Do I have to charge my battery on my PHEV

Why you need to charge the 12V battery on plug-in hybrid Electric Vehicles (PHEVs) – 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 year1.


A PHEV has two batteries – the main lithium-ion battery, and a reduced size 12V battery 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 disengage-able 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.

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Smart charging 

Investing in a smart battery charger, like the CTEK CS FREE, is the ideal way to keep your 12V battery fully charged and in the best of health. Look for a charger like the CS FREE that is a multi-functional portable charger and smart maintainer with Adaptive Boost technology to ensure it increases the lifespan of your battery.

Investing in a charger with built-in functionality for both maintenance and troubleshooting is a smart choice for the discerning motorist. It does the thinking for you, using adaptive charging to measure your battery’s health then delivering the right level of power to get it working at optimum capacity.

To find out more about the entire range of CTEK smart chargers and accessories visit

About Rob Fraser 2469 Articles
Rob Fraser – General dogsbody & Director Rob is the founder of the business. He constantly mutters something about way too many red wines one evening being to blame. Often known for taking the 4WD in the driveway over the sports car, he has travelled pretty much everywhere in Australia and when he is bored goes for a drive. He first learned to drive on the farm in a left hand drive WW11 Jeep when he was 11, and was hooked on 4WDriving way back then. In addition to 4WD he is an avid motoring enthusiast and has maintained a strong interest in the industry ever since his teens. He has owned way too many cars in his time as well. Having previously lived at the top of corporate life he retired in 2000 and hasn’t put a suit and tie on since. Cars are his passion so why not have a business doing what you love he figures. He has towed either a caravan or camper trailer to most parts of Australia, has run guided tours for camper trailers’ and instructed drivers in off road towing.