Why you need to charge the 12V battery on plug-in hybrid Electric Vehicles
The market for plug-in hybrid electric vehicles (PHEVs) continues to grow rapidly. Globally, there are now 1.76m PHEVs on the road, and this is expected to reach more than 10 million by 2030, rising at a rate of nearly 20% a year.
A PHEV has two batteries - the main lithium-ion battery, and a reduced size battery 12 volt that starts the car and looks keeps accessories like heating, air conditioning and computerised systems functioning efficiently.
A few years ago, manufacturers embarked on the development of hybrid models, equipped with a disengageable alternator, capable of reducing emissions and sticking as closely as possible to environmental standards.
But what many PHEV drivers may not realise is that, just like with traditional non-hybrid vehicles, the 12V battery on the PHEV will only charge to 80% capacity while you’re driving the car around. To bring it to 100%, you’ll always need to use a battery charger. What’s more, if you use an intelligent battery charger and maintainer to keep your battery in the best health, you can extend the lifespan of the 12V battery by up to three times!
What happens if the 12V battery is flat?
The battery can wear out prematurely if it’s left inactive (e.g. if you’re working from home, so using the car less often), if it’s overused, if it undergoes too many start-up cycles, large temperature changes or if the alternator fails.
If your battery becomes extremely discharged (below 11 volts), there’s a real risk that the battery will suffer long term damage, or even need replacing completely. Below 12.4 volts, sulphation can start to build up on the lead elements of the battery, degrading it.
At between 12.4 and 12.65 volts, the battery still has the power it needs to start the car, but a charge is recommended. You have to act quickly to prevent the battery from degrading quickly and irreversibly.
A lead acid battery is considered fully charged at 12.72 volts.
It is very important that the 12V battery is correctly charged in order to be able to start the vehicle and ensure that all accessories work properly, whether via the main battery or via a charger. A defective battery in a PHEV presents a long-term problem.
Several factors can determine how long your battery will last, for example weather conditions, vehicle type and usage.
There are several key pointers you can utilise to help increase the life expectancy of your vehicle’s battery.
Modern vehicles are controlled by numerous computers, these computers need power form the battery, so if the vehicle isn’t locked using the remote, they will continue to be on standby and consume power. Over time this will lead to the vehicle’s battery being drained.
Batteries in modern vehicles are well hidden, usually under covers in the engine bay, tucked away in the boot or under the rear seats. This means that they can be hard to inspect, so it is a good idea to ask your friendly MTA member to test your battery's state of health next time you are in for a servicer or WoF.