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ctsit avatar image
ctsit asked

Problem with Victron Mutliplus 800va Compact

Dear Community,

I recently bought:

1. Victron Mutliplus 800va Compact (plastic and not the big metal one)

2. Redondo Mini 12v 100ah battery

3. Victron SmartShunt 500a/50mv

4. The necessary mega fuse for the connection.

The purpose of the mutliplus is to operate as a UPS and support two storage devices and other smaller electronics. The storage devices are also supported by a APC ups that is connected to the Victron.

The Victron inverter is connected to grid power. (230v in Greece)

The problem I phase is the following:

Although the battery shows 100 charged (which is a per the manual from redondo which states that if the voltage is higher than 13.33v the battery is considered as 100% charged) when I activate the charge function on multiplus, the inverter tries to Bulk charge the battery and ends up connecting and disconnecting to the grip. When it changes to Absorption or Float then everything works ok without any connecting or disconnecting. It is only when it tries to Bulk charge a full battery that the problem occurs.

If the connecting disconnecting happens multiple times in a row I also receive a warning for Battery voltage ripple.

screenshot-20231116-142401.jpg

When I disable charging everything works as normal.

I am attaching screenshots of the parameterization of the inverter:

2-screenshot-20231116-142607.jpg

3-screenshot-20231116-142638.jpg

4-screenshot-20231116-142710.jpg

6-screenshot-20231116-142739.jpg

7-screenshot-20231116-142747.jpg

8-screenshot-20231116-142759.jpg

Below a screenshot from the smartshunt while not charging

smartshunt-while-not-charging.jpg

Has anybody faced similar issue and are the settings for the battery ok?

Currently I have disabled charging so no on/off connecting to grid.

Thank you all in advance.


multiple inverters
1-screenshot-20231116-142501.jpg (260.8 KiB)
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4-screenshot-20231116-142710.jpg (388.6 KiB)
6-screenshot-20231116-142739.jpg (340.1 KiB)
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8-screenshot-20231116-142759.jpg (268.6 KiB)
smartshunt-while-not-charging.jpg (237.6 KiB)
screenshot-20231116-142401.jpg (169.5 KiB)
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4 Answers
kevgermany avatar image
kevgermany answered ·

I'm not sure what the battery makers recommend, it will be in the manual. But the charge settings (absorption/float) in the inverter look to be the problem, as in too high. This causes the BMS to disconnect the battery for safety.

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ctsit avatar image ctsit commented ·

@kevgermany

Here are the recommendations from the manual from Redodo

recommendation-from-supplier.jpg

If you see the absorption suggestion is 14.4v/ 14.6v

and by the way I can't set the voltage for Bulk charge.


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recommendation-from-supplier.jpg (2.9 MiB)
Alexandra avatar image Alexandra ♦ ctsit commented ·

Absorption and bulk are the same value.

The difference between those two stages of charging is the amperage drawn by the battery.

Your absorption time is too long. Set 1 hour there.


charge efficiency 97%. SOC when bulk finished also 97%. No battery is 100% efficient.

How big are your inverter to battery cables? Are your connections tight? The fuse will be 800\12v X 1.25 so about 85A. Or a fuse close to that.although your cable needs to be rated to carry those amps as well, or the fuse won't blow.

Set the charge voltage or absorption to 14.4v (or even lower by0.2v) I agree with @kevgermany the battery is probably the one causing the DC ripple by disconnecting.

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klim8skeptic avatar image klim8skeptic ♦ ctsit commented ·
@ctsit Also change your DC input low-shutdown, DC input low restart, and DC input low pre-alarm voltages to match the values in your batt manual.
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ctsit avatar image
ctsit answered ·

@Alexandra @kevgermany

I did all the changes but still the same issue, it connects and disconnects from the grid rapidly.

And again I get a battery voltage ripple.

I had to disable the charging again to avoid the repeating connect and disconnect.

Obviously I am doing something wrong but I cant get my head around to what.

Any other ideas?

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Alexandra avatar image Alexandra ♦ commented ·

@ctsit

How have you wired them up? Are you using 35mm² cable?

