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Old 09-26-2018, 08:01 PM   #3 (permalink)
thingstodo
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Join Date: Sep 2010
Location: Saskatoon, canada
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ChargE (not yet running) - '92 Mazda MX6 LX
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Quote:
Originally Posted by Hondo View Post
My question to you guys is can I put on one more battery (I have room) to bump the voltage up to 60 volts without damaging the motor? I am not using a controller, just contactors on both sides of the motor. There is a slight load on the motor at all times to turn the Z-drive mechanism via a v-belt, but I am concerned I might over-rev the motor
I know that you can test it without harm. Wire in the extra battery with temporary cables and try it out. The human ear is pretty good at judging 'slower' and 'faster' by the pitch of the motor. 'too fast' is a bit subjective ...

If it sounds like it is not going to explode during your first test, I'd put some reflective tape on the shaft and measure the RPM with a hand-held tachometer. The golf cart motors have rated RPM on the nameplates, so you can compare. If the motor nameplate is not readable, a google search may get you your info anyway.

The hydro-static drive (is that what z-drive means?) will also have a maximum speed. That would be in the original service manual, but I'm not sure where else to look. The noise that I hear from my zero-turn mower is mostly the hydrostatic drive. I know what it SHOULD sound like, so I'd be able to tell if it was running WAY too fast. Not sure if I could tell a BIT fast though...

Sounds like you have no idea what current the motor is drawing. You may want to put a shunt resistor between the motor and the negative battery contactor. A 200 amp resistor should be fine. A shunt ammeter display or a meter that reads milli-volts across the resistor will give you approximately how much current you are drawing. The batteries will have a bit of sag, so 48V at about 50 amps would get you 2400 watts, close enough to to 3.1 HP * 746 = 2312 W. You'd only need 40 amps at 60V to get about 3.1 HP. More amps will eventually cook your motor.
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