aleuli avatar image
aleuli suggested

Multiplus charger does not reset to Bulk

Hi all,

I have a Multiplus, with AGM batteries and Venus Gx, AC coupled to an Enphase grid tie system. Got the ESS installed on the Multi, and have run in to some issues. The most annoying one is that the Multiplus charger does not reset back to bulk after discharging to minimum SOC.

So during the day the panels do charge the batteries, and during the night the batteries get discharged to Minimum SOC. But the charger never resets back to Bulk. So after reaching Float the first time, it remains in float forever. This will cause lead acid batteries to fail prematurely.

After many testings I did realize the Multiplus charger only gets reset when the grid fails(inverter goes in to island mode).

So the fix was to set the ESS to toggle the relay 1 via the "Generator start/stop" feature, every day at 6:00am for 1 minute. Plugged the relay output to Auxiliary 2 input on the Multiplus and ran enough instances of the Programmable relay and general flag assistant to make the Multi go in to island mode every day.

Now I am trying to figure how to set a timer for the power assist feature not to work until the batteries get fully charged. I don't like that on cloudy days the multi keep interrupting the charge and discharging the batteries when the panels get obscured.

Best regards,


Dominican Republic

battery chargingbug reportmultigrid
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nickdb avatar image
nickdb commented

Do you have a battery monitor/shunt? It doesn't sound like the system is discharging deep enough to trigger bulk (needs to hit float Voltage minus 5V if I remember correctly).

I ran into issues on the multi because the internal battery monitor really isn't very good and in an ESS environment gets horribly out of sync which causes all sorts of issues with the various ESS SOC thresholds you set.

A smart shunt/BMV sorted that and the charging issues out.

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aleuli avatar image aleuli commented ·

I have the Float voltage set to 55.0 Volts, at 75% discharge voltage drops to 49.75 So it is kinda close. Anyways if needs to be 5V under float, that is a problem. My batteries should not go under 70% SoC if I want to get more than 1K cycles from them.

Still I managed to auto reset the multi charger back to Bulk by forcing island mode for 1 minute every day.

This is the section of assistant settings on VE configure that did the trick:

programmable relay (2) (size:41)

*) Use General Flag

*) Set relay on

*) when Auxiliary input 2 is closed for 1 seconds.

general flag user (size:5)

*) Use general flag to ignore AC input 1

programmable relay (3) (size:37)

*) Use General Flag

*) Set relay off

*) when Auxiliary input 2 is open for 1 seconds.

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aleuli avatar image aleuli commented ·

And no, I don't have the battery monitor/Shunt. The Multi battery monitor seems to be working properly on my system. At least the voltage meter does, I've tested it with a multimeter.

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nickdb avatar image nickdb ♦♦ aleuli commented ·

The issue is more how the multi determines the % state of charge.

It can believe it is at 75% while it is actually at 85% for example. While SOC is a relative indication of charge, If your ESS limit is set to 75% the multi will stop discharging prematurely and the battery voltage will remain above the threshold for bulk/absorption so forcing a deeper discharge will resolve this.

You can also look at your battery specs and adjust the float voltage for the desired result.

We just couldn’t get ESS to work properly and consistently in a solar environment without an external battery monitor.

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aleuli avatar image
aleuli commented

Fixed my second issue, added a crontab file which change maximum inverter power to zero at 4:00 and 600 at 19:00. Now the batteries are more likely to be fully charged with solar every day.

Now I will work on tweaking the system, so the Enphase and Victron work better together. Kudos to Victron for making this system so flexible.

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