I recently installed a new MultiPlus-II 2x120V in my camper. When charging 5 BattleBorn 100 Ahour batteries, whenever the Multiplus switched to float charging (and also towards the end of Absorption charging), it would make a strange buzzing/humming noise. These strange noises do not occur when bulk charging. I returned the unit to my retailer who observed the same strange noises when tested on the bench using different batteries. Communications with Victron resulted in Victron declaring the unit was defective and authorized a replacement under warranty. Prior to picking up the second/new MultiPlus, the retailer tested the second Multiplus and it made the same strange noises. Victron stated that no one else has reported these strange noises, and has no solution.
Has anyone else with a Multiplus II 2x120V experienced any strange noises during float charging?
For me, the noise was mostly a loud humming sound. My retailer describes the sound as follows: The humming noise does get louder when in float charge which is strange. We also note a tiny clicking sound and a rhythmic buzzing as the charge current “bounces” a little bit between 0.0 amps and 3.0 amps. It is odd. Later in float mode it is making a rhythmic bzzt-bzzt-bzzt at about 2-3 Hz.
I also have a Progressive Industries 50 amp hardwired Surge Protector (EMS-HW50C). This device has a current readout of how much current is being passed to the Multiplus. Prior to the noise of the Multiplus occuring, the Surge Protector shows a 1 amp current draw. As soon as the noise starts, the Surge Protector shows 7 to 8 amps of current to Multiplus. However, an amp meter connected at the house circuit breaker box shows only about a 3.5 amp current draw, so that buzzing is injecting some type of noise on the AC line which is confusing the Surge Protector. I thought it was defective Surge Protector and a replacement exhibits the exact same behavior of a false amp draw.
Is it possible that my retailer got a bad batch of Multiplus IIs? Any ideas are welcome. However, since this issue occurs both when installed in my camper, and also when at my retailer's shop in a completely different environment with different batteries, it seems like it has nothing to do with the install/batteries/cables.
