Are PV contactors required

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dconn22 asked Sep 8, '21

Are PV contactors required

I asked this question in the Mppt section but it never showed up???
My BMS can turn my batteries off under certain [out of spec] conditions. My concern [although recently lowered] is when/if batteries are turned off power to my MPPT controller[s] will also be cut [batteries are literally turned off] but the PV power will continue to be supplied to the [BlueSolar 150/60] controller. while this "condition" will signal an alarm from the BMS If I am away the "condition" could exist for several days. I know some [cheaper] CC's aren't capable of this situation without damage. I have manual cut-offs on the PV [both legs] would contactor[s] be REQUIRED to isolate PV if/when battery power is off and if so can just one PV leg be opened [1 contactor vs two]. I understand the safety concerns about disconnecting PV first and the need for battery first for initial set-up. I have heard both absolutely yes and absolutely no on other forums so I'm hoping I can get a definitive answer here. Thanks

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Answer 1 · 2021-09-08T17:38:06Z

wkirby answered · Sep 08, 2021 at 05:38 PM

The Victron MPPTs are OK without a battery connected. Their output will shoot to the target Voltage for whatever stage they are in at the time. For example, if in bulk, the MPPT output will go straight up to the absorb Voltage.

This happens under some other fault conditions where the battery fuse opens or there is a loose connection between the MPPT and the battery. This often causes real confusion because people see a reasonable battery Voltage at the MPPT output, but 0A because the battery is disconnected.

It'd be most unfortunate if a blown fuse or battery disconnection for any reason would destroy an MPPT controller too.

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