48V to 12V Voltage Reducer DC-DC Step-Down Converter

Step-down only. 48V in, 12V out, never back.

A 48V bank makes sense for storage — thinner cable, lower current, less loss over a long run. The trouble starts the moment you want to use the power. Lights, water pumps, fridges, radios, bilge pumps, nav gear and winch controls are all 12V. Wire a 12V accessory straight onto a 48V bank and you damage it in seconds.

This is a Daygreen DC-DC buck converter that sits between the 48V bank and the 12V side and holds the output at 12V. Seven current ratings, 5A (60W) through to 60A (720W), so you size it to the load rather than buying more than you need. The supplier quotes output accuracy of ±1.5%, line and load regulation of ±0.2%, and typical efficiency of 93–95% depending on the rating.

What it is not is a charger, a battery management system or a backup supply. It converts, and that is all it does. The Limits tab spells out the rest — read it before you order, because the input range and the cooling are where most people get caught.

What It Solves

• 48V house bank, 12V loads: the shack or shed runs a 48V bank and an inverter, but the lights, pumps and radio are all 12V and need their own supply.
• Site and farm machines: a 48V utility vehicle, sweeper or scissor lift where the beacon, work lights and two-way still run on 12V.
• Telecom and remote cabinets: 48V is the standard for comms racks, so a 12V camera, router or gate motor needs a converter rather than its own battery.
• Boats with a 48V bank: a 48V thruster or trolling bank, with the nav lights, sounder and VHF sitting on the 12V side.
• Vans and caravans on 48V lithium: keeps the existing 12V fitout intact instead of rewiring the whole van when you go up to a 48V bank.

Key Features

• Seven current ratings: 5A, 10A, 20A, 30A, 40A, 50A and 60A, which is 60W up to 720W at 12V. Pick the rating on the Current selector.
• Tight output regulation: ±1.5% output accuracy and ±0.2% line and load regulation, per the supplier's figures.
• Efficiency 93–95%: typical figures from the supplier data sheet, varying by rating — the 40A unit is quoted highest at 95%.
• Three protections built in: over-current, over-voltage and over-temperature shutdown.
• No fan to fail: free air convection cooling, so nothing spins, but it does need airflow around the case.
• Three, four or five terminals: depending on the model — common negative, separate negatives, or a fifth ACC terminal.
• ACC ignition switching: on the five-terminal units, ACC is an enable line, so the converter only runs when the ignition or a switch is live. Bridge ACC to Input+ if you don't want that.
• Surface mountable case: flanged aluminium housing designed to bolt to a bulkhead, panel or rack shelf.
• Low temperature drift: ±0.03% per °C temperature coefficient.
• Size scales with rating: from 66 × 59 × 24 mm at 280 g up to 150 × 127 × 63 mm at 1600 g — check clearance before you buy the big one.

Where This Fits

This is one part of the gear that sits between a wind turbine and your battery bank. Here's the whole picture:

What Else You'll Need

• Wind turbines: vertical axis turbines from 1kW to 20kW — quiet enough to put near the house, and they charge overnight when your solar can't.
• Hybrid MPPT controllers: you can't wire a turbine straight to a battery. The controller rectifies the output, manages the charge, and brakes the turbine when the bank is full.
• A breaker on each side: this converter wants protection on the 48V input and again on the 12V output, because the output side can pull five times the current for the same watts. A manual-reset breaker doubles as the switch you use when you want it dead.
• A battery isolator: so you can pull the whole 48V bank down before you go anywhere near the terminals. Working live on a 48V bank is how people get hurt.
• A bus bar for the 12V side: once you have 12V you usually have five or six things wanting it. Landing them all on the converter's own terminals is a mess and a loose connection waiting to happen.
• Cable and lugs: flexible copper cable and pure copper terminals to make the joins properly. Crimped and sized right, not twisted and taped.
• The rest of the electrical range: bus bars, breakers, isolators, cable, lugs and Anderson plugs.

Here is the part we cannot do for you. Cable sizing depends on your run length, your voltage and your current, and the 12V output side of this converter carries four times the current of the 48V input side for the same power — a 60A unit is moving 60 amps out. Our range suits 48V and shorter runs. If you are building on 12V or 24V, work the sizing out against your own run or ask your sparky. We are not going to guess it for you.

Limits

The honest list of what this will not do. None of this is in the marketing copy, so it is here instead.

