Bluesolar MPPT 75/15 problem

[snapster]

Over the last few weeks our van and its solar panel has been sitting in the garden sucking up all the sunshine it can and squirting it into the two ( Victron LFD90) 90ah batteries.
A couple of days ago, I checked the batteries via the Victron Ap and the batteries were full, the app showed that they were in the float setting.
Today, I checked the app and, despite it being sunny, ( and the solar panel in the sun) there was no charge going into the batteries. Battery temperature was 8 degrees and the voltage was 12.52v.
The app shows there has been no charge going into the batteries for 2 days.
The app has various battery presets, and for the last 2 years, it has been operating correctly with the Victron preset. It will only work now if I use the factory default preset ( which is for AGM/gel batteries)
Any ideas why this should happen? Is my controller on the way out?
I contacted Victron but they had no idea!

 

[wildebus]

To clarify, what Batteries do you have?
Are they LFD90 Batteries (which would be Varta I think?); or are they LFP, which would be Lithiums?

The only thing I can think of to explain what you are seeing is the Battery Temperature is lower than the Charger cutoff. When you set to AGM the Temp Cutoff is disabled as not relevant. In LFP/LiFePO4, it is enabled and set at a default of 5C (see screenshot below). As an experiment try lowering that cutoff temp and see what happens (if you can connect to the controller via the Bluetooth App)

You are saying the battery voltage is 12.52V and the temp is 8C? Are you getting that from the Controller or the Battery? I am suspecting this is from the Battery?
The Victron MPPT Controllers by default read the temperature just once - when the controller wakes up at first sun and it uses that temp and that temp alone throughout the day (note: it is also the temp of the Controller, not the battery). Chances are at 7AM or whatever the time is when it wakes up, the controller is colder than 5C and so it disables the charger to protect the LFP battery. And even though the battery is now 8C, the controller remains as Charger disabled.
To check this, you can disconnect the PV panel from the charger; leave it disconnected for around 2 hours so the controller will think it is a new day (and so use a new temp check reading) and before you reconnect the PV Panel, make sure the controller is above 5C (play a hairdryer on it for a little time before you connect the PV panel back up). You'll need to do this tomorrow now of course, but remove the PV panel today ready for this test if you wanted to try it.

 

[snapster]

Thanks Wildebus for the comprehensive reply, I think you hit the nail on the head.
The batteries are not Lithium, they are normal LFD90, calcium sealed batteries.
The temperature and voltage was taken from a Victron Smart Battery Sense unit which is connected to the battery terminals and is in direct contact to the battery to sense temperature. I believe it constantly tells the controller the voltage and temperature of the batteries through a VE smart network.
I was under the impression the low temp cut off only worked with lithium batteries, but I originally had this disabled ( as well as equalisation, which equalises at 16.2v, which shuts the gas off through my crash protection unit)
A few months ago, after a firmware update, I noticed the automatic equalisation had turned itself on again (It shut the gas off! ) maybe the temp sensor turned itself on too and the BatterySense unit reacted to the low temp cutoff and stopped the controller charging the battery.
I have had the controller running the factory default today( as you say, temp cutoff is disabled), and it has worked perfectly. Tomorrow, I’ll try the LFD90 preset again and ensure the temp cutoff is disabled.
I fitted the BatterySense unit in the summer, and this is the first cold spell we have had so wouldn’t have noticed it stopping the controller charging when it’s cold.

 

[wildebus]

Let me know how you get on.
Make sure the temp compensation is enabled again as well (when the temp charge cut-off enables, the temp compensation gets disabled). And this time of year, don't be shocked at high charging voltages! they can hit nearly 15V wehrn you are used to around 14.4V

 

[snapster]

Not been cold today ( hovering around 7 degrees) so as soon as it got light, the solar panel was charging and has been all day. Only a few watts but the batteries are full now ( float charge)
I’ll keep an eye on it and see what happens if the temperature drops.