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 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. 

Smart charging 

The CS ONE battery charger from CTEK, the leading global brand in vehicle charging technology, is the ideal way to keep your 12V battery fully charged and in the best of health.  

Super smart and super sleek, the CS ONE is the only charger in the world with patented APTO^TM ‘adaptive charging’ that checks what type of battery you have (lead acid or lithium), establishes how much charge is needed and then recharges it safely. CS ONE is also really easy to use; there’s no need to worry about positive and negative terminals - just plug the charger in, pop the two black clamps on either terminal, and the charger will do the rest. For the last 20% of charge, the CS ONE gradually reduces the rate of charge so there’s no danger of overload. It will even tell you when it’s finished, and when your battery has enough charge to start the car. 

Investing in a charger like the CS ONE, with built-in functionality for both maintenance and troubleshooting, is the smart choice for the discerning motorist. The CS ONE 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, with a built-in temperature sensor that automatically adjusts the output voltage for cold conditions. With the CS ONE’s patented technology, you can even recondition your battery to restore battery health.