BRP ships every Can Am Commander with just one battery, leaving accessory installers to find their own mounting point beyond the factory tray. Most owners bolt the second cell under the driver-side seat, behind the passenger seat, or inside the rear cargo box. Your final pick depends on chassis generation, accessory load, and how much cabin space you want to preserve.
You’ll find the stock electrical layout below, mapped empty cavities for each chassis generation, and a safe wiring path that keeps your starter above 12.4 volts.
The Commander Comes With One Battery, Not Two
Every Commander rolling off the BRP assembly line carries a single 12-volt battery, usually tucked under the driver-side seat on a molded plastic tray or mounted up front near the radiator support. There is no factory second tray, no auxiliary fuse panel dedicated to a second cell, and no pre-routed cabling waiting for an upgrade. BRP left the auxiliary slot empty because most buyers never push the electrical system hard enough to need one.
The moment a winch, a 30-inch light bar, or a four-speaker audio system enters the build, the stock stator starts to struggle. The factory charging system produces roughly 45 to 55 amps at peak, and a Warn VRX or a Smittybilt X20 winch alone can pull 150 to 400 amps under load. A second battery absorbs that surge so the primary stays above the 12.4-volt threshold needed for the next cold start.
Why the Stock Stator Hits a Wall
The single 30-amp-hour battery was sized for engine cranking and a handful of small accessories like the stock halogen headlights, the fan, and the EFI module. Add a Pulse Power 2,500-watt amplifier or an XS Power D3400 deep-cycle cell and the math breaks. Voltage drops under accessory load, the stator runs hot trying to keep up, and the battery never fully recovers between rides.
Mapping the Commander Chassis for a Second Battery
Each Commander generation offers different empty cavities, and choosing the right one is the difference between a clean bolt-up and an afternoon of fabrication.
2011–2018 Chassis Cavities
Three realistic mounting zones exist inside the 2011–2018 chassis, each offering a different balance of clearance and wiring access. Under the driver-side seat sits a flat tray area roughly 11 inches long by 7 inches wide, enough for a Group 35 AGM. Behind the passenger seat, a vertical cubby accepts a taller Group 34 cell once you remove the rear panel.
Inside the cargo bed, a flat spot just ahead of the tail light housing handles the largest batteries, including some Odyssey PC1500 units, as long as you build a simple aluminum bracket.
2019+ Redesigned Platform
BRP reshaped the chassis for 2019, tightening the wheelbase and rerouting the CVT intake duct. The under-seat cavity shrank by about an inch in length, so only Group 35 batteries fit cleanly. The behind-seat cubby now holds a BMP Battery Hold-Down bracket perfectly, and the cargo-box mounting point sits closer to the tailgate hinge, which leaves room for a Genesis Offroad twin-battery tray without trimming the bed liner.
Skip any spot that sits within four inches of the exhaust pipe, the CVT housing, or the engine block. Battery cases start to soften at 140°F, and the Commander’s CVT routinely pushes ambient temps past 160°F in slow technical terrain.
Choosing Between Under-Seat, Behind-Seat, and Rear Cargo Mounts
Each mounting zone trades weight balance for cabin space, and the right answer depends on how you actually ride. The table below lines up the three common locations against the factors most owners care about.
| Mounting Zone | Battery Size Limit | Weight Position | Weather Exposure | Accessibility for Jump-Starts |
|---|---|---|---|---|
| Under driver or passenger seat | Group 35 AGM | Low and centered | Low (inside cabin) | Easy, lift seat pan |
| Behind-seat cubby | Group 34 or 35 | Mid-height, slightly rear | Moderate (cabin airflow) | Moderate, remove rear panel |
| Rear cargo box | Group 34, PC1500, or dual tray | High and far back | High (water crossings, dust) | Hard, remove cargo box lid |
Trail riders running a single light bar and a small winch usually pick the under-seat location because it keeps weight low and centered. Rock-crawling builds with a 12,000-pound winch and a 20-inch light bar tend to land in the behind-seat cubby, where a Group 34 AGM from Odyssey or XS Power stores more reserve capacity.
Dedicated overlanders and audio-heavy builds gravitate toward the cargo box, where a twin tray from Genesis Offroad or S3 Powersports holds two batteries plus a voltage gauge in one footprint.
With those mounting zones mapped, the next decision is which battery form factors and trays actually drop into them without modification.
Battery Sizes, Trays, and Kits That Actually Fit
Group 35 and Group 34 AGM batteries dominate the Commander secondary battery market for good reason: both fit the factory-width tray cavities without cutting plastic, both deliver 650 to 850 cold-cranking amps, and both tolerate the deep discharge cycles that winching demands. Lithium iron phosphate batteries from Smittybilt or Pulse Power shave roughly 15 pounds off the install but require a battery management system and a DC-DC charger to play nicely with the stock voltage regulator.
Aftermarket Tray Options Worth Knowing
Genesis Offroad sells a Commander-specific twin tray that bolts into the cargo box without drilling, complete with hold-down hardware and a built-in bus bar. Rugged Radios offers a behind-seat mounting bracket that pairs with their intercom and accessory fuse panel, which simplifies wiring when you’re adding a comm system at the same time.
