We have a Toyota Etios Liva, four years old, petrol variant. Today, my father took it for annual servicing at the authorised service centre, where the service personnel declared that the battery was "dead". Our car is not used much. Usually on an average, it is driven for around 14km per month. But last month, the car was not driven at all. I switched on the engine, the AC, lights, and defogger a few days back, and everything was working fine. Today also, the car was properly driven to the service centre without any problem. Temperature here in Kolkata didn't drop below 12°C this winter. I suspect that the battery voltage might have dropped a bit as the car was not driven for a month. The service personnel said that readings were "bad". How bad I don't know. My father didn't check the readings of the multimeter, as he is not quite interested. If I were there, I would have checked. If the battery was dead as described, would the engine have started at all? My questions are: 1. I believe it is not correct to conclude on the battery's health in this condition. I read somewhere on the net that a car battery may need more than 12 hours charging for a full charge. I think if the battery was tested for charge retention after a full charge, it would have been appropriate. Am I right? 2. The service personnel said that I have to switch on the engine of the car at least once every week, while we were told that charging the battery once a month would be good. Isn't it too much that a battery would die if not charged every week? Are car batteries so weak? 3. For what minimum time should the battery be switched on so that it can be kept alive? N.B.: I don't have the old battery, because the company offered to recycle it in exchange of some money and my father agreed. Also, the battery had a warranty period of four years, and it was declared dead just when the warranty ended. This seems a bit suspicious to me, though I cannot confirm my suspicions as I was not there when the check was done.