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Charge Controller and startup sequence

cdsolar

caduceus
Joined
Dec 16, 2022
Messages
272
Location
Utah, USA
Hi

I know that in many places, we are told to always power up the charge controller with a battery first, before connecting PV panels to it.
Ok, that makes sense, and I understand why.

My question is, what happens in a running system when the battery dies or is otherwise cut off? The charge controller is left connected to
the PVs. I have not seen how to handle this situation, given that the charge controller should always be connected to battery first.

I can think of several things to do or other scenarios:

1. use some sort of tied breaker so that if the breaker from the battery trips, it force-trips the second breaker on the link from the PVs, thus disconnecting the charge controller completely.
2. Assume the risk and (potentially) get a new charge controller.
3. Perhaps (many?) charge controllers have a way of dealing with this situation, with some sort of shutdown sequence that electrically disconnects the PVs or provides some sort of shielding when the battery dies.

I could also have missed such a discussion. (I am new here).

Any thoughts? Thank you.

-Chris
 
If you buy cheap crap, you may have to worry about it. In most cases, the "rule" does not apply. In some cases, like with Victron, the battery can be disconnected entirely, and the unit will power itself and provide PV output to the MPPT battery terminals and power loads. This is mentioned in their manual, and I've confirmed it by having the MPPT power my inverter with the battery switch in the OFF position. Of course the inverter had to already have its caps charged for this to work.

Victron does make it clear that it's important to connect the battery BEFORE the PV for the first time, so the MPPT knows the system voltage.

So,

1. no
2. yes, but low risk
3. Yep.
 
I would have a relay that shuts off the pv when the bms disconnects

Epever Tracers for example can be damaged by PV voltage alone if over 40v
 
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