CTEK D250SE
(9 reviews)
Alternator AND solar panel in a single 0.7kg box: the CTEK D250SE recharges the leisure battery without ever needing a separate solar regulator.
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Characteristics
- Charge current: 20 A (12V)
- Inputs: Alternator + solar (built-in MPPT)
- Compatibility: Lead-acid (WET/AGM/EFB/Gel), LiFePO4 lithium, 40-300 Ah
- Protection: IP65, temperature sensor, smart alternators
- Dual alternator and solar input in one box
Detailed overview: CTEK D250SE 20A alternator and solar DC-DC charger
The CTEK D250SE is a 12V 20A onboard battery charger designed by Swedish manufacturer CTEK for vehicles without access to mains power: campervans, motorhomes, 4x4s and boats. Its distinctive feature is combining two functions in one compact 700-gram box: a standard DC-DC charger wired to the alternator, and a solar MPPT (Maximum Power Point Tracking) regulator to make use of a solar panel, with no separate solar controller required.
While driving, the D250SE draws energy from the vehicle's alternator and charges the leisure battery at up to 20A. Once parked, its solar input takes over as soon as a panel is connected, accepting up to 11.5-23V and 25A. Both sources can be used together, with the unit automatically managing priority. Once the leisure battery is fully charged, the D250SE redirects maintenance charging to the starter battery, preventing it from discharging during extended stops.
With selectable charge algorithms, it is compatible with lead-acid batteries (WET, MF, Ca/Ca, AGM, EFB, Gel) and LiFePO4 lithium batteries, from 40 to 300 Ah, with output voltages tailored to each chemistry (14.4/14.7V for lead-acid, 14.2V for lithium). A built-in temperature sensor optimises charging regardless of weather conditions, and the unit remains fully compatible with ECU-controlled smart alternators, with no extra setup required.
Splash and dust resistant (IP65), protected against short circuits and designed not to disturb the vehicle's electronics, the D250SE can also pair with CTEK's SMARTPASS 120S for more advanced power management, prioritising essential loads during consumption peaks. Compact (192 x 110 x 65 mm) and backed by a 2-year warranty, it particularly suits anyone who wants to combine alternator and solar charging without stacking up separate boxes, at the cost of a more modest charge current than models strictly dedicated to the alternator, such as the Sterling BB1230 or the Renogy DCC50S.
EAN: 7340103403159
User manual / Instructions for use (PDF)
Comparison
Priced between roughly £120 and £260, the CTEK D250SE competes with the most searched-for DC-DC chargers for vans and motorhomes, in queries like "CTEK D250SE vs Sterling BB1230" or "best solar alternator charger". Here is how it stacks up against three direct alternatives: the Sterling Power BB1230, more powerful but without a solar input; the Renogy DCC50S, also dual-input with MPPT; and the Victron Orion-Tr Smart 12/12-30, known for its built-in Bluetooth.
| Criterion | CTEK D250SE | Sterling BB1230 | Renogy DCC50S | Victron Orion-Tr Smart 12/12-30 |
|---|---|---|---|---|
| Charge current | 20 A | 30 A | 50 A | 30 A |
| Integrated solar MPPT input | Yes | No | Yes (660 W) | No |
| LiFePO4 lithium compatible | Yes | Yes | Yes | Yes |
| Weight | 0.7 kg | 1.2 kg | n/a | n/a |
| Observed price | £244.46 | £118.80 | ≈ £180 | ≈ £195 |
In short, the CTEK D250SE stands out for its compact format combining alternator and solar, where the Sterling BB1230 delivers more current but stays blind to solar. The Renogy DCC50S offers both more power and a solar input at a mid-range price, while the Victron banks on native Bluetooth without a solar function. For a van already fitted with a solar panel that wants one compact, reliable box, the D250SE remains the simplest choice.
Related video
Video: D250SE & SMARTPASS 120S: Installing your system - Published on 12/11/2019
Our tester's review: Gilles Caron
Fitted to a van already equipped with a roof solar panel, the CTEK D250SE immediately simplified the wiring: no need for a separate MPPT regulator, everything happens inside this 700-gram box. On the road, the leisure battery takes its 20A from the alternator, and once parked, the solar input takes over with no intervention needed. The lithium profile handled our LiFePO4 battery perfectly, with a genuine automatic switch to the starter battery once charging finished, a real plus for winter storage. The IP65 rating let us mount it near the wheel arch without any extra protective enclosure. The only downside compared with more powerful units like the Sterling BB1230: 20A stays modest on a large leisure battery, so a full charge takes longer. The price, around £240-250, is justified by Swedish build quality and installation simplicity. For a van that already has solar in place, this is the simplest option to set up.
Frequently asked questions: CTEK D250SE 20A alternator and solar DC-DC charger
Yes. It is a dual-input charger: it charges the leisure battery from the alternator while driving (up to 20A) and from a solar panel via its built-in MPPT regulator, with no separate solar controller. Both sources can run together.
Yes, with a dedicated charge algorithm (14.2V) separate from the lead-acid profile (14.4/14.7V). It also handles WET, MF, Ca/Ca, AGM and Gel batteries from 40 to 300 Ah, selected according to the battery fitted.
Yes, it maintains stable output up to 20A even on vehicles fitted with ECU-controlled smart alternators, with no extra wiring needed for this compatibility.
Its input accepts up to 11.5-23V and 25A combining alternator and solar, with an MPPT regulator optimising panel yield. There is no official peak-watt limit; the real-world limit is the 25A input current.
Yes, it carries an IP65 rating (splash and dust resistant), making it suitable for fitting in a technical locker or near a wheel arch without any extra enclosure.
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Published on 04/09/2026