Smittybilt’s universal dual tray fits the rear cargo box on most 2015+ Commanders with minor trimming, and includes a marine-grade circuit breaker for the winch circuit.
Custom fabrication becomes necessary when you want a Group 31 lithium battery, a second Group 34 in the under-seat spot, or a battery relocation kit that moves the primary cell forward to balance a heavy rear cargo load. A local fab shop can bend 1/8-inch aluminum or steel into a tray in an hour, and powder-coating the bracket keeps corrosion off the metal after mud baths.
Wiring the Secondary Battery Safely With an Isolator
Connecting two batteries with a jumper wire is the fastest way to drain both at the same time. A battery isolator, sometimes called a voltage-sensitive relay or a smart isolator, is the only safe way to share charging current between the two cells while keeping the starter protected.
Tap Points and Routing
The accessory fuse panel under the driver-side dash provides a fused 12-volt source for the isolator’s trigger wire. Run 4-gauge or 2-gauge cable from the primary battery’s positive terminal, through an inline fuse mounted within 12 inches of the battery, to the isolator’s input post. From there, another fused cable runs to the secondary battery’s positive terminal.
Ground both batteries to the chassis using the factory ground strap point near the engine block, scraping paint off the contact area so the connection reads zero ohms.
When the Stock Stator Needs Help
Can-Am’s stock stator produces enough current to refill one battery between rides. Add a second battery, a 110-watt light bar, and a winch that pulls 250 amps under load, and the stator falls behind.
A DC-DC charger, such as a Pulse Power 20-amp unit or a BMP charger kit, steps the stator’s output up to the voltage the second battery actually needs to reach a full charge, and it prevents the alternator from cooking itself trying to keep up.
Proper wiring keeps the system reliable, but a bad mount can undo all that careful electrical work.
Mount the inline fuse within 12 inches of each battery’s positive terminal. A short unprotected cable between the battery and the fuse is the most common cause of cab fires in dual-battery UTV builds.
Common Mounting Mistakes and How to Avoid Them
Even a clean install can fail early when one of these three mistakes shows up.
Heat Exposure
Placing the second battery against the exhaust shield or directly above the CVT housing cuts its lifespan in half. AGM batteries rated to 12 years at 77°F drop to roughly four years at 120°F, and the Commander’s CVT shroud runs hotter than that on slow climbs. Mount at least four inches away from any heat source, and add a heat-reflective mat if the bracket has to sit closer than that.
Vibration Damage
Skipping the rubber isolators between the battery and the tray cracks the case walls within a season of desert riding. Use the foam spacers that ship with the tray, and torque the hold-down bolts to the manufacturer’s spec, usually 8 to 10 foot-pounds. Over-tightening bows the battery top and shortens the internal plates.
Weatherproofing Gaps
Cargo-box and behind-seat mounts soak up water crossings and dust far more than cabin seats do. Seal the cable entry points with marine-grade heat-shrink, cap any unused bolt holes with silicone, and wrap the positive terminal in a rubber boot. A dielectric grease coating on every ground point prevents the corrosion that slowly eats a chassis-mounted ground strap.
Bottom Line
The most popular Can Am Commander secondary battery location is under the driver-side seat, because it keeps weight low, stays out of the weather, and accepts a Group 35 AGM without custom fabrication. Heavier accessory loads push the answer to the behind-seat cubby or the rear cargo box, where larger Group 34 cells and twin-battery trays make room for winches, light bars, and audio systems that would otherwise drain the starter.
Pair the location with a smart battery isolator, fused 4-gauge cabling, and a chassis ground at the factory strap point, and the second battery becomes a quiet upgrade that just works.
FAQ
Where is the secondary battery located on a Can-Am Commander?
Factory Commanders do not have a secondary battery location. Aftermarket installs typically place the second battery under the driver-side seat, behind the passenger seat, or in the rear cargo box, depending on chassis year and accessory load.
How do you access the auxiliary battery in a Can-Am Commander?
Access the auxiliary battery by removing the driver-side seat pan (two plastic fasteners and a slide-off motion) for under-seat mounts, by pulling the rear cabin panel for behind-seat mounts, or by lifting the cargo-box lid and unbolting the tray for cargo-box installations.
Do all Can-Am Commander models have a secondary battery?
No. BRP ships every Commander with a single battery under the driver-side seat or near the front radiator support. A secondary battery is always an owner-installed upgrade, never a factory option.
Can you add a second battery to a Can-Am Commander?
Yes, and the install usually takes three to five hours with a twin-battery tray, a smart isolator, and fused 4-gauge cabling. The most important step is routing the ground strap to a clean chassis point near the engine block.
What size battery fits in the Can-Am Commander secondary battery tray?
Group 35 batteries fit the under-seat cavity on every chassis generation. Group 34 batteries fit the behind-seat cubby and the rear cargo box. Larger Group 31 lithium cells require a custom bracket or a battery relocation kit.
How do you wire a dual battery setup on a Can-Am Commander?
Wire a dual battery setup by running fused 4-gauge cable from the primary battery to a smart isolator, then another fused cable from the isolator to the secondary battery. Ground both batteries at the factory chassis strap point and tap the isolator’s trigger wire into the accessory fuse panel under the dash.
