Victron Multiplus not giving full charging amps

[jordanbigel]

I read through the replies to date and all of them ask good questions, some of which I see the OP has addressed. I don't see any smoking gun here so far.

I can add this, I have an almost identical setup with a MP 2 12/3000/120 and a bank of LFP totaling about 1200ah. When on shore power, with the bank at around 30% SOC, the charger is in Bulk mode, I am seeing up to about 109 amps going into the batteries (depending on what other power I am drawing at the time) via my BMV-700 monitor. I am in California, the ambient temp her is in low to mid 70s (not hot like inland) but on really hot days I still see the same output.

I have the MP input AC current limited to only 18amps* and I am still getting close to 110amps going into my bank at about 13.4v. I have the "Charge Current" set to 120, which is the max. I think the default is 80 - is it possible you have not changed this setting?

From everything you described re: wire size, distance, etc., your MP should be putting out as much as mine. Can't say what is wrong, but you should pursue this until you get it to work right.

*The reason I have AC current limited to 18 is because I have a water heater running on a circuit which does not pass through the MP.

[ItDepends]

Originally Posted by jordanbigel

I read through the replies to date and all of them ask good questions, some of which I see the OP has addressed. I don't see any smoking gun here so far.

I can add this, I have an almost identical setup with a MP 2 12/3000/120 and a bank of LFP totaling about 1200ah. When on shore power, with the bank at around 30% SO, the charger is in Bulk mode, I am seeing up to about 109 amps going into the batteries (depending on what other power I am drawing at the time) via my BMV-700 monitor. I am in California, the ambient temp her is in low to mid 70s (not hot like inland) but on really hot days I still see the same output.

I have the MP input AC current limited to only 18amps* and I am still getting close to 110amps going into my bank at about 13.4v. I have the "Charge Current" set to 120, which is the max. I think the default is 80 - is it possible you have not changed this setting?

From everything you described re: wire size, distance, etc., your MP should be putting out as much as mine. Can't say what is wrong, but you should pursue this until you get it to work right.

*The reason I have AC current limited to 18 is because I have a water heater running on a circuit which does not pass through the MP.

You will find that 109Amp into 13.4 volts IS full output. The charger is reated at 120 A @ 12 V, or 1440 watts. That's exactly what you are seeing. 1440 W.
You will NEVER see 120 Amps into 13+ volts.

I am not at all sure why nobody seems to understand this...

[jordanbigel]

Originally Posted by ItDepends

You will find that 109Amp into 13.4 volts IS full output. The charger is reated at 120 A @ 12 V, or 1440 watts. That's exactly what you are seeing. 1440 W.
You will NEVER see 120 Amps into 13+ volts.

I am not at all sure why nobody seems to understand this...

Don't recall writing that I expected more. Did I? Didn't mean to.

And of course your math is accurate.

[ranger58sb]

Originally Posted by Zanshin

How did you set the limit to your Victron? There are 2 methods - DIP switches inside the unit or via software. With software, there's the method using bluetooth and an app if you have the appropriate devices installed,

If you mean VictronConnect.... FWIW, I haven't found a way to do that?

Ditto with the "Reset History" command; online examples suggest there's a Reset History command in Setup, but that doesn't appear on our VictronConnect version. Had to use the BMV-712 to clear history (just after we installed new batteries the other day).

I don't see (haven't yet found?) the battery charge current limit change possible in the BMV-712, either.

In the manuals, I've only found the DIP switch method... and that's only in the EN-language version of the MultiPlus 12/3000/120-50 and 24/3000/70-50 manual, not in the EN/ES version for the same MultiiPlus.

-Chris

[ranger58sb]

Originally Posted by ItDepends

Also, do not forget the Victron battery charger is a constant POWER device, not a constant CURRENT. The 120 Amp rating is at 12 Volts, so 120*12=1440 Watts.

The MAXIMUM current you should expect to see at 13.4V is 1440W/13.4V= 107A Not everything you think are missing, but half of it!

Be SURE to review all the settings. The default current limit for the charger is 80 Amps. Suspiciously close to your actual output. Did you deliberetly increase it to 120? Are you sure? If not...

Thanks for mentioning that limit; I'm just going through set-up myself, after installing new batteries...

My softcopy of the EN-language version of the 12/3000/120-50 and 24/3000/70-50 manual says "5.5.1.3 Battery charge current limitation (default setting 75%)"

So that would be 90 Amps for OP, yes? (And 52.5A for our 24V version...)

-Chris

[ItDepends]

Originally Posted by ranger58sb

Thanks for mentioning that limit; I'm just going through set-up myself, after installing new batteries...

