Charger Fault Codes: What Your Scrubber Charger Is Telling You and How to Fix It
Floor scrubber charger fault codes and LED patterns explained: no battery, timeout, overtemp, AC faults and profile errors, with meter checks and fixes.
Key takeaways
- Charger faults come from the charger's own controller, so the code list is in the charger manual, not always the scrubber manual.
- A timeout fault usually means the battery could not reach target voltage in time, which often points to a failing battery.
- A deeply discharged pack may be below the charger's minimum detect voltage.
- Wrong charge profile is a common cause of faults and short battery life after a battery change.
- Check AC supply and DC connections before replacing a charger.
A charger fault code means the battery charger's own controller detected a problem during charging, such as no battery detected, battery voltage out of range, a charge that took too long (timeout), overheating, or an AC supply fault. Charger codes are separate from the scrubber's controller codes and are often shown by LED blink patterns on the charger itself.
That separation causes a lot of confusion. Many scrubbers use an on-board charger made by a third-party charger manufacturer, and its fault table lives in the charger's manual or on a label on the charger case, not always in the scrubber operator manual. If the code list is not in your scrubber manual, look on the charger label for the charger maker and model, then find that manual. Off-board chargers on larger machines work the same way.
What the charger is detecting
A modern charger runs a charge profile (a series of stages, typically bulk, absorption and finish or float for lead-acid; constant current then constant voltage for lithium) and checks the battery at every stage.
| Condition | What is measured | Common meaning |
|---|---|---|
| No battery or battery not detected | DC voltage at the output below a minimum | Disconnected battery, blown fuse, very deeply discharged pack |
| Battery voltage too high | DC voltage above the range for the selected profile | Wrong profile or pack voltage, or wrong charger for the machine |
| Charge timeout | Target voltage not reached within the stage time limit | Failing battery, shorted cell, load running during charge, undersized charger |
| Over-temperature | Internal charger temperature high | Blocked airflow, hot room, failing fan |
| AC fault | Input voltage or frequency out of range | Weak outlet, long extension cord, tripped circuit |
| Output short or reverse polarity | Abnormal current or reversed voltage | Wiring fault, reversed connection |
| Internal fault | Self-test failure | Charger repair or replacement |
| BMS communication (lithium) | No permission or data from the battery | Communication cable, BMS fault, wrong charger |
Some chargers will not begin charging a lead-acid pack below a minimum detect voltage, because they cannot tell a deeply discharged battery from no battery at all. The threshold differs by charger.
Typical display wording and LED patterns
On LED chargers, expect a separate status LED (or a bar of LEDs) that shows charge stage in normal operation and blinks a pattern on a fault. Some use a number of flashes to identify the fault; others use red versus amber or green. On chargers with a small display, expect wording or an abbreviation related to no battery, timeout, overvoltage, undervoltage, high temperature, AC input, or profile. Some scrubbers also relay a charger status message to the main display. See how to read scrubber error codes for the counting method; filming the LED on a phone is the most reliable way to count flashes.
Common triggers, ranked by likelihood
- AC supply problem: outlet dead, tripped breaker, long or thin extension cord, or a shared circuit dropping voltage.
- Loose DC connection: battery connector not fully seated, corroded charger plug, or a blown charger output fuse.
- Pack deeply discharged below the charger's detect voltage, often after storage or a machine left on.
- Failing battery causing a timeout because it never reaches target voltage.
- Wrong charge profile selected for the battery type, especially after switching to AGM, gel or lithium.
- Overheating from a charger mounted in a hot, unventilated spot or packed with dust.
- Load running during charge, such as a key left on, which can confuse charge termination.
- Charger internal failure.
Step-by-step diagnosis
Safety: chargers contain mains voltage. Do not open the charger case. Charge in a ventilated area away from sparks, especially with flooded batteries.
- Check the AC side. Plug a known working device into the same outlet. Avoid extension cords, or use a short, heavy gauge one if unavoidable. Confirm the charger's AC indicator lights.
