What your battery's voltage — or hydrometer — is really telling you. Pick your battery type, punch in one reading, get a straight answer.
1 — Select battery type
Flooded is the old-school battery with caps on top.
82%
Resting reading: 12.55 V • Flooded lead-acid
✓ Good to go
Healthy charge. Ride it, or keep it on a tender if it’s going to sit.
EMPTY25%50%75%FULL
⚠️ Lithium curve is flat: LiFePO₄ sits around 13.0–13.3 V for most of its charge. Near the top and bottom, a tiny voltage change means a big change in charge — don’t trust voltage alone below 12.9 V or above 13.35 V.
Let the battery rest at least 4 hours after riding or charging. Right after a ride it reads high — that’s surface charge lying to you.
VOLTS
State of charge82%
What it meansHealthy
SG
Full is 1.265, dead is about 1.110 — at 80°F. If your reading is way off that scale, double-check the hydrometer float isn’t sticking.
°F
Hot acid reads low, cold acid reads high. We correct it for you: ±0.004 for every 10°F away from 80°F.
You read1.255
Corrected @ 80°F1.255
State of charge94%
6-Cell Health Check Flooded only — the test that catches a dying battery
Punch in all six cells. Healthy cells stay close together. One cell lagging more than 0.050 behind the best cell = that cell is failing. No charger will fix it.
Enter your six readings above.
Use these charger settings For flooded lead-acid
How long to charge it? Estimate — chargers taper off at the end
Ah — on the label. Most bikes: 8–14 Ah. ATVs / boats are bigger.
Amps — a tender is 0.75–1.5 A. Bigger isn’t always better on a small bike battery.
Time to full—
Math: missing Ah ÷ charger amps, plus ~20% for taper & losses. Your current charge (82%) is already counted in.
Quick-reference chart Flooded — resting voltage
Charge
Voltage (resting)
Level
Rest at least 4 hours before you trust a voltage reading. Measuring right off the charger or right after a start will read high.
Garage rules for batteries
⏱ Rest it first
Wait at least 4 hours (overnight is best) after riding or charging before measuring. Surface charge makes a weak battery look strong.
🔌 Measure at the terminals
Clean posts, meter directly on the battery — not through a pigtail or a corroded ground. Bad connections fake a bad battery every day.
💧 Top flooded cells with distilled water only
Tap water kills plates. Fill to the split ring, charge, then check again — acid level rises as it charges.
⚠️ Never let lead-acid sit discharged
Below 50% it sulfates — hard crystals form on the plates and capacity never fully comes back. If it’s going to sit, it goes on a tender.
