My BlueSolar with bluetoooth dongle is showing a higher battery voltage around .3v than actual. I have checked this with 2 multimeters that both show the same as my 712 smart bmv. I have checked at the battery connection point. It is updated to firmware v1.46
Is the MPPT charging at that point or is it resting?
How do the Voltages compare at night time?
The difference is at bulk, absorption and float stages. How do you tell at night as the BlueSolar turns off and I can not connect to it via Bluetooth.
It can also be a rounding issue. The charger is not designed to be used as a multimeter. So the software does not report it to us the users with the same resolution as as a multimeter. But this does not affect its own functioning.
I am using the lithium setting and on this stetting the voltage determines the change stage. As such I would expect it to be closer than it is. I.e The voltage for absorption stage is set to 14.4. When the voltage reaches 14.4 on the BlueSolar mppt is reduces the amps because it thinks the batteries are fully charged. But the batteries are actually only at 14.0-14.1. Thus they will never reach full charge on the solar. I could increase the charge voltage setting but I am worried that it will correct when I am not looking and overcharge.
A voltage rise at the MPPT terminals when they are charging is a normal electrical effect. It is not desirable, but it is expected and predictable (see image attached for formula).
It can be reduced by using larger, or shorter wires between the MPPT and the battery or DC bus, reducing the resistance. You should also make sure that all connections are clean and tight, so there is no opportunity for any additional resistance (more voltage rise).
It can also be overcome by attaching a compatible bluetooth dongle to the MPPT and setting up a VE.Smart Network to share the more accurate voltage of the BMV-712 with the MPPT for charging purposes.
It can also be acceptable to do nothing. As the battery fills up, the amount of Amps required to maintain the charging voltage is reduced. As the current is reduced, the voltage rise decreases (it is a factor of the current). So as the battery becomes full, the voltage reading at the MPPT will become more accurate. When the battery is finally full, the current should be near 0, and the battery voltage should be more accurate.
Voltage rise calculation formula- though everyone just uses a program now- 
Would this still be the case though when I disable the solar charger through the Victron connect app. The attached screenshots are taken when the charger is disabled.
I will see if I can work out the VE smart network. I could not seem to find where to connect the MPPT to the network. Perhaps I have an older dongle?
@guystewart did you see my last response?
I know my mppt's running full power have a voltage difference between the mppt/battery of 0.3v.
A SmartNetwork between a SBS or BMV and mppt's solves this voltage difference.
Hi Guy,
I am also seeing high voltage readings on the 100-50 MPPT controller. I my case the voltage difference is around 0.6 volts, when the solar panels are producing about 100 Watts.
i have checked voltage reading at the batteries, and at the MPPT terminals. Both these readings agree with the battery monitor, ie 0.6 volts below the MPPT reading. I have also checked voltage drop across wiring between MPPT and battery and the voltage drop is negligible.
The high voltage reading means that the MPPT moves to absorption and float well before the batteries are fully charged, so is a serious concern.
Any ides on things that I should check?
thanks
Gordon
I'm currently having the same issue as the others. My 150/35 reads correct battery voltage with no solar power going into the battery, but is 0.4v higher once the battery begins charging.
How can this be called a voltage drop when for some reason the CC is outputting a higher voltage. Wouldn't a voltage drop issue be the opposite?
You are seeing a voltage drop along the cable between the mppt and battery.
I also noticed if after the battery is full and floating if I disable then re-enable the charging in the 150/35 app menu the voltage spikes to about 18v then goes down again which can take 10-20 seconds. These are LifePo4 batteries so not good to go over voltage.
I can overcome this problem by turning on DVCC and shared voltage sense SVS. This reports the correct voltage from the shunt or BMV to the solar charge controller and my MPPTs then show the voltage the shunt measures close to the battery.
