Is 14.7 Volts Too High on a Battery?

For a typical 12‑volt battery, 14.7 volts is normal while actively charging a flooded or AGM lead‑acid battery in cool to moderate temperatures, but it’s too high as a long‑term float voltage, too high for many gel batteries and warm/hot conditions, and suspiciously high if the battery is at rest. In vehicles, alternator outputs around 14.4–14.7 V are common; sustained readings above about 15.0 V usually indicate a regulation problem.

What 14.7 Volts Means Depends on Context

Battery voltage must be interpreted with respect to battery type, whether it’s resting or being charged, and ambient temperature. Lead‑acid batteries (flooded, AGM, gel) have different safe charging targets. Lithium iron phosphate (LiFePO4) has tighter limits. Temperature compensation also shifts the correct charging voltage significantly.

At‑Rest Voltage Expectations

A fully charged, rested 12‑volt lead‑acid battery should sit around 12.6–12.8 V with the engine and charger off for several hours. Immediately after charging, a “surface charge” can hold the voltage near 13.0–13.2 V briefly before settling. Seeing 14.7 V on a battery that is supposedly at rest usually means it’s still being charged, the meter is inaccurate, or there is a system fault.

Charging and Float Voltage Targets by Battery Type

The safe range for 14.7 V depends on chemistry and the charging stage. The following guidelines reflect common manufacturer recommendations at about 20–25 °C (68–77 °F); always check your battery’s datasheet for exact values.

• Flooded lead‑acid (FLA): Bulk/absorption typically 14.4–14.7 V; float 13.2–13.8 V. A brief 14.7 V during absorption is normal; holding 14.7 V indefinitely is not.
• AGM (sealed lead‑acid): Bulk/absorption typically 14.4–14.7 V; float ~13.2–13.6 V. Many AGMs tolerate 14.7 V in absorption; follow brand specs.
• Gel: Lower limits—often 14.0–14.4 V max in absorption; float ~13.5–13.8 V. 14.7 V can overcharge and gas gel batteries.
• Lithium iron phosphate (LiFePO4, “12 V”): Typical full‑charge targets ~14.2–14.6 V; continuous float not required. 14.7 V may be at or above some BMS over‑voltage cutoffs.
• Automotive alternators (12 V systems): Common regulated outputs 13.8–14.8 V depending on load, temperature, and state of charge. Brief excursions within this range are normal; persistent >15.0 V is a red flag.

In short, 14.7 V is the high end of normal for FLA/AGM during absorption, generally too high for gel batteries, and not appropriate as a continuous float level for any lead‑acid battery.

Temperature Compensation

Correct charging voltage decreases as temperature rises and increases as it gets colder. A typical rule of thumb for lead‑acid batteries is about −3 to −5 mV per cell per °C (roughly −0.018 to −0.030 V per 12‑V battery per °C) referenced to 25 °C. That means a 14.4 V absorption setpoint at 25 °C could be about 15.1 V at 0 °C, but only ~14.0 V at 40 °C. Many modern chargers and some vehicle systems adjust automatically; if yours doesn’t, 14.7 V that’s acceptable on a cold day can be excessive in hot weather, accelerating water loss and plate corrosion.

When 14.7 Volts Is a Problem

Some conditions make 14.7 V an indicator of risk or a system fault. Watch for the following scenarios.

• Resting battery shows ~14.7 V with no charger/engine running: likely still being charged, surface charge not bled off, meter error, or wiring issue.
• Gel battery on charge at 14.7 V: above many gel specifications; risk of gassing and damage.
• Hot ambient temperatures (for lead‑acid): 14.7 V may be too high without temperature compensation, causing overcharge.
• Continuous float at 14.7 V: inappropriate for long‑term maintenance; should be ~13.2–13.8 V.
• Vehicle alternator holding >15.0 V for long periods: possible regulator/ECU fault or poor grounds; can damage electronics and the battery.
• Lithium (LiFePO4) battery near or above BMS limit: 14.7 V may trigger over‑voltage protection; use a charger/profile designed for LiFePO4.
• Physical warning signs: audible boiling/hissing, strong sulfur smell, hot or bulging case—stop charging and investigate.

If any of these apply, reduce the charging voltage, verify equipment settings, or have the charging system inspected to prevent battery damage.

How to Check Safely and What to Do

A few quick checks can confirm whether 14.7 V is appropriate and keep your battery healthy.

1. Verify with a calibrated digital multimeter at the battery posts; don’t rely solely on dashboard readings.
2. Note conditions: engine on/off, charger connected, ambient temperature, and battery type/label.
3. If assessing resting voltage, turn everything off and let the battery sit 4–12 hours before measuring.
4. Check the battery’s datasheet for recommended bulk/absorption and float voltages and apply temperature compensation if needed.
5. On vehicles, measure alternator output at idle and ~2,000 rpm with lights/HVAC on; sustained >15.0 V suggests a regulator or wiring/ground fault.
6. Use a smart charger with the correct profile (FLA, AGM, gel, or LiFePO4) and temperature probe when possible.
7. For flooded batteries, periodically inspect electrolyte levels and top up with distilled water as required.
8. For LiFePO4, ensure your BMS limits and charger setpoints align; consider a DC‑DC charger when charging from an alternator.

