question

Niko Järvinen avatar image
Niko Järvinen asked

Multiplus 12/1600/70 not charging at full rate

I just finished installing my multi and 280Ah of lifepo4 batteries with REC BMS. Everything else seems to work fine but I can't get multi to actually charge at 70A. It claims it's charging at 60-62A but when measuring with Fluke clamp meter it shows only ~50A flowing. Additionally my BMS shunt shows the exact same reading as fluke does so I'm betting that the Multiplus current measurement is nowhere near accurate...

How do I get the missing 20 amps of charging out of multi? That's quite a big drop from the expected value and increases significantly the charging time for a 280Ah bank..

I have the weak AC off, 70A set as the limit in the settings. Environmental temp is around 27-29C where batteries and multi are. Batteries were at around 70% when I started charging so they should be easily able to take the full 70A.

And to be clear the REC BMS is not communicating with Victron yet so that can't be the issue either.


Edit1:

Additional info as requested. Screenshots of the settings at the end of the message. During the screenshot I had set the device not to charge so I can make sure it's cooled and not doing anything for a while so when I flip the charging switch there can not be any issues with heat in the beginning at least. The environment is around 25C right now so even if it was slightly derating due to temp it should not be too many amps as per this doc https://www.victronenergy.gr/upload/documents/Output-rating-operating-temperature-and-efficiency.pdf

Multiplus firmware version 481 which should be the latest as no updates are available.

AC is grid AC right now so no limitations on that side.

Did a new test with no AC loads on at all and multiplus in charge only mode. Discharched the lithium battery to 30% so it's nowhere near full.

Voltage at victron end:13.5V

Voltage at battery terminals: 13.3V

Still Victron showing about 62A in victron connect but real amps about 52A. And victron is in bulk charge mode.


Additionally I'm able to easily pull 130amps from the batteries and with solar + multiplus able to charge at 80A. Smart solar MPTT has the same voltage levels as Multiplus as well. So definately seems that there's a problem with the multiplus...



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MultiPlus Quattro Inverter Chargerbattery chargingLithium Battery
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Niko Järvinen avatar image Niko Järvinen commented ·
Bumping this up if anyone has any ideas...
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Erik Sporns avatar image Erik Sporns commented ·
also bump, experiencing the same issue. not more than 50a, doenst matter what battery state, also rec bms (12v 400ah)
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Paul B avatar image Paul B commented ·

Hi Tuxie

what is the DC voltage output at the time at the Battery and also at the Inverter

what is the mutliplus absolution voltage settings

some screen shots of your settings would help as well

also what firmware is in the multiplus

whats is supplying the power to the multiplus ie mains or generator and its voltage and amps incoming

whats is the AC load output at the time

have you got a GX device connected and if so has the DVCC option been turned on and had a max charge current set as this also limits output DC current


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raphael avatar image raphael commented ·

Your Environmental Temperatures might be too high or your ventilation is poor. The MultiPlus is rated for 70A output at 25°C.

Check the Voltage at the Battery + and - cables of the MultiPlus when it is charging. Maybe you set the end of charge voltage too low and you have too much voltage drop over the cables to the Battery.

If you have a GX device, you can connect the REC-BMS to VE.Can or BMS-Can on the Cerbo GX. Then you can switch DVCC on and the MultiPlus gets the accurate readings for current, voltage and temperature from the BMS.
Manual for REC Q BMS_Victron compatible.pdf

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Niko Järvinen avatar image Niko Järvinen raphael commented ·
Ok I added all the info requested to the original message and also redid the test.. No joy. Still absolutely the same issue.
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6 Answers
Alexandra avatar image
Alexandra answered ·

Unlike on the AC input, the multi does not have a way of measuring the DC current or charge current to the batteries. It is more of a 'calculated' amount. That is why most people add a bmv or shunt or have smart batteries.

