Customer support


Welcome to CTEK and thank you for being a valued customer.

We are here to help and in this section you will find FAQs, troubleshooting, warranty information and video tutorials. If you can’t find what you are looking for, please contact us.

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Top 10 FAQ

  • D250SA: Which fuse size shall I use for D250SA?
    See answer

    30 A

  • D250SA: Which battery sizes can D250SA be used with?
    See answer


  • D250SA: Which cable dimensions should i use for D250SA?
    See answer

    Please refer to the ''Cable and fuse recommendations'' in the manual.

  • D250SA: Where in the vehicle shall i fit the D250SA?
    See answer

    Close to the secondary battery and as cool as possible.

  • D250SE, D250SA: How do I know if my vehicle has a smart alternator?
    See answer

    Cars manufactured 2015 and later have smart alternator. Vehicles prior to 2015 please refer to vehicle manufacturer.

  • D250SE: Can I use D250SE for lithium batteries?
    See answer

    Yes it works both with lead-acid and lithium (12V LiFePO₄) batteries.

  • D250SA: Can I use D250SA for lithium batteries?
    See answer

    No, it works only with lead acid batteries.

  • CT5 START/STOP: What do the three stages on the charger mean?
    See answer

    Check mode means that the charger is checking the battery’s state of health and preparing to charge. If the battery is in good condition, the Check stage doesn't take more than a few moments.
    The Charge mode LED shows while the charger is filling the battery, and Care shows when the battery is fully charged and the charger has automatically switched over to maintenance charging.

  • D250SA: Where would I use the D250SA?
    See answer

    Any application involving a secondary battery or solar panel- please refer to manual or web page for fitting instructions.

  • Batteries: Can I charge Lithium batteries with a regular CTEK charger and vice versa?
    See answer

    No. Lithium batteries needs a different charge than lead/acid batteries. Due to severe risks if overcharging, we do not recommend using a CTEK charger that is developed for lead/acid batteries, for that purpose.
    Charging lead/acid batteries with a Lithium charger does not give the best result and cannot be recommended.

  • General: A CTEK charger is so small. How can it charge so quickly and efficiently, when compared with ordinary chargers?

    CTEK's chargers use the same type of technology that computers use to reduce dimensions, to increase power and to charge using a well controlled and 'pure' current. Also, think how big mobile telephones were 15 years ago and how small they are today, and can even so do so much more.

  • Charger functions: Absorption

    The control of gassing within the battery is very important when charging. At the end of the Bulk stage the battery is beginning to gas freely, if we were to continue with constant current and voltage the battery would gas excessively. In Absorption the voltage is now constant and the current is reduced to take the battery from 80% to 100% with minimal gassing, the CTEK charger is constantly responding to the amount of current the battery is taking and reducing accordingly.

  • Batteries: AGM

    AGM stands for Absorbed Glass Mat and differs from a standard Flooded battery in that the electrolite is held on a glass mat and pressed against the active plate area, instead of being allowed to flood around the plates. This type of battery has a low internal resistance and can accept charge very quickly making it ideal for the modern start stop systems. If the battery casing should become damaged the electrolite will not leak out.

  • Charger settings: AGM / * Snowflake

    Because the AGM battery has a low internal resistance it can accept a higher charge voltage, in this mode the Bulk charge rate is 14.7v which is the optimum chare rate for the AGM type battery. In cold weather the internal battery chemistry slows considerably, this leads to the battery being reluctant to accept charge at a normal rate. By raising the charge rate to 14.7 (15v on the Polar) the battery accepts charge more readily

  • Marine: Are the primary and secondary sides galvanically separated in your chargers?

    Yes, all CTEK chargers are galvanically separated.

  • Charger functions: Are there CTEK chargers for other battery types?

    CTEK also produces the CTEK LITHIUM XS charger, which has an ideal charging programme for 4x LiFePO4 (lithium iron phosphate) with a nominal 12V terminal voltage.
    The CTEK LITHIUM XS can also communicate with the battery's built-in electronics if the electronics have shut down the battery to protect it against deep discharging.

  • CTX BATTERY SENSE: Battery Sense Software update

    12th July Issues have been reported with the latest update on our Battery sense app – our developers are currently working hard to rectify the issue. In the mean time we have taken the decision to roll back to the previous version of the app, We have been assured this will happen over the next few days - iOS first then Android to follow.

  • Charger settings: BOOST

    This mode is used on the much larger professional units and is designed to eliminate acid stratification on larger batteries or battery banks. The voltage is increased anything up to 15.8V in 12V mode or 31.6V in 24V mode, and a timer is user selectable between 8 hrs and 24hrs.

  • Charger functions: Bulk

    A stage of intelligent charging where the battery is taken to approx 80% of full charge. This is achieved with constant current and a rising voltage. The cut off voltage can vary dependant on the type of battery being charged e.g. Flooded battery has a bulk charge voltage of 14.4v whereas the AGM has a cut off voltage of 14.7v. Note possible temperature compensation that makes the voltage vary depending on ambient temperature.

  • Batteries: CA/CA

    Calcium Calcium batteries are a flooded low maintenance or maintenance free battery usually VRLA type . During construction some of the Antimony used in the construction is replaced by Calcium (2% approx). The benefits are a more robust grid, low water loss and longer shelf life.