The D250SE (CTEK Part No. 40-315) is a DC to DC fully automatic charger that’s designed to charge a Service Battery and is powered by the alternator/starter battery. With dual inputs the D250SE is also solar compatible (a standard solar controller is not necessary). The D250SE charger supplies up to 20A of power to any 12V lead-acid or lithium service battery from 40–300Ah. It also works if the starter battery and service battery are different chemistries, for example if the starter battery is lead/acid and the service battery is lithium. (Note: a service battery may also be called an auxiliary/aux battery, house battery, secondary battery, or backup battery.) This is a great charger for our V1 and V2 Lithium Deep Cycle Batteries.
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Description
CTEK D250SE 12V Smart Charger 20AThe D250SE (CTEK Part No. 40 315) is a DC to DC fully automatic charger thats designed to charge a Service Battery and is powered by the alternator starter battery. With dual inputs the D250SE is also solar compatible (a standard solar controller is not necessary). The D250SE charger supplies up to 20A of power to any 12V lead acid or lithium service battery from 40300Ah. It also works if the starter battery and service battery are different
Dual Inputs
The D250SE CTEK Charger has dual inputs and can charge the service battery from the alternator or a solar panel or both. The charger is designed to work with smart alternators and can still operate if the alternator is shut off but the vehicle has access to solar or wind power. So it can use power from the alternator, solar panel, wind power, or any DC power source can be used through the solar input port (within voltage spec). The D250SE can also charge the service battery from the solar input and the alternator in parallel using its built-in regulator to save fuel.
Optimum Charge
Continuous charging while the vehicle’s on the move means the batteries are fully charged in the shortest possible time. The built-in temperature sensor compensates for hot or cold conditions to prevent the battery from overheating or overcharging, so it always gets the optimum charge.
When the service battery being maintained is fully charged, the D250SE will automatically redirect overflow charge power to top-off the starter battery. The D250SE can maintain a stable output up to 20A to vehicles fitted with smart ECU controlled alternators.
LITHIUM
5-Step Program
- Accept*: Tests if the battery can accept charge. This step prevents that charging proceeds with a defect battery. (*Step 1 for lead/acid is Desulphation)
- Bulk: Charging with maximum current until approximately 90% battery capacity*. (80% capacity for lead/acid.)
- Absorption: Charging with declining current to maximize up to 95% battery capacity*. (100% capacity for lead/acid.)
- Float: Maintaining the battery voltage at maximum level by providing a constant voltage charge.
- Pulse: Maintaining the battery at 95–100% capacity. The charger monitors the battery voltage and gives a pulse when necessary to keep the battery fully charged.
Video about D250SE Charger
Specs
- CTEK PN: 40-315
- Input: 11.5–23V, 25A
- Output: Max 14.4/14.2/14.7V, 20A max
- Back-Current Drain*: Less than 1Ah/month
- Ambient Temperature: -4°F to +122°F (-20°C to +50°C)
- Battery Types: 12-Volt WET, EFB, Ca/Ca, MF, AGM, GEL, Lithium (LiFePO4, Li-Fe, Li-iron, LFP)
- Battery Capacity: 40–300Ah
- Insulation class: IP65 (splash and dust proof)
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
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★★★★★ 5
Happy with this purchase
Size: 25FT, Color: White
Perfect, love the wall clips, adhesive is good!
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Reviewed in the United States on March 23, 2026
★★★★★ 5
Perfect solution
Size: 20FT, Color: White
Incredible value - solves our phone charging needs without bulky chargers attached to traditional extension cords… aesthetically superior with outlet cover and flat cord that we plan to conceal between tiles. A+
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Reviewed in the United States on January 28, 2026
★★★★★ 5
Great Extension Cord for hard to reach places.
Size: 5FT, Color: White
Wasn't sure if I would like this or not but I really do. We have the stand up version (not by same vendor) but really liking this smaller version that I was able to stand on edge and not take up valuable room on my side table. We used it for the outlet under the bed to the bedside table. Has enough power to run multiple items with no issues. I like that it comes with USB, C, 2 prong, 3 prong. I didn't use the included cover but that was because we had something else plugged into the other socket.
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Reviewed in the United States on May 19, 2026
★★★★★ 5
Perfect!
Size: 5FT, Color: White
Perfect for getting all the cords under control!
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Reviewed in the United States on February 15, 2026
★★★★★ 4
Decent
Size: 20FT, Color: White
I needed a heat gun to make it a little more pliant to get the kinks out but otherwise I loved it
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Reviewed in the United States on April 1, 2026