MPPT battery voltage difference

Continuing the saga of the misbehaving MPPT....

I'm coming around to the idea it may be faulty, the two that work are showing the correct battery voltage and the third (the naughty misbehaving one) has the voltage cycling over about 5-10s from 55v down to 38v, then jumping back up to 55v and repeat... Which may explain also explain the cycling idle, flick to 30-150w charge, then back to idle.

They are all wired off the same lynx distributor 1000, I haven't been over to check the actual voltages, but the cycle speed is a bit quick for my multimeter to keep track.

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wkirby ♦♦ commented · Feb 15, 2023 at 08:41 AM

My first thought is that the battery is not connected to that MPPT (open fuse) or it has a very poor connection to the battery.
If you disconnect the PV to that MPPT does it still show a battery Voltage?
If the battery is disconnected in some way, then the PV is powering the MPPT and as the tracker scans the PV the output Voltage will swing all over the place. No current or very little current will flow resulting in low power output which you can see.

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chrisr wkirby ♦♦ commented · Feb 15, 2023 at 11:22 AM

@WKirby thanks for the idea, I've done that and the voltage dropped to 0v and the MPPT turned off, I'm not actually on site so monitored it remotely on VictronConnect while someone turned off the PV isolators. I've got some fuses on order so I'll swap one out when they come and see if that sorts it.

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wkirby ♦♦ chrisr commented · Feb 15, 2023 at 01:08 PM

Excellent, so leave the PV isolators switched off until you resolve the problem with the battery side and the MPPT comes on, running from battery power.

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