Power to switch controller on

Ask questions and get answers if you hit a snug or unsure how to set up your ride
Santacruz
Posts: 9
Joined: Mon Apr 22, 2019 3:35 am

Power to switch controller on

Unread post by Santacruz » Wed Mar 18, 2020 5:41 pm

I am just finalizing my build.
I am wiring in the 18F 8kw controller I bought a while back.
I have a pre charge system set up. It checks the circuit then charges the capacitors and then switches the relay for main power.
This is controlled from a 12v key switch.
My question is, can I use the relay power (when it switches on) to power the ignition switch of the controller or does this have to be powered first?

PVadmin
Site Admin
Posts: 55
Joined: Sat Feb 09, 2019 5:55 pm

Re: Power to switch controller on

Unread post by PVadmin » Wed Mar 18, 2020 11:58 pm

Here is the recommended sequence:
1. Connect pre-charge circuit to charge the capacitors (have to be all the way up to the battery voltage, not just 12v or so)
2. Connect the main power (normally that would be the battery positive to the controller batt+ via a circuit breaker, relay, or such)
3. Connect the ignition to the battery positive to turn the controller on (ready to drive)

If the question is specifically whether you can connect the Ignition wire to 12v, instead of the battery voltage, the answer is No.
The battery voltage goes to via the ignition to the controller step down converter where it's reduced to 15v or so. This voltage is used to drive the mosfets and is further stepped down to 5v to power the low voltage electronics. Battery state of charge is also measured via the ignition wire so that the MCU knows when to shut off the mosfets on over or under voltage events. You want to power the ignition from the battery positive.
Santacruz wrote:
Wed Mar 18, 2020 5:41 pm
I am just finalizing my build.
I am wiring in the 18F 8kw controller I bought a while back.
I have a pre charge system set up. It checks the circuit then charges the capacitors and then switches the relay for main power.
This is controlled from a 12v key switch.
My question is, can I use the relay power (when it switches on) to power the ignition switch of the controller or does this have to be powered first?

Santacruz
Posts: 9
Joined: Mon Apr 22, 2019 3:35 am

Re: Power to switch controller on

Unread post by Santacruz » Thu Mar 19, 2020 2:39 am

Okay, thank you.
Sorry my post was not clear.
My set up is, 12v key switch to precharger. This uses a resistor to charge up capacitors. When charged, the precharger sends 12v to the relay, that then connects the battery to the controller.
My question is whether I could connect the ignition power to the main battery power that is switched by the relay.
So when the caps are charged up, the relay would supply full battery voltage to the controller and ignition wire.
I was just trying to avoid have 2 key switches.

PVadmin
Site Admin
Posts: 55
Joined: Sat Feb 09, 2019 5:55 pm

Re: Power to switch controller on

Unread post by PVadmin » Thu Mar 19, 2020 5:17 pm

Yes, you can turn on the ignition together with the main battery. The voltage supplied to the ignition is the same as in the battery positive terminal. You may want to add a 1A fuse in line if the wire going to the ignition.

Santacruz
Posts: 9
Joined: Mon Apr 22, 2019 3:35 am

Re: Power to switch controller on

Unread post by Santacruz » Fri Mar 20, 2020 3:57 am

Okay.
Thank you very much for the advice.

Santacruz
Posts: 9
Joined: Mon Apr 22, 2019 3:35 am

Re: Power to switch controller on

Unread post by Santacruz » Sat Mar 21, 2020 3:11 pm

Sorry for all the questions, but one last one.

From the controller I have a yellow and red wire in a plug labelled ignition.
If I understand the wiring diagram, then the red is battery voltage from the battery supply to the controller and the yellow is battery voltage when connected to the red wire.
As the main supply on my build will switch the power on to the controller, can I, then just use a 1amp fuse to bridge the red and yellow ign. wire (Plug)

PVadmin
Site Admin
Posts: 55
Joined: Sat Feb 09, 2019 5:55 pm

Re: Power to switch controller on

Unread post by PVadmin » Wed Mar 25, 2020 2:34 pm

Yes, you can do that.
Santacruz wrote:
Sat Mar 21, 2020 3:11 pm
Sorry for all the questions, but one last one.

From the controller I have a yellow and red wire in a plug labelled ignition.
If I understand the wiring diagram, then the red is battery voltage from the battery supply to the controller and the yellow is battery voltage when connected to the red wire.
As the main supply on my build will switch the power on to the controller, can I, then just use a 1amp fuse to bridge the red and yellow ign. wire (Plug)

Santacruz
Posts: 9
Joined: Mon Apr 22, 2019 3:35 am

Re: Power to switch controller on

Unread post by Santacruz » Wed Mar 25, 2020 3:15 pm

Thank you very much for the advise.

Post Reply