Battery problems are the most common reason floor scrubbers get taken out of service. Not because the batteries are bad — but because they were not charged or maintained correctly. The good news is that proper battery care is simple and takes only a few minutes per week. The bad news is that most facilities skip those few minutes and end up replacing batteries years before they should. This guide covers the charging practices that keep your scrubber running and your batteries lasting.
![Maintenance worker checking battery water levels on a floor scrubber charging station]()
Understanding Battery Types
Floor scrubbers use three main types of batteries, and each has different care requirements. Flooded lead-acid (wet cell) are the most common and most affordable. They need regular watering with distilled water — check weekly. They last 3–5 years with proper care. They produce hydrogen gas during charging, so ventilation is essential. AGM (absorbent glass mat) are sealed and maintenance-free — no watering required. They cost 20–30% more than flooded but last 4–5 years. They are more tolerant of deep discharges and charge faster. Lithium-ion are the newest option. They are lightweight, charge in 1–2 hours instead of 8–10, and last 5–8 years. But they cost 2–3 times more than flooded batteries. Most walk-behind scrubbers use flooded or AGM. Lithium is becoming more common on larger ride-on machines where weight savings and fast charging justify the higher cost.
The Golden Rules of Charging
RULE 1
Charge after every use — even partial use
Flooded and AGM batteries last longest when they are charged after each use, regardless of how much charge was consumed. Running the machine for 20 minutes and parking it without charging creates a "partial state of charge" condition that leads to sulfation — the buildup of lead sulfate crystals on the battery plates. Sulfation reduces capacity permanently. If a battery is left partially discharged for days or weeks, the sulfation becomes irreversible. The rule is simple: plug in the charger every time the machine is parked, even if you only used it for 15 minutes. The charger is designed to handle partial charges without damaging the battery.
RULE 2
Use the correct charger for your battery type
A flooded battery charger is not the same as an AGM charger or a lithium charger. Each battery chemistry requires a specific charging profile. Using a flooded battery charger on an AGM battery will overcharge and damage it. Using an AGM charger on a flooded battery will undercharge it and reduce capacity. Always use the charger that came with the machine or an approved replacement. If you replace the battery type (for example, upgrading from flooded to AGM), you must also replace the charger. The charger and battery must match — this is not optional.
3–5 yrsFlooded Battery LifeWith proper watering and charging discipline
4–5 yrsAGM Battery LifeNo maintenance required, but must charge correctly
50%Life Reduction from NeglectIncorrect charging can halve battery lifespan
8–10 hrsStandard Charge TimeFlooded and AGM need a full charge cycle
RULE 3
Charge in a ventilated area
Flooded lead-acid batteries produce hydrogen gas during charging. Hydrogen is explosive at concentrations above 4% in air. A well-ventilated charging area is required by safety codes and common sense. The charging station should have airflow — either natural ventilation (open door or window) or mechanical ventilation (an exhaust fan). Do not charge batteries in a sealed closet or storage room. Keep the area free of sparks, open flames, and smoking. Install a Class C fire extinguisher within 10 feet of the charging station. For AGM and lithium batteries, the hydrogen production is minimal, but good ventilation is still recommended.
Safety reminder: Hydrogen gas is odorless, colorless, and explosive. Charging batteries in a confined space without ventilation creates a serious safety hazard. If you can smell "rotten eggs" (hydrogen sulfide) near the charging station, stop charging immediately and ventilate the area. This smell indicates a serious battery problem. Evacuate the area if the smell is strong and call a qualified technician.
![Floor scrubber battery charging best practices infographic with 6 steps]()
Watering Flooded Batteries
Flooded lead-acid batteries need water added regularly. The water level should cover the battery plates by about 1/4 to 1/2 inch. Use only distilled water — tap water contains minerals that damage battery cells and reduce capacity. Check water levels weekly: remove the vent caps and look inside each cell. If the plates are exposed, add distilled water immediately — but only after charging. Adding water before charging can cause the electrolyte to overflow during charging. The best practice is to check water levels after charging and add water if needed. Never overfill — the water level should be just below the bottom of the fill well. Overfilling causes electrolyte to spill out during charging, which corrodes the battery terminals and the surrounding components.
Cleaning Battery Terminals
Corroded battery terminals reduce charging efficiency and can cause charging failures. Inspect terminals monthly. White or bluish corrosion on the terminals and cable connections should be cleaned promptly. To clean: disconnect the cables (negative first, then positive), mix a paste of baking soda and water, apply it to the terminals with a brush, scrub gently until the corrosion is removed, rinse with clean water and dry thoroughly, apply a thin layer of petroleum jelly or battery terminal protector to prevent future corrosion, and reconnect the cables (positive first, then negative). Keep the terminal area clean and dry between cleanings. Corrosion that is left untreated for months can eat through cable ends and require replacement of the battery cables.
