path the robot follows, running wires to it from a benchtop power supply is not an option.
I don’t want to attempt to hook up typical hobby shop batteries in parallel because I don’t want current flowing from one battery to another when their voltages are different.
So, here is my question:
Does anyone have a recommendation for a battery(s) to use to get 16,000-20,000 (or more) mAh of useful capacity into my robot?
The Goldilocks battery will be not too heavy, not too big, easy to charge, have a stable output voltage when under a load, be able to supply current surges, not an environmental/safety hazard, retain 100% of its initial capacity after hundreds of recharge cycles, etc, and not be outrageously expensive.
Here’s a bulky 7.2V 10000 mAh NiMH pack.
[Tenergy Power
What dopes the robot do? Does it move? Would lightening the robot a bit help with the power usage? Would implementing slew rate code (jpearman’s) stop current spikes on the initial movement that might use a bunch more battery life? (Kind of like stepping on the gas in your car)](Tenergy Power)
To get high capacity, you are probably looking at higher voltage also. The batteries we use in the broadcast industry for cameras are like this (an example).
Most, if not all, will be 14.4V nominal. You would then need a high power voltage regulator to drop this down to 7.2V, this will also give you a more stable voltage as the battery discharges. The downside to this solution is cost, batteries like this run anywhere between $400 and $1000. The regulator would need to handle the high current demands of the motors. perhaps something like this (although this is only 75W).