MPPT Blinking Bulk LED on one of two charge controllers

I have an off-grid system with 4 x Trinasolar 405W – 11.77A (Imp) – 41.4V (Voc) Panels wired as 2 x Series strings. Each string connected to a Victron BlueSolar MPPT 60A/150V charge controller MC4. Both controllers feeding four Rolls 6v S6-L16 Batteries (24v series) going to Victron Multiplus 24/3000/70-50.

Yesterday I checked the system, with batteries fully charged (in storage mode) and noticed that one of the charge controllers was in float and the other showed the bulk LED blinking slowly. I tested the panel voltage to each controller and the one with the blinking LED was receiving zero voltage (other controller fine at 70+ volts). So, I switched off the panels at the circuit breakers before the controllers and, surprisingly, when tested, both sides were producing voltage around 70V… as soon as I switched breakers back on – no voltage to the blinking controller!

I have ordered a VE Direct Bluetooth Dongle so I can then connect and look for error codes etc. But I wondered if anyone could offer an explanation?

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Mike Dorsett commented · Nov 18, 2023 at 10:02 PM

This sounds like the internal fet of the charge controller has either been turned on by the processor, or has melted during an over voltage event. This can be tested with a clamp meter on the pv input cable to measure the pv current. If high, the fet is shorted, if low, you have a high resistance connection in your pv string.

The controller should be removed from the system and bench tested, try doing a factory reset too.

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