AGM battery charging and MPPT

[bowring]

Hello

My boat setup is
House bank
4 x 6volt AMG batteries wired up in series and parallel to make 575amh 12v
AMG Batteries require 14.8 boost and 13.8 float
40amp Solar MPPT Tracer AN charger set to fload with is 14.8 boost and 13.8 float
2 x 200w 18v (open circuit 20v) solar panels
160 amp alternator with external regulator which charges 14.8 boost and 13.8 float
Shore power charger Studer 80amp 14.4 boost and 13.8 float
Votronic Battery Monitor
Battery Monitor II

I have been told that each morning (while not on shore power) the solar MPPT charger should see boost charge 14.8v. What I am getting is a slow creep up to 13.7

My question is why cant I get 14.8v from the MPPT Solar

Image 1 while under motor
Image 2 while sitting on shore power

[smac999]

It will creep to 14.8 as the batteries get full. Might take all day. Or they may never reach that with solar only if the batteries are low. Chart the amps as well.

[sailorboy1]

Some solar chargers sense when other charging sources are on and the batteries are charged. Turn off your battery charger and see what happens.

Btw 14.8 is pretty high for most agm batteries

[bowring]

Originally Posted by sailorboy1

Some solar chargers sense when other charging sources are on and the batteries are charged. Turn off your battery charger and see what happens.

Btw 14.8 is pretty high for most agm batteries

Thanks Sailorboy

14.8 is what is recommend by the supplier

I have tried this and it slowly creeps up but but never above 14.2
The solar panel supplier says it should see 14.7-14.8 within 15min of adding a load
I would have thought that I would only see this if the batteries are fully charged

[Dsanduril]

During initial charging your MPPT controller provides the maximum current it can get based on the solar system attached. If your batteries can accept all of that current at 13.7V (or whatever) then that is all you will see. Only when the batteries begin to get full will the voltage rise. When the voltage reaches 14.8V (or whatever you have set) the MPPT controller will start to reduce current and hold that voltage. This will only happen when the current available from the solar system exceeds the amount the batteries can accept.

This is exactly the same as your battery charger and your alternator, but both of those can provide far more current (80A or 160A vs. ~30A maximum from your solar system) so for the same state of charge on the batteries they will reach 14.8V much sooner than the solar system.

Put it another way, with all of your charging source your batteries (and their state of charge) determine the voltage. Only if the battery SoC reaches a point where the voltage rises will your charging sources start to regulate on voltage.