Batteries and charging

Batteries

Three battery chemistries now share the same battery boxes on powersports machines, and they want three different things from a charger. A flooded battery has removable caps and loses water. An absorbed glass mat battery is a sealed lead-acid design that holds its electrolyte in a fibre mat, needs no watering, and tolerates vibration far better.

A lithium iron phosphate battery is a different chemistry entirely: much lighter, with a different resting voltage, a different charge profile, and a genuine cold-weather characteristic that surprises owners the first winter. Two practical points matter most: a charger built for lead-acid can damage a lithium battery, particularly one with a desulphation or repair mode, and most powersports batteries die in storage, not in use.

A healthy 12-volt lead-acid battery rests at 12.6 to 12.8 V when full and a lithium iron phosphate battery at 13.3 to 13.6 V.

The three chemistries side by side

Lithium iron phosphate

None; store charged and check resting voltage; Delivers less current when very cold until warmed by a brief load; Lithium-specific profile only; never a desulphation or repair mode.

Cold cranking amps and the group size stamped on a case are Battery Council International measures, so they compare directly between makers. They do not convert between chemistries: a lithium battery with a lower stated capacity in amp-hours can crank an engine that a lead-acid battery of the same rating will not, because the two chemistries deliver current differently.

What the voltage tells you

Measure with a multimeter across the terminals after the machine has sat for a few hours, so the surface charge has settled. The first table is the Battery Council International chart for a 12-volt lead-acid starter battery (flooded or AGM).

0%

11.89 V; Flat; it may not recover if it has sat flat for weeks.

At rest, ignition off; 12.6 to 12.8 V; 13.3 to 13.6 V.

While cranking; dips to about 10.0 V; dips to about 11.5 V.

Engine running (charging system)

14.0 to 14.5 V; 14.0 to 14.4 V.

A reading at the terminals with the engine running that stays near the resting figure points at the charging system (stator, regulator-rectifier or wiring), not the battery.

Why storage kills more batteries than riding does

This is one of three separate clocks a stored machine runs on at once: see the storage and winterization page for how the fuel system's chemistry and the coolant and brake fluid clock fail on their own separate timelines. Every battery self-discharges when it sits. A machine that is parked is rarely fully disconnected: alarms, clocks, immobilisers and engine management modules all draw a small standing current.

On a lead-acid battery, sitting at a low state of charge causes lead sulphate crystals to form and harden on the plates, which permanently reduces the capacity that can be recovered. That process is what a season in a shed does, and it is not reversible past a point.

A maintainer that holds the battery at a correct float voltage prevents it entirely; it is a much cheaper intervention than a battery. The important qualification is that the maintainer has to match the chemistry: a lead-acid maintainer applied to a lithium battery can push it outside its safe voltage window. A desulphation pulse mode is specifically hostile to lithium.

Both chemistries deliver less current when cold. The lithium curve falls more sharply near freezing and then recovers once a brief load warms the cells, which is why headlights-on-for-thirty-seconds works on lithium and does nothing for lead-acid.

Why a lithium battery cranks slowly in the cold

A lithium iron phosphate battery in cold conditions can refuse to turn an engine that it would spin easily at room temperature. Then work perfectly a minute later. This is not a fault. Internal resistance rises sharply as the cells get cold. The standard remedy is to draw a small current for perhaps thirty seconds, turning the headlight or the ignition on and leaving it, which warms the cells internally enough to restore cranking current.

Owners unaware of this conclude the battery has failed. Some lithium batteries returned as faulty are working normally. The behavior is a genuine trade-off against the weight saving, and it matters most on machines started outdoors in winter.

Before you buy a replacement, check these three

Physical size and terminal orientation

Batteries and charging questions

What is the difference between AGM and a conventional battery?

An absorbed glass mat battery is still lead-acid. But its electrolyte is held in a fibre mat, not sloshing about as liquid; that makes it sealed, spill-resistant, far more tolerant of vibration, and free of the watering requirement a flooded battery has. It charges on a normal lead-acid profile, ideally with an AGM setting.

Can I use a normal charger on a lithium motorcycle battery?

