48V battery voltage replace all or one battery?

[wingnut2000]

2015 rxv

Three of the batteries must be stock and are just black and one is a us battery

Two of black batteries measured 13.7 and one was 13.6 and the us battery was 12.8v and the total pack at 53.8. Should I just replace the ya battery? Thoughts?

[wingnut2000]

Should I replace the one with the lowest voltage?

[scottyb]

I would decide by age and condition. Replacing a single battery in a pack always results in that new battery being reduced to the condition of the remaining batteries rather quickly. So don't think you still have one new battery if it has been 6 mos or year in a pack with old batts.

For 12v batteries, replace all the batteries if the majority of the mixed pack is 2.5 yrs old.
Or if their capacity is below 80% (figure based upon your use requirements) or specific gravity tests read below 1.238

Also your 53v figure is 'hot off the charger' reading let the pack rest for 12 hours after a charge to get the true voltage reading the pack can actually hold.
Use this chart below

[meimk]

First let the batteries settle. The rule of thumb is 12 hours after the charger has completed it's cycle. Take voltage readings then and see where everything is. Reading fresh off the charger doesn't give a realistic reference point.
Do some searching on the site for some of the many threads on battery testing. A basic "state of charge" test like that is useful, but not the whole story. Next step is to see how they handle a load. Those other threads will inform you how to test that.
If those 3 batteries pass those tests you COULD keep them and replace the 1 battery, but understand it would be a compromise. Even if they are good now the 3 older batteries will no doubt fail before the new "replacement" would. The limited capacities of the older batteries will limit performance, run time & life span of even the new battery.
As I said, read some of those other threads. Lots of information to be had.

[cgtech]

Rxv never came from factory with "just black" batteries. Trojan and US brands only.

[wingnut2000]

2 are 13v, 1 at 12.9v, 1 at 12.3v after sitting over 12 hours

[scottyb]

Equally important what voltage they drop to under load.
If you could assign a number to them 1-4 and list the starting voltage and the under load voltage for each one... we could better ***** their condition


Load should be a hard start acceleration uphill.