- Check the DC connection. Key off, then inspect the charger connector and battery connector for burned, loose or pushed-back pins. A connector that is hot after charging has high resistance.
- Measure pack voltage with the charger unplugged. Compare it to the nominal voltage. A 24 V lead-acid pack reading far below about 20 V, or a 36 V pack far below about 30 V, may be under the charger's detect threshold. Check each battery: one battery near zero can mean a shorted cell or an open internal connection.
- Measure voltage at the charger output connector while charging. It should rise slowly over the charge. If the charger output is present but the battery terminals do not see it, the problem is in the cables, fuse or connector between them.
- Check the profile setting against the battery label, using the charger manual. For lithium packs, confirm the charger is approved for that battery.
- Look at the timeout pattern. If the charger reaches the absorption stage but never finishes, check specific gravity (flooded) or individual battery voltages. One battery charging to a much higher or lower voltage than the rest is a strong clue.
- Check temperature and airflow. Clean vents and confirm the fan runs, if fitted.
Fixes
| Finding | Fix |
|---|---|
| AC supply weak or interrupted | Use a dedicated outlet, remove extension cords, reset breaker |
| Burned or loose DC connector | Replace connector and contacts; check cable crimps |
| Pack below detect voltage | Have the pack recovered and tested; investigate why it was over-discharged |
| Timeout with one weak battery | Replace the weak battery or the set depending on age |
| Wrong profile | Set the correct profile, then run a full charge; monitor the next few cycles |
| Overheating | Relocate or ventilate the charger; clean dust |
| Internal fault | Replace or repair the charger |
Charger types and profiles are explained in battery chargers. If you are opportunity charging, see opportunity charging, because partial charges can trigger some charger warnings and also affect lead-acid life. Flooded packs also benefit from periodic equalizing charges when the charger and battery maker recommend them.
Reset behavior
Most charger faults clear by unplugging the AC cord, waiting a short time (often around 15 to 30 seconds, check the manual), and plugging back in, or by disconnecting and reconnecting the DC side. A timeout fault that returns every cycle is a battery problem until proven otherwise. Some chargers hold the fault until the DC connection is broken, so unplugging AC alone may not clear it. Lithium BMS-related faults can require a specific wake or reset procedure from the battery maker.
Fault record worksheet
- Charger maker, model and the profile or algorithm number selected (from the label or display)
- Exact LED color, blink count and which LED, or the display message
- Charge stage at the time of the fault, and hours into the charge
- AC outlet used and whether an extension cord was involved
- Pack voltage before charging and each battery's voltage
- Voltage at the charger output and at the battery terminals during charge
- Battery type and age, and last time it was watered (flooded)
- Room temperature and whether the charger was hot
- Whether the key was off during charging
For a battery that will not take a charge at all, see battery not charging. Low voltage messages that appear while scrubbing belong in battery and low voltage faults.
Frequently asked questions
Where do I find my scrubber charger's fault codes?
Check the charger's own manual or the label on the charger case, since many on-board chargers are made by a separate charger manufacturer. The scrubber manual sometimes includes a copy of the charger code table.
What does a charger timeout fault mean?
The charger could not bring the battery to its target voltage within the time limit for that stage. A failing or shorted battery is the most common cause, followed by a load running during charge or a wrong charge profile.
Why will my charger not detect the battery?
The connection may be loose or the fuse blown, or the pack may be discharged below the charger's minimum detect voltage. Measure pack voltage with a meter and check each battery and connector.
Can I use any charger on my floor scrubber batteries?
No. The charger must match the pack voltage and battery chemistry and use the correct charge profile. The wrong profile can undercharge, overcharge or damage the batteries, and lithium packs usually require a charger approved by the battery maker.
How do I reset a floor scrubber charger fault?
Usually by unplugging AC and disconnecting the battery connector for a short time, then reconnecting. If the same fault returns, find the cause rather than resetting repeatedly.