I am “reviving” a Sears/Craftsman “C3”-powered radio controlled truck (product name “RC Truck”!) which involves keeping the existing motors, body, and wheels, but replacing everything else.
Reviving a Sears C3 RC Truck (slippery slope!)
More specifically, this includes a Futaba T2PH 75MHz AM Tx/Rx/Servo kit, a BaneBots BB-3-9 3.5A cont/9A peakESC, and an 18V HF cordless drill power pack.
What I have now, after some weeks of work, runs, but it appears that I seriously underestimated the motors’ current requirements: the BaneBots 3.5A ESC I selected is sufficient to drive the motors from my 18V battery pack, but only if I’m extremely gentle on the throttle. If I start slamming the transmitter from full forward to full reverse the motors become “sluggish”: the wheels turn very slowly and the current jumps to more than 10A.
With some generous advice from the sci.electronics.design newsgroup I was able to wire up a “visual ammeter” using a pair of back-to-back LEDs and a couple of 0.47ohm5W resistors. This doesn’t give me an exact current draw, but it tells me that a 3.5A ESC is 'way underpowered. <grin!>
Intermittent sluggish performance from homebrew R/C Truck
Finding a replacement ESC at a “reasonable price” has been surprisingly difficult. Apparently this combination of specs is an unusual one:
- Brushed motors
- 25A+ continuous
- 18V battery pack
The 18V25 seems to fit the bill. Do I actually need a 25A ESC? I don’t know, and I don’t know how to simulate a realistic “load” on the motors that doesn’t involve either abrading the skin off my hands or a lot of running. (This kind of testing was much easier when I had younger brothers to help out: “Hey, Bruce! Put your hand on this rapidly rotating wheel here…” <grin!>)
I do know that the motors (two, wired in parallel) together draw 1.3A at 12V unloaded (truck lying on its back), and I know that when the motors are starting they draw more than 10A for some visible fraction of a second, but apparently much less than 10A when running flat out. The motors are “380”-sized brushed DC motors labelled “STANDARD MOTOR RS380-ST/3265 – SMCD348310”; I did find a 'Web site called standardmotor.net, but I can’t get past the home page.
So here’s what I’d like to know before I ask you all to FedEx an 18V25 eastward to Richmond: based on the (admittedly sparse) information provided, does it sound like the 18V25 will work in my application? Or is there something in my description that hints that even 25A might not be enough?
Thanks in advance for any feedback.
“We are what we repeatedly do. Excellence, then, is not
an art, but a habit.” – Aristotle