CTEK D250S (56-677) & D250SA (40-186)


Question: What is the difference between the D250S and D250SA?
Answer: The D250SA unit will be permanently replacing the older D250S version as of the 1st of 2018. The D250SA has increased efficiency with smart alternators which we are seeing more of in the auto market.

Question: Why is the alternator indicator light flashing?
Answer: Check the wiring setup of your battery bank, this unit will only work with 12V battery setups. If your battery bank is wired up in series for a 24V setup then this light will blink and continue to do so until you bring it down to 12V.

Question: Why is the power LED lamp not lit?
Answer: Make sure the system is properly connected and the ground terminal firmly tightened. Check that the voltage on the service battery is higher than 9 volts as the power LED lamp lights up when +9 volts is detected.

Question: Why is the power LED lamp flashing rapidly?
Answer: The charger has gone into power save mode due to low voltage form the starter battery.

Question: Why does the D250S Dual not start charging?
Answer: In order to start charging, the supply voltage from the D250S Dual needs to be above 13.1V at the service battery input, or above 11.5V from the solar input on the D250S Dual. In addition, the voltage on the service battery has to be above 5V for the charge process to begin. Measure the voltage of the batteries, and verify that they are within the levels specified above.

Question: Why does the D250S and D250SA not stop charging the service battery even though the alternator or charger on the starter battery has been turned off?
Answer: When the engine is turned off, the D250S and D250SA will continue to charge the service battery from the starting battery until the starting battery reaches a voltage level of 12.8V. Please note that this will NOT drain your starting battery, the voltage cut off level of 12.8V prevents this from happening. If there is power being generated by a solar panel thats hooked up to the D250S or D250SA unit then it will charge & maintain from this power source.

Question: What do the Symbols on the D250S and D250SA mean?

Question: Why is the error lamp flashing?

Question: Do I need an external regulator if I use a solar panel?
Answer: Negative, the CTEK D250 unit will act as the regulator

Question: Does the starter battery and the service battery need to be the same type?
Answer: No, you only require the service battery to be lead acid

Question: Can I use the D250SA for lithium batteries?
Answer: No, its works only with lead acid batteries.

Question: How do I activate the smart alternator setting on the D250SA
Answer: The D250SA has a wiring harness with a black and red wire, the red wire must be connected to an Ignition signal wire +15 (DIN 72552). Basically, the D250SA red wire needs to be connected to a connection that is live only when the ignition is on - this can be done either at they ignition relay strip of the vehicle or a fuse box. The point is the D250SA should sense +12V when the vehicle is running and 0V when the vehicle is off which enables the unit to adjust the acceptable input voltage.

Question: How do I know if my vehicle has a smart alternator?
Answer: Cars manufactured 2015 and later have smart alternators installed, all prior models will not unless installed by a 3rd party (aftermarket).

Question: Which fuse size shall I use for D250SA?
Answer: 30 Amp

If your all set you can head back to the CTEK D250S or the CTEK D250SA product page. If you were not able to get your issue resolved or question answered then please feel free to reach out to us via our contact us page.