Why Snowmobile Batteries Die in the Cold (and How to Pick One That Won’t)

A battery makes power through a chemical reaction, and cold slows that reaction down. Internal resistance goes up and available capacity goes down. At around -18°C, a battery delivers roughly half the capacity it would in a warm garage.

The good news: that loss is temporary. Warm the battery back up and the capacity comes back. The bad news: your engine is having a hard morning too. Cold oil is thick, everything is stiff, and the starter needs more current at the exact moment the battery has less to give.

That's why the number that matters on a sled battery is CCA, or cold cranking amps. It's measured at -18°C: the current a battery can deliver for 30 seconds without dropping below 7.2 volts. Higher CCA means more margin on a cold morning. It's also why the snowmobile batteries worth buying list it up front.

Cold on its own is survivable. Cold plus a low charge is how batteries actually die.

The electrolyte in a fully charged lead-acid battery is mostly acid, and it won't freeze until somewhere around -59°C. As the battery discharges, that electrolyte turns more and more into water. A deeply discharged battery can freeze at -3°C to -8°C. Ice expands, plates warp, and the case can crack. That battery isn't coming back.

A dead battery doesn't freeze because it's cold. It freezes because it's flat.

Sleds are great at going flat. They sit for eight months. Batteries self-discharge even with nothing connected, and anything that draws a little power with the key off, like a gauge memory or an accessory wired straight to the battery, speeds it up. Yuasa's own numbers show a 10 milliamp draw takes a 20 amp-hour battery from full to half in about six weeks. Park it in April with a draw like that and it's well past flat by the first snowfall.

Keep it charged and it can't freeze. That's the whole trick.

A cheap multimeter tells you most of what you need to know, and it takes five minutes. The catch is timing. Test a battery right after charging or riding and it'll read high from surface charge. Let it sit for at least an hour first. Or switch the key on with the lights running for about three minutes, shut it off, and wait ten.

Then put the leads on the terminals and check the reading against the card below. These numbers are for AGM, which is what most modern sleds run. Yuasa's rule is blunt: if an AGM won't come back above 75% after a full charge, it's probably done.

Load test

Voltage tells you charge, not strength. A tired battery can show 12.8 volts and still fold the second the starter asks for real current. A load test puts a heavy draw on the battery for 10 seconds. If the voltage drops below 9.5, replace it. Most battery shops and parts counters can do one in a couple of minutes.

Charging system check

If batteries keep dying on you, the battery might not be the problem. Get the track off the ground on a stand, keep everyone clear of it, start the sled and hold it at 3,000 to 4,000 rpm. You should see 13.5 to 14.5 volts at the battery. If it sits under 13, the sled isn't charging it, and a new battery will just die slower.

Open our snowmobile batteries collection and you'll find four types. They don't behave the same in the cold.

AGM

The default, and for most riders the right call. Sealed, maintenance-free, spill-proof, and it handles vibration well. Yuasa, Motobatt and Kimpex make up most of what we carry.

Gel

A close cousin of AGM. Also sealed and maintenance-free. Treat it the same way, and if your charger has a gel setting, use it.

Conventional

Mostly older sleds. Cheaper, but it needs its water level checked, and Yuasa recommends checking a stored conventional battery every month instead of every three months for an AGM.

Lithium

Lighter by a long way, holds its charge well in storage, and cranks hard when it's warm. The catch is the cold. BS Battery's spec sheet for its BSLi-13 lists discharging down to -20°C, but charging only from 0°C up. Below freezing, a lithium battery can start your sled but can't take a charge back from it. Lithium also has its own charging rules: Skyrich warns that chargers with an automatic desulfation mode can destroy it.

We carry lithium from Skyrich and BS Battery. They earn their place on a mountain sled where every kilogram counts and the sled sleeps in a heated garage. If yours parks outside overnight, AGM is still the safe bet.

Start with fit. Batteries come in specific case sizes and terminal layouts, and the wrong one either won't sit in the tray or puts the positive terminal where your cable can't reach. Our Battery Finder matches your make, model and year to the right size. Use it before you buy anything.

Then look at three things:

• CCA. Match or beat what your owner's manual calls for. More is fine. Less is a gamble every cold morning.
• Your accessory load. An electric shield, heated grips, a GPS and a light bar all pull from the same charging system. If you run a heated visor from our electric snowmobile helmets lineup, give yourself some margin.
• Factory activated or acid pack. Factory-activated batteries ship filled, sealed and charged, ready to install. Batteries sold with an acid pack get filled at home and need an initial charge before they go in. Skip that step and it starts its life undercharged.

An easy upgrade

If your sled takes a YTX14-size battery, the Yuasa GYZ16H fits the same footprint with 4 more amp-hours and 40 more cold cranking amps, according to Yuasa. Same tray, more margin when it's -25°C. Just check the terminal layout matches your old battery. The GYZ16HL is the reverse-terminal version.

Most battery failures are really charging failures. The fix is a proper automatic charger, not the old trickle charger on the garage shelf.

Yuasa's guidance for powersports batteries is specific:

• Charge at about one-tenth of the battery's amp-hour rating. A 14 Ah battery wants about 1.4 amps. Don't go over 3.
• Skip car chargers and high-rate chargers. Yuasa says using one to speed things up voids the warranty.
• Old-style trickle chargers aren't safe to leave connected for long periods. A smart charger can stay on an AGM indefinitely.

For most AGM owners, something like the Yuasa 1A Automatic Charger and Maintainer is the right tool. Yuasa built its own chargers after finding that third-party units it tested didn't fully charge its AGM batteries. Lithium owners need a lithium-aware charger, like the Battery Tender Power Tender Lithium and AGM, which lets you select the chemistry. The full lineup is in our battery chargers and tenders collection.

Storage that works

No smart charger? Disconnect the battery cable for storage, check an AGM every three months, and charge it whenever it reads low. Lithium is easier to store but less forgiving of a slow drain: Skyrich says to disconnect it completely if the sled will sit for more than two weeks. The rest of the put-away list is in our seasonal maintenance guide.

Plug it in in April. Unplug it in December.

1. Warm the battery if you can. A night in a heated garage beats everything. If the sled lives outside and the battery comes out easily, bring it inside the night before.
2. Lithium? Wake it up first. Switch the key on and run the lights for about 30 seconds before cranking. Skyrich recommends this in the cold because the draw helps warm the battery.
3. Short cranks. Three to five seconds, then give it 30 seconds before trying again. Long cranks drain the battery faster than they help.
4. Put the charge back. A hard start takes a lot out. Let it idle a few minutes, then ride for 20 to 30 minutes before you shut it down again.

And if it still won't go, our guide on the easiest way to tow a snowmobile exists for a reason.