The 12V battery: small battery, big symptoms
The single most common reason a Leaf will not start, wake up or charge, and the first thing we test.
The single most common reason a Leaf won't start, wake up or charge is a flat or tired 12 volt battery, the small conventional battery that boots the car's computers before the main pack comes online. Leafs are hard on them because the car keeps waking itself to manage the pack.
It does no cranking, just constant small loads, so it fails differently from a petrol car's battery. Instead of a slow crank you get a car that does nothing, or a dash full of warning lights that have nothing to do with the real problem. On an import it is often still the original battery, or an unbranded replacement fitted to get the car sold.
We test the 12V properly under load rather than reading a voltage off it, and we carry the correct replacement to fit the same day. If the battery tests fine we keep looking, because a 12V that keeps going flat is usually telling you about the charging behaviour rather than the battery itself.
We are an AA Battery Service partner and stock AA 12v batteries, which come with up to 36 months warranty.
It is also worth knowing before a WOF: a tired 12V throws warning lights that fail an inspection even when nothing else is wrong.
Frequently asked
Why does my Nissan Leaf have a 12v battery?
It boots the car's computers before the high-voltage pack comes online. Without it the car does nothing, no matter how healthy the main battery is.
Why do Leaf 12V batteries fail early?
The car keeps waking itself to manage the pack, so the 12V sees constant small loads and no cranking. That pattern wears it out differently from a petrol car's battery.
Can you replace a Leaf 12v battery the same day?
Yes. We test it under load and carry the correct replacement to fit while you are here.
Related
Book a 12V battery test
Tested under load, replaced the same day if it needs it. Penrose, two minutes off the Southern Motorway.
Booking request
We reply within the hour, Mon–Fri 7:30am–5pm.