MultiPlus Compact and MPPT non agreeing on Bulk/Float

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amidships asked Jul 28, '22

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 Controllers SmartShunt multiplus ve.bus VE.Smart Network EasyPlus

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Answer 1 · 2022-07-28T05:59:40Z

Alexandra answered · Jul 28, 2022 at 05:59 AM

@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 commented · Jul 28, 2022 at 07:01 AM

@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 ♦ amidships commented · Jul 28, 2022 at 07:06 AM

@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 Alexandra ♦ commented · Jul 28, 2022 at 07:20 AM

@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 ♦ amidships commented · Jul 28, 2022 at 07:39 AM

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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amidships Alexandra ♦ commented · Jul 28, 2022 at 07:56 AM

1 x 200Ah LifeP04

I feel have configured both MPPT and EasyPlus Compact in the same way in terms of Absorption Voltage (14.20V) and Float Voltage (13.50V)

But if there are no other possible explanations, I will recheck them both.

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Alexandra ♦ amidships commented · Jul 28, 2022 at 07:45 AM

@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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amidships Alexandra ♦ commented · Jul 28, 2022 at 08:02 AM

Thanks @Alexandra I will compare the re-bulk offsets values as well between the MPPT and EasyPlus. Now I don't have access to them but maybe I will post time here at later point.

You wrote "The mppt will also go into bulk to supply AC loads.", that do you mean with that? AC loads are only provided by my Inverter/Charger EasyPlus Compact.

Right now there are no AC loads and the Inverter Charger is in AES mode

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Alexandra ♦ amidships commented · Jul 28, 2022 at 08:36 AM

Ah the AES explains alot then. I never saw my system go out of float in that mode.

And your solar should contribute to loads, that is the point of a solar system.

I have a 12/1600 with 75/15 added a 100/50 and they both contribute tAc loads when I use those devices.

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amidships Alexandra ♦ commented · Jul 28, 2022 at 08:53 AM

I will put the EasyPlus in charger-only mode, verify the charge parameters on EasyPlus and MPPT and verify if the Bulk/Float discrepancy is resolved

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Answer 2 · 2022-07-28T11:58:07Z

JohnC answered · Jul 28, 2022 at 11:58 AM

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 commented · Mar 19, 2023 at 01:55 PM

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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