Last updated September 2026.
A phone running navigation on a bike drains faster than most people expect — GPS on, screen on or mirroring to a CarPlay screen, cell radio hunting for signal in the hills. On a hot day the phone also throttles its own charging to protect the battery, so a weak charger can lose ground even while plugged in. This is how to keep a phone alive for a full day of riding, from simplest to most involved.
The options, ranked by how much work they are
- A power bank in a tank bag or jacket pocket. Zero installation, works on any bike, and a 10,000 mAh bank charges a phone twice. The only downside is remembering to charge the bank. If you ride occasionally, stop here.
- A USB charger in the bike’s accessory socket. Many bikes have a 12 V or USB socket from the factory. A $15 adapter and a cable and you’re done. Watch the socket’s rating — some are 1 A and won’t keep up with a phone running navigation.
- A hard-wired USB charger. A $20–30 waterproof USB outlet wired to the battery, ideally through switched power so it turns off with the ignition. This is what most regular riders end up with. It’s an hour’s job.
- A wireless charging mount head. Quad Lock, SP Connect and Peak Design all sell weatherproof Qi heads that charge the phone while it sits in the mount, wired to the battery. Convenient; slower; and they overheat in sun.
- Skip charging the phone: use a CarPlay screen. Counterintuitive, but relevant: a screen that mirrors your phone still drains it, just less than a phone with its own screen on. And some screens accept a USB cable to the phone for wired CarPlay, which charges it at the same time.
Hard-wiring a USB charger
The proper solution. Buy a waterproof motorcycle USB outlet — look for USB-C PD or at least 3 A per port, an inline fuse, and a rubber cap — and wire it to the battery. Two ways to do that:
- Direct to the battery. Simplest. The socket is always live, which means a phone left plugged in overnight (or a charger with a parasitic draw) will flatten the battery over a few days. Most modern chargers draw almost nothing with no phone attached, but “almost” isn’t zero.
- Through a relay on switched power. Tap a circuit that’s only live with the ignition on — a tail light or the accessory circuit — to trigger a relay, and run the charger’s power through the relay from the battery. The charger turns on and off with the key. This is the setup I run on both bikes and the one I’d recommend for anything that stays plugged in.
A few brands sell “switched” USB chargers with a built-in ignition-sense wire, which saves adding a relay. Same idea, one fewer part. Whichever you choose, fuse it at the battery end.
If your bike has a Battery Tender / SAE pigtail already fitted for a trickle charger, you can buy a USB adapter that plugs into it. That’s the laziest hard-wire and it works fine as long as the pigtail is fused.
Wireless charging heads: the heat problem
Quad Lock’s weatherproof wireless head (about $70), SP Connect’s charging module and Peak Design’s Qi2 mount all work as advertised in mild weather. In direct summer sun, a phone that’s already warm from GPS and screen mirroring gets warmer from the induction coil, hits its thermal limit, and stops charging — often while showing the charging icon. Riders in Arizona and Texas learn this the first week. The fix is a wired cable to the phone, which charges faster and generates less heat, or accepting that wireless is for commuting and shoulder-season riding.
How much power does a phone actually need?
Running navigation with the screen on, a modern phone draws roughly 1.5–3 W; mirroring to a CarPlay screen with the phone screen off is a bit less. A 5 V / 2.4 A USB port supplies 12 W, so any decent charger keeps up in normal conditions. Where it goes wrong is heat throttling (phone limits intake to protect the battery) and cheap 1 A sockets. If your phone loses charge while plugged in, it’s one of those two, not the bike.
Will it drain my motorcycle battery?
While riding, no — the alternator covers a 12 W draw easily on anything bigger than a small scooter. Parked with a charger wired direct to the battery and a phone plugged in, yes, over a day or two. Use switched power or unplug the phone. A charger with nothing attached draws a negligible amount; the phone is the load.
What I run
Both bikes: a waterproof USB-C outlet on the bars, wired to the battery through a relay triggered from the tail-light circuit, fused at the battery. On the Ténéré, that also feeds the CarPlay screen’s USB power lead. On the GS, which has factory power in the Nav Prep, the outlet just charges the phone in the tank bag. A 10,000 mAh power bank lives in the tank bag as insurance on multi-day trips. Total cost of the wiring on each bike: about $40 and an hour.
For where the phone sits while it charges, see Best motorcycle phone mounts. If you’re powering a CarPlay screen and it keeps dropping, the cause is usually power — that’s in CarPlay keeps disconnecting: 9 fixes.