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Does Dynamic cut-off make sense for Lithium systems?

Dynamic cut-off is an option only available on systems running as ESS, i.e. the ESS assistant has been installed and configured on the inverter device, and there is a GX gateway present on the system.

AFAIK, dynamic cut-off exists so as we can set a lower cut-off voltage for when there is a large current coming from the battery, since the battery has not actually been discharged, but all that's happening is extra voltage drop due to internal resistance and such, i.e. when the load is lifted, the voltage wire rise considerably.

So, I guess dynamic cut-off makes perfect sense for lead batteries, where -for example- you could safely pull a 12V lead down to 10V when there is a 2C load on it.

However, in my opinion, dynamic cut-off doesn't make any sense for Lithium batteries. Why? Because Lithium batteries have a build-in BMS that will block discharging when the battery's minimum threshold (or a cell's) is reached. This will definitely happen when there is a hard load on the battery. So, it doesn't make any sense to adjust dynamic cut-off for a lithium battery at a lower value than the battery's BMS minimum voltage setting. That said, it doesn't make any sense to enter a higher value, either.

So, what's the point of dynamic cut-off for Lithium batteries? Please elaborate.

thanar asked
thanar commented ·

3 Answers

Why is MPPT charge voltage 30V in a 24V ESS system?

I have 2 100/30 Smartsolar MPPTs integrates with a Quattro 5000 into an ESS, running on 24V lithium batteries.

I understand that with ESS the inverter takes control of the charging profile from the MPPTs.

However, I was looking under “Networked Operation” section of my MPPTs and noticed the following screenshot

Why/how is charge voltage 30V?!?

Nothing anywhere is set to that voltage

Not the MPPTs locally

Not the bmv’s battery settings

Not the inverter veconfig settings

So I’m confused as to where this is coming from and how/why.

I doesn’t appear to be causing any issues as charging appear normal, but...

Should I be concerned about this?

Thanks in advance


geomz asked
thanar commented ·

1 Answer

Multiplus voltage differences


I'm reading in this community for a while now and get many help/hints to setup my storage system. But now I have a questions and didn't find this kind of topic in this community before.

I have just changed my installation from a Multiplus II 3000 GX to a Multiplus II 5000 GX. It is an grid connected ESS System with 5* Pylontech US3000C. Everything works well so far.

But there is one issue that bothers me a bit. The Multiplus have a voltage difference of 0,30 V between the Multiplus itself and monitored in VRM Portal "VE.Bus DC Voltage And Current" and the real voltage. The BMS from Pylontec and all the other voltages monitored and shown by the GX device shows 0,3 higher voltages. I also messured everything with a multimeter and the higher voltages are correct. If I messure also directly with my multimeter on the DC terminal of the Multiplus directly (without calble and inverter/charger are off) the voltage ist 0,3 Volt higher than monitored by the Multiplus.

As the Multiplus uses this messured voltage to steer everything, the real voltage is everytime higher. For example I need to set charge voltage limit to 50,0 Volt to get 50,3 Volt in reality. Also if I don't limit the charge voltage, the real charge limit will be not 52,4, but 52,7.

It may be that these deviations are normal and are the usual variations of measurements. In this case it is ok. But as I still have the possibility to return the Multiplus and to get a new one, I want to be sure. My former Multiplus II 3000 had a deviation of 0,1V.

What are you experiences and values? Are your messured DC voltage by Multiplus the same like messured from BMS/Multimeter/reality or do you have also these kind of deviations?

Many thanks in advance.

Bye Dirk

dirk-s asked
anieuwstadt answered ·

6 Answers

BMS-712 flashing “charging” and — for SOC

Yesterday I disconnected from shore power (30amp) and immediately lost power. Multiplus II inverter was in an “unknown” state and BMS had no SOC and was flashing “charging”. I can run off shore power but as soon as I disconnect I lose power. Checked voltage in both GC3 270ah batteries and they are 13.43. MPPT, Linx Distributor, and inverter say they are in absorption mode at 14.20 volts. Help? @bpohli

bpohli asked
Mike Dorsett answered ·

1 Answer

Voltage difference Multiplus2, MPPT100/20 and BMS without load

Hello, is there a way to calibrate measured volltage for Multiplus2 and MPPT100/20

Measured with multimeter without any load on battery I got the same voltage like the BMS.




gesiima asked

0 Answers

Clarity on amp usage when comparing 12 V bulb via MPPT v's 240 V bulb via inverter

Sorry if this question is somewhat amateur, but I'm rather new to this ....

