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i have a Multiplus 12/3000-16, BMV-712, 75/15 ( 3x), Venos OS, all FW up to date,
The Multiplus absorption and float voltage alway 0.1-0.2V too low ore too high.
I try to use DVCC ( only ) shared Voltage & shared temp sensor. The voltage is more accurate, but the multiples don't want to leave absorption to float. As I understand it, if you activate "limit current" this is normal, but without it this shouldn't happen...
Sorry, it's not clear what the problem is.
Are you unable to set the values you want?
Are the values measured with a meter different to those on the BMV
Or is it simply never going into float?
i set absorption ( ve.config tool ) to 14V, float 13,5V.
the result is (measured by BMV close to the battery and BMS) 13.9V, 14.1,14.2V and float 13.6V
anyway, very inaccurate.
then i try to give the multiplus the more exact voltage measurement from the BMV via DVCC.
this ends in a more precise voltage at the battery, but also in the fact that the multi no longer leaves absorption to float.
Assuming the 75/15s are MPPT Solar controllers.
Also assuming the cabling is correct, no high resistance/voltage drops over poor or loose connections, fuses, switches etc.
Absorption voltage seems to be low, but we've no battery info.
Multi voltage will be adjusted according to temperature, assuming the temp sensor is fitted correctly. This is based on 25C and when temp is lower, voltage will increase for lead based batteries.
Set things on the MPPTs will also affect voltage. Many people set solar slightly higher than the multi to prioritise and keep solar charging going when enough light.
Battery voltage will drop under load especially high load. Shouldn't drop much below the absorption level on the multi, though. Assuming grid power is on and sufficient.
Net result is that voltage settings on the multi are just one indication of your battery voltage. The BMV measures actuals. Trying to configure the multi or MPPTs from BMV values is going to mess you around a lot. You should go the other way - set multi and MPPT s from battery maker's specs. Use BMV to monitor. And calculate SOC, which will be good if configured correctly.
ok,
battery is Winston 200Ah
2-wire BMS, multiplus is configured for 2-wire BMS / LiFePo4 w/o tempcomp. 14V/13.5V
Load ist more ore less 10-30W ( rpi,display & USB hub ), cable is 4x 50mm² with Klauke cable lougs, crimptool is also Klauke.
The problem is:
1. the configured voltage 14/13,5V isn't accurate. If 14V is configured and the BMV & BMS measured 14.18V that has nothing to do with cable resistance. The multiplus output voltage has to be fixed 14V13.5V, not 14,1V 14,2V
2. why DCVV with only shared voltage/temp affected the Multi don't want to leave absorption to float ?
screenshot w/o DVCC, BMS 123electric Batteryvoltage is BMV. 
Screen shot from the Pi?
Looks like the voltage differences are because of different instrument readings. Not sure about the variations, could be loads coming in or out. Might also be the BMS.
How long in absorption? Default is up to 8 hours, can be configured. As it's lithium, you can reduce this a lot in the settings.
Have you compared the voltage readings at the multi with a voltmeter?
yes, it's from the Pi.
absorption time is 1h.
the BMV and BMS readings are almost the same and real ( FLUKE Multimeter).
according to my understanding the multi voltage has to be fix. Set and forget 14V/13.5V.
But if the voltage at the battery is higher, the Multi must also apply a higher voltage, otherwise where is the higher voltage supposed to come from? the multi itself reads 14.09V ok, let's take that as a tolerance, but 14.19V
once again: why does the multi increase the voltage at the output w/o DVCC ? and why DVCC with only shared voltage/temp affected the Multi don't want to leave absorption to float ?
The other charger ( Orion, MPPT ) can do that with no problem exactly 14V/13.5V.
You didn't mention that Orion before.
Best guess is that either the solar or orion are causing the voltage difference. Maybe disconnect each and all to stabilise, then see.
Odd thing is that the multi is putting out quite a lot of power. Makes me wonder where it's going. Adds up to 'charge' and DC, but do you have a DC load bypassing the 712 and coming from the battery?
...macht es den Eindruck als wüsste ich nicht wie DC Batterieladen funktioniert ? spreche ich chinesisch ( ok mein englisch ist nicht perfekt ), habe ich die zwei Frage unklar formuliert ? Ich bin gelernter Elektroniker und bin seit 20 Jahren im Geschäft verstehe genau was dort passiert, wann warum von wo Strom fließt und wieso wann wo wie viel Spannung anliegt.
the Orion is off, the MPPT is Off there is no more active charger, nada, nothing nichts....
if the orion were running you would see current from DC to battery, there is no current from DC to battery only to DC, also you can see the Starter voltage is low because the engine is off and when engine is off, the Orion is also off.
now the multi is in float (w/o DVCC ) the voltage is 13,6V. 0.1V to high. Voltage and current check with Fluke Multimeter and clamp meter.
the power readings/claculation is also a little inaccurate when the multi charges, as you can see ( video screenshoot ) https://www.dropbox.com/s/j0kclb4g1sw7bm2/Bildschirmaufnahme%202022-02-08%20um%2017.42.23.mov?dl=0
once again: why does the multi increase the voltage at the output w/o DVCC ? and why DVCC with only shared voltage/temp affected the Multi don't want to leave absorption to float ?
