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amidships avatar image
amidships asked

MultiPlus Compact and MPPT non agreeing on Bulk/Float

Hello,

I have a 200Ah LiFeP04 battery being charged by both MultiPlus Compact 12/1600/70-16 and by SmartSolar MPPT 75/15

When the system is attached to the mains, I have seen situations (i.e. early morning) when the MPPT start charging in Bulk mode while the Multiplus is in Float mode. why is this happening?

The MultiPlus is connected to the same VE.Smart network as the MPPT using the VE.Bus SmartDongle. In the system, we also have a SmartShunt 500a


VE.Smart Network details:

  • MultiPlus (SmartDongle): transmits battery voltage and battery temperature
  • SmartShunt: transmits battery voltage and battery current
  • MPPT: reads battery voltage and current from SmartShunt and BatteryTemperature from SmartDongle


Any suggestion? Thanks

MPPT ControllersSmartShuntmultiplus ve.busVE.Smart NetworkEasyPlus
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2 Answers
Alexandra avatar image
Alexandra answered ·

@amidships

Unless I missed something the VE Bus smart dongle is not compatible with the VE smart network.

Or at least is not yet supported.

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amidships avatar image amidships commented ·
@Alexandra , that it's weird since it's working perfectly fine in the Victron Connect app. Anyways, how is this relevant to my problem? In the Victron App, both the MPPT and the Multiplus are showing the correct (and the same) battery voltage, the problem is that the Mutliplus is charging in float and the MPPT is charging in bulk
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Alexandra avatar image Alexandra ♦ amidships commented ·

@amidships

What is means by not compatible it does not share or receive the information and use it.

And the mppts will be in bulk if they are supplying loads. They may not necessarily be charging the batteries.

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amidships avatar image amidships Alexandra ♦ commented ·


@Alexandra The are no loads connected to the loads terminal of the MPPT so all the output is going to the battery

EasyPlus Compact is connected to the mains and charges the battery in float mode.

MPPT is charging in bulk mode from the sun

The voltage of the battery is rising (because of the MPPT Bulk) instead of staying around 13.50V (as the EasyPlus is trying with Float)

This is what I don't understand.

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Alexandra avatar image Alexandra ♦ amidships commented ·

What batteries do you have?

Are you wanting your batteries to stay in float? The mppt will rebulk if the rebulk offset value was reached.

The multiplus may have a different setting.

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Alexandra avatar image Alexandra ♦ amidships commented ·

@amidships

The mppt will also go into bulk to supply AC loads.

The rebulk offset on the mppt may have been reached.

See here.

Re-bulk voltage offset Sets the re-bulk voltage offset. This offset voltage is used to determine when the float stage stops and the bulk stage starts again, i.e. the charge cycle resets and starts at first charge stage again. An example: If the re-bulk offset is set at 0.1V and the float voltage at 13.8V, the charge cycle will restart once the battery voltage drops below 13.7V (13.8 minus 0.1) for one minute.

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JohnC avatar image
JohnC answered ·

Hi @amidships

I don't believe the Multi will sync charge states with a mppt. Because it's not designed to. You really have to take a step back and think about this, in particular what you want to achieve.

This is hard to explain, but maybe an example.. Eg. I use a genset to boost solar, but only on bad days. I set the Multi to charge Absorb at 0.1V less (in 48V) than the mppt, and this ensures the mppt always has priority (the Multi backs off when Abs reached, while the mppt might never actually see Abs). And the batts get charged regardless.

And if I had 24hr grid, I might set the Multi to a flat Float V deliberately, so the batts only get the one Abs cycle per day (from the mppt). And/or have the Multi charge auto-turned off if SOC is above a set value (to leave room in the batts for the solar). Plenty options, but a GX device makes this sort of thing easier.

And I wouldn't care if the Charge states never matched, because I don't really want them to.

Think about it..

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amidships avatar image amidships commented ·
Hi @JohnC ! Thanks for you input. I guess I lack on the basic knowledge about what strategy would be best when the same battery system is connected at the same time to off shore power and solar (basically when an RV is attached to mains)

Do you have a useful link to documents that explain this?

Would Cerbo GX help me with this scenario and how?

Thanks!

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Related Resources

MPPT Product Page

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MPPT 150/60 up to 250/70 Manual

SmartShunt Product Page

SmartShunt Installation Manual

SmartShunt Quick Installation Guide

SmartShunt Datasheet

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Additional resources still need to be added for this topic

VE.Smart Networking Manual