In the following scenario I have:
- one 5 W / 240 V LED bulb connected to a 240 V inverter (5 / 240 = 0.021 A)
- one 5 W / 12 V LED bulb connected directly to the MPPT (5 / 12 = 0.42 A)

Do you agree my calculations are correct; does this effectively mean the 12 V solution places a greater load on the battery and will consequently deplete the battery more quickly than its 240 V counterpart?

Best regards

bazil asked
Michelle Konzack commented ·

2 Answers

High Lines Voltage with Isolation transformer and Multiplus

System Description on sailboat:

  • Isolation Transformer 3600VA
  • Multiplus 24/300/70
  • Shore power 120V (nominal)
  • System Power 220V (nominal)

The only load on the transformer is the Multiplus.

We currently are in a location where the lines voltage is running right at the very top of the USA grid specification (127V). Coming out of the transformer we have 272V. This is over the maximum high voltage cutoff for the Multiplus (270V), so it stays in "Inverting" mode.

My understanding is that applying a load on the transformer output will drop the voltage to something like (127*2*1.05)= 267V which is still high, but would allow the Multiplus to make its line connection and charge our batteries and pass through AC power. Unfortunately, without extensive rewiring there is no way to apply a non-voltage sensitive load to the transformer.

Is there any other way to make this connection work? I have reviewed previous posts on similar issues, and it seems the answer is "no," but maybe something specific to my situation is possible? It frustrating to have to run the generator while shore power is available, but just 1 or 2 Volts too high (but still within local grid power specification!)

I appreciate that the usual issue with marina shore power is LOW voltage and this might be the reason for the 5% voltage boost out of the isolation transformer, but this is not the first time we have had this issue and the high voltage problem has been much more often the issue for us.

billknny asked
pwfarnell answered ·

2 Answers

fluctuating AC output voltage

I added a new widget to my VRM page and noticed the voltage on the multiplus is fluctuating quite a bit, I have checked all the wiring and it appears fine.
Anyone have any suggestions what could be going on here ?
Setup is 48v 930ah (C5) traction battery
Victron 48/8000/110
Fronius 8.2-1
250/100MPPT ve can
Smartshunt 500
Cerbo GX
Off grid


scraggs asked
scraggs commented ·

1 Answer

Solution for a large voltage drop AC In for Multiplus 12/3000/120


I have installed a Multiplus 12/3000/120 on a sailing yacht and I notice a large voltage drop on the AC In side.

- All cables from shore plug up to AC In are 2.5mm2
- Cable distances are from shore plug to yacht = 15m / from yacht in to Multiplus = 5m
- I have one RCD between shore and the AC In (also one after AC Out)
- Voltage from shore without load is 218V
- Voltage AC In drops from 218V to 205-210V when charging at 90Amps 12V
- I notice a quite large negative power reading on the AC Out (up to -100W)
- When decreasing the charger output to <30 Amps 12V the AC In voltage rises to around 216V and the AC Out power reading rises to around -10W
- When not connected to shore, the inverter gives a normal 230V to the AC Out

You can find a screenshot below of the Victron Connect which shows all figures.

Is this issue purely depending on the Marina I'm berthing (old cabling, trafo issues...) or are there any internal/installation aspects I might be looking into?
Is the AC Out negative reading a side effect of the voltage drop on the AC In?




basile-cools asked

0 Answers

Multiplus II charger voltage inaccurate

I just installed a MP2 in my RV. The charger is set up according to the setting recommended by the battery manufacture: Absorption 14.4V and Float of 13.8. Most of the time the MP shows appropriate DC voltage in this range but only produces around 13.1 to 13.5 V verified by a multi meter. This low voltage allows the battery to discharge even while plugged into shore power. If I change a setting by even .01 V on the MP, it quickly displaces it current produced voltage and then jumps back up the appropriate charge voltage and charges the battery. This however only stays this way for a short time and then the voltage being produced drops back down in the 13.2-13.5 range while the display still shows a voltage in the 13.9-14.2 range. I have updated the firmware, but that did not seem to make a difference. Both picture were taken at the same time. Any suggestions?



pilotchuckles asked
sdmccart answered ·

4 Answers

Help with Isolation Transformer and Quattro Voltages

We are in a marina in the Dominican Republic that provides a very clean but high voltage of 135.6 volts at the pedestals. Obviously, this is higher than spec but they say they do it so that everyone on the docks has the voltage needed for their vessels.

