Cheap car lighter slow voltmeter

A very cheap voltmeter to measure car battery that fit into the car lighter slot. The voltage measurement is somewhat quite accurate despite of its cheap quality - the price is around $1.2 USD on eBay. Using this volt meter we can measure the battery capacity where anything that is within 12.2 volt and above indicates the battery capacity is still in good condition. Otherwise anything that is below 12.2 volts indicate the battery about to run out of charges especially in my case when it goes down to 10.7 Volt the battery could no longer can start the car engine (Perodua Alza).