Powered panniers

On longer motorcycle trips, I often struggle to keep all my devices charged. When I camp for a few days, I can't find a wall socket. When I sleep in hostels, I don't want to leave my things unattended. Even when I sleep in hotels, I'm too exhausted to think about it.

It might seem like a trifle, but when you travel by motorcycle, you only get a few hours a day to feed yourself, clean yourslef, plan the route ahead, keep the bike running, and charge your gear. The small annoyances add up.

Instead, I wanted to charge my devices on the motorbike, inside my panniers, and preserve my energy for other things.

The general idea

Thinking inside the box

Bringing power inside the pannier was no walk in the park. I needed a connector that could be exposed to mud, dust and torrential downpours, and still work safely. It had to be easy to connect and disconnect, because I take the panniers off every night.

I wasted a whole day on Digikey, looking for the perfect connector. As the bill of material ran close to 100€, I remembered about SAE connectors. They're tough, they're waterproof, and they're an automotive industry standard. Oh, and they're also dirt cheap. I found an SAE panel mount connector on Amazon, and lots of cheap cables and connectors to bring the system together.

I placed the connector on the rear of the pannier. This way, I can check if the luggage is secured, locked and connected in one glance. If I placed it in the front, I'd bump into it when moving on the bike and destroy it. The front side also tends to get caked in bugs and mud. If I placed it on the inner side, I'd likely forget it's there and tear it off on the first day.

I used a step drill bit to make holes for the connector, and bolted it in place with a layer of automotive silicon in the middle. That's the same silicon they use to install windscreens, so it ought to keep the water out. I used waterproof washers on the other side, just in case. As I tightened the bolts, the extra silicon oozed out, and I wiped it off with a rag. I put the connector under running water for 15 minutes, and it didn't leak.

I wanted to use M5 bolts for the connector, because I already pack the right tools, but the holes were too small. I used smaller M3 bolts and added a 5.5mm socket to my packing list.

All in all, it turned out exactly as I hoped. The connector is tough and waterproof, and it looks halfway decent.

Inside the panniers, I fit two 12V cigarette lighter plugs in a plastic enclosure. The enclosure can quickly be opened for inspection during border crossings.

I used the 4 bolts that stick out of the SAE connector to secure the enclosure to the pannier. Instead of soldering the wires in place, I used removable Wago connectors. This should make field repairs much easier. I only need a Phillips screwdriver and a 5.5mm socket. I could also transfer the enclosure to a different set of panniers later.

This project coincided with my switch to USB-C. I charge all my devices with the same cables, wall sockets and car adapters. It saves a lot of space and weight.

I put a USB-C PD adapter in each cigarette lighter plug. One charges two devices at once, and the other delivers up to 72 Watts, enough to charge my Macbook.

If USB-C falls out of fashion, I can replace those adapters with something else.

From the battery to the panniers

This is roughly how I wired everything together between the battery and the panniers. I designed the circuit to be modular, flexible and field-repairable. I used SAE connectors to connect the components together. Nothing is glued or soldered in
place. If something needs maintenance, I can just disconnect it and pull it out. My mini compressor and my battery tender also use SAE  connectors, so I can just plug them in.

My Macbook draws up to 87 Watts (4.3A @ 20.2V), my phone up to 15 Watts (1.67A @ 15V), and everything else up to 10 Watts (2A @ 5V). In any case, the power draw is capped by my USB-C car adapters. One delivers up to 72 Watts, and the other up to 36 Watts. In other words, we top off at 108 Watts.

My heated grips also draw up to 39 Watts1. That brings us to roughly 150 Watts.

I also have a mini air compressor that draws up to 72 Watts. If we wanted to charge everything, keep our hands warm and reinflate a tire at the same time, we'd draw roughly 220 Watts. Realistically, that never happens, so let's stick to 150 Watts. At 12 volts, that's 12.5 Amps. 16 gauge wire should be enough1, 2.

That black enclosure in the middle is the relay box. It connects the other components to the ignition switch. When the ignition is off, the entire circuit is off. If I leave something plugged in overnight, I won't wake up to a dead battery. That's a risk I can't afford to take when I'm driving through deserts, several thousand kilometres from home.

Inside the relay box, I use screw terminals and Wago connectors, no soldering. I can modify the circuit using the tools I usually carry. Again, this greatly simplifies field repairs. The relay circuit itself is Bigpie's Fuse Box. It's great, except that it uses full-sized ATC fuses, while the motorbike uses mini ATC fuses. I need to carry two kinds of spare fuses. Fortunately, they're not very heavy.

I also had some issues with the screw terminals. They're a tad flimsy. When I opened the relay box to take photos, one of the connections came undone.

The relay box is right under the seat. I was a bit worried about water getting in there. After spending a few hours researching expensive waterproof grommets, I called my father, who reminded me about hot glue.

Finishing touches

Once the circuit was tested and working, I held everything in place with cable ties. I added green tape on everything I added, to make it easier to identify what came with the bike, and what didn't.

Final result

It's winter, and we're in the middle of a global pandemic, so my powered luggage didn't see much action. However, I tested it with all of my devices, and it works great. I'm looking forward to a proper field test.