A smart alternator will not fill a second battery on its own · review

ECTIVE BB 20C PRO, 20 A adjustable, 12 V to 12 V review

A 20 A DC-DC charger with the output current selectable at 5, 10, 15 or 20 A, Bluetooth monitoring and both CI-Bus and CAN-Bus interfaces for integration into a caravan system.

By Jean-Benoit Buisson

The bottom line The only DC-DC charger here whose current can be set to suit the bank, with a published capacity range and two bus interfaces. It has no solar input and describes no engine detection, both of which cheaper units in this family provide.

A 20 A charger built to fit into a caravan rather than beside one.

The current, chosen rather than fixed

5, 10, 15 or 20 A. Every other DC-DC charger in this family has one output current. A 100 Ah LiFePO4 bank and a 30 Ah one want different charge rates, and this is the only unit here that lets the installer set it.

The capacity range, published

10 to 200 Ah recommended. Six chargers here and one states which banks it suits. Combined with the four current steps, that turns a compatibility question into an arithmetic one.

The bus interfaces

CI-Bus and CAN-Bus, for integration into an existing system. A caravan with a habitation control panel can show the charger’s state there rather than requiring a separate application.

What it costs

No solar input, which two cheaper chargers in this family include, and no published engine detection. For a caravan towed by a modern vehicle, that second question needs the manual.

Availability

German Amazon store quoted about 199 € when this page was compiled.

American, British, French, Italian and Spanish Amazon catalogues carry an entry for it, with nobody selling.

These figures are what Keepa reported on the day this page was last updated. Availability and pricing move without notice.

Prices quoted in this text were read on 16 September 2026. The live price is at the top of the page.

What it gets right, and what it leaves out

Strengths

The output current is selectable in four steps, so a small bank is not charged harder than it should be
A recommended bank capacity range is published — 10 to 200 Ah — which nothing else here gives
CI-Bus and CAN-Bus interfaces for integration into an existing caravan system

Compromises

No solar input, on a unit priced above two chargers that have one
No engine detection mechanism described
No enclosure rating, cable size or fuse specification

Specifications

Output current	Selectable at 5, 10, 15 or 20 A, second bullet — the only charger here with a user-set current
Input range	12 V to 12 V, from the title; no voltage range is published
Engine detection	Absent as a described mechanism; the first bullet refers to controlled charging while driving
Profiles	AGM, gel, flooded and LiFePO4, third bullet, for recommended bank capacities of 10 to 200 Ah
Solar input	None
Cable	Nowhere in the listing
Fuse requirements	Nowhere in the listing
Heat management	Nowhere in the listing
Amazon reference	B0GJTMWMMX (same reference on 6 Amazon marketplaces)
EAN	4260725127536

Questions owners ask about this one

Why select a lower charge current?

Because a battery has a maximum charge current of its own, and a small bank behind a 20 A charger may be charged harder than its maker permits. The recommended range of 10 to 200 Ah, published with four current steps, lets the two be matched.

What do CI-Bus and CAN-Bus add?

They let the charger report into a caravan’s existing control system rather than only to a phone. On a vehicle where the habitation panel already shows battery state, that is the difference between one display and two.