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Breaker Placement and help with Visualization Of Current FLow

aaron_c

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Jun 18, 2020
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I'm giving my plans a final once-over and I noticed that there's a part I'm not so sure about. It's the wiring around the inverter/charger, and it confuses me because the inverter/charger both uses energy from the batteries and provides energy to the batteries, depending on the situation. SO here's a piece of my wiring diagram, the part I'm confused about is circled:

1606158360824.png

Essentially, I'm confused about whether I've got the positive and negative terminals being wired the right way. And I'm confused about whether my breaker should be on the wire it's currently on or whether it should be on the 1AWG wire that connects the inverter/charger to the negative buss bar.

My confusion is this: When I picture current flowing from the battery to the inverter (and back), it goes like this: Battery -> 200A Fuse -> Disconnect -> Positive Buss Bar -> 175A Breaker -> Samlex EVO Inverter/Charger -> Negative Buss Bar -> Battery Monitor -> BMS -> Battery. So far so good. And it would make sense to connect the negative buss bar to the DC Neg Terminal and the positive buss bar to the DC Pos terminal on the Samlex EVO.

But when I picture current flowing from the Samlex EVO to the battery, it goes like this: Samlex EVO -> Negative Buss Bar -> Battery Monitor -> BMS -> Battery ...er...and then I guess the current stops? Or if it doesn't it continues in the circle, going through the positive buss bar and back to the Samlex.

Anyhow, when I picture the current originating with the Samlex EVO, it seems like I'd want to connect the DC Neg lead terminal of the Samlex EVO to the wire that goes to the Negative Buss Bar. And that I'd want to put the 175A breaker on that cord. This doesn't appear to be right--I've checked the documentation and it clearly has the negative buss bar connecting to the DC negative of the EVO (with the breaker on that line) but I don't understand how to visualize the current flow when charging, nonetheless.

It feels like I'm just being dyslexic or something and that this is probably super-simple. But I am confused, particularly because the designation of wires as "positive" and "negative" would appear to be relative to the position in the circuit of the power source and the power consumer. Depending on whether the EVO is acting as an inverter or charger, those positions change.

Can anyone help clear this up?
 
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Everything looks good. I think the confusion is that it's either taking power from the batteries or charging them from AC input, so the flow direction reverses and completes the circuit in full... charging starts at samlex, flows to battery and returns to samlex.

When powering from the batteries, starts from battery, flows through samlex and then returns to battery.
 
Ah, that makes sense. The flow direction reverses! That's what I was missing...
 
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