No, not safely. Lithium iron phosphate needs its own charge profile, and lead-acid chargers with desulphation, repair or equalise modes apply voltage pulses that are specifically hostile to lithium cells. Use a charger with a lithium mode, and if in doubt about an older charger, do not use it. The battery costs far more than the charger.

Why will my lithium battery not start the bike when it is cold?

Because internal resistance rises sharply as the cells get cold, so the battery cannot deliver its normal cranking current until it warms. The standard remedy is to draw a small load for about thirty seconds, headlight or ignition on, which warms the cells internally. It then usually cranks normally. This is expected behavior instead of a fault.

Is a lithium battery worth the extra cost?

It buys a large weight saving, a very low self-discharge rate and a long service life if it is charged correctly; it costs more up front, needs a compatible charger, and has the cold-start characteristic above. On a machine ridden in warm weather where weight matters, the trade is good. On a machine started outdoors in winter, debatable.

Why do powersports batteries die over winter?

Because every battery self-discharges when it sits, and most machines have a standing draw from alarms, clocks and engine management even when switched off. On lead-acid chemistry, sitting at a low state of charge hardens sulphate crystals onto the plates and permanently reduces recoverable capacity. A maintainer prevents it and costs far less.

Should I leave a maintainer connected all winter?

Yes, provided it is a maintainer, not a plain charger and it matches the chemistry. A maintainer holds a correct float voltage and stops. A simple charger that keeps pushing current will cook a lead-acid battery and is dangerous on lithium. Check the specification of what you own and not the word on the box.

What is CCA and does it matter on a small machine?

Cold cranking amps is a standardized measure of the current a battery can deliver at low temperature for a defined time while holding a minimum voltage; it matters because starting is a current problem instead of a capacity problem. Comparing cranking figures is more useful than comparing amp-hours, especially between different chemistries.

Can I fit a bigger battery than the original?

Only if it fits the box, the terminals are the right way round, and the charging system can support it. Physical fit and terminal orientation cause most failed purchases. A larger capacity will not strain a healthy charger. But it does take longer to bring back to full charge after a deep discharge.

My battery keeps going flat even though I ride regularly?

That is usually a charging system or parasitic draw problem, not a battery problem. A new battery will simply be ruined in turn. Measure the voltage at the terminals with the engine running at the speed the manual specifies, then measure the current drawn with everything switched off. One of the two measurements normally identifies it.

What resting voltage means a battery is charged?

A full 12-volt lead-acid battery (flooded or AGM) rests at about 12.65 V, 12.45 V is 75 percent, 12.24 V is 50 percent and 11.89 V is flat. A full lithium iron phosphate battery rests at 13.3 to 13.6 V, so reading a lithium battery against the lead-acid chart gives the wrong answer. Measure after the machine has sat for a few hours so the surface charge has settled.

Can a battery test fine and still not start the engine?

Yes, and it is a common pattern. A resting voltage test measures state of charge; a load test measures whether the battery can deliver current. A sulphated lead-acid battery often shows full voltage at rest and collapses the moment the starter engages. If it cranks slowly and the voltage plummets under load, that is your answer.

Do I need to disconnect the battery for storage?

It removes the standing draw, which helps. But it does not stop self-discharge and it means resetting clocks and sometimes relearning idle settings. A maintainer left connected is the better solution because it addresses both the draw and the self-discharge. If neither is possible, disconnecting is better than leaving it connected and unattended.

Where the figures and rules come from

Standard

Battery Replacement Data Book and BCI group size / cold cranking amps definitions : Battery Council International; Research; BU-903: How to Measure State-of-charge, Table 3: BCI standard for state-of-charge estimation of a starter battery : Battery University (Cadex Electronics). Checked 2026-09-30. Rechecked annual.

Service intervals: the counter that governs a stored machine

Storage is a calendar problem, and the battery is only one of its casualties.

Brake fluid and coolant die in storage too; The other two items a season in a shed consumes without the machine moving.

Blink codes and warning lights caused by low voltage; A weak battery produces symptoms across an entire electrical system.