TOKYO -- Electric vehicles will indicate how much charge they can still hold under proposed guidelines being drawn up for carmakers by the Japanese government.
The Ministry of Economy, Trade and Industry envisions the dashboard displaying the health of the lithium-ion batteries, whose capacity gradually shrinks under repeated charge-discharge cycles.
By establishing a framework to measure capacity, the ministry seeks to help develop a market for used electric vehicles and encourage battery reuse.
The draft guidelines will be unveiled as soon as September and may be finalized within the year.
Automakers are expected to respond positively and will be asked to introduce the gauge in future models. The gauge will show charge capacity relative to when the vehicle was purchased.
Nissan Motor's Leaf already offers a battery health indicator, but not all electric vehicles do.
The ministry is expected to settle on a gauge design for automakers to adopt: either indicating the decline in capacity on a scale as with the Leaf, or showing the current full-charge range relative to the vehicle's initial range.
Electric vehicles, which are expected to come into wide use, require servicing when battery capacity declines.
Nissan has introduced an initiative in which a subsidiary collects old Leaf batteries and refurbishes them for reuse in other electric vehicles or elsewhere.
Knowing a battery's charge capacity will aid in determining an electric vehicle's value in the used-car market or the battery's value to the recycling industry.