question

Hi @ThisBigRoadTrip

If your mppt is holding the set Float V, and is only giving "3.5 to 4 amps" at the end of the day, then your batts are likely fully charged and just can't accept more current. Especially if you were previously happy with 5A (what Victron call the 'Tail Current').

That you can't find a balance in your battery monitor, is an issue with the battery monitor. That it calls itself an Amp-Hour-Counter raises red flags with me. The energy contained within an AmpHour discharging at 12.5V is far less than that charging at 13.5V, so unless it's compensating for that, can never balance. This and SOC drift will accumulate by the day until you synchronize/adjust it.

I use a Smartshunt, but consider it's base purpose to be as an Ammeter. How well that gets translated to SOC is for me to determine in the settings I give it to use. And they change for my batts between summer and winter too - not much, but enough to warrant a settings tweak.

Take care using a battery monitor without reverting to 'first principles' to check it. That 'Tail' is oh-so-important..

Thanks @JohnC

The. battery monitor kit (I thought) uses a DC shunt to establish how much power is being used by appliances. This is the unit I have. I know it is not perfect, but has always seemed to be providing feedback that was in line with what I expected.

We replaced a GoPower solar controller. After some research it seems that unit had a similar bulk/absorb voltage but the setup of the Victron has me floating at 13.3v and the GoPower was set by default (and could not be changed) at 13.7a. Moving up the amperage on float charge seems to have a reasonable effect on the number of amps I am getting in for a large chunk of the day. That voltage difference, and resulting amps registering on the Magnum battery monitor. Would likely make up the shortfall.

Is the new controller going into float before the old one did. It is possible to alter the settings on the absorption time as detailed in the manual. For example on my system it was going into float earlier then I liked so now I have set a fixed absorption time of 4 hours and a tail current of 7 Amps (1% of my 700 Ah battery bank) so it stays in absorption for either 4 hours or until the current drops below 7 Amps rather than using the default adaptive absorption time. As my batteries are new, I know that they have a tail current below 7 amps when fully charged. The one warning is that if the tail current you set is too low then it may never be reached and you could be in absorption for too long and overcharge the battery. This is why it is also good to set the maximum absorption time.