Voltage doubles when battery charged and converter goes to no load conditions.

[Maplhgr]

Your loss of reference voltage from the bms is an interesting contribution. Now what do do about it.

 

[MemoriesByTheMile]

Yes. With battery switch off and anti reverse fuse pulled charger indicates 27 volts. No load condition. This is test progressive dynamics tech had ne perform before warranty replacement.

Switch turned off and fuse pulled - in my mind that doesn’t ensure the battery is disconnected. I would physically detach the cables from the battery bank and then test the battery - this ensures that NOTHING is back feeding voltage to the battery.

 

[Rich W.]

Yes. With battery switch off and anti reverse fuse pulled charger indicates 27 volts. No load condition. This is test progressive dynamics tech had ne perform before warranty replacement..

Btw.. curiously the replacement board serial number is identical except for last number which is only 4 digits higher…
Bad batch?

This is a 12 volt converter only. Lithium switch on board boosts output to a nominal 14.6 volts per manual

Switch turned off and fuse pulled - in my mind that doesn’t ensure the battery is disconnected. I would physically detach the cables from the battery bank and then test the battery - this ensures that NOTHING is back feeding voltage to the battery.

exactly!

 

[Maplhgr]

Well thanks for the help… I figured it out…. The dometic ac/dc cooler was feeding back into the converter when it went to no load condition. Had all Dc load fuses out to protect equipment from high voltage and thought to check load side of each to ground for potential… Eureeka. 27 volts on cooler circuit fuse load side with fuse out.