How do You Know if the Inverter Battery is Fully Charged?

If you are in a solar powered RV or living off the grid, your system no doubt has an inverter. It is the perfect match for solar panels as it converts DC power into AC. To run any device the inverter must have a battery, so how will you know if the battery is ready to be used? This article shows you how to do this in different ways.

Most inverters have a display which indicates the battery charging status. If there is no display, a light or sound will notify you when the battery is fully charged. A charge controller, voltmeter and multimeter can also provide information on the battery charge.

That is a concise explanation, but now let us look at these options in detail.

Check the Inverter Display

A lot of modern inverters have a display screen that supplies system information. This includes the battery status. Once you connect the battery to the inverter, you will be able to see its charge status displayed in percentage.

Other inverters have a light or sound mechanism built in. The design varies from unit to unit. But in atypical system, specific light colors denote whether the battery is charging, charged or not charging. There are also indicators if the inverter battery is running low, overloading and so on.

Some inverters incorporate sound. A beep notifies you when the battery is fully charged. With other inverters it is a combination of light and sound.

The light colors and sounds will vary from manufacturer to manufacturer. Refer to your inverter manual for details on the battery charging status indicators.

Check the Charge Controller

In a solar panel system, the charge controller manages the charge going into the battery. A good product like the Renogy 60A MPPT Solar Charge Controller has a display which indicates the voltage.

When an inverter battery is charging, the voltage is 14.4-14.6 volts. When the charge is almost done, the voltage drops to around 13.7 volts. When the battery charge reaches float level, the charge controller should indicate it is full.

A high quality charge controller provides all the information you need about the battery charge. The display will indicate if the charge is in absorption, bulk or float. The controller will also display error messages if there is a problem with the battery.

If you are running a solar system, you can check the battery charging status from the inverter or the charge controller. Some solar panel systems may also have a battery status checker built in. Again the setup will differ from one system to the next so check your charge controller user guide.

Use a Multimeter

A multimeter measures various aspects of a battery including the voltage, current, ohm, resistance etc. It is used similarly to a voltmeter and provides accurate readouts. Before using one, make sure the battery to be tested has not been used for at least two hours.

To test the battery you need a good quality multimeter. A good option is KAIWEETS multimeter because of its simplicity and reliability. This video shows you how to use this tool.

Use a Voltmeter

Another way to monitor an inverter battery charge is through a voltmeter. A voltmeter is used to measure electric potential between two points in an electronic circuit.

To use a voltmeter, connect it to the red and black terminals of the battery. Do this only if the battery has not been used for at least two hours. Do not test a recently used battery as the voltmeter will give imprecise readings.

Once the voltmeter is connected to the battery, check its display. If the battery is fully charged the voltage should be 11-13V. If the voltmeter says 13 volts, the battery is fully charged. If the reading is 11 volts or below, the battery has died.

Why is the Inverter Battery Not Charging?

Check the connections first. If there is a loose wire it could account for the lack of charge. If the wires are fine, it is either the battery or the inverter.

Dead battery. If your battery is old, it could be nearing the end of its life cycle. As a battery gets old, it takes longer to charge and loses power quickly. Eventually the battery charging capacity reaches its limit and can no longer carry a charge. The only solution is to replace it.

Corrosion. It is also possible the battery has been corroded. This can happen if the battery has been exposed to moisture or water. Examine the battery terminal for signs of corrosion. If there is, mix baking soda with water. Use a scrub to apply the mixture onto the terminals. Try charging again after cleaning.

Inverter problems. If the battery is new, the problem might be the inverter. Let us look at the possibilities.

Make sure the inverter is plugged in. The connectors have to be secure. Unplug the inverter and plug it in again.

Reset. Sometimes all the system needs is a reset. Press and hold down the power button for 15 seconds. When the light starts flashing, release the button. Try charging the battery again after the inverter has reset.

Usually this solves the problem. If it does not, there could be a hardware failure with the inverter. If the troubleshooting guide cannot help, the inverter might be damaged and need repair.

Why is the Inverter Battery Always Charging?

There are two possible reasons for this. The first is that the battery is too old and can no longer generate the voltage needed to stop charging. This can also happen if the battery has been damaged.

The other possibility is that your inverter is in UPS mode. If it is, turn to normal mode. This should fix the problem.

Inverters also have a trickle charge mode. If turned on, it will continuously charge the battery so it is always full. This feature ensures that the battery is always fully charged. Depending on the inverter, you may or may not be able to turn this feature off.

Frequently Asked Questions

How do you charge a dead inverter battery?

If the battery is damaged there is no way to recharge it. If it is just completely drained, you should still be able to recharge it. Recharge as you would any normal battery, but this will take longer.

Some batteries like lead acid are not meant to be fully discharged. Doing so could lead to long term damage which is why you should only use 50% of its capacity.

Why is the battery taking so long to charge?

If the battery is completely depleted. It can take several hours to fully charge. It also depends on what type of battery you are using. Lead acid batteries take more time to charge than lithium for instance.

The battery age also plays a part. The older a battery gets, the longer it takes to recharge. This is normal and occurs in all batteries. But good ones have a long life cycle and can handle plenty of charges.

Where is the inverter reset button?

Most inverters do not have a reset button. You have to press and hold the power button until the lights flash. That takes anywhere from 15-30 seconds.

Can I charge different types of inverter batteries?

Do not mix inverter battery types. If you want to use three batteries, they must be the same time. If one is lithium, all of them must be lithium. If one battery is AGM, all must be AGM.

Can an inverter overcharge batteries?

Most inverters sold today can detect when the battery is fully charged. It will automatically stop charging to prevent overload. Others have a trickle charge mode but either way, there are built-in safety measures against overcharging.

Is it better to use a digital or analog multimeter to read battery charge status?

A digital tool provides very accurate readouts but there are also good analog multimeter tools. For ease of use however, digital is better