CTEK MXS 5.0 Charger

CTEK MXS 5.0 Charger FAQ: Lights and Troubleshooting

CTEK MXS 5.0 Lights Meaning: Power, Green and Stage Lights

Each light on the MXS 5.0 tells you something different. Here is what CTEK says each one means.

  • Power light (green): lit steady when the charger is plugged into a power outlet. If it flashes, the charger is in energy save mode: no battery is connected, or the battery is below 2 volts.
  • (!) Error light (red): lights when the charger detects a problem, for example when the clamps are connected the wrong way round. The questions below cover what to do.
  • Step 1 to step 8 lights: show how far the charge has gone. Every charge cycle starts with a desulfation phase. When step 4 is lit, the battery is ready to start the engine. When step 7 is lit, the battery is fully charged. Step 8 is pulse maintenance for long-term storage.
  • Program symbols: show the program you picked with the MODE button: 0.8A for smaller vehicles, 4.3A for medium-sized vehicles, AGM for AGM batteries, and RECOND for deeply discharged batteries. The program starts two seconds after you select it.

Question: Why is my CTEK MXS 5.0 stuck on stage 4?
Answer: Step 4 can stay lit for up to 8 hours, and steps 1 to 4 together can take up to 36 hours, so a long stay at stage 4 can be normal. Step 4 already means the battery has enough charge to start the engine. If the charger has not reached step 7 within 50 hours, CTEK treats that as an error: disconnect the charger manually.

CTEK MXS 5.0 Error Light and Charging Questions

Question: The (!) light is illuminated
Answer: There are a few different reasons that could result in this light popping on. Reverse polarity - make sure that the positive and negative battery clamps are connected correctly and directly to the terminals of the battery if you're using a CTEK accessory that is permanently mounted to your battery then make sure the connection is correct and tight. Outside Drains - There are loads being put on the battery which require more power than the charger can provide. Bad Battery - disconnect the battery from the charger and then reconnect. Pay attention to the light display. Then check that the positive clamp is on the positive terminal and that the battery is a 12V battery, then restart the charger with the MODE button. If the error comes back at the first light, the battery is seriously sulfated; at the second light, it cannot accept a charge; and if the charger gets past the fourth light and errors out at step 5, the battery is unable to retain (keep) the charge it is receiving. In each case CTEK says the battery may need to be replaced.

Question: What does a flashing green power light mean on the CTEK MXS 5.0?
Answer: The green power light flashes when the charger is in energy save mode. CTEK's documents describe this as a flashing power light; they do not describe a flashing (!) error light. It means the charger is not connected to a battery, or the battery is below 2 volts, too low for the charger to engage. Check the clamps, the quick connector and any accessory cable, or try another battery.

Question: The charger never gets to its eighth light
Answer: The eighth light is the pulse maintenance step, and the charger only reaches it after about 10 days of float charging, so you may not catch it lit. When it is lit, the charger is maintaining the battery for long-term storage. Step 7 lit means the battery is fully charged, so seeing step 7 and not step 8 in the first days is normal.

Question: When should I use the recondition mode?
Answer: Use RECOND for a deeply discharged battery, for example one that ran all the way down because the lights were left on. You select it by hand, it adds an extra step to the charge cycle and raises the charging voltage to 15.8V, so disconnect sensitive electronics first. Never use RECOND on a GEL or AGM battery.

Question: When all of the lights are lit up on the CTEK MXS 5.0 charger and I change the charging mode the unit goes back down to only the fourth stage light, is this right?
Answer: Yes, this is normal. When you change the charging mode, let's say from the car program to the snowflake (AGM) program, the charger starts the new program two seconds after you select it and begins a new charge cycle, which CTEK starts with the desulfation phase.

If you're all set, you can head back to the CTEK MXS 5.0 Charger product page. If the charger itself is faulty, CTEK warrants the MXS 5.0 for 5 years from the date of purchase. If you were unable to resolve your issue, send us a message on our contact us page, or browse the other answers in our CTEK FAQ center.


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