• It will not step up: every unit here is 48V in, 12V out. There is no step-up model in this listing, so it will not run 48V gear from a 12V battery. If you need to raise voltage, this is the wrong part.
• It is not a 24V converter: only the 5A unit accepts down to 18V. The 10A and everything larger want a minimum of 30V at the input. Do not buy a 20A expecting it to run off a 24V bank.
• There is a ceiling at 60 Vdc: and a 48V bank sits well above 48V while it is charging. A flooded lead-acid bank on an equalise cycle can push past 60V. Check what your charger actually puts out at the top of its cycle, and if it can exceed 60V, ask your sparky before you wire this in.
• It is not a battery charger: it holds a regulated 12V. That is not a charge profile, so it will not properly charge a 12V battery on the output side. It is there to run loads.
• It is not a BMS or a UPS: no cell monitoring, no low-voltage cut-off for your bank, no backup when the input drops out. When the 48V side goes, the 12V side goes with it.
• No fan means it needs air: free air convection only. Run one flat out in a sealed box with no clearance and the over-temperature protection will shut it down. That protection is doing its job, not failing.
• We cannot confirm a waterproof rating: the supplier calls the case sealed but quotes EN 50498, which is an automotive EMC standard and says nothing about water or dust. There is no IP rating on this product. Mount it out of direct weather and spray.
• Input-to-output isolation is not stated: the supplier does not say whether input and output share a ground. If your installation depends on an isolated output, do not assume this gives you one.
• No Australian approval is claimed: the supplier's images carry CE, FCC and RoHS marks. We have sighted no certificate, and no RCM registration or AS/NZS listing has been verified. Say so to your sparky rather than assuming.
• We will not size your cable or your fuse: that depends on your run and your load, and getting it wrong is a fire. Fit fusing on both sides sized to your cable, and ask a licensed electrician if you are not certain.

Q & A

Which current rating do I need?

Add up the continuous 12V current of everything that will run at the same time, then leave headroom for start-up surge on motors, pumps and compressors — those can draw several times their running current for a moment. A 30A unit gives you 360W at 12V. If you land close to the limit, go one size up. A converter run flat out with no airflow gets hot, and the over-temperature protection will shut it down mid-job.

What input voltage does it actually accept?

It depends on the rating, and the supplier's own material disagrees with itself. The body copy says 30–60V across the board. The data sheet lists 18–60 Vdc for the 5A and 30–60 Vdc for the 10A through 60A. We have published it per rating in the Specs tab rather than pick one range and hope. Watch the top of the range as much as the bottom — 60 Vdc is the ceiling, and a 48V bank on charge sits a long way above 48V. If your bank runs near either end, email us before you order and we will confirm with the supplier.

Does it need a fuse, and where?

Yes, on both sides, and sized to your cable rather than to the converter. Some units in this range ship with a small inline blade fuse next to the terminals — you can see it in the supplier photos. Do not treat that as your system protection. It protects the converter, not your wiring. Fit your own fusing and an isolator on the 48V input and on the 12V output, and if you are not confident sizing them, ask your sparky.

Which way round does it wire, and what is the ACC terminal?

Terminals are labelled on the case. Three-terminal units share a negative; four-terminal units have separate input and output negatives; five-terminal units add ACC. Input+ and Input− go to the 48V bank, Output+ and Output− to the 12V load — get that backwards and you will destroy it, so check the legend before you tighten anything. ACC is an enable line: run it to the ignition or a switch and the converter only works when that circuit is live, which stops it drawing from the bank while everything is parked up. If you want it running permanently, link ACC to Input+.

How should I mount it, and how hot does it get?

Bolt it through the flanges to something solid — a bulkhead, a panel or a rack shelf. The metal case is the heat sink, so the fins want clear air around them and ideally the fins facing up. No fan means no noise and nothing to seize, but it also means it relies entirely on convection. Do not bury it in insulation, do not box it in tight, and keep it off timber and away from anything that minds heat.

What happens if I overload it?

The supplier lists over-current, over-voltage and over-temperature protection, so in normal use it should shut down rather than let go. That is a safety net, not a running strategy — a converter that keeps tripping is undersized, and repeatedly cooking it will shorten its life. Size it for the real load with headroom and it should never see the protection at all.

Some of the photos say 13.8V — which one am I getting?

Fair question, and it is our gallery that causes it. Daygreen builds this converter in a 12V line and a 13.8V line, and a few of the supplier photos in the gallery are from the 13.8V range. Every variant sold on this page is the 12V version — that is what the Current selector lists and that is what ships. If you specifically want the 13.8V version, email us before ordering and we will check whether we can get it.

How long does delivery take, and what does it cost?

Delivery is free to Australia and New Zealand. Allow 10 to 14 days from the day you place your order — that is from the order, not from the day we dispatch it — and allow up to 3 weeks to be safe. Regional and remote addresses take longer again.

Is there a video of it working?

Not yet. If you want to see one before you buy, email help@bushline.com.au and we will get footage up.

Specs

By Current Rating

Figures below are the supplier data sheet rows matched to the ratings we sell. Everything is 12 Vdc output.

Wiring

Three terminal: Input+ to battery positive, Input− to ground. Output+ to load positive, Output− to ground.

Four terminal: Input+ to battery positive, Input− to battery negative. Output+ to load positive, Output− to load negative.

Five terminal: as per four terminal, plus ACC to the ignition or a switch. ACC is an enable line — when that circuit is off, the converter does not run, so it isn't drawing from the bank while the vehicle is parked. If you don't want the ACC function, link ACC to Input+.

Isolate the bank before you start, check the terminal legend on the case before you connect anything, fuse both sides to suit your cable, and check the sizing against your own run length or ask your sparky.