Victron Multiplus Compact 2000 without voltage sensing?

[svlamorocha]

Hello experts

I have been up until late last night troubleshooting a Victron Multiplus Compact 2000 that gives a "Low Batt" error. I need some help!

When I opened the units (2 in parallel) was surprised to find that these things do not have terminals to connect voltage sensing wires aka V-sense wires. The owner´s manual talks about them and the install manual shows them but the units do not have them.

(Just to make things absolutely weird, the manual you can see in your web browser by clicking here http://www.victronenergy.com/upload/...2%20-%20EN.pdf has the V-sensing wires but if you download it and open it with Acrobat you do not see them.)

I would expect that a voltage sensing wire would be used in this thing because even when running the things at 200A (measured at the battery; including other loads) the voltage drop between battery and the Multipluses is about 0.55V. (This is consistent with a 18ft cable run of 107 mm2 ) Therefore at 50% SOC the 12v at no load turn into say 11.5V loaded at battery the terminals and 11.0V at the Multipluses...


Now the questions:
- Has anyone been able to make these untis work reliably to their full rated capacity without voltage sensing?
- Is it true that some of these units have voltage sensing terminals and other don´t?

C

[careka]

Hmm, i am just about to by one...

[roetter]

I always thought the voltage sensing is for the charger not for the inverter portion. My Multi Plus 3000 had the voltage sense connections.

[Fuss]

If you don't have enough battery capacity, then these units will drag the voltage down if they themselves are supplying near their full capacity. There are 2 combined so I assume that they are used hard sometimes.
I use my 3000 24v without voltage sensing.
For these 2 units, I would imagine that you would need 1000 ah + of 12v batteries with very fat cables with proper connections to avoid problems.

[svlamorocha]

Originally Posted by Fuss

If you don't have enough battery capacity, then these units will drag the voltage down if they themselves are supplying near their full capacity. There are 2 combined so I assume that they are used hard sometimes.
I use my 3000 24v without voltage sensing.
For these 2 units, I would imagine that you would need 1000 ah + of 12v batteries with very fat cables with proper connections to avoid problems.

Agreed. I have been on several boats with 2000's and 3000's and the only one that worked perfectly had a new 780Ah bank at 12V and fat wires as required by Victron. I am surprised over and over when I see folks trying to save money on the cables that Victron wants. I thought about voltage sensing as a way to avoid mitigating the effect of voltage drop. I was not happy when I saw that the V-sense dissapeared on the way from brochure to reality.
C

[careka]

So for a bank of 4 x 165 amp Gel , a inverter of 2000watt is to big or ?

[Scott Berg]

I've never seen an installation of a Multi Plus w/o sense wires; I'll check with Victron about the current models and post their reply. I was a dealer for them for years and installed quite a few units, mostly 2.5's and 3's… Remember that you can set the low voltage cut off in the software.

[svlamorocha]

Originally Posted by careka

So for a bank of 4 x 165 amp Gel , a inverter of 2000watt is to big or ?

I do not know about gel batteries but I have no reason to believe that it makes a difference. Victron recommends that the 2000 should be used with battery capacities between 350 and 1000Ah.

This is particularly relevant for an owner that is not technically inclined and will get frustrated when they get low voltage alarms when drawing large inverter loads from a battery that is not fully charged.

C

[svlamorocha]

Originally Posted by Scott Berg

I've never seen an installation of a Multi Plus w/o sense wires; I'll check with Victron about the current models and post their reply. I was a dealer for them for years and installed quite a few units, mostly 2.5's and 3's… Remember that you can set the low voltage cut off in the software.

Scott
Thanks for the tip re: software. I am tired of dealing with supposed inverter technicians that do not even have the Victron software and cable. Now that you raise this I will just but the thing and do it myself.

C

[Scott Berg]

Ok
Where are you?
I could loan them to you if you can easily find them

S

[goboatingnow]

Originally Posted by svlamorocha

I do not know about gel batteries but I have no reason to believe that it makes a difference. Victron recommends that the 2000 should be used with battery capacities between 350 and 1000Ah.

This is particularly relevant for an owner that is not technically inclined and will get frustrated when they get low voltage alarms when drawing large inverter loads from a battery that is not fully charged.

C

Firstly voltage sense is irrelevant for the invertor side of the unit. It can play no part. The invertor has to operate on the delivered voltage. Sense wires have nothing to do with invertor operation

Secondly you have upwards of 4000kw which is upto nearly 400 A on a < 700aH battery bank that could be undercharged. and your wondering why you're getting low voltage alarms. !!!!


If they are gels , these have no place on a boat , they tend to be undercharged unless subject to long periods of trickle charge final charging. Gels will spend their life on a boat undercharged. Given the wire runs there could be quite a drop during charging , that's making the issue worse

Way too big inverters on far too small a bank. ( that's more then likely undercharged )

What AC loads are being pulled off when the low bat kicks in.

Dave

[FlyingCloud1937]

Originally Posted by careka

So for a bank of 4 x 165 amp Gel , a inverter of 2000watt is to big or ?

Before losses to the inverter that's about twice the Pukert factor of a 12 volt bank setting at 12.5 volts. 4 times Pukert if running 2 X 2Kw inverters in parallel.

Now factor in voltage drop in the cable, and inverter losses, lower resting voltages, and other 12 volt nominal loads running from the bats.

and

anything running for longer than a minute or 2, and yes,

your bank is to small.


Lloyd

[svlamorocha]

Originally Posted by goboatingnow

Firstly voltage sense is irrelevant for the invertor side of the unit. It can play no part. The invertor has to operate on the delivered voltage. Sense wires have nothing to do with invertor operation

Thanks. The physics of that is 100% clear. Unfortunately the owners are led to believe that the unit has voltage sensing at the battery and the alarms and panel readings are based on battery voltage, which they are not.

How can it be OK to say that the thing has voltage sensing and then you open the cover and the terminals are not there?

Originally Posted by goboatingnow

Secondly you have upwards of 4000kw which is upto nearly 400 A on a < 700aH battery bank that could be undercharged. and your wondering why you're getting low voltage alarms. !!!!

Way too big inverters on far too small a bank. ( that's more then likely undercharged )

What AC loads are being pulled off when the low bat kicks in.

Dave

No one has ever dared to draw 4000 VA. I tested at 200A at 50% SOC (per panel) and got 11.5V at the battery and 11V at the inverter when the alarm kicked in less than a couple of minutes. The bank´s capacity is 780Ah (4 new Trojans in 2x2 configuration) . I am yet to get good data on battery condition (new but who knows how were they maintained before delivery) to cover the battery angle.

The alarm in the VE panel is set at 10.5V and I am still wondering whether this "low batt" alarm is a different alarm or Multiplus measures voltage differently than my Fluke tester (applied at the inverter input). I am still awaiting word from Victron on that.

[svlamorocha]

Originally Posted by Scott Berg

Ok
Where are you?
I could loan them to you if you can easily find them

S

Thanks; I am in Argentina. I go back to the states I will buy one set...
Thanks again. C

[pbiJim]

Originally Posted by svlamorocha

(Just to make things absolutely weird, the manual you can see in your web browser by clicking here http://www.victronenergy.com/upload/...2%20-%20EN.pdf has the V-sensing wires but if you download it and open it with Acrobat you do not see them.)

Might you have an older version of Acrobat reader on your computer that that could be incorrectly interpreting the graphics in the document when it is opened as a local file? Perhaps your browser is newer & shows all the graphics when the document is viewed there?