Change both Batteries or just 1 and wait?

[Lynx]

One of my batteries died after 2 1/2 years of use. The other is still holding a charge.

Most say to change both at the same time others say as long as you are not using them together it is OK.

Should I change both?

Should I watt until the other one dies to change it?

Thanks, Have time to kill for a while.
James

[s/v Faith]

It depends on how they are used.

  If you have 2 12v batteries that you use in parallel then you need to change them both.*  If you have a separate house and starting battery you need only change one.

  If you use 2 6v batteries in series then you can change 1, but might want to just change both.



*Batteries have an internal resistance that increases with age.  If 2 batteries that are of different types or ages are placed in parallel the newer will slowly discharge into the older over time.

[Karletto]

use a multimeter to check the voltage on the good one. in my opinion a battery that was drained to the maximum has to be dumped because it will drain much, much faster after charging. ok, few more chargings won't hurt. i read that when cells come together the battery is drained to the maximum/ can be dumped. the level of the acid has to be 5mm - 1cm above the cell.

change 1 battery only

[newt]

I've done the cheap thing and changed one on my boat. Just ruined a good battery in a couple months time- changem both would be my vote.