1. You could start with lower charge amps.

2. Try with dynamic current limit off.

Have you ever (when inverting) tried an overload test?

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djsmiley avatar image djsmiley commented ·
Voltage ripple is an wiring issue. For a 800VA I would recommend 16mm2 if its a short wire run (<1m) or 25mm2 if its 1-3m.

Also, use proper fuses, especially the cheap breakers can cause similar issues.

How is it all connected?


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ctsit avatar image
ctsit answered ·

I am using 25mm2 cables, as per the specification.

Everything is tide down very well both on the inverter side, battery side but also the shunt and fuse (will try check again though)

As a fuse I use the victron 60amp since I don't think I will go over that.

Lastly the over all length of the cable is about 2m for each positive and negative and is including the segment between battery and fuse and battery and shunt.

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ctsit avatar image
ctsit answered ·

Furthermore, I noticed that as long as the charge voltage remain under 13.98v then the system charging works normally.

As soon as it goes over 13.99v then cuts off grid power and I get the Voltage Ripple message, more specifically I reduced the charge current to 1amp and noticed that the system didn't cut off grid until the charge voltage was more than 13.98v.

After a while the charge changed to absorption and now that I change the current back to 20amp there is no disconnect from grid due to the absorption state.

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djsmiley avatar image djsmiley commented ·

How is the cell balance? If the cells are not in balance, 14V might already trip the BMS.

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ctsit avatar image ctsit commented ·

I don't think I have access to cell balance information. I am using the redodo Mini battery 12.8v 100ah which does not provide any insight to cell balance.

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k-k avatar image k-k commented ·

Is redodo demanding to charge the batterie before you connect/use it at an inverter?

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k-k avatar image k-k commented ·

If you have a voltage above 13,33V at batteriepoles (after 3-8 hours DISconnected =zero load | zero charge) measured, lets assume one cell is still a bit low, maybe you try the lowest possible charge e.g. 1A for a couple of hours with 13,85V.

If you charge with the MultiPlus (not with an external charger)

is the incoming 230V for the MP stable? Have you tried to switch off "the extras" like wide frequency acceptance or ups function just to give the batterie some more time to charge without demanding loads from the MP in a conservative way?

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ctsit avatar image ctsit commented ·

Hi @k_k before I connected any load to the mutli I did exactly that.

I had the multi connected to the battery without any load. In fact the multi was set to charge mode only. I had this for a day or two. Once the voltage of the battery reached a pick then it started to connecting and disconnecting from grid.

In my previous posts I was saying that the mutli had a stable connection to the grid once it was on Absorption. Actually this is not true it started disconnecting again once I activated charging again and despite the fact that it went straight to absorption.

I have the setup as my primary UPS for the storage equipment in my office so I am deeply concerned with this behavior.

Yes the incoming voltage is stable.

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k-k avatar image k-k ctsit commented ·
Storage equipment means exactly what? Memory cluster (lots of pc/diskarrays||psu->phaseshift) or refrigerators (cooling||impedance->ampere). Especially fridges may have great surges. It is not impossible to have delta's like 8 to 12 -> so 60Watt continous power -> 720Watt peak/starting power. (Stonebreakers delta up to 16).

Office -> 1 or 2 laserprinter attached to 230V line in stby mode can "kill" the ups at hard line-reconnect.

Are all devices in the office on the "red ups-line"? - if so unplug them all and replug them one after one. Prior to that plug in a incandescent light bulb (DE: Glühlampe) and watch for flicker and hum deviation while connecting the rest. Replug means device-power-switch is "on" while plugging it in the outlet. You could have a defective PFC-filter or line-filter.

So you can find out whether starting all together put a too high demand on power-assist.

One thing i don't understand is the picture passthru - the frequency should be the same for in & out because in/out must be bridged. Voltage x current doesn't match the power, wether for in nor for out. Are in and out reversed?


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ctsit avatar image ctsit k-k commented ·

Hi @k_k

I use the setup for back up of:

1. 2 synologies storages with a total of 9 disks. Their over all pick power demand is less than 300w.

2. A small 8 switch no POE so its power demand is less than 30w

The most power hungry is

3. A gaming computer with 600w pick power demand.

In reality I have never seen a total of more than 650w pick demand even with everything running at pick.

