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zed-must asked

Flat batteries - even on shore power

Hi, i have a new boat with a new multiplus 3,000 inverter charger + mppt solar controller. On 3 separate occasions we have returned to the boat after 10 days away to find our 550ah battery bank completely flat. Our consumption when not on board is low - around 10a. Solar should keep well ahead of that, but last time we went away we left the shore power plugged in to be sure. When we returned the batteries were again flat! The shore power was on and working with no reported outages.

The only error on the multiplus is a ‘temp sense error’ which only happens when the unit is switched on.

If we stay on board for a week or so we monitor the system daily and see that the batteries are kept at close to 100% on either shore power or engine alternator. We are now terrified of leaving the boat with even the bilge pump on for fear of returning to a dead boat again.

A separate problem is that the mppt has stopped working but we think thats a faulty unit so thats going back to victron.

Any ideas? Thanks

Multiplus-II
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Paul B answered ·

Number 1. you should be looking at Battery Voltage NOT SOC. to get the correct battery status

Battery voltage will always give you a correct battery level and then compare this to the SOC and read up on how to get the SOC working correctly from There, this will depend on what battery monitor you have.


on a 12 volt lead Acid Battery system with No charging or power draw for 1 hr a full battery will read 12.7 volts, in its current condition.

down to around 12.2 -12.3 which is around 50% discharged


The Victron MPPT regulators are very solid units so this is unlikely to be faulty. if its a smart solar unit then check it out using the victron connect app, if its a bluepower unit I would strongly suggest you purchase a bluetooth dongle to suit,


These give you 30 days battery voltage history and the solar output levels and much more


Also have a look at this post re the SOC if you have a BMV bat Monitor that is

https://community.victronenergy.com/questions/25836/bmv-700-shows-85-but-battery-voltsage-is-1185v.html


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zed-must avatar image zed-must commented ·

Thx, i dont know what you mean by SOC? See attached pic which shows voltage was good up to one point when everything went dead. I have no idea why. Again, mains power was plugged in at the time

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