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von-baron avatar image
von-baron asked

BlueSolar MPPT 150|60 Battery Voltage Sensing

I have a BlueSolar 150|60 charging into a 26.5 Volt 400Amp/Hr LiFePO4 (Winston 8 cells) battery system.

I also have a Victron SmartShunt, 500Amp.

The cable from solar charge controller is 35mm2 and less than 600mm on the positive and 300mm on the zero volt lines. The positive line passes through a 60Amp fuse for the solar and then a BlueSeas 350Amp isolation switch then a final 100 Amp main battery fuse.

When charging, say at 30 to 40 Amps from the charge controller, I notice a voltage drop between the terminals of the charge controller and battery terminals, as to be expected, of around 150mV just on the positive line, and around 20-30mV on the zero volt line.

I understand the electron flow, no problem about this part, but, knowing other devices such as the SmartSolar with Bluethooth and that it is able to communicate to the SmartShunt to get battery sense, my question is, how then might it be possible to have a BlueSolar charge controller get external battery sense ?

And without using a Colour Control with DVCC, which I do not have.

My thinking is that it would have been a sensible idea for Victron to have a connection into the BlueSolar charge controller to allow a simple wire connection back to the battery terminals to have accurate information.

I can see that there would be many people who would have simple systems and then come across this issue, or maybe without knowing it, possibly leading to an under charged battery.

To get around the situation for the time being, I need to increase the charge voltage set point by the amount that is dropped, which in my opinion is not so ideal.

I use a VE.Direct cable to a dedicated laptop running GNU/Linux with the VictronConnect appimage, as well as being able to connect via Bluetooth to the SmartShunt, which all works very nicely.

What approaches or solutions have others found ?

I appreciate any answers.

MPPT ControllersLithium Battery
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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

You can add Bluetooth to your MPPT using the VE.direct Bluetooth dongle.

https://www.victronenergy.com/accessories/ve-direct-bluetooth-smart-dongle

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klim8skeptic avatar image klim8skeptic ♦ commented ·

@von baron besides adding a smartnetork between the mppt and smart shunt, a Bluetooth dongle allows monitoring and control of the mppt via a phone or tablet.

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von-baron avatar image von-baron klim8skeptic ♦ commented ·

Thanks Matthias and Klim,

I can see that that 'Smart Network' solution is not a solution for me, by having to add a Bluetooth dongle to the charge controller.

With a Victron 'VE Smart Network', the SmartShunt sends battery volts and current. The solar controller already knows current, just that it has a bad indication of what the true battery volts is while delivering high current, by virtue of not so good design.

To have to buy a external 'dongle' device to simply measure this important voltage and digitise it, do some other magic within a micro-controller and then have to send it out using radio waves to a 'dongle' which is then connected via serial communications to the solar controller 200mm away seems idiotic to me as I am sure it would to you.

A good design would have this fixed with a simple wire as is often used in other circuits to compensate for voltage drop. The internal circuit, the ADC would use this directly instead of being connected to the main 35mm2 battery line.

Since I already have connection to the solar controller via the VE.Direct interface as mentioned to a dedicated laptop, a phone or tablet offers no additional advantage for the setting up basic monitoring.

I bought the BlueSolar MPPT charge controller specifically without the Bluetooth interface as I will use the VE.Direct interface with my control system (think SCADA), and understood that the charge controllers with bluetooth were less able to play communications on the VE.Direct interface while the Bluetooth was enabled, from my reading some time ago, there was a definite 'gotcha' in there I recall. Maybe my understanding was not totally correct on this or maybe the firmware for those units has changed to allow full and simultaneous communications on both the Bluetooth and VE.Direct interfaces. Nonetheless, the idea of having a simple solar charging system using a BlueSolar MPPT charge controller is negated by the fact it is not able to directly and accurately sense the battery terminal voltage while supplying a good amount of current.

It seems many of these devices have the work 'Smart' in them, if only they truly were from a design point of view.

It might be that I need to send the true battery volts to the BlueSolar charge controller from my SCADA system. But it shouldn't need to be that way.

Thanks for input so far.

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