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
4.8 ★★★★★
Based on 1895 reviews
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Product Reviews
★★★★★ 5
They work! Even if you hate socks
I am not a sock wearer. Can't stand having my foot entirely shrouded in cloth. I don't wear socks with my sandals, slides, clogs and other shoes most of the year. Only on the coldest winter days. I know, It's weird. So, with my sock phobia one thing that happens is your heals get dry and rough. I opted to try these because the toes are free. I barely notice the socks on my heels/ankles when my toes get air (outside of bedcovers always). I put good thick lotion on my heels and sides of feet. A little less on the toes so they don't stain anything. The silicone lining on the heel holds that lotion against the affected areas. In a couple days my feet felt soft and looked pretty. No cracks, no white roughness. They look pink and freshly spa-ed. Fit is good on size 9 feet with thickish ankles. Highly recommend.
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Reviewed in the United States on September 2, 2025
★★★★★ 5
Nice Socks, Bad Shipping
The socks are definitely worth the price. They are cozy and non constructive. They colors are nice. My only complaint is the method in which it was shipped. Slapping a mailing label on a clear bag is not acceptable. The shipper didn't consider protecting my privacy. I hate to think if it was something extremely private. Consumers deserve better when it comes to the content of their mail.
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Reviewed in the United States on September 19, 2025
★★★★★ 4
There’s room for improvement
These heel support socks are quite comfortable to wear, the cotton blend fabric is soft and breathable. The built-in gel continuously moisturizes the heels, and the effect is more noticeable than applying lotion alone. I usually soak my feet in warm water before bed, apply lotion, and then use these socks. The elasticity is just right, and they don't constrict my feet. If the gel coverage area were a bit larger, the protection would be more comprehensive. Overall, they offer good value for money and are a practical foot care item.
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Reviewed in the United States on December 1, 2025
★★★★★ 5
They worked
I got these for my elbows because I think I might have eczema on my elbow. They work very well. However I do wish they were a little looser. As far as putting them on your heels, the fit works well.
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Reviewed in the United States on April 2, 2026
★★★★★ 5
Good Results
I have always struggled with dry, cracked heels, but I’ve finally found a solution that keeps them consistently hydrated: these special socks with a moisturizing silicone lining on the heels. My heels now feel incredibly soft, but it’s important to note that consistency is key.
Wearing these socks every night before bed has made a significant difference. It’s not enough to just wear them once and expect results; you have to be diligent and make it a part of your nightly routine. After a few weeks of nightly use, my heels are much softer and no longer cracked.
What I love about these socks is how easy they are to use. Just slip them on before going to sleep, and the silicone lining does its magic overnight. By morning, my heels feel smooth and well-moisturized.
For anyone struggling with dry heels, I highly recommend these socks. Remember, the secret is consistency. Stick with it, and you’ll see the difference!
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Reviewed in the United States on June 28, 2024
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