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th3p4rk2 avatar image
th3p4rk2 asked

Multiplus 24v 3000va dc input restart value

I have a multiplus 24v 3000va


It runs off of 4 x 210ah deep cycle AGM


When we are on sites we run the unit on mains power and leave our air conditioner running.


Last week someone tripped over the cable whilst we were out, losing mains power and so when we got home the batteries were completely flat.


Now the multiplus has an inbuilt function to prevent this occurring.


I have the cable and the VE configure 3 software.


I go to the inverter tab and the ‘Dc Input low shut down’ is set to the default value which is 18.60v. (Completely flat battery)


I want to change to 23.80v which should be between 35-40% of my battery capacity because going below 50% damages them and reduces life.


So I change the value to 23.80v. (35-40%)


Now there is also a value ‘dc input low restart’

This means if the inverter shuts off because the batteries drop below 18.6v, the inverter won’t work until they have been charged up again to this value.


The problem is the minimum possible value is 25.80. (Higher than a full 24v battery bank!)


When a 24v battery bank is full (100%) it should read 25.46 so the only way to reset the inverter is to have it plugged into mains charging.


Now this is a great idea in theory, it forces me to charge my batteries up completely if they become exhausted below my desired cutoff value of 23.80v.


The problem is, the low light switch is activated just by switching off the inverter. When you turn it back on, the low battery light becomes activated and the only way to restart the inverter is to plug into mains even though my battery bank is 100% charged. (Reading 24.56v)


Obviously not ideal on a Motorhome which is often 200km from the nearest PowerPoint.


Why can I not set this value below 25.80? I would like the inverter to begin to function again when the batteries are maybe 80% (25v).


Thanks in advance,


Tony

SOC
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6 Answers
Paul B avatar image
Paul B answered ·

you cant do this because of voltage bounce it goes low on load that once the load is remoived the voltage bounces back up.


maybe use a BMV-712 and us the relay on that to open the remote switch.

or setup a assiatant in the multiplus to turn of when SOC gets to a nominated figure

you would have to turn on the internal battery monitor and this only really works if you don't have and other DC draws off the batteries.


here is a link to some assistant setup options

https://www.victronenergy.com/live/assistants:introduction


https://community.victronenergy.com/questions/8933/example-of-using-assistants-partial-off-grid-boat.html


the above maybe of help

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JohnC avatar image
JohnC answered ·

Hi T. This issue seems to also be of concern to the Li people particularly. Maybe we can expect future improvements? Anyhows, some thoughts..

@ 24V, you have a min 2V to play with between min & restart. So do your best to find the right range.

I note you switch off the inverter. Fair enough to dodge the standby load. But when you switch it back on it will want to 'preload' it's caps, etc. So expect a downward spike on batt V when that happens. It can be fast, like a spark, but may influence what you see. (There's a clumsy way to workaround that, just ask if it's an issue).

Any sort of charge at all will soon lift batt very quickly if it's mostly charged, even a single panel.

If you're 'headin bush' though. maybe consider easing your settings before you leave. Given you may need ac to do that, hey.



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th3p4rk2 avatar image th3p4rk2 commented ·

Would installing a ‘victron battery protect’ BP 65 fix this issue? I was hoping not spend more money on another product particularly given the inverter should be capable of doing this already but happy to order one if it will fix the issue.

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th3p4rk2 avatar image
th3p4rk2 answered ·

Right, set back to default settings and will purchase a ‘battery protect’. Not happy that I have wasted $100 on the overpriced USB cable to use a setting that is essentially defective.

Now I have to spend another $70 on a product to do something I should already be able to do. Not impressed really, won’t be recommending the multiplus to others.


Feels like an apple product, buy the bare bones and then buy all the extras to keep the revenue coming in.


There’s no reason why I should not be able to have the unit cut out when the batteries reach 40% and then be able to either automatically restart or manually override when the batteries exceed my desired voltage, without the need to screw the front off and connect my computer to it.





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JohnC avatar image
JohnC answered ·

I can sympathize with you getting 'excited' about this. Please try to understand it's the very nature of Pb batts that causes the issue and can easily show a 2V variation depending on load when the batts are not under charge. It's not an issue confined to Victron kit either.

I considered suggesting a BatteryProtect, but I didn't think it would help you muchly. You don't want to spend more, and I appreciate that too. An open budget would suggest a BMV, GX box, www, portal access, and email warnings. Nice, but I'm not suggesting that either.

In the washup, bigger batts may be the only real 'cure' for this.

But for now, you have kit that can at least be adjusted, and there will be an optimum point that may come close to suiting you. Have a go trying to find it.. good luck too.



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Michael Riley avatar image
Michael Riley answered ·

I have a similar issue and live on a sail boat. Victron 24v/2 x 200 AH LIPO connected to a 24/5000 MultiPlus (+ Battery Protect x2, Venus etc.). The 'DC minimum restart' value is the issue. Updated to lastest VE.configure (90.04.220) running through CrossOver on a MACBOOK Pro via Victron Remote so do not need to unscrew the front panel. There is 'plenty' of energy left in the LiPO bank at 26.35V which is the 'minimum' value able to be set in VE Configure. Why? I understand that it should not be 'easy' to simply put in any value but as I understand it from Victron own doco/info the damage to this battery does not occur until cell voltage at 2.8 (22.4 V) and I am happy to run regularly down to 3.16 (25.3V) so why cannot the DC restart be say... 3.16v/cell (25.32 V). This information is available from the battery (Smart) or total from Lynx or Venus on my system. The MultiPlus appears to need to get into bed with the rest of the smart sibling devices and operate as part of the Victron team. It should be a simple enough matter to change the minimum value to '<read XX> from your minimum pre-alarm value set on the same VE.Configure page.

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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Hi @Michael Riley

I don't really understand what you are writing, but...what firmware are you running on the inverter?

older firmware has some limitations on delta between shut-down and restart voltage, but shouldn't be an issue with LiFePO4 batteries...what shutdown and restart voltage are you using now?

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Michael Riley avatar image Michael Riley Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

@Daniël Boekel (Victron Energy Staff) Perhaps it is my poor english. See attached (2 images) s/w for multi is 2614430 and the correct term is 'DC input low restart'; showing 26.35V. When I try to set lower limit it gives and error and states that minimum value is 26.35. Trust this assists.

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multi-24-5000-sw-version.png (265.7 KiB)
multi-dc-input-low-restart.png (133.9 KiB)
Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ Michael Riley commented ·

Hi @Michael Riley

yes the restart-value moves with the shutdown value.

when you upgrade the firmware of the Multi, and use the latest version of VE.Config (or VictronConnect) you should be able to have these values closer together.

https://docs.victronenergy.com/victronconnect-vebus.html#firmware-updates

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Michael Riley avatar image
Michael Riley answered ·

@Th3p4rk2. Sorry if your post got a bit hijacked there by a 24/5000 lithium issue on DC restart value for Multi. My apologies. Hope you are progressing your issue satisfactorily.

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