No idea from where to start. Multiplus II DC problems

Question

question

deunan asked Dec 19, '23

No idea from where to start. Multiplus II DC problems

Hello,

I have some problems with my MP II, 48 5000. Some day ago i noticed some problems while charging my battery from grid. The power fluctuated up and down every few seconds. Today i was playing to dbus-spy to check the status of some parameter and i discovered that the DC voltage read by the MP is a mess. It swings from 38 to 40 Volts when the battery don't get charged and when it raises again to 50V it get charged again. I verified with multimiter at the MP terminals and the reading it's almost correct.

Measured on the Lynx distrbutor it's correct as the bms and mppt report to the venus.

Both bms and mppt never show this change of voltage read from the MP. I have the feeling it started with v508 and i would like to downgrade to 506 but where to find it?

Before to send it to the dristributor i would like to reflash it and give another try.

Now i have no load on it, just grid in and the battery. The bms read 52.83 V, the MP read is 55.2 as the multimeter at the battery connection.

Multiplus-II charger

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Modifications Space

Node Red Space

Answer 1 · 2023-12-20T06:15:39Z

JohnC answered · Dec 20, 2023 at 06:15 AM

@Deunan

Try this link..
https://updates.victronenergy.com/feeds/VEBus/firmware-archive/

If you can't access it, sign into Victron Professional and look under the 27 series VE.Bus firmwares for an 'Archive' link to it.

I doubt very much that reverting fw alone will fix this. Your post history shows that you're somewhat adventuresome (that's fine though), and may be doing something else that may cause it. Like maybe using the Charge Current assistant?? Usually DVCC set to use a V from a device other than the Multi could be expected to remove such control issues if the Multi was actually misreading V. But we can't tell from here what you're actually attempting.

5

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

deunan commented · Dec 20, 2023 at 07:50 AM

Thank you a lot for the link, it's exactly what i was looking for.

Yes, i'm a bit adventurous, but all the adventures like non Victron Mppt and other things i tried to integrate are on another system. This is almost pure Victron gear for a smaller/test system. It's just 2 400W panels connected to a 100/20 Mppt, venus os on rasp, lynx power-in, MP II/48/5000/70-50 230V and a 15Kwh battery with the new JK BMS. Yes, i was using the charger control assistant combined to ignore AC to control partially the charge but i deleted all of them for the tests. I have read again my question and probably i have not been very clear on an aspect (english is not my main language). When the MP not charge cause it read low voltage, the low voltage is comfirmed with a multimeter measuring at the battery bolts on the MP itself. Voltage read by MPPT and BMS are different and stay over 52/53V. I add a screenshoot from the vebus using dbus-spy. BatterySense/voltage it's correct. 52.89 sent by BMS i presume. Multimeter comfirm it on the busbar wich is a lynx power in. But Dc/0/voltage is 40.92, Device/0/diagnostic/Ubatterminal is 42.32 and

Device/0/diagnostic/Ubatvsense is 39.72. A multimeter on the MP's battery bolt swings between that values. This evening i will try with the downgrade. In the worst case i will open a ticket with the reseller or call the italian distributor.

Thanks again for the link.

0 ·

deunan deunan commented · Dec 20, 2023 at 08:39 AM

Forgot to add the fileivm2biwaA5.png

0 ·

ivm2biwaa5.png (92.3 KiB)

JohnC ♦ deunan commented · Dec 20, 2023 at 10:13 AM

@Deunan

It wasn't very clear before, but if the actual V on the Multi's terminals is different from the battery/mppt then you have a wiring issue between the devices.

Check all terminals/crimps/switches/fuses/etc. Even on the legs within the Lynx. The point of the V drop should be easily detected by multimeter. Even switches and fuses can be faulty internally.

I hope I understand this correctly, because it's an easy fix.

0 ·

deunan JohnC ♦ commented · Dec 20, 2023 at 09:30 PM

This weekend i will have some time to try to check all the cabling. For now it will stay off until then. I will keep you updated about the result

0 ·

deunan JohnC ♦ commented · Dec 23, 2023 at 10:53 AM

Thank you a lot for the suggestion. Now it's working and charging my battery with 1400W without problems, the DC side is normal. At the end was a single loose connection, the negative cable going to the inverter, inside the Lynx Power-In. After checking the other connections i flipped up the switch. No low voltage warnings anymore since 3 hours.

Thank you again.

0 ·

question