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MultiPlus - DC input low restart value - Cant set lower than 21.8?

VEConfig wont allow me to adjust the value of "DC input low restart" to below 21.8.

I can properly set values of "DC input low shut-down" & "DC input low pre-alarm" to 19V, which is what my lithium battery is rated for, but with the "DC input low restart" value fixed at 21.8 or above, this prohibits me from turning on the inverter unless the battery is 50% SOC or above.

Anything I'm missing here?

Thanks

MultiPlus Quattro Inverter ChargerVEConfigure 3
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4 Answers
wkirby avatar image
wkirby answered ·

For most battery types that are expected to be used this is a very low value. It is most unusual to ever venture to this low end of this setting.

I might be wrong, but It seems like you are using 3.7V cells in a 6S configuration. Most of the 24V "Power Wall" people run these cells 7S to overcome these compatability issues.

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I am using a Tesla model S 24V 250ah battery. 19V is stated to be around 20% SOC, 25V is 100% SOC.

Ideally I would have all 3 of these values (shut down, restart, pre-alarm) set around 19V, when I took the picture I was trying to see if I could get the "low restart" value to drop if I dropped the other values..

Could we please implement a workaround for this? I need absolutely need to be able to turn on the inverter at 19.5V.

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brock answered ·

I am having the same problem. I have the same battery but a multi plus inverter. How do we contact in the United States for technical support? Please Let me know if you find a way around this.

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rockatron avatar image
rockatron answered ·

Heya Brock, thank you for chiming in. I agree that the "DC low input restart" should be customizable below 21.8V. If Victron did not want the inverter being run at values below 21.8V, then it should clearly be imposing this minimum voltage on the "DC low input shut down" parameter, not the "restart" parameter. Also I agree with you that there is a software problem considering that the "restart value" should not be affecting anything until the voltage has first dropped below the "shut down" value.


Ideally we would customize and add a 250aH 3.2V cell in series to our model S battery to get the overall voltage higher, but this is not preferred. Option #2 is to add a second battery in parallel so that the higher capacity makes this far less of a daily problem.


I think we are kind of SOL unless Victron makes this "restart" parameter more customizable. Technical support is only granted through your "Victron Dealer", which for me is the internet store, thus, no help.

Thanks for your reply

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Wow wish I would have looked into the tech support before I bought this inverter. I never would have guessed we can get no support without going to a dealer. Tom Morton (Mortons on the move) (solar-phase-3-the-inverter) the same setup as us and I wonder if he is having the same problem. I will be leaving some reviews around. this should be known to new potential buyers. Victrons website says 19-33 Vdc Nothing about voltage must over 21.8v to turn on inverter.

Mostly all inverters have a minium restart voltage level which is higher than switch off Voltage, so i am woundering that you are woundering. So if you don't know bevore and buy online without asking a prof dealer before don't be angry on Victron. Its not the fault of victron. You have to inform befor if you decide to take a reused batterie which is definitly a "non" Standard System and which is not build for such systems. The need of changing software has nothing to do with simple support.

I am totally fine with the (restart voltage limitations). The way this normally works is if you hit the (low voltage disconnect voltage) the inverter shuts down. Then as you charge your battery the (restart voltage) must be reached before it will restart. This is to keep from short cycling your system. All great and fine. But this is not what is happening. What is happening is if I turn the inverter on at 24v and (Leave it on) I can drain the battery down to 20v with no problem. (All within the 33v-19v range). Now if I turn it on at 24v and drain it down to 21.8 turn it off and try to turn it back on it will not allow me to. I guess what I am trying to say is if this is how it is suppose to work they should not call it a min restart voltage. It should be called min start voltage. Restart voltage means you have hit the disconnect voltage. And as far as support I would just like to talk to someone from victron who can explain to me why it is set up this way.

You missed thats voltage after starting and restarting is the exaktly same initial situation. So in every normal situation it would really sensless that a startlevel is lower than restart level, because the reason of it is the same. As already written the Problem is simple your special battery that has a non general voltage range for a 24V system. Tesla batterys are nice for hobbists but the problems with it in 24V Systems are well known.

Hi Brock,

One of the reasons why Victron encourages the dealership support model and provides training to dealers is so when users wish to buy a big piece of equipment like an inverter the dealer can ask the right questions to make sure the equipment is suitable for the application.

There are always limits with this power system equipment and they multiply when multiple variable elements are combined.

We really try to document and make clear the limitations and I always try to improve things so ends users and dealers get the right information before the sale. Victron would prefer a customer get the right thing, than be unhappy with their Victron.

We are often recommended in the home brew and alternative market because of the community support, relatively tolerant attitude to experimental systems and wide band tolerance to things like voltages.

Please before you get too upset at Victron, also do research about other brands and see you might have the same issues there also.

brock avatar image brock Guy Stewart (Victron Community Manager) ♦♦ ·

I am not upset with victron. If I can't get this resolved it will get returned no big deal. As for research I am calling Magnum inverters tech support line (really handy thing for customers) To see if the DC low restart voltage is imposed before the DC low disconnect has been reached. Maybe I am wrong. And I am not saying I know more than victron. I just would like to speak to someone with the knowledge to explain to me technical reason for this.

The technical reason is 19V is the absolute minimum for operation. Sorry to say that these (and nearly every other inverter) was fundamentally designed for a lead acid 6, 12 or 24 x 2V cell.

A 19V lead acid bank with no load on a 24V system is dead flat, no usable power.

When the inverter first starts it will have a start up load and draw down that voltage below the minimum, so there needs to be sufficient head room to allow for that to occur without power cycling. eg 19V on, 18.9V off, 19V on, 18.9V off, etc. 21V allows enough to be sure the inverter can safely start up.

It would be good to hear from Magnum (and others) themselves but their manual specifies their Low Battery Cut In (LBCI) voltage as 25V on page 51, and this is not adjustable page 58.

https://www.wholesalesolar.com/cms/magnum-energy-ms4048-inverter-installation-manual-791197892.2940243.pdf


wkirby avatar image
wkirby answered ·

Like Peter said, most inverters (Mastervolt, Schneider, Magnasine, MPP etc.) have this limitation, it is a physical hardware limitation of power electronics. Startup involves higher inrush currents and so the startup Voltage must be higher than a running Voltage. Also, startup means startup from any state, whether that's from an automatic undervoltage (<19V) event or by the user switching it on. The machine needs to start up either way.

This is the scenariio for my MultiPlus 24/3000/70 - 230V version.

If I set DC Low Shutdown to 19V, then my lowest DC Low Restart minimum is 21V.
If I set my DC Low Shutdown to 18.6V, then my lowest DC Low Restart minimum is now 20.6V

If your limits are different then you can see that the lower limits are dictated by the capabilities of the hardware, they are there for a reason and are not by some whimsical frivolity.

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