These steps help distinguish normal charging behavior from overvoltage conditions that shorten battery life or risk failure.

What If It’s Not a 12‑Volt Battery?

Voltage expectations scale with nominal system voltage. A 6‑volt lead‑acid typically charges around 7.2–7.35 V (float ~6.6–6.9 V), while a 24‑volt system typically charges around 28.8–29.4 V (float ~26.4–27.6 V). Reading 14.7 V on a true 24‑volt system would be abnormally low.

Summary

14.7 V is generally acceptable for a 12‑volt flooded or AGM battery during the active absorption phase—especially in cool weather—but it’s too high for continuous float, often too high for gel batteries and hot conditions, and inappropriate if the battery is supposed to be at rest. In vehicles, 14.4–14.7 V is common; persistent readings above about 15.0 V warrant inspection. Always confirm battery type, temperature, and charger/alternator settings against the manufacturer’s specifications.

Is 14.8 overcharging?

Use A Multimeter
When the vehicle is started, without the introduction of a load (the lights or air conditioner), the volts will usually rise to an average of 14 volts. If the multimeter reads at more than 14.8 volts, then this can be considered as overcharging.

Is 14.7 volts overcharging?

If you have a multimeter handy and you’re confident in checking it yourself, you can check the voltage of the battery – if it’s reading anything above 14.7-15 V with the engine running, then it’s possible the alternator is overcharging.

Is 14.8 battery voltage good?

A 14.8V reading is potentially acceptable for a running car battery, falling at the high end of the normal charging range (around 13.9-14.8V), but it could also be slightly high depending on the battery and vehicle. For lithium batteries, 14.8V can be too high for LiFePO4 types but normal for 4-cell LiPo or NMC (Lithium-ion) batteries. Always consider the specific battery type and context, such as temperature, to determine if 14.8V is truly good or potentially indicates overcharging. 
For Car Batteries:

• Normal Range: A healthy car battery system with the engine running typically charges between 13.7 and 14.7 volts. 
• Context Matters: A reading of 14.8V is at the upper limit of this normal range and is sometimes considered normal, especially if it doesn’t vary much, according to a Reddit thread. 
• Potential Issues: If the voltage stays at 14.8V or higher, particularly in warm weather, it could be overcharging and may damage the battery over time. 
• Check for More Information: Compare your reading to your vehicle’s manual and ensure the reading isn’t much higher, such as above 15 volts, which would be more concerning. 

For Lithium Batteries:

• Different Types, Different Voltages: Opens in new tab14.8V is normal for a 4-cell LiPo or NMC (Lithium-ion) battery but is considered too high and could lead to overcharging for a LiFePO4 battery. 
• Check Battery Specifications: Opens in new tabAlways verify the recommended charging voltage for your specific lithium battery to ensure safe operation. 

What to Do:

• Check Other Readings: Monitor the voltage for consistency. If it varies significantly or stays above 15V, it indicates a problem. 
• Consider Temperature: Cold weather can sometimes cause higher charging voltages, so consider the ambient temperature when evaluating the reading. 
• Inspect Connections: A 14.8V reading might be normal, but sometimes bad connections or a failing regulator can cause it to appear high, so also check wiring. 

Is a 14.7 V battery good?

Yes, a battery voltage of 14.7 volts is generally good, indicating a properly charging 12-volt system like a car battery, as the ideal charging range for a fully charged battery with the engine running is typically 13.7 to 14.7 volts. This voltage ensures the battery receives sufficient power to stay charged without being at a dangerous overcharge level, though it’s good to check for readings consistently above 15 volts.
 
This video explains the ideal car battery voltage range: 1mOBD InsightsYouTube · Feb 13, 2025
What 14.7 Volts Means for a Car Battery

• Normal Charging: When the engine is running, the alternator sends power to the battery to keep it charged and to run the vehicle’s electrical systems. A reading of 14.7 volts is at the high end of the normal charging range. 
• Engine Running vs. Off:
  • With the engine off, a fully charged 12-volt battery should read around 12.6 to 12.8 volts. 
  • With the engine running, the voltage should be higher, in the 13.7 to 14.7-volt range, to indicate the alternator is working correctly. 
• Not a Cause for Concern: A voltage reading of 14.7 volts doesn’t typically signal an issue, but rather that the battery is absorbing a sufficient charge. 

When to Be Concerned

• Consistently High Voltage: Opens in new tabIf you consistently see voltages above 15 volts, you might be overcharging your battery. 
• Low or Fluctuating Voltage: Opens in new tabA voltage consistently below 13.7 volts while the engine is running, or one that drops significantly after starting, could indicate a problem with the charging system. 
• Battery Age: Opens in new tabEven with good voltage readings, an old battery may need replacement, as its capacity to hold a strong charge can decrease over time.