Renogy 12V 40A DC-DC Charger
#4 in DC-DCFull review
A cheap, quiet way to add alternator charging to a van or camper with a lithium house battery. Pay more for Victron if you want built-in Bluetooth.
Amazon $177.64$177.64
The Renogy 12V 40A DC-DC Charger is the better charge controller overall, rated 3.8 to 2.4. The Renogy 12V 40A DC-DC Charger leads on value and features. The Renogy 12V 40A DC-DC Charger costs $227.21 less ($177.64 vs $404.85).
CTEK D250SE
#11 in DC-DCFull review
For owners of small lead-acid or lithium banks who want a sealed, set-and-forget charger that also keeps the starter battery topped up. Bigger lithium banks need a higher-current unit.
Amazon $404.85$404.85
Prices were last checked October 22, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the Renogy 12V 40A DC-DC Charger for value ($4.44 per amp of charge current vs $20.24 per amp of charge current) and features (Bluetooth add-on, lithium profile, temperature sensor, smart-alternator support vs lithium profile, smart-alternator support; no Bluetooth).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every DC-DC charge controller; a clear win is highlighted. How we rank explains each one.
| Factor weight | Renogy 12V 40A DC-DC Charger | CTEK D250SE |
|---|---|---|
| Overall rating | 3.8/5 | 2.4/5 |
| Value 35% | 87 $4.44 per amp of charge current | 0 $20.24 per amp of charge current |
| Features 25% | 82 Bluetooth add-on, lithium profile, temperature sensor, smart-alternator support | 45 lithium profile, smart-alternator support; no Bluetooth |
| Efficiency 20% | 50 94% peak efficiency (maker rating) | 50 efficiency not published (neutral score used) |
| Warranty 20% | 25 2-year warranty | 25 2-year warranty |
Specifications
| Renogy 12V 40A DC-DC Charger | CTEK D250SE | |
|---|---|---|
| Charging | ||
| Type | DC-DC charger | DC-DC charger with MPPT solar input |
| Charge current | 40 A | 20 A |
| Battery voltage | 12 V | 12 V |
| Lithium profile | Yes | Yes |
| Custom profile | Yes | No |
| Temperature sensor | Included | No |
| Peak efficiency | 94% | - |
| Standby draw | 15 mA | - |
| Inputs | ||
| DC input range | 12 to 16 V | 11.5 to 23 V |
| Isolated | No | - |
| Smart alternator | Yes | Yes |
| Ignition sensing | Yes | - |
| Monitoring and build | ||
| Bluetooth | Optional add-on | No |
| Display | No | - |
| Load output | No | No |
| Cooling | passive (fan-free) | - |
| Water resistance | - | IP65 |
| Dimensions | 9.31 x 6.00 x 2.30 in | 192 x 110 x 65 mm |
| Weight | 4.1 lb | 1.5 lb |
| Warranty | 2 years | 2 years |