How to know battery going to be flat?

[Ghost777]

To me just every 18months change a new battery don't save that little money. Best is when battery is about 12months ++ just drive to some friends workshop to check the battery see how much is the %%%% left. Than every 18months just change.

[Hachi]

To me just every 18months change a new battery don't save that little money. Best is when battery is about 12months ++ just drive to some friends workshop to check the battery see how much is the %%%% left. Than every 18months just change.

 

I changed every year and sell off the old one thru carousell. For my case is aorund $50 after factoring the old battery price. A fair price to pay for a peace of mind.

[Benzw205]

Would like to share my older post:

"Dry" batteries are mostly valve regulated lead acid batteries (VRLA battery). If a car is parked mostly at open car park, daily mileage is long, eg >80km daily, coupled with higher alternator voltage, >14.2V, VRLA will not last long . Because it would dry up prematurely due to overcharging. In this case , flooded lead acid battery is better as you could top up with battery water or deionized water (DI water). But even flooded lead acid battery is used, under the same condition, the battery will last only 2 years. For VRLA 1 year 6 months or less.

If all these conditions are not present at all, it is not uncommon to see a flooded battery lasts for 4 years. Take note after 2 years, frequent top up is needed.

There are simple steps to verify roughly the battery would last for another 3 months if you have a simple voltmeter:

1. Engine off, it should be 12.4 to 12.8V. If less than 12.2V, replace battery sooner. If it's only 10V, most likely battery will refuse to start engine as 1 cell is dead (there are 6 cells in a battery).

2. Start engine, just idling, no air con and lighting etc, it should be 13.6 to 14.4V..... Your alternator is charging normally.

3. Engine off, turn on normal beam head light, let the battery discharge for 3 mins while measuring.

A new battery would likely discharge to 12.1V and start to rebound to 12.2V and hold there for very long. A weak battery would discharge to 11.8V and never rebound but hold for a while then continue to drop. Change it sooner. An in between battery would rebound at 12.0V and hold there for quite long. The key word is rebound.

4. Off head light, put back the positive cap and keep your voltmeter.

 

hello, do you think that a AGM battery is always better ? And anyway always needed when car has engine start/stop ?

 

Thanks.