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Where to attach 2 SCCs?

corn18

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Sep 9, 2021
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I am planning to hook one SCC to the positive terminal of one battery and the other SCC to the positive terminal of the second battery. Mostly because the first battery + terminal is getting full. I want the ability to charge the batteries without the main breaker on, that is why I am going directly to the batteries. Any issues with doing it this way?

DC wiring 290RL.jpg
 
You should connect everything to the bus bars.
Why? I want the batteries to stay charged while sitting at the storage lot. That won't happen if they are attached to the bus bars. Or should I not do that?
 
Your shunt/battery monitor is useless if only some things go through it.

Why do you want to charge with the main switch off?

I would hook up everything through the bus bars and then turn off the items you don't want on all of the time. My system doesn't have a main battery switch. I have a main switch between the positive bus bar and the inverter. I have a main switch between the positive bus bar and my DC loads. And I have a breaker that acts as a disconnect between the positive bus bar and the SCC. This way I can turn off individual items as needed. If I ever want the whole system down I turn off the two switches and open the breaker. Then I disconnect one battery wire.
 
Your shunt/battery monitor is useless if only some things go through it.

Why do you want to charge with the main switch off?

I would hook up everything through the bus bars and then turn off the items you don't want on all of the time. My system doesn't have a main battery switch. I have a main switch between the positive bus bar and the inverter. I have a main switch between the positive bus bar and my DC loads. And I have a breaker that acts as a disconnect between the positive bus bar and the SCC. This way I can turn off individual items as needed. If I ever want the whole system down I turn off the two switches and open the breaker. Then I disconnect one battery wire.
The shunt still reads the current from the SCCs when the main switch is off and the SCC is connected to the battery terminal.

I want to recharge the batteries in storage in case they haven’t gotten fully recharged after a trip.

I can turn off DC loads with the converter CB. I can turn off the SCCs with their CB. The main batt switch turns off AC and DC loads. When in storage, all loads are disconnected and I can choose to keep one or both SCCs connected to the battery.
 
@rmaddy I think I am leaning your direction. I can hook the 2 SCCs to the bus bars. I can control DC loads with the converter/charger CB. I can control the AC loads with the 2 remote panels I have hooked up to the inverters. I only turn them on when I need them. So when I want to charge the batteries with solar, I turn on the main breaker and connect the 2 SCC CBs.
 
Another advantage is that by not turning off the main switch you do not need to worry about precharging the inverters before turning the main switch back on again. I simply set my inverter to the Off position when I have no AC loads and it does not use any power at all.
 
BTW - I'm not a fan of your pre-charge setup being on the main battery switch. It's only needed for the inverters but with your setup it sends a little bit of power to everything, not just the inverters. This is one reason I have a separate switch just for the inverter. My pre-charge setup is just on the switch for the inverter so it doesn't affect anything else.
 
Another advantage is that by not turning off the main switch you do not need to worry about precharging the inverters before turning the main switch back on again. I simply set my inverter to the Off position when I have no AC loads and it does not use any power at all.
That makes sense. What happens when you turn your inverters on? I assume the caps charge then and produce an inrush current that the BMS sees. Do you use a precharge? I could add a switch for the inverters and route the precharge around that vs what I have.

I would put a switch between the + bus bar and the 2 inverters. Then run the precharge circuit around only that.

DC wiring 290RL.jpg
 
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Assuming you turn the inverter on and off using its own on/off switch (not from an external switch added between the inverter and bus bars) and the battery is never disconnected from the inverter then you do not need to pre-charge. Pre-charge is only needed when battery power has been removed and is about to be reconnected.
 
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