CTEK Power Inc Battery Chargers - CTEKD250S
This charger manages input current from up to 2 DC power sources to charge and maintain 12V batteries. Charges starter and service batteries in trucks, campers and boats where AC power is unavailable.
Features:
- 5-Step battery charger uses DC power input to charge, monitor and maintain 12V batteries
- Performs reliably and is virtually maintenance free
- Works great for situations where 110V AC power is unavailable
- Synchronizes DC power input from up to 2 sources
- Accepts power from alternators, solar panels and wind generators
- Uses maximum power point tracking technology to achieve most efficient charge from solar panels
- Eliminates the need for separate regulators
- Can be left connected to batteries for months, keeping them at full charge
- Charges and maintains starter and service batteries
- Monitors and charges each battery (starter or service) separately from the other
- Keeps batteries at peak charge without overcharging or undercharging
- Switches automatically to pulse-maintenance phase after batteries are fully charged
- Maintains battery life by reducing risk of overheating and sulfation
- Ensures maximum battery charge in minimum time by adjusting output based on temperature of battery
- Keeps you informed of the charging process
- Indicates which inputs are providing power
- Shows when full charge has been achieved
- Splashproof and dustproof
- Includes charger with temperature sensor, owner's manual and protective case
Specs:
- Application: 12V starter batteries, service batteries and banks of service batteries
- For trucks, campers, RVs, 4WDs, boats and tractors
- Boat installations must follow ISO 10133
- Even for housing that lacks access to 110V power and relies on batteries
- Battery types supported: wet, MF, AGM and most gel batteries
- Battery capacity range: 40 Ah - 300 Ah
- Charge cycle: 5-step, fully automatic charger with pulse maintenance
- Input voltage range: 10V DC - 22V DC
- Output ratings:
- Maximum voltage: 14.4V DC, temperature compensated
- Maximum amperage: 20A
- Dimensions of case: 7-3/8" long x 5-1/4" wide x 2-1/2" tall
- 2-Year warranty
The CTEK D250S DUAL battery charger will keep your 12V service batteries and your 12V starter batteries at peak charge. The charger accepts power from up to two 12V DC input sources, such as alternators and solar panels or wind generators, to charge your batteries. To get the most efficient charge from a solar panel, the charger employs maximum power point tracking technology. output from a solar panel varies based on sun angle. The charger can adjust to this variation. An included battery temperature sensor lets the charger adjust its output based on the temperature of the battery, allowing for highly efficient charging. The five-step charging process uses switch-mode, pulse-maintenance technology to protect your batteries and maximize their life.
Multiple 12V DC Input Sources

The above diagram illustrates the D250S receiving input current from both a solar panel and an alternator and charging a service battery. The charger is made just for situations in which no 110 AC power is available, making it great for the marina, farm or any remote place not connected to the grid.
CTEK D250S DUAL Charging Process
A goof-proof design distinguishes CTEK's new-generation chargers from the competition - you don't have to be a mechanical guru to keep your battery working at top efficiency. CTEK's patented charging system monitors your battery, providing exactly the charge it needs during each unique charging stage. Superior and safe, this five-step process uses switch-mode, pulse-maintenance technology.

- Desulfation stage is the initial charging phase. This stage uses electronic pulses to desulfate batteries by converting lead sulfate crystals back to usable sulfuric acid.
- Bulk stage is the main charging phase. This stage accounts for 80 percent of the charging process and uses a constant charge level.
- Absorption stage completes the charge (to virtually 100 percent) using diminishing current to prevent battery damage.
- Float stage keeps the battery at 100-percent capacity for about 10 days to ensure that it can maintain a full charge.
- Pulse-maintenance stage begins after the float stage is complete. During this stage, the charger maintains the battery at the optimum charge level of 95 percent to 100 percent. It recognizes any drop in voltage and sends a corresponding pulse of current to keep the battery properly charged. Pulse maintenance can be continued for months at a time.
Protects the Battery
CTEK's patented switch-mode, pulse-maintenance charging system is designed with the most up-to-date technology to safely charge your battery. Using carefully monitored, low-grid voltage, CTEK's patented process differs from competitors' chargers by providing the precise final voltage that your battery needs to maintain the optimum charge level. This sophisticated, interactive device will never overcharge or undercharge your battery. You can leave it attached to the battery for months, making it perfect for seasonal vehicle storage.
Won't Cause Overcharging or Overheating
Overcharging can cause gassing, which can lead to acid concentration and corrosion of the battery's lead plates. It can also cause the battery cells to dry out ("boil dry"), which can allow the battery to overheat and cause a fire.
Won't Cause Undercharging or Sulfation
Undercharging can be just as damaging to your battery as overcharging because chronic undercharging leads to sulfation. Sulfation occurs when the lead and lead dioxide of the battery's plates react with sulfuric battery acid to produce lead sulfate. This in turn is converted back to lead, lead oxide and sulfuric acid. A small, unavoidable amount of sulfation and gassing naturally takes place as a result of the chemical processes occurring in lead-acid batteries. However, extensive undercharging causes extra lead sulfate to accumulate on the lead plates of the battery. Because the crystalline form of the sulfate cannot hold an electrical charge, excessive sulfation greatly diminishes the charging ability of the battery, eventually rendering it unusable.
Provides Desulfation Using a Patented Process
Desulfation is the reversal of sulfation damage. The CTEK charger's unique process not only prevents the undercharging that produces excess sulfation, but it also includes a desulfating step that can often "revive" a lightly sulfated battery. It accomplishes this with carefully monitored electronic pulses of energy that help to break down the lead sulfate crystals, allowing the battery to accept a charge once again.
Ensures Consistent Charging with Low Ripple-Wave Percentage
Ripple-wave percentage is the quantity of disturbances exhibited in current and voltage. CTEK's low-ripple design regulates the incoming current before passing it on to your battery, ensuring a consistent charge. Unlike an old-style charger, this CTEK charger maintains precise control over the output current, keeping a battery healthier, more productive and longer lasting.
Protects 12V Electronics
The charger uses sophisticated circuitry that is designed to be compatible with today's sensitive electronics and audio equipment. CTEK's low ripple rate eliminates the danger of causing damage to electronic devices that are connected to the battery.
Keeps You Informed