My softcopy of the EN-language version of the 12/3000/120-50 and 24/3000/70-50 manual says "5.5.1.3 Battery charge current limitation (default setting 75%)"

So that would be 90 Amps for OP, yes? (And 52.5A for our 24V version...)

-Chris

Yes. The only thing to be careful of is the charger current limitation is actually not ratioing the current (Yes, that is what it is called, I know!) but rather the power. So the maximum output at 100% for the OP at 13.4V is actually about 109A, and 75% of THAT is about 81 Amps. That's so close to what he is seeing, I'd bet that's the actual issue.

This can confuse people a lot when we talk about higher absorbtion voltages.

My battery bank absorbs at 28.8V. My charger is rated to 70A@24.0V By the time the charger approaches 28.8V the maximum output is only 58A, and we still haven't subtracted any loads!

[jr_spyder]

Thanks for all the input so far. The wind came up and my boat was desperately pulling at the dock lines demanding to go out for a romp. Good fun, back now.

I'll get out my Fluke clamp/DMM and start measuring everything as suggested.

I have the MK3-USB interface and the app on my laptop. The setting are the default as suggested by Battle Born, with the max amps definitely set at 120.

I'll dive back into all of this later today. Thanks so much for the excellent advice. Stay tuned...

JR

[CharlieJ]

@ItDepends #17:

You will find that 109Amp into 13.4 volts IS full output. The charger is reated at 120 A @ 12 V, or 1440 watts. That's exactly what you are seeing. 1440 W.
You will NEVER see 120 Amps into 13+ volts.

I am not at all sure why nobody seems to understand this...

I just reviewed all of the Victron 3kW MultiPlus documentation and haven't seen this referenced anywhere.

The Datasheet states 120A @ 75F ambient. The TechMan states the same. Where did you find this referenced?

@jr_spyder
During my doc review this jumped out at me; you haven't mentioned if you have voltage sense installed. Do you?

[tanglewood]

Originally Posted by ItDepends

You will find that 109Amp into 13.4 volts IS full output. The charger is reated at 120 A @ 12 V, or 1440 watts. That's exactly what you are seeing. 1440 W.
You will NEVER see 120 Amps into 13+ volts.

I am not at all sure why nobody seems to understand this...

I get what you are saying, but where does Victron say it's rated as you describe, i.e. output limited to 1440W?


I have also seen mixed answers about whether the temp ratings and de-ratings are based on ambient temp, or the temp of the FET heatsink internal to the Multi. Anyone know definitely which it is?

[smac999]

Originally Posted by ItDepends

You will find that 109Amp into 13.4 volts IS full output. The charger is reated at 120 A @ 12 V, or 1440 watts. That's exactly what you are seeing. 1440 W.
You will NEVER see 120 Amps into 13+ volts.

I am not at all sure why nobody seems to understand this...

I find that hard to believe. As the charger is using many of the same 3000w rated components of the inverter.

I’m pretty sure I have seen 120a @14v from a multi.

Every other charger I have seen will put out full current at bulk voltage.

[jr_spyder]

Ok, I'm back on it. First, here are some screen shots of my settings:









More data next...

[smac999]

What do the amps on your bvm show or clamp meter? . If you have one. I have seen the amps displayed wrong on inverters before.

Also turn off the battery monitor function inside the inverter/ charger. That will be useless.

[jr_spyder]

I have a new Fluke 376 FC clamp meter that I bought just for this project so I could be sure I understood loads on the batteries. Using that here is some data I collected as suggested above. Note this data was not taken at exactly the same time as the pictures above, so please don't try to compare them.

DC voltage drop test:
@ MP terminals 13.6
@battery bus: 13.4 (0.2 drop)

DC Amp test:
@ MP B+ cable 74.4 amps (at this time the live app data said the output was 85 amps)
@ battery + bus 74.4 amps (no drop)

AC voltage drop test at MP:
Before turning on unit 119.8
After 116.4 (3.4 vac drop)

Ambient temp in locker after ~20 minutes: 87 degrees F. This would cut output by ~5%.

The way I understand it none of this data explains way I'm getting around 72% of the expected 109 amps.

???

[jr_spyder]

Originally Posted by CharlieJ

@jr_spyder
During my doc review this jumped out at me; you haven't mentioned if you have voltage sense installed. Do you?

Charlie, no, I don't have voltage sense installed. I see it might help.

An interesting thing about the voltage drop is that when I measured the voltage when the charger was off and batteries were at about 40% SOC I got 12.9 at the MP and 12.9 and the batteries. No drop. With the charger on and at 13.6 is see a 0.2 drop.

[smac999]

You can’t have voltage drop without current. So off both voltages are the same.

If you invert 160a you would see 0.4v drop the other way.

I would say you have a issue with the inverter. The fact the real amps are 10 off what it thinks isn’t a good sign either.