Understanding the charging system in our boat with solar/AGM

[serpa4]

So, my 2018 came with the AGM/140watt solar system. The charge controller is 2 channel with 10% to start battery and 90% to house battery and nothing for the thruster/generator battery.
On a perfect mathematical day, it might see theoretically 9.3 amps x 13.5 volts to the house and 1 amp to the engine battery.

The C30 has 2 ACR (automatic charge relays) between the house and starter and between starter and thruster battery.
The ACR specs say: connect the house to engine battery when voltage exceeds 13.6 volts for 30 seconds or voltage exceeds 13.0 volts for 2 minutes. And if the engine battery sees 13.6 volts then the 2nd ACR connects the engine battery to the thruster battery.

So, looking at the wiring diagram I see the following:
House battery positive to to input/hot side of house battery cutoff switch. Hot side of house cutoff switch connects to the cold side of the parallel switch and the cold side of the parallel switch goes to the charge relay for the engine. Then the engine charge relay connects to the thruster battery.
So, if the solar is providing charging (up to 9 amps) to the house battery, the ACR should see the increased voltage on the house battery and close the ACR relay and allow those amps go from house to the engine battery. The thruster ACR should see the charge from the engine battery and thus close and send some engine charging to the thruster battery. I.e. a waterfall effect.
1) so why do we have a 2 channel solar charger for house and engine? If solar charges house, house then closes ACR and charges engine. Then engine charges thruster.
A single solar charge controller should charge all batteries through the two ACR relays.

I'm guessing that the single 140 watt panel will not sufficiently charge the house battery enough to make the ACR to the engine close and start charging the engine battery and thus not enough charge passing through another ACT to connect the engine to thruster battery. Then again, the ACR works on voltage and not amps. So, they should connect when solar sends 13.6 or whatever voltage to the house battery.

I'm installing a lot more solar for time on anchor without running the generator. I'll have a single large solar charge controller and let the waterfall effect charge all batteries.

 

[Submariner]

I wouldn't expect to get more than about 35Ah a day out of the 140 watt panel. It's not enough on our boat. I upgraded our solar charger controller a few weeks ago to a Victron MPPT 100/30 in preparation. Next step is to order two 150 watt panels for 300 watts total.

 

[scross]

The 140 watt panel with the old tech PWM controller are so inefficient compared to what’s available today. The MPPT controllers are much more efficient. The commonly quoted 20% more efficiency of MPPT is probably to optimistic but still the MPPT is going to give you more amp hours in a day to the batteries when compared to the PWM controllers.
For about the same size as a 140 watt solar panel, you can now get a 200 watt panel for about $200.
If you assume the MPPT controller to be 15% more efficient and the 200 watt panel to be 40% more productive, combining them could give you up to 60% more amp hours per day than the stock set up that comes standard in the RTs.

 

[serpa4]

I scored 2 sunpower 435 panels 1 year old for 150 each. Will soon have 870 and MPPT.

 

[Cutwater28GG]

my setup

http://www.tugnuts.com/viewtopic.php?f=5&t=16203&p=109584#p109584

its important to think of it as a system as generally when you upgrade one component you just move the bottleneck to another place. be it charge acceptance speed, battery capacity, solar capacity etc. as a result there is likely a big difference in what you should install for the larger CW30 /T31 with 4 house batteries vs the smaller boats with 2 house AGM's. The new boats with lithium setups change the solar game completely.