How to Check Inverter Is Charging Battery


You can check if your inverter is properly charging the battery using a few simple methods. Observing the inverter’s status lights, measuring battery voltage with a multimeter, and performing a load test are straightforward ways to confirm charging status.

In this article, we will follow step-by-step instructions for checking whether your inverter is charging your batteries. You’ll also get troubleshooting tips for solving charging problems and maintenance recommendations for maximizing battery life.

Knowing how to verify charging periodically will help keep your backup power system in top condition.

Methods to Check if Your Inverter Is Charging the Battery

Terminals and wires for charging battery

There are several straightforward ways to verify the charging status. Let’s use each method to keep your inverter battery in optimal condition.

Observe the Battery Status on the Inverter

Most inverters have built-in lights or displays that provide status information. Check your inverter display for the following indicators that relate to battery charging:

  • Power Light: Illuminates when the inverter receives AC input power to charge the battery.
  • Charging Light: Turns on when the inverter actively charges the battery from the AC input or solar panels.
  • Percentage Display: Shows the current battery state of charge or charging level.
  • Fault Light: Indicates an issue with charging or the battery.

If the charging light or percentage readout confirms charging is happening, your inverter is working to charge the battery. The absence of these signs could mean charging is interrupted.

Measure Battery Voltage

You can directly check the battery voltage with a multimeter from the battery terminals, which is easy to use and inexpensive to purchase.

Here’s how to measure voltage:

  • Turn off the inverter and disconnect any AC power inputs.
  • Set your multimeter to voltage measurement mode, usually marked with a “V” symbol.
  • Attach the black multimeter probe to the battery’s negative (-) terminal.
  • Attach the red probe to the positive (+) terminal.
  • Note the voltage reading on the multimeter display.

For a standard 12V lead acid battery, a voltage of around 13.5V indicates proper charging. A reading below 12.4V shows an undercharged battery.

Regularly checking voltage identifies charging issues before they become problematic.

Check the Specific Gravity of a Lead Acid Battery

Battery hydrometer tester on white background

Measuring specific gravity with a hydrometer is another way to verify charging status, particularly for flooded lead acid batteries.

Follow these steps:

  • Let the battery rest for a few hours without charging or discharging.
  • Remove the caps from each battery cell.
  • Draw electrolytes into the hydrometer and note the reading for each cell.
  • Replace the caps when done.
  • Compare the average reading to the recommended level, usually around 1.265 for lead acid.
  • A low specific gravity signifies an undercharged battery. Over time, this accelerates sulfation and battery degradation.

Monitor Battery Charging Mode

Inverter Chargers and solar charge controllers go through various stages in the charging process to safely bring a battery to full capacity.

Many have displays that indicate the currently active charging mode, providing charging status info:

  • Bulk: Rapid initial charging up to 80% capacity.
  • Absorption: Slow charging up to 90-95% capacity.
  • Float: Trickle charging to hold at full capacity.

Progression through each stage verifies proper charging. Stalling at a stage may signal an issue. Check your charger or controller manual for details on readings.

Perform a Load Test

You can confirm the battery’s charge level through a simple load-testing process:

  • Disconnect AC input power to the inverter.
  • Connect a light bulb or small appliance load to the inverter.
  • Let it run for a few minutes and observe brightness/performance.
  • A bright, steady light or regular appliance operation indicates a good battery charge.
  • Dimming or appliance issues signify low battery capacity.

Try Charging the Battery

If measurements show an undercharged battery, connect an AC power source and actively charge it for a few hours. Then, re-check the voltage or load test performance.

If charging improves readings, it indicates the inverter is able to charge when provided with power.

Check Inverter Settings

If your inverter allows it, log in and check settings related to charging. Ensure float voltage is properly set for your battery type and that charging is enabled.

Incorrect settings could prevent charging. Reset to factory defaults if uncertain.

Inspect Wiring and Terminals

An old battery with corroded terminal

Loose, corroded, or damaged wiring and terminals can interrupt charging between the inverter, battery, and panels/AC source.

Inspect connections for any issues and clean or replace wiring as needed.

Consider Battery Age and Health

If an older battery won’t charge fully or holds charge poorly, it may end its lifespan. Reviewing purchase records and maintenance history provides clues to battery health.

Check for bulging, cracked cases, and corroded terminals. Frequent voltage drops also indicate wear.

Have an Expert Evaluate Components

While there are several steps you can take to check if your inverter is charging your battery, If you’re unsure of battery health, or measurements imply an issue with charger components, have an electrical expert inspect the system.

Solar systems can be complex, and an expert can identify issues that might not be immediately apparent to you. They can use specialized tools to diagnose faults and recommend inverter repairs or replacements.

Troubleshooting Inverter Charging Problems

If measurements or tests indicate your inverter battery is not charging properly, there are several possible causes to investigate.

Let’s look at common charging problems and solutions to get your system working again.

Problem #1: Loose or Damaged Wiring

Loose battery and AC input connections are one of the most common reasons for charging problems. Vibration and corrosion over time degrade connections.


  • Inspect wiring for any loose, burnt, or damaged connections
  • Check that cables are sized sufficiently for the inverter load
  • Clean any corrosion present on terminals and connections
  • Tighten all loose battery cables and AC input connections
  • Replace any damaged wiring with appropriately sized replacements

Proper terminations are critical for seamless charging.

