What Happens if Inverter Battery Water is Low?

As an Amazon Associate, this site earns commissions from qualifying purchases. For more details, click here.

If you use lead acid batteries with an inverter, you probably refill the battery with water every few weeks or so, depending on the manufacturer recommendation. But why is this necessary, and what will happen if you do not add any water?

Inverter batteries will self discharge if the water drops below the required level. Without water, the battery is going to stop running and the inverter will no longer be able to power any load.

Why Inverter Batteries Need Water

The lead plates in lead acid batteries are immersed in sulfuric acid and electrolytes. Gassing takes place as the battery runs, and this leads to water loss. Without water, the battery cannot charge.

Water is a critical element in lead acid batteries. If there is insufficient volume – or none at all – the battery will eventually cease to run.

Suppose you have a 3000 watt inverter running a 2800 watt load. Usually the system can keep the load going for an hour. But now you notice the battery loses charge more quickly.

That will occur if there is not enough water. Unless it is refilled, the battery is going to simply run out of energy.

When the battery can no longer hold a charge, the inverter also stops working. Without the battery power source, there is no way for the system to power its appliance load.

If you do not want to deal with battery maintenance, get a lithium battery. These have longer life cycles and do not need any upkeep. Based on research a good choice is the Weize 100ah LiFePO4 lithium battery. It is zero maintenance and can run almost to a full discharge.

Why Inverter Battery Water Drains Fast

The water in lead acid batteries are supposed to last for specific periods, but this varies depending on the brand or manufacturer. But if you notice the water level drops too quickly, there are many possible culprits.

The most likely reason for rapid battery water drain is wear and tear. Or the charge controller might be damaged. Other possible reasons are incompatible chargers, improper installation, poor ventilation and insufficient capacity.

Low Ah capacity. Some batteries have incorrect amp hour capacities labeled on them. You should only buy from reputable companies to ensure high quality and accurate specs. Make sure the battery is designed to work with different types of inverters, in particular yours.

Poor ventilation. Inverters have to be installed in well ventilated areas. And this is also the case for their battery bank.

Lead acid batteries in particular need ventilation to function properly. Do not place the batteries near a heat source or any combustible object. Keep them as far from furnaces and engines as possible.

Too much sulfation. The battery might be overloaded with sulfate. This can occur if you accidentally refilled it with acid instead of water.

This can potentially damage the battery so have it replaced as soon as possible. Left untreated, this is going to increase the battery temperature and make it unsafe to use.

Damaged charger. If you are using an inverter charger, it is possible the charger itself is damaged. It might be producing more current that the system can work with. You have to adjust the settings or replace it.

Battery wear and tear. As batteries get older, their ability to hold a charge or water weakens. In this case the only option is to replace them.

When Should I Fill My Inverter Battery with Water?

The water level should be half an inch higher than the flat lead plates. Do not allow the water to drop below the plates as it could damage the battery.

Check the manufacturer guidelines on how often to refill the battery. We recommend checking at least every few weeks. But this is going to vary from one brand to another so follow the specifications for your specific battery.

The more times a battery is recharged, the more water it loses. While the manufacturer may recommend a specific schedule, make adjustments if your usage exceeds the average.

Because inverter usage varies you have to do the refill according to your needs. The battery type, quality and recharge frequency all determine how quickly the water dissipates.

Temperature affects all solar batteries , but especially SLA and FLA. The hotter it is, the faster water dissipates. The opposite is also true. If it is cold in your area, the water level will hold longer

How Much Distilled Water is Needed by an Inverter Battery?

this will also depend on the battery manufacturer. You need to strike a balance between not putting enough water and trying to avoid an overflow.

The water level should be 1/2 inch over the plates. That is enough for almost all lead acid batteries. Water level indicators make it easier to determine how much is required so over fills can be avoided.

Lack of water causes sulfation, but too much water is just as bad. The acid could spill over and damage the battery. If the battery is connected to the inverter the acid might damage other components.

Managing battery water refills is not as difficult as it sounds though. Modern lead acid batteries have made it easier to determine how much water is enough. Once the indicator is at red, fill it up with the needed amount and it is good to go.

How Do I Know if My Inverter Battery Needs Water?

Batteries have green and red markings. If the indicator is at the red, the battery needs water. If it is at green, the water level is sufficient.

These indicators and marks may vary in design but the purpose is the same. It removes the guesswork and ensures you know when refilling is required.

When the indicator shows red, refill the battery with distilled water as per manufacturer instructions. Make sure the inverter is turned off before doing the refill.

Once refilled the battery should be up and running. Keep in mind if the battery is old the water level might drop off rapidly even if the inverter load is the same.

As long as the battery and inverter functions properly, there will be no issues with water refilling. If you refilled correctly and the battery does not run like it used to, there could be issues with the battery or charger.

What Will Happen if There is No Water in an Inverter Battery?

Without water the battery will not function correctly. Lack of water will kill the battery if not refilled in time. This is why manufacturers make it clear that water refilling is a requirement.

Hot, dry weather obviously leads to faster water loss. But overloading the inverter is another factor.

Take a 5000 watt inverter running on a 24V 250ah battery bank. On paper, the battery can handle up to 6000 watts an hour. But batteries lose capacity faster when more amps are drawn.

So if the inverter runs at a full 5000 watt load the battery is pushed to the limit. And if you overload the inverter, more current flows into the battery.

More battery current leads to faster water losses. If you run a 5000 watt load continuously, the battery will require constant recharging. This is going to take its toll on the battery and the inverter as well.

The bottom line is this: if you are going to use lead acid batteries, refilling with distilled water is part of the maintenance. There is no going around it.

The battery will need the water to function. Without the water the unit will not run, and without a power source the inverter will not work.

Maintenance Tips For Inverter Batteries

  • Keep an eye on the water indicator levels. This will tell you when the battery will need it.
  • Install the battery in a cool, well ventilated location.
  • Use the battery within its capacity. Do not attempt to overload or overcharge it.
  • Make sure the wires connecting the battery and inverter are the proper size.
  • Note the frequency of the water refills. If the battery starts requiring more refills, you may have increased the inverter load too much. If the load has not changed, there might be a problem with the battery itself.


By now it should be clear that lead acid batteries absolutely require water. If you use them for your inverter, make sure to refill them as often as required. Doing so ensures the inverter will load your appliances and run them smoothly.