Ignition or enable key switch..

[thelarkbox]

Not a feature supported by the controller i intend to use a but i would like to implement an ignition style on/off switch.

But i somehow suspect such a thing as pictured above would not hold out very long turning on and off the battery power.

I have googled for 'ebike contactor circuit' without much success. I cant be the only bod considering this?

I imagine whats needed is some sort of voltage dropper to drop the 36-42v of the battery down to logic levels, a voltage divider or a proper step down regulator?
a dc relay or contactor able to handle the voltage and peak amp draw from the controller 42v 15a, and just wiring the dropped down 'logic level' voltage <12v to the coil of the relay/contactor via the ignition key switch thus making or breaking the power connection to the battery via the live pole.

having a vague idea is one thing what i would like to find is a parts list and a circuit to follow..

an ebay search for 42v dc relay turned up this.. but would a low battery say 36v be sufficient to power a 48v coil to engage the relay?

I feel like im missing something crucial here and am overlooking the obvious??

 

[saneagle]

Not a feature supported by the controller i intend to use a but i would like to implement an ignition style on/off switch.

But i somehow suspect such a thing as pictured above would not hold out very long turning on and off the battery power.

I have googled for 'ebike contactor circuit' without much success. I cant be the only bod considering this?

I imagine whats needed is some sort of voltage dropper to drop the 36-42v of the battery down to logic levels, a voltage divider or a proper step down regulator?
a dc relay or contactor able to handle the voltage and peak amp draw from the controller 42v 15a, and just wiring the dropped down 'logic level' voltage <12v to the coil of the relay/contactor via the ignition key switch thus making or breaking the power connection to the battery via the live pole.

having a vague idea is one thing what i would like to find is a parts list and a circuit to follow..

an ebay search for 42v dc relay turned up this.. but would a low battery say 36v be sufficient to power a 48v coil to engage the relay?

I feel like im missing something crucial here and am overlooking the obvious??

If you only want to switch off the controller and LCD, put the switch on the red wire that's in the LCD cable. Those things use very little current - something like 200mA.

 

[thelarkbox]

If you only want to switch off the controller and LCD, put the switch on the red wire that's in the LCD cable. Those things use very little current - something like 200mA.

Well initially it was a simple plan to isolate the battery but that works too i guess and should be A LOT easier and cheaper too which is never bad.. let me sleep on it Cheers.

 

[saneagle]

To isolate the battery, there are two ways. You can either make a simple MOSFET switch, or you can hack into the BMS, but to do that, you'd have to have a switch that's open when locked and closed when unlocked.

MOSFET switch. You don't need an etched PCB. You can just drill a bit of fibreglass or thin plywood and join everything with wires:

 

[thelarkbox]

To isolate the battery, there are two ways. You can either make a simple MOSFET switch, or you can hack into the BMS, but to do that, you'd have to have a switch that's open when locked and closed when unlocked.

MOSFET switch. You don't need an etched PCB. You can just drill a bit of fibreglass or thin plywood and join everything with wires:
View attachment 54285

View attachment 54286

You Star, exactly what my google skills failed to find for me..

Im sure i can find some perfboard for the job.
trigger pulled on mosfets and a switch..

is that an electrolytic capacitor or isnt it relevant

 

[thelarkbox]

yes its an electrolytic cap since it needs to have a higher voltage capacity than the battery source doh! its late ..