Charging issues

[loanrangie]

Although i possibly not the answer i will post it anyway just to get others perspectives.
The telltale light on my aux battery is showing clear ie charge required, main battery although indicator is green voltage is low.
At rest main batt reads 12.5 and aux 12.2 as measured yesterday afternoon, with engine running voltage at main batt is 14.49 ish so alternator is fine and aux reads 14v at terminals.
To me this would suggest my 2yo main battery is failing which makes the VSR divert charge to main and not aux although while running 14V at aux terminals suggests otherwise ?

[DiscoMick]

12.5 is OK. Maybe the problem is the auxiliary.

[350RRC]

When doing a major rebuild of my POS years ago I installed a Redarc isolator and a standard lead acid battery as the auxiliary. Main battery was a Willow calcium with a few years already on it.

The aux gradually died over time even though it wasn't connected to anything but the isolator.

A bit of research at the time found that Redarc recommended both batteries be the same (from memory).

Now they recommended that they are both of 'similar chemical characteristics'.

I now have identical Willow batteries ( the old fashioned ones without the 'magic eye' of death ) installed and all is perfect after two years.

DL

[loanrangie]

Both batteries are the same lead acid type and similar age, not having any starting issues but previously the main would generally rear around just under 13V and aux was similar.
Might check the earthing in case they have corrosion on them.