From the maker
What the catalog says
Manufacturer, model, ratings and which terminal does what come from the catalog. A newer revision, or the nameplate on the unit in your hand, can say something different — when it does, the nameplate wins.
Buck-Boost DC-DC 25A
Victron Buck-Boost 25A
Buck-boost DC-DC converter for Euro 6 smart-alternator vehicles. 25A output; programmable, supports B2B charging from 10–30V input. Common in vans where the alternator regulates down at idle.
The reference run on this page is 3 m one way, sized against ABYC E-11. Your own run will differ, and the canvas sizes that one.
Wiring diagram
How the Buck-Boost 25 is wired.
The drawing shows where the feed, the return and the fuse land on this part. The starter uses the same reference circuit and sizing assumptions. Read the installation notes for manufacturer requirements before adapting the runs.
Build it out
Build the system it goes in.
Open the canvas with Buck-Boost DC-DC 25A already placed, then add your batteries, charging, distribution and loads around it.
Every cable you draw there is sized against ABYC E-11, from the same tables as the reference on this page.
Technical reference
Specs, terminals and the parts around them.
The catalog facts for this part, which terminal takes what, and the hardware you'll want around it. Check the nameplate on your own unit before you order.
Catalog specification
- Rated output
- 25 A
- Planning charge current
- 24 A
3 m reference run
12 V system
- Wire
- 10 mm² · 8 AWG
- Fuse
- 35 A
- Design current
- 25 A
- Voltage drop
- 2.2%
Sized against ABYC E-11. Boats built to UK or EU rules answer to ISO 13297 — check these figures against it before you build. The design current is the unit's rated output. The length is one way; voltage drop includes an equal-length return. The shared starter uses 3.048 m (10 ft) runs unless a shorter run is stated. These are example assumptions for you to adapt to your own installation.
Supporting parts
- 6 m total of 10 mm² (8 AWG) marine cable
- Terminations for 10 mm² cable, matched to the equipment's screw terminals, leads or studs
- 35 A fuse and holder on the positive run
- Heat-shrink, strain relief and terminal boots sized to the cable
Check stud sizes, fuse type, run length and how warm the space gets against the gear you actually have before you order.
Terminal map
Catalog connection points, current direction and planning limits. Check the manufacturer's pinout and connector ratings before installation.
IN +
in-pos
positive · input
IN −
in-neg
negative · input
OUT +
out-pos
positive · output
OUT −
out-neg
negative · output
Method & provenance
What is known, assumed and computed.
The manufacturer publishes some of these numbers and Crimp works out the rest. It's worth knowing which is which.
ABYC E-11
What Crimp worked out
Sized against ABYC E-11. Boats built to UK or EU rules answer to ISO 13297 — check these figures against it before you build. The run length and the current above are what drive the result. Crimp doesn't know how warm your space gets; draw the cable inside an engine-bay zone on the canvas and it sizes for the heat.
Next step
Draw the Buck-Boost 25 into your own system.
It lands on the canvas already placed. Add what it connects to, and every run gets its wire and fuse as you draw.