More problems.
I developed the circuit using an 18Volt cordless drill battery and motor.
Thinking it worked, I installed in the bicycle.
There was always a small spark when I connected the 18V battery. I thought it was due to the capacitors charging, so ignored it.
The bike battery is a 24V 6AHr lithium-ion unit connected to a 250W brushed motor.
When the battery is connected there is a large spark that jumps across the screw terminals I'm using. Its enough to burn the connections. It also trips the battery management system built into the battery. This causes the output voltage to fall to about 3V. It stays at 3V unless the battery is disconnected and, on reconnection, it happens again.
Disconnecting the motor reduces the spark. I'm assuming the pulse affects the 08M2 or the Mosfet so that the Mosfet turns on long enough to trip the BMS.
On another forum devoted to drone flying a member described a similar problem to mine. The fix was to wire a resistor in series with the positive screw terminal connection. The idea is that the resistor closes the circuit first, charging the capacitors so that there is no spark when the main positive wire is connected. They used 470ohm. I had a 100ohm so used that. It cured the spark but, if I dawdled over connecting the main positive lead, the current through the resistor would heat up. The current draw (no motor connected) is 80mA. That seems a bit high. The current draw for the two regulators should be about 16mA. The 08M2 and MCP1407 might be a few mA.
My questions are these:
Why the spark? The amount of capacitance I have in the circuit in about 110uF.
What causes the motor to turn on?
Is there a way of suppressing the spark other than using a resistor?
Why is the current draw so large?
Thanks,
Brendan
I developed the circuit using an 18Volt cordless drill battery and motor.
Thinking it worked, I installed in the bicycle.
There was always a small spark when I connected the 18V battery. I thought it was due to the capacitors charging, so ignored it.
The bike battery is a 24V 6AHr lithium-ion unit connected to a 250W brushed motor.
When the battery is connected there is a large spark that jumps across the screw terminals I'm using. Its enough to burn the connections. It also trips the battery management system built into the battery. This causes the output voltage to fall to about 3V. It stays at 3V unless the battery is disconnected and, on reconnection, it happens again.
Disconnecting the motor reduces the spark. I'm assuming the pulse affects the 08M2 or the Mosfet so that the Mosfet turns on long enough to trip the BMS.
On another forum devoted to drone flying a member described a similar problem to mine. The fix was to wire a resistor in series with the positive screw terminal connection. The idea is that the resistor closes the circuit first, charging the capacitors so that there is no spark when the main positive wire is connected. They used 470ohm. I had a 100ohm so used that. It cured the spark but, if I dawdled over connecting the main positive lead, the current through the resistor would heat up. The current draw (no motor connected) is 80mA. That seems a bit high. The current draw for the two regulators should be about 16mA. The 08M2 and MCP1407 might be a few mA.
My questions are these:
Why the spark? The amount of capacitance I have in the circuit in about 110uF.
What causes the motor to turn on?
Is there a way of suppressing the spark other than using a resistor?
Why is the current draw so large?
Thanks,
Brendan