question

peternielsen avatar image
peternielsen asked

ESS with 2-wire BMS and MPPT

Hi,

In a system with a Multi 2, SmartSolar MPPT and a 2-wire BMS will the MPPT stop charging as well when Multi is asked to stop and the same goes for charging on low battery signal from BMS ?

/peter

MPPT ControllersMultiplus-IIESSBMS
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1 Answer
wkirby avatar image
wkirby answered ·

Yes, EES reason code #3 will show - "BMS has disabled charging". VE.Bus BMS menu will show "Allow to charge = No"
MPPT's will support loads, but charging current to the battery will not be allowed.

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peternielsen avatar image peternielsen commented ·

@WKirby Great thx, now another question arrises. How can the MPPT support loads if it's not charging i mean doesn't it provide power on the battery positive/negative which also goes to battery ?

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wkirby avatar image wkirby ♦♦ peternielsen commented ·

There are actually two options when setting up the 2-wire BMS Assistant:
Force to float Voltage or Disable charger.
I use force to float, this way the MPPT charger only makes the power needed to power the loads. The only battery current is enough to maintain the float Voltage (not very much).
Indeed the battery is loaded to FORCE to the float Voltage as quickly as possible, MPPT power will be reduced or cut until the float Voltage is reached.
In my case, full power grid backfeed takes place to reach down to float Voltage very quickly.

I did not use "Disable charger" option.

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ac-victron avatar image ac-victron wkirby ♦♦ commented ·

When I leave Remote L floating, the charging of the battery stops as expected, but so does the output of the MPPT, and as a result, the system gets its power from the battery instead of the panels. I think this could be fixed using the option you describe "force to float". But I can't find this choice anywhere in the tools I have to control the MPPT (Victron Connect or Cerbo GX). Where should I look for it?

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marekp avatar image marekp ac-victron commented ·

@ac_victron

It is in the "2-signal BMS support" assistant. or in the ESS assistant.

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