Problem #2: Tripped AC Input Breaker

AC input breaker in electrical cabinet

AC input breakers trip and disable charging when drawing too much current. This might happen if an inadequate circuit size was installed.


  • Reset the AC input breaker to see if charging resumes
  • Make sure the input circuit amp rating exceeds the inverter’s maximum charging current
  • Reduce the number of loads also drawing on the AC input circuit
  • Have an electrician upsize the shore power wiring and breaker
  • If tripping persists, the circuit needs upgraded capacity.

Problem #3: Weak or Imbalanced Battery Bank

A battery bank containing older or mixed batteries may not accept a charge properly. Weak batteries drag down others.


  • Use a multimeter to test the voltage of each battery
  • Check for bulging, corroded, or cracked cases indicating wear
  • Look for specific gravity imbalances between cells
  • Replace any batteries more than 5 years old
  • Ensure all batteries are the same type and capacity

Re-establishing a balanced bank of new batteries solves many issues.

Problem #4: Faulty Battery Charger

If batteries, wiring, and AC input are fine, the inverter’s charging circuit could malfunction. Damaged components prevent proper charging.


  • Check inverter diagnostics for any charging faults
  • Contact the manufacturer to troubleshoot charger issues
  • Have a technician evaluate and test the charging components
  • Repair or replace the faulty charging system as needed
  • Serious internal issues require qualified experts for diagnosis and repair.

Problem #5: Wrong Battery Type Setting

Inverters must charge lead acid and lithium batteries differently. The wrong setting prevents reaching full capacity.


  • Double-check your batteries are compatible with the inverter
  • Review the inverter manual regarding battery type selection
  • Log into the inverter and verify the battery type setting is correct
  • Adjust the setting as needed based on your actual batteries
  • Consider updating the inverter if settings revisions don’t resolve it

Matching the charge profile to the batteries is essential.

Problem #6: Dead Inverter Battery

An old or damaged battery bank may not receive and retain an adequate charge. This forces the inverter into constant charging attempts.


  • Use a multimeter to check each battery’s voltage after charging
  • Perform a load test to determine usable capacity
  • Check for bulging, leaking, or warped battery cases
  • Review battery age and maintenance history
  • Replace dead batteries and consider a new bank if old or mismatched

Replacing defective batteries provides a permanent solution.

Maximizing Inverter Battery Life and Performance

Inverter charging batteries in a cabinet

Once your charging issues are resolved, proper care and maintenance are key to ensuring battery longevity and efficiency.

Here are top tips for getting the most from your inverter batteries:

Fully Recharge Monthly

Allowing batteries to discharge deeply too often shortens their lifespan. Fully recharge at least monthly when not in heavy use.

Some inverter chargers have a battery storage mode that periodically recharges without overcharging.

Clean Terminals Regularly

Corrosion on terminals interrupts the charging current flow. Clean terminals with a wire brush and baking soda solution every few months. Dielectric grease then applied prevents future corrosion.

Check Water Levels

For flooded lead acid batteries, monitor water levels in each cell monthly. Refill with distilled water as needed to keep plates fully submerged. Low electrolyte exposes plates to the air, ruining batteries.

Prevent Overcharging

Avoid constantly leaving batteries at 100% state of charge when possible. This accelerates the corrosion of plates.

Disconnect shore power when batteries are full. Some chargers have maximum setpoints to prevent overcharging.

Maintain Ideal Temperature

Heat accelerates the ageing of batteries. Store batteries in the coolest area possible, ideally 70-80°F.

Avoid placing in hot engine rooms or directly on concrete floors. Provide ventilation around batteries.

Equalize Flooded Batteries

For wet cell lead acid batteries, perform an equalizing charge every 6-12 months. This helps counteract sulfate buildup and cell imbalances that reduce capacity.

Frequently Asked Questions

How Often Should I Check if My Inverter Is Charging the Battery?

It’s recommended to check the charging status about once a month when regular usage is light.

Check more frequently if you’ve been relying on battery power heavily or have noticed dimming lights that could indicate a struggling battery bank.

Is a Battery Maintainer Better Than My Inverter for Charging?

Inverter chargers are typically superior since they are designed specifically for the battery bank and have protective setpoints to avoid over or undercharging.

Maintainers can be used additionally to keep batteries topped off.

What Is the Best Voltage for Charging Lead Acid Batteries?

For optimal longevity and capacity, flooded lead acid batteries should charge to a maximum voltage of around 14.4 – 14.7V.

This provides a sufficient overcharge to saturate the plates without excess gassing or corrosion.

Why Does My Inverter Drain the Starting Battery Despite Being Connected to House Batteries?

Some current will leak through isolation diodes, slowly draining the starting battery over time.

Using a battery isolator completely blocks current flow versus just limiting it. Check that your isolator is working properly.

Can I Tell if My Battery Is Charged by Looking at It?

There is no reliable visual indicator of battery charge level. Checking voltage and specific gravity are the only sure ways to know if batteries are fully charged or not.

The level of electrolytes can vary depending on plate ageing.

Is It Normal for Battery Charging to Take a Long Time?

Yes, charging time increases as batteries age and lose capacity. Fully recharging an older or large battery bank can take 12 hours or more.

If charging seems excessively slow, the battery cables may be undersized or need replacement.

What Is the Benefit of 3-Stage Charging?

It optimizes charging by applying a higher bulk voltage to rapidly charge, then tapering voltage down to prevent gassing or overcharging as the battery tops off.

This minimizes damage while reducing charging time.

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