question

Magnus Pernemark avatar image
Magnus Pernemark asked

Bug in Multiplus 2 when switching to Float

I use three MultiPlus-II 48/3000 in grid-tie ESS setup.

I charge the batteries to 56V (absorption), it sits there for a while while batteries balance.
After a set time it enters Float at 55.40V.

When the multis change to Float they discharge at maximum inverter capacity for a few seconds, in my case over 6000W.
On a sunny day when my PV inverter is already exporting 15000W, an additional 6000W is a little too much.
The jump from absorption to float ignores grid-set-point, it ignores the ramp up/ramp down settings. It goes from 0 to MAX in a millisecond.

I cannot see this discharge in any of the widgets in vrm, but it is there, trust me. I see it in real-time if I look at vrm and I also see it in my other monitoring system. 18900W was exported at 11:27 (5/6-2021) exactly when multiplus went into float.

It is not a one-time thing. It happens everytime absorption changes to float.
1622930087821.png1622930176000.pngI guess discharging to reach float is by design, but could it be done a little slower?

Multiplus-IIbug report
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3 Answers
ddickov avatar image
ddickov answered ·

Hi there just to ask if you have tried saving your settings and updating the firmware MK3-USB required just incase you weren’t sure, updating the firmware may help or not if not I would maybe check the battery bank health also, if in doubt and all else fails I would send it to victron for repair it costs much less in the long run. Hope this helps david

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Magnus Pernemark avatar image Magnus Pernemark commented ·

I haven't updated to the very latest firmware, but the change log does not say anything about absorptuon or float.

This has nothing to do with the battery. The battery does not control victron at all. The battery bms is not connected to victron.

The probabillity of it being a hardware issue is slim to none. All three multiplus switch to float exactly the same time, and start inverting until battery voltage is float value.


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Magnus Pernemark avatar image
Magnus Pernemark answered ·

@Guy Stewart (Victron Community Manager) how do I go about to report a bug? I think I have found an actual bug in the firmware of the multiplus-ii?

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Hi @magpern,

Make sure you are running the latest firmware on all devices, also the latest version of VE.configure, and the latest ESS assistant version is loaded (it will need to be removed and re-added).

If the issue still persists, then please post all those version numbers, and I will ask someone to have a look.

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Magnus Pernemark avatar image Magnus Pernemark Guy Stewart (Victron Community Manager) ♦♦ commented ·
I upgraded to the 485 firmware, and the bug is gone. Now when switching to float, it does not discharge at maximum capacity for a few seconds. It just stops charging! Good!

Case closed

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nuxland avatar image
nuxland answered ·

I still have this 200A discharge from batteries when from absortion to float. Can this be made slower, because in offgrid you do not have grid to dump that load. How it is done in offgrid mode?

I have 3 phase 5000W multiplus 2 with firmware 498 and ESS configured.

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Related Resources

MultiPlus-II Product page 

MultiPlus-II Manual

MultiPlus-II 230V Datasheet 

VE.Bus Error codes

Additional resources still need to be added for this topic