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Duncan I avatar image

SmartSolar 150/35 float voltage issues

Apologies if I'm reheating an old topic,


I have a technical question regarding the float voltage for SmartSolar 150/35.


I have an off grid system in UK running 6 SmartSolar 150/35 MPPT’s in synchronisation, the remainder of my system consists of Venus GX, 3 Multiplus Compact 24/2000 running in parallel, a BMV702 and 683Ah Rolls 5000 series batteries all fed by 8KW of Solar PV panels.


All the kit is running on the latest firmware (the MPPT’s are running v1.50)


The 6 MPPT’s and the BMV702 are connected to the Venus GX with a mixture of VEDirect and USB and all seem to be playing nicely together and sending data to VRM.


The MPPT’s are synchronised using Bluetooth and again play nicely except for the Float set point voltage; the Rolls batteries require a float voltage of 27v, so that is what I set the MPPT’s to using the Victron Connect app (which incidentally doesn’t work on my Android phone running Lollipop), but each day the system seems to choose a different voltage set point anywhere between 26.6 and 27 volts. When the system goes into float it is very stable at whatever voltage it has chosen for the day but it is never the 27 volts I have set (I have repeatedly checked that all 6 MPPT’s are set to the same Bulk, Absorption and Float voltages).


Do you have any ideas what could be causing the problem?


Would it help if I installed a Smart dongle on the BMV702 and synchronised it with the MPPT’s to relay its voltage data directly via Bluetooth?


MPPT - Solar Charge Controller
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3 Answers
Duncan I avatar image
Duncan I answered ·

Thanks for reply, yes I am using DVCC with all sharing activated. The master Multiplus has a temperature sensor. I had a spare sensor so wired it up to the Venus GX and monitored the results for several days, it appears to have hugely improved the float voltage ( now typically only 0.01 - 0.02 volts from setpoint which I call a result. Fair comment on my Lolipop phone OS.

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@Duncan I

I'm still not sure what you're doing here, but I don't want to mislead you.

Your batts are FLA's and should be using temp compensation. And when that's happening the setpoint(s) get changed on the hop, and the new target isn't published in the app, but you can see it change via V, and the VRM graphs may flatline at the revised setpoint, which is not what you've set as a target cos it's been recalculated for you.

It may possibly show small variations over the day as with DVCC it will now work in real time, and not lock in for the day.

It's winter for me right now and not unusual to see +0.5V added to my target settings (48V system), cos my batts are cold. They warm as the day goes on, and maybe go to +0.3V, which is what I expect, and indeed want it to do.

Might this be what you're seeing?

rzirzi avatar image
rzirzi answered ·

I have similar problem with my SmartSolar MPPT 100/15. Please see post topic: SmartSolar MPPT 100/15 Float state voltage. Maybe there is a firmware bug/hardware failure?

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JohnC avatar image
JohnC answered ·

Hi @Duncan I

My first thought would be temperature compensation, but you don't mention the same happening in Absorb. There is no Bulk setting in Victron kit.

You seem attached to your Bluetooth, but with a wired GX, it's possibly being pushed aside if DVCC is enabled, and effectively unnecessary. Adding a temp sensor in that case certainly is, as your Multiplus master should have that, and may well be passing that on already to the GX (and subsequently the mppts) in real time.

Please tell us more about what you're using, DVCC?

And oh, your Android Lollipop is too old, even with legacy versions of the Victron app/firmware.


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