Alternator charging combo with solar panel via B2B and isolator

[Logan]

Consequently, I would dump the lead acid house battery and simplify everything like this:

The lead acid house battery is a factory fit under the bonnet and the LiFPo 150ah will not fit in that spot under the bonnet so no need to remove it, more simple to leave it where it is and use it the way you show in the image in my post above.
Then I can have a 3 way switch in my power board to swap the main feed coming into the "house" part of the van from either battery depending on charge rates of either battery, required use at the time, sun available, etc etc. Using it as a back up stand by.

 

[FilterGuy]

1. In the image above when the vehicle is being driven will "load 2" be drawing from the charger or the battery?

If the load is small, it will usually be drawing off the charger. A larger load might draw from both.

2. Is the DC charger connected to the same wire that is connected to the "load out" on the mppt?
Or is it more correct to say: DC Load 2, mppt load out and the LiFPo are all connected together?

I had always assumed that mppt had a load out and a battery out like the $20 PWM that is fitted on my van at present.
It however has a "load out" but is not connected, it has been wired to pull load straight from the battery which I have seen the load draw the lead acid house battery below 10V if I am not watching the volt meter because the pwm can not disconnect the power as the load is not being pulled via the load terminal on the pwm.
So I assume I have to pull the load thru the load out on the mppt or am I missing something?

The 'load out' on chargers are usually pretty low power, so I would not use them. Some of the chargers have features where it will turn on the load at night so you can have a night light but other than that I look at them as fairly useless on all but the smallest systems. Even then.... I question their utility.

Just hook the load, the battery-out of the SCC and the output of the DC-DC charger all to the battery.

 

[Logan]

Just hook the load, the battery-out of the SCC and the output of the DC-DC charger all to the battery.

Thanks.

If the load out on the mppt is not used how does it, (or what) shuts down the load draw from the battery when it gets flat?

 

[FilterGuy]

Thanks.

If the load out on the mppt is not used how does it, (or what) shuts down the load draw from the battery when it gets flat?

There are multiple levels to the answer.

The inverter is typically the largest load and most people will set the cut off voltage on their inverter to a voltage that protects the battery.
Unfortunately, if you also have DC loads, they can drain the battery as well. You have a few choices:

1) If the DC loads are small enough, and the 'load' terminals on the SCC has a low-battery disconnect, you can run your loads off of it. However, the load output on the SCCs are typically pretty small. You will have to run the numbers to find out. (Since a lot of your DC is over on the lead-acid battery, maybe you will be OK.

2) Use a Victron battery protect to cut off the DC loads when the voltage gets too low

3) Let the BMS on the battery be your low-disconnect. Some folks do this, others say the BMS should only be a last line of defense and the loads should be cut off before the BMS does.

BTW: Notice that you have the same (Worse?) issue on the Lead-Acid house battery.... nothing there will cut off the load if the battery gets low.

 

[Logan]

The inverter is typically the largest load and most people will set the cut off voltage on their inverter to a voltage that protects the battery.
Unfortunately, if you also have DC loads, they can drain the battery as well. You have a few choices:

Thanks.
As I'm using an all in one MPPSolar unit the inverter in it or the settings within it will do the job.
So I will use the victor dc-dc combined with the above mppt unit.
Thank you very much for all your time and effort to clarify this for me. Thanks to you and others on the board I now have a good understanding of what I need to do. Just got to await the ordered components to arrive now