24 Volts is a very low reading for the battery pack so it may be old or worn out. The battery pack should be at 27.6 Volts when fully charged (13.8 Volts per battery). The battery pack is considered to be fully discharged when it reaches 21 Volts.
At 24 Volts the battery pack is 55% discharged and only has a 45% charge in it.
Although 24 Volts is enough to operate the controller, the battery pack may be dropping too much Voltage under load which is causing the throttle lights to not turn on and the controller to not operate the motor. The controller shuts off power to the motor when it detects a battery pack Voltage that is 22 Volts or under.
We recommend testing the Voltage of the battery pack when the power switch is off, and then again when it the power switch is on. If the battery pack Voltage drops to 22 Volts or less when the power switch is on then the battery pack does not have enough Voltage to power the controller. Since there are no lights illuminating on the throttle chances are pretty high that the battery pack's Voltage is significantly dropping when the power switch is on otherwise at least the low light on the throttle would light up.
On the SPD-SD400 controller, it is not safe to unplug the throttle and test the controller's throttle connector because its pins are too close together to touch multimeter probes to without causing a short circuit which would destroy the controller. With those type of small black connectors that the throttle connector has, the only safe way we know of to perform Voltage tests is by making a test plug with pigtail wires that plugs into the connector to be tested.
Since the battery pack is at a 55% discharged level with no load on it we recommend to test the Voltage of the battery pack with the power switch on before testing the throttle because if the battery is not working properly then the throttle cannot be tested until it is replaced.
A problem that we have encountered before with our test equipment is inaccurate Voltage readings due to a worn out 9 Volt battery in the multimeter. If the multimeter has a worn out battery then its Voltage readings can appear on the readout as being much higher than they actually are. The 9 Volt battery on our multimeter wore out around a year ago and we were getting a 91 Volt output reading on a 48 Volt battery charger. Then after we replaced the battery in the multimeter the same battery charger's output Voltage reading dropped down to 56 Volts which is right where it should be.
Please let us know how it goes.
(Reposted with better formatting)
I made a pigtail connector using a breadboard so I could probe each wire safely. With everything connected I get:
+24V (Orange) = 0.07V
-Negative (Black) = 0V, and continuous with Ground (Grey)
+5V (Red) = 0.49V
1V-4V Signal (Green) = 0.79V, regardless of throttle position
Ground (Grey) = 0V, and continuous with -Negative (Black)
Still no lights on the throttle. Interestingly, if I disconnect the -Negative (Black) wire from the throttle, it lights up, indicating full power. It still won't run the motor, though.
With the -Negative (Black) wire still disconnected, the green signal line shows 0V with the throttle in any position.
Without the -Negative (Black) wire connected, I see over 25V on the +24V (Orange) wire and 5.1V on the +5V (Red) wire. As mentioned, the green signal line shows 0V with the throttle in any position.
I want to verify the operation of the controller without the throttle. If I disconnect the throttle cable, how can I test the controller?
I am thinking about connecting a 1.5V alkaline battery across the Signal (Green) wire and the Ground (Grey) or -Negative (Black) wire, to simulate output of the throttle. Will that work?
Are the throttle wires inserted into the connector as shown above?
The throttle connector wires do not match the colors in the image posted above.
Counting down from the top we have:
I'll try disconnecting and shorting the green and red wires from the controller and let you know what happens. If it runs full speed as expected, does that mean my throttle is defective?
I tried disconnecting the throttle and shorting the green and red wires on the controller. There was no response from the controller at all. So I think perhaps I've got a bad controller, and the throttle may be fine.
Anything else I can do to verify the controller?
I tested again with the green and red wires shorted on the controller, while monitoring the battery voltage. With the power off, battery voltage is 25.7V. With the power on, the voltage only drops 0.1V to 25.6V.
I'm thinking the problem is the controller.
With the green and red wires still shorted, I tested the voltage across the motor outputs of the controller, and got 0V.
However, If I check the voltage from battery ground to either one of the motor outputs, I get 22V. If I turn off the power and monitor this voltage, it rises slowly when I switch on the power and steadies out at 22V after about 10 seconds. The voltage drops slowly when I shut off the power. I actually tested this with and without the green and red wires shorted, and got the same results.
So what I see from the controller is 0V output across the motor outputs under any circumstances. Both outputs rise to 22V relative to battery ground when power is switched on.
Can you think of anything else to try?
I bought a THR-500-2 throttle and an SPD-SD400 controller. Can anyone confirm if these two are compatible?
I just finished my build (modified mobility scooter), and I'm not getting any output from the controller.