Easy-to-read indicator lights on the charger keep you informed of the charging process. The D250S DUAL shows you which power supplies are providing electric power to the charger. It lets you know when the service battery is being charged and when the starter battery is being maintained. The D250S DUAL also lets you know if certain errors occur.
Additional Specs
- Back current drain: less than 1 Ah per month
- Ripple wave: less than 4-percent variance
- Ambient temperature: -4 F to 122 F
- Insulation class: IP65
56-677 CTEK D250S DUAL DC/DC 12V 5-Step, Pulse-Maintenance, Lead-Acid Battery Charger
Customers compare CTEKD250S to these similar products
Ask the Experts about this CTEK Power Inc Battery Chargers
- Battery Charger for Maintaining the Charge on a 2005 Ford Excursion Diesel with 2 Odyssey Batteries
- The CTEK Battery Charger, item # CTEKD250S, is designed to charge an auxilliary battery form the vehicle alternator output or from the starting battery on the vehicle. This charger would not work for your application unless you have a solar panel that can be ran to the positive input side of the # CTEKD250S charger. In that case the solar power can be used to help maintain the vehicle batteries and keep them from overcharging while you are away from the cabin for extended periods.
If you are
view full answer...
- Does The CTEK D250S Battery Charger # CTEKD250S Come With A Solar Input
- The CTEK D250S Battery Charger, part # CTEKD250S, does come with an auxiliary input for connecting to a solar panel without the need for a regulator. I am including a picture of the CTEK D250S battery charger to the right.
You would connect your solar panel to the two top connectors. The connector on the top left is for solar panel in and the connector on the top right is for solar panel ground (-).
view full answer... 
- Charging an Auxiliary Battery and Dual Trailer Batteries with the # CTEKD250S Dual Battery Charger
- Yes, charging the auxiliary battery in the engine compartment and helping to maintain the two 12 volt batteries, that are connected in parallel, in the camper with the CTEK Battery Charger, item # CTEKD250S, is possible.
Essentially this charger is boosting the input signal from the charging source. The best source is the vehicle alternator. If the charging source is the vehicle alternator the D250S will boost the charge to the auxiliary battery without affecting the charge going to the vehi
view full answer... 
- Will the CTEK DC Battery Charger Help to Bring an Auxiliary Optima Yellow Top Battery to Full Charge
- You are correct, that an alternator is not designed to fully charge a depleted battery. In your case the Optima yellow top is being significantly discharged and will eventually need to be charged with a good battery charger like the CTEK MULTI US 7002, # CTEK56353, or the CTEK MULTI US 3300, # CTEK56158.
The CTEK Battery Charger, item # CTEKD250S, can be used to boost the charge that your alternator is sending to the second, yellow top, battery that you are using to power the fridge. This wil
view full answer... 
- How to Charge Multiple Batteries and Prioritize Charging and Power Output
- The first thing you are going to want to do is determine what is drawing power from the battery and repair it. Otherwise a charger will not be able to charge the battery properly. You can use the CTEK D250S DUAL Universal 12-Volt Battery Charger, # CTEKD250S, but to prioritize charging and power output to different sources you will need to add the SmartPass, # CTEK56676. I have included a link to the instructions that show how to wire everything up. I have also included a link to our FAQ article
view full answer...
- Can a CTEK Battery Charger Charge a Trailer Battery Through the 7-Way 12 Volt Circuit
- The issue is that the amperage coming through the 12 volt pin on a 7-Way trailer connector is not enough to charge a battery. Even with heavy battery cable most vehicle alternators are not capable of providing enough amperage to charge a trailer battery in transit.
It seems like you should get more out of the battery but if the loads are heavy and it is a long distance that would have big impact on the battery longevity.
Traditional chargers only trickle charge a battery and do not work t
view full answer...