The problem is that our Victron Isolation Transformers take that 135.6 voltages and add an additional 5% per its specifications. This new voltage of about 142 volts is obviously quite high and exceeds the Quattro maximum input voltage by two volts - having the result that it won't then start the charge our batteries.

Looking for solutions here.

atarlecky asked
pwfarnell commented ·

3 Answers

Lets try a second time. Whats the Voltage accuracy of Victron products?


It seems questions often arise on this forum about the Voltage accuracy of Victron units and variances between voltages measured vs what's displayed on the app.

SINCE there is zero information about the accuracy of the Voltage meters in Victron products, it makes sense that some questions be answered on this community page, which is there to help Victron users!

Elvis, Kevgermany - You didn't like my replies to you and those who commented on my previous question, before you got offended and blocked my account - Maybe go back and read the "so called assistance" that was provided and understand I'm not some completely useless person "like you all suggested" and as a result I gave blunt responses in return showing my appreciation for the RUDE/little assistance and belittlement I received for you.

I fielt my replies were warranted, considering the attitude and belittlement I got from a number of you. All because I don't have access to a "very expensive" FLUKE DMM!

• My questions of how to confirm accuracy of a DMM, fell on deaf ears.

• My questions of the products number/model number of the voltage meters in Victron products, so I could answer the above question, fell on deaf ears.

• My question about how you can all guarantee the accuracy of Victron voltage meters when you all told me that unless a DMM is calibrated every year its not guarantee accurate, so I clearly asked how and why the Victron units can/are still considered accurate when they aren't calibrated every year? This fell on deaf ears.

• How can Victron products be guaranteed to have accurate Voltage if they're not regularly calibrated?

• Exactly what accuracy percentage does a Digital Multimeter need to have to be considered accurate enought to perform testing?

^^^These are SIMPLE QUESTIONS that will help MANY future Victron users and save them from having to create posts/questions when it's already been answered (the whole point of this community according to community guidelines)...

Let's watch you delete my account again for trying a second time to ask BASIC questions all because you assume I'll abuse you - The difference is that if you actually provide clear answers and don't provide VAGUE information, or try to waste my time asking for irrelevant information and/or imply I'm useless, then my replies will be respectful.

If you waste my time again, be rude or vague you will get blunt/rude replies in return - Not sure why you're surprised by this.

* I've been told I'm blunt due to my Autism, but that won't change the sour people who have been offended at my responses to them after they wasted my time, or implied I am useless (which in itself) is very insulting to me!

^^^ You offended me and/or wasted my time first before I gave it in return...

not-a-hard-question-to-answer asked
Charles Gibbs edited ·

3 Answers

Volt drop when connecting mppt 75/15 to solar panel.

I have recently brought a solar kit. With a victon 175w panel and a victron mppt 75/15. Once installing it has worked for around 5 days. The last couple of days it produced nothing. Even though good sunny days

When looking into today I found the solar panel at 19v when testing disconnected from mppt. When introducing mppt it drops to around 13v. This causes the batteries not to charge.

Has the mppt failed?


joshuaafc1 asked
klim8skeptic commented ·

4 Answers

(3) 12 volt 100amp travel trailer lead battery and batteryprotect

I have (3) 12 volt 100ah lead acid deep cycle batteries in parallel for a total of 300ah that are charged thru the travel trailer WFCO power converter / charger whenever plugged in to 120volt outlet. I'm Looking to be able to automatically have the12 volt load disconnect from the batteries when they hit 50% to prevent damage then come back on when i recharge thru the WFCO.

1. can i use the batteryprotect? Got a wiring diagram?

2. While I have a total 300amps, I'll never use that much amperage and estimate at the most I would use 60 to 100Amp. What size would be necessary?


inspector-h asked
Michelle Konzack answered ·

1 Answer

PWM LCD USB 12V 5A : 1.1v voltage at PV terminals while PV disconnected


Equipment : PWM LCD USB 12V 5A + PV victron 30 wc + battery superpack 12.8v lithium.

With the PV (30 wc) disconnected, there is always 1.1V displayed by the "PV voltage display" and by voltmeter measurement of the +/- PV terminals of the controller. The battery is 100% charged. Is this normal? Is this residual voltage coming from the battery?

pgu asked

0 Answers

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