6 picks compared, with specs, filters and a calculator to find the right size.
A DC-to-DC charger charges your house, camper or trolling battery from the vehicle or boat alternator while the engine runs, with a charge profile set for flooded, AGM or lithium. Some also take a solar panel. Our charging time calculator shows how many hours of driving each size needs.
| Product | Best for | ||
|---|---|---|---|
| Renogy 12V 20A DC-DC Charger 20 A · 292 W output | Small campers and boats with one lithium or AGM house battery. | Check price (paid link) | |
| CTEK D250SE 20 A · Solar input with MPPT | Trucks and campers that want alternator and solar charging in one small box. | Check price (paid link) | |
| Victron Orion-Tr Smart 12/12-30 Isolated 30 A · Bluetooth | RVs and boats with smart alternators, and anyone who wants app control. | Check price (paid link) | |
| REDARC BCDC1240D 40 A · Solar input with MPPT | Overland rigs and campers running a big house battery with solar on the roof. | Check price (paid link) | |
| LiTime 12V 40A DC-DC Charger 40 A or 20 A, selectable · Flooded, gel, AGM, lithium | Lithium house batteries on a budget, mounted inside a camper or truck cab. | Check price (paid link) | |
| Renogy DCC50S 12V 50A with MPPT 50 A · Solar input up to 660 W | Bigger RVs and vans with 200 Ah or more of lithium and a solar array. | Check price (paid link) |
A simple, compact charger that works with both traditional and smart alternators. Pick the battery type on the unit, including lithium (LiFePO4) or your own settings.
Best for: Small campers and boats with one lithium or AGM house battery. Check price on Amazon (paid link) Specs from renogy.comA sealed, splash- and dust-proof charger that charges from the alternator or a solar panel, with a temperature sensor for compensation. It suits 12 V batteries from 40 to 300 Ah, including lithium.
Best for: Trucks and campers that want alternator and solar charging in one small box. Check price on Amazon (paid link) Specs from ctek.comA Bluetooth charger you set up and watch from the VictronConnect app. It starts and stops on its own by sensing when the engine runs, uses a 3-stage charge, and keeps the input and output electrically separated.
Best for: RVs and boats with smart alternators, and anyone who wants app control. Check price on Amazon (paid link) Specs from modernbike.comA potted, rugged charger built to handle heat, water and dust. It charges from the alternator or a solar panel through its built-in MPPT regulator, and supports lead-acid, calcium, gel, AGM and LiFePO4 batteries.
Best for: Overland rigs and campers running a big house battery with solar on the roof. Check price on Amazon (paid link) Specs from redarcelectronics.comA budget charger with a switch to drop to 20 A for a smaller battery or alternator. It has over-voltage, low-voltage, over-temperature, short-circuit and reverse-polarity protection. It is not fully waterproof, so mount it somewhere dry.
Best for: Lithium house batteries on a budget, mounted inside a camper or truck cab. Check price on Amazon (paid link) Specs from litime.comA high-output charger that takes the alternator and up to 660 W of solar at once through its MPPT input. An optional Bluetooth module lets you watch it from the Renogy app. Also sold in a 30 A version.
Best for: Bigger RVs and vans with 200 Ah or more of lithium and a solar array. Check price on Amazon (paid link) Specs from renogy.comNo products match those filters. Try clearing one.
Pictures are our own illustrations of each type of product, not photos of the actual products. Specs come from the manufacturer or retailer listing linked on each card and were checked in October 2026. Models and prices change, so confirm details on the listing before you buy. As an Amazon Associate I earn from qualifying purchases.