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I have a 20amp mppt charge controller (EP Solar tracer 20a). In the manual it states:

WARNING: Connect battery terminals to the charge controller BEFORE connecting the solar panel(s) to the charge controller. NEVER connect solar panels to charge controller until the battery is connected.

However, if the breaker (or fuse) between the battery and controller is ever tripped, then it will essentially put the system into this state.

Is there any way to prevent this from happening? Or is this not something that I should really be worried about?

Update:

Currently the charge controller is connected to the same breaker as the system load (mainly for the convince of being able to disconnect the entire system in 1 switch). I'm wondering if this might make the scenario above more likely to occur and if I shouldn't run a separate fused line to the battery directly from the charge controller.

Here is a diagram of what my current wiring looks like:

enter image description here

NOTE: I couldn't find the breaker symbol so I used the switch. Also the circles are junction blocks that I added for convenience

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  • \$\begingroup\$ Can you show the expected wiring diagram. You should probably add a relay that only connects the solar panel when the battery power is attached to the controller. I am sort of surprised that is not built in, or included in the recommended wiring diagram. \$\endgroup\$ – Trevor_G Apr 3 '17 at 17:28
  • \$\begingroup\$ @Trevor ya the suggest wiring doesn't saying anything about it. \$\endgroup\$ – NSjonas Apr 3 '17 at 17:49
  • \$\begingroup\$ Then yes, I'd add a relay downwind of both breakers, maybe solid state to make it fast and low drain on the battery. \$\endgroup\$ – Trevor_G Apr 3 '17 at 17:55
  • \$\begingroup\$ ALternative would be to use a "ganged" breaker so you can not turn off one without the other. But that will not protect you from a battery disconnect, intentional or otherwise. \$\endgroup\$ – Trevor_G Apr 3 '17 at 17:56
  • \$\begingroup\$ Hopefully the controller is robust enough to handle the switching time. \$\endgroup\$ – Trevor_G Apr 3 '17 at 17:57
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I'd make the battery breaker a double and use one side to feed a relay on the solar lines, maybe solid state to make it fast and low drain on the battery. As shown below. The reason for the ganged breaker is I am not sure what the output of the controller will do when the breaker opens. It may still drive out a high voltage for a while before it dies...

schematic

simulate this circuit – Schematic created using CircuitLab

You need to chose a relay that has a coil/activation voltage that is the same as your battery voltage, and can carry the current expected from the solar panel.

Potential issues: 1. Hopefully the controller is robust enough to handle the switching time. 2. If the batteries drain too much the relay will drop out.

Alternative would be to "gang" the battery and solar breaker so you can not turn off one without the other. But that will not protect you from a battery disconnect, intentional or otherwise.

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