Can I use a car battery charger's 2 amp setting on a motorcycle?

Often, yes, if your battery is around 8 Ah or larger and the charger matches the battery type. Check the charge rate against the battery's amp-hour rating first.

Can I jump-start a motorcycle from a car?

It can be done with the car's engine off and careful connections, but it's not the same as charging. Our jump-start guide covers the precautions.

How long does it take to charge a motorcycle battery?

It depends on how flat it is and the charger's output. A low-amp charger can take several hours to overnight to fully charge a dead battery.

Can I leave a car charger connected to my motorcycle all winter?

Only if it's a smart charger with a maintenance or float mode suitable for your battery type. Old manual chargers can overcharge a small battery if left on.

Can you use a car battery charger on a motorcycle battery?

You can use a car battery charger on a motorcycle battery only if it has a low-amp setting suited to a small battery and a mode that matches your battery type. Many car chargers put out too much current for a motorcycle battery, which can overheat it, boil off electrolyte or shorten its life. Lithium motorcycle batteries need a charger with a lithium-specific mode, and a standard car charger can damage them.

Here's how to tell whether your car charger is safe to use, and what to use instead if it isn't.

Can you use a car battery charger on a motorcycle?

It depends on three things: the charger's output, the battery's size and the battery's chemistry.

Motorcycle batteries are small. Many hold around 5 to 20 amp-hours (Ah), compared with roughly 40 to 80 Ah or more for a typical car battery. A charger sized for a car can push current at a rate that's fine for a car battery but harsh for a little motorcycle battery.

Battery Tender's motorcycle charging guide says the battery industry standard is to charge at a rate no higher than 10 to 25 percent of the battery's Ah capacity. It adds that chargers rated around 750 milliamps to 1.25 amps fall in the safe range for nearly all motorcycle batteries from 7 to 30 Ah.

Motorcycle battery size	Max charge rate (10–25% of Ah)	Typical car charger settings that fit
5 Ah (small scooter or dirt bike)	About 0.5 to 1.25 A	Usually none; most car chargers start too high
8 Ah (many sport and standard bikes)	About 0.8 to 2 A	A 1 or 2 A setting, if available
12 Ah (mid-size bikes)	About 1.2 to 3 A	A 2 A setting
20 Ah (cruisers, touring bikes)	About 2 to 5 A	A 2 A setting; some 4–5 A settings

Your battery's Ah rating is usually printed on its label. If you can't find it, look up the battery model number.

The risks of using a car charger on a motorcycle battery

Too much current

High charge current heats the battery. On a flooded lead-acid battery, it can boil off electrolyte. On a sealed AGM battery, excess heat and gassing can permanently reduce capacity. Charging too fast also tends to leave the battery less fully charged than a slow charge would.

Overcharging on old-style chargers

Older manual chargers and simple trickle chargers keep pushing current even after the battery is full. Battery Tender's guide warns that a trickle charger left connected risks overcharging and electrolyte boil-off. A small battery reaches full charge quickly, so this problem shows up faster on a bike than on a car.

Wrong mode for the battery chemistry

Many motorcycles now use lithium iron phosphate (LiFePO4) batteries. Battery Tender notes that lithium batteries need a charger with a dedicated lithium charging profile, and that charging one on a lead-acid-only setting can cause permanent damage. Some car chargers also have a desulfation or "repair" mode that's harmful to lithium batteries.

Not sure what you have? Our comparison of AGM, lithium and gel motorcycle batteries explains how to tell them apart.

How to tell if your car charger is safe for your motorcycle

Check the charger's label or manual for:

A low-amp setting within 10 to 25 percent of your battery's Ah rating.
An automatic or "smart" charging mode that tapers off and switches to float or maintenance when the battery is full.
A setting for your battery type, such as standard, AGM or lithium.
No forced desulfation or high-voltage recovery mode turned on, especially for lithium.
12-volt output. Most motorcycles use 12 volts, but some vintage bikes and small machines use 6 volts.

If the lowest setting is 6 amps or more, it's too much for most motorcycle batteries. Use a dedicated motorcycle charger instead.

How to charge a motorcycle battery with a car charger safely

If your charger passes the checks above:

Turn the bike off and remove the key, and work in a well-ventilated area, since lead-acid batteries can give off flammable hydrogen gas while charging.
Check the battery. Don't charge a cracked, swollen or leaking battery.
Connect positive first, then negative, to the battery terminals or to the bike's charging lead if fitted.
Select the lowest suitable amp setting and the correct battery type.
Plug in the charger and switch it on.
Check on it. If the battery gets hot to the touch, smells or hisses, stop.
Disconnect in reverse, with the charger unplugged first.

For a full walkthrough, see how to charge a motorcycle battery.

Is a dedicated motorcycle charger worth it?

For most riders, yes. A small smart charger or maintainer designed for powersports batteries usually costs less than a replacement battery and can stay connected during storage. Many come with a pigtail lead you can leave attached to the battery for quick hookups.

Prices vary by brand and features, but basic maintainers are commonly in the $25 to $60 range, and lithium-compatible models often cost more.

Charger vs maintainer: what's the difference?

The words get used loosely, but they describe different jobs:

A charger brings a discharged battery back up. Higher-output units do it faster.
A maintainer (sometimes called a tender) supplies a small current and switches to float mode to hold a full battery at the right voltage during storage.
A trickle charger supplies a small, constant current that doesn't shut off. It's the type most likely to overcharge if forgotten.

Many modern smart chargers do both charging and maintaining. If you store the bike for the winter, a maintainer that matches your battery type is the tool you want connected, not a car charger left on a high setting. Disconnect and check the battery every few weeks if your charger doesn't have an automatic float mode.

Charging vs jump-starting

Charging slowly restores a battery. Jump-starting just gets the engine running. Jumping a motorcycle from a running car can expose the bike's electrical system to a higher charging voltage, which is why most advice is to keep the car's engine off. Our guide on how to jump start a motorcycle covers the safe way to do it.

When a charger won't fix the problem

If the battery won't hold a charge, keeps going flat or the bike drains it overnight, the battery may be worn out or something else may be wrong. Common culprits include a failing stator or regulator rectifier, a parasitic drain from accessories, or a battery that's simply reached the end of its life. Our guide to why a motorcycle battery keeps dying walks through how to narrow it down.

When to see a mechanic

Stop and get help if:

The battery is swollen, cracked, leaking or gets hot while charging
The battery dies again within days of a full charge
Lights dim at idle or the bike won't start even with a charged battery
You smell burning from wiring or the charger
You're not sure whether your battery is lithium or lead-acid

A shop that does motorcycle electrical repair can load-test the battery and check the charging system. Find one through our motorcycle repair directory.