V70 Charging issue
 

Hi,
I have a 2014 V70 D5 (Authorities spec.)
I have an issue with the charging system, the main battery is new, with the same Type (AGM) and the same 70Ah capacity as the OEM. I have also replaced the secondary battery with one with specs exceeding the original. I have cleaned the main ground connection to the body and checked the battery cables, they seem visually fine.

The issue I have is that the main battery charges very slowly when the engine is running. Though I don't have any issues with starting, the battery is rarely above the 72% State of Charge required for the Start/stop system to function.

I have VIDA and DICE.

I have reset the BMS, and after a few days, the State of Charge is consistent with multimeter readings at the battery. So it seems that the BMS is functioning as intended, VIDA also shows BMS calculations and communication as OK, and there are no DTCs relating to the charging system.

I have taken many readings whilst the engine is running, both stationary and driving
When the engine starts, the charging current can be 15A - 20A, but that rapidly drops off over around 2-3 minutes to give the following average values:

When the SoC is around 60-70% the voltage reads 14.85V to 14.9V and the charging current is between 4A - 6A, (Conventional charging).

When the SoC reaches about 72%, the current drops to around 2A - 3A, with the voltage still at 14.85V to 14.9V (Conventional charging).

On the rare occasions that the SoC reaches 80%, then it switches to "Brake energy regeneration, quick", the voltage drops to 14.25V with a current of 2A-3A. (I haven't had a chance to take readings whilst driving at this SoC yet).

If I drive the car for around 30 minutes, the SoC only increases by 3-4% maximum.

I understand that the charging system is designed to adjust how the battery is charged depending on the SoC, but the current it is charging at (during conventional charging at least) seems very low to me.

Can anyone shed any light on what the expected charging current should be, and whether I should be looking at the alternator / regulator, or elsewhere to resolve this?

Thanks in anticipation