Power Supply - Fuses & Relays
Power Supply - Fuse & Relays
When it comes to fuses and relays, the biggest struggle for me was to pick a form factor for everything. There are quite a few different form factors for both relays and fuses. Since space is limited on a motorcycle, I tried to pick the smallest form factor I could.
Relays
I ultimately ended up going with Plug-in Micro ISO relays like this one. More information can be found here about these relays. These relays are nice since they are high current relays and can handle most anything I was going to throw at them. Like most electrical devices and components, there are a lot of options in terms of manufacturers. TE Connectivity and Song Chuan are just two that seem to be the most popular but others should work just fine.
Eventually found an even smaller relay form factor that I wish I had gone with (ISO 280 Mini Relay), but I was already at the final steps of designing a holder for the relays and creating a new holder was not something I wanted to invest any more time into. Like mentioned in the overview, if I were to start again from scratch, I'd instead choose a PMU device instead.
As described in a later section, I used a custom 3D-printed fuse and relay holder. There are off-the-shelf holders that are modular that you can use as well. I decided to forgo this route as none of them had the capacity I needed and were within an acceptable size to fit into the sub-frame area.
4-Pin & 5-Pin Relays
I feel like the topic of 4-pin and 5-pin relays is better discussed other places like here. A simple Google search will also help explain the differences as well. It is important to note however that both styles are used in this build and the custom holder is modular to accept each style. It is also important to note where each style needs to be located in the holder. If in doubt, you can use 5-pin relays everywhere.
Flyback Voltage Protection
Although Fueltech does not specify the need to manage flyback voltage for their ECUs, except for yellow outputs. Documentation on this is quite limited from Fueltech unfortunately and it is a good idea to implement this protection regardless, especially on any relays that the ECU controls directly. This can be done either with a resistor or diode that is integrated into the relay itself. Diodes offer the best protection but from what I have found are a real struggle to find but not impossible. Relays with built-in resistors seem to be much more common. When using relays with built-in diodes, the relay holder must be wired correctly because the polarity of the relay's coil will matter due to the inclusion of the diode. If this polarity is incorrect, you will short circuit the relay. Relays with a resistor are not polarity sensitive in this way. Nonetheless, when wiring the relay holder, pins 85 and 86 should always be wired in their correct orientations, even if you are not planning on using a relay with a diode. For my build I used 5-pin relays in most places with a diode, but there were instances where a 4-pin had to be used because of clearance issues.
After completing the wiring of the relay holder, and I made a cover to fit over it, I realized that the position of this holder conflicted with the sub-frame. I ended up finding some short versions of the micro-relay, but only with 4-pin style and with a resistor, not a diode. I looked and looked for the diode version, but no one seems to sell them.
Turn Signal Logic Relays
IMPORTANT: For relays 14 and 15 (left and right turn signal logic relays), you must NOT use a relay with a diode. The logic in this circuit will cause the relay to short circuit due to the coil being powered in the opposite direction from standard.
LED Flasher Relay
Since I am using LED turn signals and tail lights, I needed a flasher relay designed for LEDs. I went with this simple one here. Any 2-pin flasher should work here, just make sure pin orientation is correct and matches the Fuse/Relay holder.
Fuses
Fuse selection was a little bit easier than selecting the relays. I went with ATM Mini Blade Style fuses. These are very common and do not need any elaboration on them here.
Diodes
I used a total of four diodes in this Power Supply (not including integrated diodes in relays). These control grounding current flow between the Neutral and side stand switches and their respective indicating lights. The best solution for this was to use two DEUTSCH DT04-4P-RT01 receptacles. More information on these can be found here. This was the best alternative I could find to accomplish what I needed.
These diodes are needed (like in the OEM setup) to prevent undesired grounding in the starter relay circuit. I just expanded upon this logic as I included a sidestand down warning light which is not in the OEM setup.