Charging Deep-Dive

Charging Explained

Learn how Li-ion charging works, interpret charging logs, and understand Zero's recommendations for battery longevity.

TL;DR

Li-ion batteries charge in two phases: Constant Current (CC) for bulk charging, then Constant Voltage (CV) as cells approach full. For longevity, charge to 80-90% for daily use and avoid leaving the battery at 100% or 0% for extended periods.

CC/CV Charging Process

Lithium-ion batteries use a CC/CV (Constant Current / Constant Voltage) charging protocol to safely and efficiently charge cells:

1
Constant Current

Charger delivers maximum current while voltage rises. This is the "bulk" charging phase — fastest rate of charge.

Typical: 0% → ~80%

2
Constant Voltage

Voltage held at max (4.2V/cell), current tapers down. This "absorption" phase tops off cells safely.

Typical: 80% → 100%

3
Termination

Current drops below threshold (C/20 or similar). BMS signals charge complete.

Log shows: Charged To Full

Interactive CC/CV charging curve — hover to see values

SOC (%)

Current (A)

Voltage (V)

CC→CV transition (~80%)

Notice: In CC phase, current is constant and SOC rises quickly. In CV phase, voltage is constant but current tapers — the last 20% takes as long as the first 80%!

Zero Charging Hardware

Charger	Power	0-95% Time*	Notes
Standard Onboard	1.3 kW	~9 hrs	Included with bike
Charge Tank	+1.3 kW	~4.5 hrs	Optional accessory
Level 2 (J1772)	6 kW	~2 hrs	SR/F and newer
DC Fast (CHAdeMO)	Up to 6 kW	~1 hr	Select models with option

* Times approximate for 14.4 kWh pack. Actual times vary with temperature and SOC.

For detailed charger specifications, see the ZeroManual Chargers page and official Zero charging recommendations.

Best Practices for Longevity

Do

• Charge to 80-90% for daily use
• Store at 50-70% SOC for extended periods
• Charge in moderate temperatures (15-35°C)
• Let the bike cool after hard riding before charging
• Use a timer to stop at target SOC if needed

Avoid

• Leaving at 100% for days/weeks
• Letting SOC drop below 10%
• Charging in extreme cold (<0°C)
• Charging immediately after high-temp riding
• Frequent DC fast charging if avoidable

Why 80%?

Li-ion cells experience accelerated degradation above ~80% and below ~20% SOC. The last 20% of charge also takes disproportionately longer due to the CV phase. Charging to 80% gives you most of the range with less wear and faster charge times.

Charging in Your Logs

Look for these indicators in your BMS logs during charging:

Field/Event	Meaning
M:Charge	Active charging session
Charged To Full	Charge completed (100% SOC)
I: -15A	Charging current (negative = into battery)
SOC rising	SOC increasing over time
PT/BT	Temperature during charge (should stay <45°C)
B	Cell balance — may increase then stabilize

Sources:

Battery Basics Next: Riding & Regen

Charging recommendations are general guidelines. Always follow your Zero Owner's Manual for your specific model.