Will Your Bike Run a 12V Heated Liner? The Amp Math Most Riders Skip
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Heated gear is sold on warmth and never on electrical load, which is why so many riders find out the hard way that their bike cannot carry it. The number that decides it is 6.4 amps, and here is what to do with it.
What the number actually says
The Gerbing 12V heated jacket liner 2.0 draws 6.4 amps from a 12 volt supply, which is about 77 watts. That single figure is the whole argument. It is not a small accessory load, and it is the number most riders never look at before buying.
Six point four amps is roughly the same current a pair of auxiliary driving lights pulls, and rather more than a phone charger or a GPS. A bike that accepts a phone charger without complaint can still be unhappy about 6.4 amps of continuous draw, because the difference between intermittent and continuous load is what overheats wiring rather than what drains a battery.
Doing the math on your bike
The sum is simple once you accept that nothing is free. A motorcycle's charging system has a total output, and everything on the bike is drawing from it: headlight, tail light, ignition, fuel pump, instruments, heated grips if you have them. Whatever is left over is your headroom for heated gear.
So the question is not whether your bike has a 12 volt system, because every bike does. It is whether the charging system has 6.4 amps spare at the speed you actually ride. A bike idling in traffic has far less spare capacity than the same bike at highway speed, because alternator output rises with engine speed. That is the failure people hit: the liner works fine on the open road and flattens the battery in town.
The number to find: your bike's charging system output at riding rpm, minus the draw of everything already on the bike. If the remainder is not comfortably above 6.4 amps, the liner is going to be a compromise rather than an addition.
Why the harness goes to the battery
Gerbing's 12V garments are wired to a fused harness that connects directly to the motorcycle battery rather than through a 12 volt accessory socket. That is not marketing convenience, it is the amp rating. Accessory sockets and their wiring are built around much lower continuous currents, and pushing 6.4 amps through a plug designed for a phone charger is how you get a melted connector at the side of the road.
A direct fused lead also gives the garment a path with no intermediate connection to corrode, which matters on a bike that sees Atlantic Canada salt and rain. The fuse is the protection: if something shorts in the garment, the fuse goes rather than the loom.
12V wired or 7V rechargeable
Gerbing separates its 12V wired system from its 7V rechargeable system, and the load question only applies to the wired one. The rechargeable batteries carry their own energy and therefore their own runtime limit, but they add nothing to the bike's electrical load.
That is the real trade. Wired gear runs as long as the bike does, at the cost of a 6.4 amp continuous draw and a harness fitted to the bike. Rechargeable gear costs nothing electrically and asks you to manage batteries instead, which on a cold multi-day ride means charging them every night.
The order to do this in
Fit the harness first, fused, direct to the battery, routed so it cannot chafe against a frame edge. Then check the bike's charging headroom before you rely on the liner on a long ride, because discovering the limit in the dark on a November evening with a dead battery is a bad way to learn it.
Then test it on a short ride in daylight. Watch for a dimming headlight at idle, a battery light, or a dash that resets when the liner cycles up. Those are the symptoms of a charging system already at its limit, and they show up long before the battery goes flat.
Frequently Asked Questions
How many amps does a heated jacket liner draw?
The Gerbing 12V heated jacket liner 2.0 draws 6.4A from a 12V supply, which is about 77 watts.
Can I plug heated gear into a 12V accessory socket?
No. Gerbing's 12V garments use a fused harness wired directly to the motorcycle battery, because 6.4A continuous is well beyond what an accessory socket and its wiring are built for.
Will my motorcycle run 12V heated gear?
It depends on charging-system headroom at riding rpm, not on whether the bike has a 12V system. Subtract everything already drawing on the bike from the charging output, and see what is left over 6.4A.
Does the 7V rechargeable system load the bike?
No. Gerbing's 7V rechargeable garments carry their own batteries, so they add nothing to the bike's electrical load, at the cost of runtime and nightly charging.
Sources
- Gerbing heated clothing. Product range and the 12V wired system specifications.
- Gerbing FAQ. Separates the 12V wired system from the 7V rechargeable system and describes the fused battery harness.