Common Charging Mistakes
Overcharging: Leaving the charger connected for days after the battery is full. Modern automatic chargers switch to a maintenance mode when the battery is fully charged, but older chargers may not. Overcharging boils the electrolyte, damages the plates, and shortens battery life. Undercharging: Not allowing the battery to reach a full charge before use. Frequent partial charging without occasional full charging leads to sulfation. Charging a frozen battery: Never charge a battery that is frozen. The electrolyte expands when frozen and charging can cause it to crack the case. Let a frozen battery thaw at room temperature before charging. Mixing old and new batteries: Always replace batteries in complete sets. Mixing a new battery with an old one in the same machine causes the new battery to be dragged down by the old one and shortens both their lives.
Quick troubleshooting guide: • Battery won't charge — check the charger fuse, the charging port connection, and the battery voltage (below 18V on a 24V system may not be recognized by the charger) • Battery runs short — check water levels (flooded), check for sulfation (old battery), check the charger output • Charger shows error — check the battery type setting, check for loose connections, try a different outlet • Corrosion on terminals — clean with baking soda paste, apply terminal protector, check for overfilling
A large hospital system in the Midwest managed a fleet of 25 floor scrubbers across three facilities. Their battery replacement costs were running $12,000–15,000 per year — they were replacing batteries every 18–24 months instead of the expected 4–5 years. The facilities director brought in a battery specialist to audit their charging practices. The findings: charging stations were in storage closets with no ventilation, operators were using the wrong charger for the battery type on 8 of the 25 machines, battery water levels had not been checked in over 6 months on most machines, and several machines were being left partially discharged for days at a time. They fixed all four issues in two weeks: moved charging stations to ventilated areas, matched every charger to the correct battery, trained operators on weekly watering, and established a "charge every time" policy. The following year, they replaced only 3 battery sets instead of 12. Battery replacement costs dropped from $13,500 to $3,200. The training and corrective actions cost under $2,000. The lesson: battery problems are almost always charging and maintenance problems, not battery problems.
Weekly battery checklist: ☐ Charge after every use — no exceptions | ☐ Check water levels (flooded batteries only) after charging | ☐ Use only distilled water — never tap water | ☐ Verify the charger is on and showing the correct status light | ☐ Confirm charging area is ventilated | ☐ Inspect terminals for corrosion | ☐ Log the charge in a maintenance log (date, machine, time plugged in)
Frequently Asked Questions
How often should I water my floor scrubber batteries?
Check water levels weekly for flooded lead-acid batteries. Add distilled water when the plates are exposed or the level is below the bottom of the fill well. Always add water after charging, not before. Most batteries need water every 2–4 weeks depending on usage and charging frequency. AGM and lithium batteries do not require watering. Mark your calendar with a weekly reminder — missed waterings are the leading cause of premature battery failure.
Can I leave the battery charger plugged in all the time?
Yes, if the charger is a modern automatic charger that switches to a maintenance/float mode when the battery is full. These chargers monitor the battery voltage and only apply charge as needed. Older chargers without automatic shutoff can overcharge the battery if left connected for extended periods. Check your charger's specifications. If your charger does not have an automatic maintenance mode, unplug it once the battery is fully charged and reconnect it before the next use.
How do I know when my batteries need replacement?
Three signs: reduced runtime (the machine runs for significantly less time than when the batteries were new), longer charging time (batteries take much longer to reach full charge), and physical signs (swollen battery case, cracked case, excessive corrosion, or the "rotten egg" smell of hydrogen sulfide). Most flooded batteries last 3–5 years. AGM batteries last 4–5 years. If your batteries are approaching these timeframes and showing any of these signs, plan for replacement.
What is the best temperature for battery charging?
Batteries charge most efficiently at 50–85°F (10–30°C). Charging in extreme cold slows the chemical reaction and increases charging time. Charging in extreme heat (above 100°F / 38°C) can cause the battery to overheat and reduce its lifespan. If your charging station is in an unconditioned space that gets very hot or cold, consider insulating it or moving the charging station to a climate-controlled area. Batteries stored in freezing temperatures should be fully charged before storage — a fully charged battery will not freeze until around -70°F, but a discharged battery can freeze at 20°F.
Should I replace batteries in sets or individually?
Always replace batteries in complete sets. A 24V system typically uses two 12V batteries connected in series. If one battery fails, replace both at the same time with a matched pair. Mixing a new battery with an old one creates an imbalance — the old battery drags the new one down, and both batteries age faster. The same applies to 36V systems (three batteries) and 48V systems (four batteries). Always replace all batteries in the set at once.
Having battery issues with your floor scrubber? Donnie at TerraScrub can help you diagnose the problem, recommend the right battery type for your machine and usage, and set up a proper charging routine. Reach Donnie at Donnie@terrascrubx.com or on WhatsApp.
