Voltcraft bt 3 12v digital lead acid battery tester voltcraft bt 3 p the voltcraft bt 3 12v digital lead acid battery tester is ideal for quickly and simply measuring the remaining power in 12v vehicle and solar batteries p p this battery tester loads the battery at high current and measures the battery voltage under load batteries in poor condition will drop when measured under load and can thus be identified within seconds the whole test process is automatic i e you simply start t