12V 40A DC to DC Battery Charger
Sold by Renogy UK
From £109.99
Renogy UK's price when we last checked, on 2 September 2026. They run promotions and price by variant, so confirm the current price on their page before you buy.
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Overview
12V 40A DC to DC Battery Charger
40A, 584W, supplied with the temperature sensor and ignition wire. The middle of Renogy's alternator-only range — a sensible step up when 30A is not putting enough back on a driving day and you already have solar handled separately.
- 40A maximum output, 584W
- Euro 6 smart alternators, 12–16V input; traditional 13.2–16V
- 94% charging efficiency
- Temperature sensor and ignition wire included
- Reverse polarity, overvoltage, overcurrent and over-temperature protection
- 1.88kg, 236.5 × 152.5 × 58mm
What 40A is worth on a driving day
40A is roughly 500Wh per hour of driving into a 12V bank. Two hours on the motorway is a meaningful refill for a 200Ah pack — the point at which alternator charging stops being a trickle and starts being your primary source between October and March, when the roof contributes very little.
Check the alternator can give it
Drawing 40A at the leisure end means pulling appreciably more than that from the alternator once you account for the cab loads already on it. On a small van with a modest alternator, running this flat out alongside headlights, heater blower and heated screen is asking a lot. If in doubt, size down rather than up — or check the alternator rating before committing.
Before you order
Terminals take 8AWG to 6AWG. Fuses are specified at 60A input and 50A output. The included temperature sensor is worth fitting rather than leaving in the box: it lets the charger back off when the battery is cold, which is exactly when you want it to.
Renogy's published figures
Taken from Renogy's own specification for this product, on the date shown by the price. Anything wired into 230V mains should be signed off by a qualified electrician.
Build notes for this part
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Useful product advice, installation considerations and occasional offers for this part of your van build.