However the problem with the multiplus going on and off grid happens without any load attached to it. I mean that the power out power strip wasn't even connected.

I believe that I am messing something with the charging of the battery. But can't figure out what.

When the charge power is 1amp nothing trips. When I increase it to 10amps it starts doing its think again.

The overall purpose of the installation is for me to learn so I can install a bigger 10kwh system (with different equipment of course). I am obviously failing.


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k-k avatar image k-k ctsit commented ·
Can you measure amperes when you start the "ups-line" at once while all devices are connected and powerswitches are all on. This means measuring the inrush current, not the more or less static load after all device have started and doing full workload.

If possible put all 230V devices on a distribution "spider" to one 230V plug and use this for the MP and test that plug also again your houshold wall outlet wether it trips the fuse.

Maybe as last resort: lend another 12V 100Ah (or more!) batterie to test the MP. As i remember 100Ah is the minimum request for 12/800VA MP.

lf the MP is then not "spinning around" you should try another brand of LiFePO4.






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k-k avatar image k-k k-k commented ·
Edit: you could buy another LFP same brand/type and wire it parallel (cable diameter 16/25mm" or same as first batt). You have 12Vdc so you're lucky -> plus on plus, minus on minus direct at thr batteries.


I read in my manual for 12/800 -> 100 to 400Ah and ripple-warning just means too small capacity also.
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ctsit avatar image ctsit k-k commented ·

@k_k

So today I discharged the battery to about 55% and then charged it up.

While the battery was lower than 97% I was bulk charging with 35amps without any disconnection from the grid.

Once it reached 97% it disconnected once and when connected again changed to absorption and for a while it was ok. At 98% SOC it started disconnecting and connecting again even in absorption. It stopped only when I changed the charge current to 1amp.

I will try to add another battery, with Black Friday coming I believe they have a good offer on Redodo so I will check them out.

If I purchase a second battery, instead of having minus to minus and positive to positive wouldn't it be better to have them connected each to a busbar and then the inverter also connected to the same busbar (one for positive and one for negative)

I know it maybe an overkill but from an optimisation perspective wouldn't it be better.

Thank you for taking the time to help me out with this.

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k-k avatar image k-k ctsit commented ·
Of course, busbars are a good solution. Especially if you plan for the future.
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k-k avatar image k-k k-k commented ·

@ctsit if you use a second batt: disconnect the old batt and put the new batt side by side (thermal). Make a connection minus to minus (small wire e.g. 2,5mm² is ok) use a car headlamp 12V 55W or similar. Make 2 cables with a crimped AMP 6.3mm and a (6 or 8mm) eye-lug. Connect the light bulb, put it in a ceramic coffe mug and connect the "old" plus with the "new" plus via lamp. Why? If there is a difference in SOC's of the batts it will be equalized. Current is limited via lightbulb, so BMS won't cut. Let sit overnight.

After that reconnect both batt with 25mm² of same lenght.

You might read https://community.victronenergy.com/questions/244749/what-can-cause-small-multiplus-to-fault-under-grid.html?childToView=245211#answer-245211

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ctsit avatar image ctsit commented ·

For now and since the battery is toped up, I disabled charging.

I will reenable if the voltage becomes to low. So now it is in Passthrough mode.

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Alexandra avatar image Alexandra ♦ ctsit commented ·
Did you change your SOC when bulk is finished percentage, and the efficiency factor?

If it takes the amps, then starts the ripple at the top, the protections on the battery are kicking in.

So the SOC when bulk is finished let's the inverter know to back off the amps, you need to do this longer before the top.

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ctsit avatar image ctsit Alexandra ♦ commented ·
Yes I changed the SOC after bulk to 97% and the efficiency to 0.97.

However the voltage of the battery after bulk is over 13.33 which is the voltage that redodo considers the battery completely full. For example now I have deactivated the charging function, so it is in Passthrough.

The battery voltage is 13.59v which should mean that the battery is fully charge. This is what the smartshunt shows. however because I made the change the Multiplus shows 98% SOC.

While it was charging in absorption yesterday the smartshunt showed High Voltage warning.

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