This is the object of today’s post. The battery industry raised the voltage a few years back from a maximum of 4.2 V to the present-day value of 4.35 V. This was responsible for adding approximately 4 to 5% to the energy density. A new crop of batteries is now beginning to operate at 4.4 V, adding an additional 4 to 5% to the energy density.
We noted that 12.6-12.7 Volts is the normally voltage for a fully charged battery, and showed which voltages correspond to which approximate charge % level. Be aware with analysing voltage – it doesn’t show the health of the battery per se, it just shows how much charge is in the battery at the moment you measure.
Contrary to what you might think, voltage levels are actually lower when you start your car. You may expect a sudden surge due to the energy needed to whir the car into life, but a healthy car battery will have around 10 volts when the engine is being started, before quickly escalating to the running voltage levels.
It also changes according to the weather; a 12V car battery’s voltage falls in low temperatures. As a result, then, if you measure could be that your vehicle battery’s voltage is 12.5V and yet it’s actually fully charged. The same applies if your battery has been around the block a few times ie. it’s getting old.
UK mains voltage is standardised to 230 volts. When we talk about car battery voltage, we are usually talking about 12V batteries — that is, batteries that provide 12 volts under a nominal load. That being said, there are different types, you may come across van or leisure batteries, for example.
In many battery types, including lead acid batteries, the battery cannot be discharged below a certain level or permanent damage may be done to the battery. This voltage is called the "cut-off voltage" and depends on the type of battery, its temperature and the battery's rate of discharge.