14.8volts

[PabloPicasso]

So it's the change in voltage charge since last season that has me thinking. There's no change to wiring systems, no new gear fitted etc.

 

[ianj99]

So it's the change in voltage charge since last season that has me thinking. There's no change to wiring systems, no new gear fitted etc.

So how has the battery been stored? If its not been kept charged eg with a trickle charger, then it will potentially have lost a lot of capacity. I suggest connecting a load of a few amps and measuring how long it takes for the voltage to drop to 12v then remove all load. Recheck the voltage after 15mins. Once it drops just below 12v off load this means there's about 40% remaining. Hence you can work out the actual capacity and compare with what it should be (its not an exact test as the AH capacity depends on the discharge rate among other factors but if the results indicate a big loss of capacity, this may explain the rapid increase in voltage that you saw)
Ian

 

[halcyon]

So it's the change in voltage charge since last season that has me thinking. There's no change to wiring systems, no new gear fitted etc.

Have you checked the voltages yet ? until their is some specific data it is impossible to come up with options.

Brian

 

[johnalison]

I can't speak for Garmin but my Raymarine instruments overread by about 0.2 or 0.3v. It is necessary to check with a decent multimeter, preferably at the battery.

 

[charles_reed]

I would look for under sized cable or bad connection, no way should the alternator or battery voltage show those voltages at that state of charge.

Brian

For your farther edification, voltage is taken at input into a 3-way splitting diode.
There are no faulty connections - they all check out @ 0.1 or less on continuity.
Voltage sensing is on battery #1.
I made no comment on "state-of-charge", so must assume prestidigitation - usually the boat has been @ anchor for 3-5 days with no charge except that from 328w of solar panel.