The Definitive Guide to Battery Maintenance

Replacing batteries in your floor scrubber or burnisher can be expensive. With the right maintenance program, you can make sure you’re getting as much out of your battery pack as possible. In this post, we’re going to cover everything you need to know about maintaining cleaning machine batteries.

Types of Lead-Acid Batteries

There are two kinds of lead acid battery constructions that you might find in an NSS cleaning machine.

Flooded cell, sometimes called “wet batteries”. These are the lowest cost type of battery. These also need to be maintained by monitoring and filling the battery cells with distilled water. There is a trade-off between battery cost and maintenance cost.  Flooded batteries have removable vent caps for adding distilled water.

AGM (Absorbent Glass Mat) Batteries. These batteries are maintenance free. These batteries are sealed, so the cells don’t need to be monitored or filled with distilled water. Just plug in the charger when the machine is not in use. These batteries cost a bit more to manufacture, so they cost more. Typically, the money saved in maintenance labor will offset the additional cost.

What’s Inside a Lead-Acid Battery?

A lead-acid battery is constructed from a series of lead plates that are coated with lead dioxide. The battery is filled with a battery electrolyte solution, a mixture of sulfuric acid and water. When you discharge the battery, the acid is reacting with the lead dioxide to generate electricity. When you charge a battery, you’re using electricity to reverse the chemical reaction, causing the sulfate ions to move back into the acid solution.

How Long will Lead-Acid Batteries Last in a Cleaning Machine?

The useful life of a battery pack will depend on how it was maintained and how much runtime you need when you’re cleaning. If the batteries are well maintained and charged regularly you can expect about 500 discharge charge cycles from a battery pack. For typical applications, that’s about 18 months of useful life.

What Kinds of Things Will Reduce the Battery Pack’s Useful Life?

Anything that causes “sulfation” of the battery plates will reduce the battery’s capacity. Sulfation is when crystals of lead sulfate build up on the battery plates. The more sulfation that occurs in a battery, the less capacity the battery has to power your cleaning machines. Some causes of sulfation are avoided by how we’ve designed our machines, other causes can be avoided if you follow some simple rules. 

Over-discharging the batteries. If a battery is over-discharged, lead sulfate crystals can form. All NSS equipment is designed with a low-voltage shut off. This prevents your machines from over-discharging.

Over-charging the batteries. If a battery is over-charged, lead sulfate crystals can form. All NSS equipment is designed to prevent over-charging. Our chargers are programmed to prevent over-charging, so as long as you’re using the charger that came with the machine, you won’t have this issue.

Long-term storage of batteries. All batteries self-discharge as they sit idle and when the battery voltage drops too low, sulfation happens. This is where you can make a difference. All NSS battery chargers will switch over to a battery maintenance mode when the batteries are fully charged. This maintenance mode keeps your batteries fully charged, as long as the charger is plugged in. Need to store your machines for a few months? No problem. Just make sure the charger is plugged in and, if you have flooded cell batteries, make sure you have the right amount of electrolyte in the battery. (Instructions for topping off flooded batteries are below).

Too little electrolyte, flooded batteries only. If the battery plates are exposed to air, sulfation occurs very quickly. Always monitor flooded batteries to prevent plate exposure.

How to Maintain a Battery Pack

Safety Warning! Review the Operation Manual that came with your machine before performing these procedures. Battery acid is corrosive and can cause severe burns. Wear proper personal protective equipment when working around batteries. Batteries emit hydrogen gas, which can be flammable. No smoking, open flames, or sparks near the batteries.

Step 1. Every 4 discharge cycles. Check the electrolyte level (flooded batteries only). IMPORTANT: Check the electrolyte level in each cell of each battery when the battery is fully charged. The cells are not connected, so you have to check each and every one. Remove the vent cap and look inside the battery cell with a flashlight. There should be about ¼ of an inch between the electrolyte level and the bottom of the battery fill well. Do not overfill the batteries with distilled water. When the battery is charged, the battery electrolyte will expand. If the batteries are too full, battery acid will spill out of the vent.  Use a battery filling bottle to make adding distilled water easier (see picture below).


Step 2. Once per month. Inspect the battery cables for damage. Replace the battery cables if you see cracks in the insulation.

Step 3. Once per month. Clean the battery terminals by removing corrosion with a brass brush. Removing corrosion helps maintain conductivity and prevents overheating.

Step 4. Once per month. Check the battery terminal hardware and make sure it is tight. If it’s loose, tighten the nut on the battery. Caution! Do not overtighten the nut. The best practice is to use a torque wrench and tighten the nut to 60 in-lbs.

Step 5.  Once per month.  Equalize charge the battery pack.  Equalize charging a battery pack helps reduce sulfation.  Learn the right way to do that in this blog post, How to Opportunity Charge the Right Way.

How to Correctly Charge Lead-Acid Batteries

Always charge your battery pack when you’re done using the machine. Even if you only used it for a short amount of time, plugging in the charger is the best thing you can do.

Step 1. If you have flooded batteries, make sure the plates inside the battery are covered. If you need to add distilled water, be sure to just cover the battery plates. Never try to charge a battery with any of the plates exposed to air. Do not overfill discharged batteries. The battery electrolyte will expand during charging, so you need to leave room for the expansion.

Step 2. Put the machine in a well-ventilated room. Batteries emit hydrogen when they are charged, which can be flammable. Be sure to allow proper ventilation. See the operation manual for complete safety instructions.

Step 3. Plug in the battery charger. Be sure to use the charger that came with the machine. It is designed to precisely and properly charge your battery pack. You might overcharge or undercharge your battery pack if you use the wrong battery charger.

Step 4. Wait for the charger to finish. This might take a while. Fully depleted batteries can take up to 16 hours to charge back to 100%. Undercharging your battery pack is a very common way to cause it to wear out prematurely.

Replacing a Battery Pack

Eventually, you’re going to need to replace your battery pack. Any NSS service center can help you replace your battery pack. If you do it on your own, be sure to check the operation manual before installing a new set of batteries. Depending on the batteries you buy, you might need to make and adjustment to the battery charger. NSS battery chargers can charge almost every brand of battery on the market, but the charger may need to be set to a different algorithm to match up with the batteries you purchased. If you need help finding a service center, use our contact form and we’ll help you find one.

Tips for Setting Up Your Own Battery Maintenance Program

  • Record keeping is EVERYTHING! Keep good notes. Keep track of the date the batteries were put into service and each maintenance check and action. To help you get started, here’s a free Microsoft Word editable Battery Maintenance Log Form.
  • Make yourself a battery maintenance tool kit. Put all your safety equipment, tools, and distilled water in a designated place. Set yourself up for success by planning ahead.
  • If you have flooded batteries, consider installing a battery filling system. A battery filling system replaces the battery vent caps with a series of tubes and fittings. You can fill your battery pack to exactly the right amount using a single remote fill point. It’s a real time-saver and helps cut down on overfilling mistakes. NSS has two battery filling kits available, one for 24V machines and one for 36V machines. Talk to your local NSS distributor about adding battery filling kits to your machines.

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