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Niko Järvinen avatar image Niko Järvinen commented ·

That's fine if we're talking about the "stats" that multi is showing. As I said I already have a BMS that's showing the actual amps... However the issue here is actual performance of multi which is 30% lower than advertised... The datasheet does specify 70A charging which should be achievable and the reason I got this multi is because the advertised 70A charging so I can charge in about 3 hours instead of 5 hours...

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Alexandra avatar image Alexandra ♦ Niko Järvinen commented ·

If your cables are longer and small then you may be getting drop over them? Or some high resistance connections like on lug crimping? I think the issue is more setup specific.

Ours is charging this morning at around 65A this morning, but I do know my cables in my system are a bit long, so for that reason we have the provided cables to a bus bar and ran 95mm to the battery bank..

We measured with both the shunt and meter.


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Alexandra avatar image
Alexandra answered ·
@Niko Järvinen

So after a few days of experimentation, we have worked out that the ac input also has a bearing on the charging amps.

Have used longer and shorter extension cables. Thinner and fatter gauge wiring, even changing to a cheaper plug on the all changing the charging amps coming in. Got it as low as 55A from the normal 65A.

We used the same settings the whole time.

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Niko Järvinen avatar image Niko Järvinen commented ·
Interesting. When you had the issue of 55A only, did you see if you can run AC loads at the same time? In my case I was able to run 1.2kW water heater at the same time as charging the battery at 55A.. So the AC side was not limited for sure... And when turning off the water heater the system still only charged at 55A...
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Alexandra avatar image Alexandra ♦ Niko Järvinen commented ·
No we didn't run full loads and test. We first wanted to see about the charge issue as an isolated problem.


All we can say is that you are running into ohms law in your system somewhere. The current voltage resistance relationship is an inescapable demon.

Other possible culprits are inter bank connections or in one battery we had (chinesium all the way) the links between cells caused high resistance points. Changing those made a huge difference to the bank especially charge and discharge efficiency.

In other high amp systems it is often lug crimps and cables or corrosion.

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Philip avatar image
Philip answered ·

I'm having the sam issue with charging at maximum ca 55A with two Multi 12V/1600VA in parallel (summary c.a. 110A instead of 140A) when charging from grid. Settings are the same as above. Discharging works great and I'm able to push it up to 220A with loads of 3000W, cabling is excatly the same lenght and mostly 150mm2 crosssection. Any advises?


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louie52 avatar image
louie52 answered ·

I had the same issue with charging from grid at 26A instead of 35A (Multiplus 12/800/35).

After I purchased the MK3-USB interface to look deeper into the machine, I noticed the battery charging current (probably factory setting) was set on 26A. After I changed it to 35A which the maximum the sofware allows to do, the problem was solved.

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mr-manuel avatar image mr-manuel commented ·

I have the same problem and reached max. 62.5 A for a short time.

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Did you change this setting?

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I have a MultiPlus II-GX 48/5000/70-50 used with a PV Inverter connected to the AC Out (1:1 rule) and the rest on AC In. The PV is producing more than enough power ~5.5 kW to provide the energy. Since it's not reaching the 70 A charging the energy gets exported.


The battery is capable of 125 A charging and discharging. The cables to the battery are 1 m long and have 50 mm². The battery voltage range I'm using is from 54.00 V to 63.90 V (18x LFP4 cells).

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olegv avatar image
olegv answered ·

See please my experiments with charge current :)

https://community.victronenergy.com/questions/194351/3ph-multiplusii-1ph-ac-input.html

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Juha Tuomala avatar image
Juha Tuomala answered ·

I was wondering the same, Quattro gen2 and only after switching off the Weak AC input it started charging over 40A current. Higest is now 55A, but my battery is quite full. Interesting to see if it reaches to nominal 70A when empty.

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lebtwl avatar image lebtwl commented ·
Thanks and boy am I glad I found this! I was struggling with the same problem on two Multiplus 24/3000/70. Charging was not going higher than 45 amps into my Victron Lithium batteries. Switching off Weak AC input fixed the low charge amps.
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