I connected my gearmotor to a homemade 8 x AA batteries (brand new) pack wired with 22awg wires and tape to hold it altogether. It is not perfect (sometimes I loose the contacts and need to move the batteries in the pack to get the tension back) but I get 12.6V. When running under load, it goes down to 12.2V. Even if specs gives a 95mA of no load current, I get 70mA when running with my load which is “too low” in my opinion. The output speed is 0.88rpm (68s/turn) measured. This lower speed is not an issue to me (even if a higher speed would be better), nor the lower current is.
I wonder if it is normal or if something is wrong in my circuit?
Hmmm, there is probably a manufacturing tolerance for this motor and depending on how much grease was used and how much friction is going on internally may affect the RPM.
I feel like 0.88 RPM is a bit on the low side. I do wonder what would happen if you used a 12v power supply instead(pretty common for computer speakers and other devices).
You could try taking the gearbox apart and adding some of your favorite grease to the gears. I personally use Park Tools bike grease for stuff like this because I have a big tub of it(used to fix bikes as a hobby). It seems to do the trick, though, I am sure there is better stuff out there.
I guess you don’t have any documentation on the gearmotor other than what is on your website. I find a bit strange that if the mechanical side lowers the speed of the motor that the current is not higher than expected. Anyway I will try to use a 12V power supply (ordered yesterday) and grrease (multi-purpose synthetic) the gears to see what happens. Otherwise, I’m happy that the gearmotor draws less current than announced.
Two motors of the same type will generally NOT run at the same no-load RPM or have the same no-load current draw. There are manufacturing differences in magnetic field strength, bearing friction, etc.
Are you needing the motor to turn at a specific speed? A 12 volt DC 1 RPM motor might not turn at exactly 1 RPM with no load just due to variances in manufacturing or even the temperature you’re using the motor at. You could even try 10 motor and chances are good that they all turn at a slightly different speed for a given voltage. Once you put a load on the motor the RPM is going to drop and the current will rise.
I don’t need a specific output speed. I just need to determine the maximum current it will draw if I use 100 of these motors in 100 different assemblies to design my power supply circuit.
Currently, I expect to use a battery and a charging system running full time (like a solar panel exposed to sunlight 24h/day would do) . I know I will have to control the charge cycles depending on the type of battery I will use (Sealed Lead-Acid, Ni-MH, Ni-Cd, Li-ion, etc). I just want to make sure I will be able to recharge the battery fast enough between the motor actions to prevent the battery from emptying and getting a system not working because of this.
With the informations you gave me all, my guess would be to expect the motor to draw a maximum of 250mA in normal operation which is 50% of its stall torque and I should be safe with that.
