Symptoms of a Bad Battery on an Electric Golf Cart: Tests, Fixes & When to Replace

Is your electric golf cart losing pep? Spot the signs of failing batteries and learn simple tests to confirm issues before they strand you mid-round.

Typical warning signs include reduced driving range, sluggish acceleration, longer charging times, and visible damage like bulging or leaking. Other indicators are a significant voltage drop under load, a charger that never seems to shut off, or performance that changes from day to day. If your electric golf cart shows any of these, it’s time to test the pack.

How do you know if your golf cart battery is bad?

Range collapse: Your cart can no longer complete the same route it managed a few months ago—even after a full charge.
Sluggish launch & hill fade: Noticeable hesitation off the line or severe speed drop on modest inclines.
Endless charging: The charger runs unusually long or never reaches “full,” often a sign of sulfation (lead-acid) or imbalance.
Voltage sag under load: Headlights dim heavily on takeoff; a voltmeter shows a sharp drop when you accelerate.
Visual alarms: Swollen cases, wet/acid residue on tops, warped caps, cracked housings, or green/white corrosion on lugs.
Smell & heat: Rotten-egg odor (hydrogen sulfide) or hot cables/terminals during normal driving or charging.
Inconsistent day-to-day behavior: One weak battery drags the whole string; performance varies as it warms or cools.

Simple diagnostic flow (at home)

Let the pack rest: Charge fully, then rest 6–12 hours with the charger off so surface charge dissipates.
Measure at rest: With a multimeter, check whole-pack voltage and then each battery. For healthy lead-acid at rest:
- 6V ≈ 6.3–6.4V, 8V ≈ 8.4–8.5V, 12V ≈ 12.6–12.8V
- 48V pack (lead-acid) typically ≈ 50.5–51.5V
A unit that reads markedly lower than mates is suspect.
Do a load test: Drive up a gentle hill or accelerate on level ground while watching pack voltage. Excessive sag (or a single battery dropping much more than others) confirms internal weakness. A shop can perform a formal carbon-pile load or conductance test.
For flooded lead-acid only: Use a hydrometer to check specific gravity in each cell after charge; wide cell-to-cell differences indicate failure or stratification.
For lithium (LiFePO₄): Check the BMS/app for cell balance, fault codes, low-voltage cutouts, or high internal resistance. A healthy pack holds voltage under normal loads with minimal drop.

Factors that accelerate battery failure

Deep discharges: Regularly running below ~50% state of charge shortens lead-acid life dramatically.
Improper charging: Using the wrong profile, leaving the pack discharged, or storing fully empty for weeks.
Heat & cold: High temps speed chemical aging; cold slashes available capacity and can trigger cutouts.
High loads: Oversize tires, heavy passengers, or steep routes increase current draw and heat.
Bad connections: Corroded/loose lugs cause voltage drop and heat, damaging batteries and controllers.

How do you tell if you need new golf cart batteries?

Replace the pack (or the failed unit in a matched set) when the evidence stacks up:

Range is down 25–50%+ versus your normal route despite a verified full charge.
Load test fails: Resting voltages look okay, but the pack sags well below normal under modest acceleration.
Age & cycles: Lead-acid typically lasts 3–6 years in regular use; lithium often 6–10+ years. Near end-of-life, symptoms cluster.
Visible damage: Bulging sides, cracked cases, leaking electrolyte, or melted posts = replace immediately.
Charger behavior: Repeatedly long charge times, frequent equalization without improvement, or failure to reach finish voltage.
Uneconomic mix-and-match: In series packs, replacing one old lead-acid battery with a new one can cause imbalance. Most of the time, replace the full set to restore performance and cycle life.

Before you blame the batteries, rule these out

Tires & brakes: Low pressure or dragging brakes mimic “weak battery” symptoms.
Cables & lugs: Clean/retorque; hot or discolored lugs indicate high resistance.
Charger: A failing charger underfills the pack; test with a known-good charger when possible.
Controller/motor issues: Fault codes, overheats, or sensor failures can also sap performance.

Care tips to extend life (and delay replacement)

Charge after each use with a chemistry-correct smart charger; keep vents/fins clear.
For flooded lead-acid: Check water monthly (after charge) and top with distilled water to the proper level; keep tops clean and dry.
For lithium: Keep firmware/BMS updated; avoid storing at 0% or 100% for long periods—40–60% is ideal for extended storage.
Store cool & ventilated; disconnect parasitic draws for long off-seasons.
Drive smoothly and avoid repeated hard launches that spike current and heat.

Bottom line

If your cart is losing range, feels sluggish, charges forever, or shows swelling/leaks, suspect the battery pack. Confirm with resting-voltage checks, a simple load test, and (for flooded lead-acid) a hydrometer. When symptoms persist—especially with age and failed load tests—it’s time for new batteries. A healthy pack restores quiet power, dependable range, and safe performance for your electric golf cart.