question

@mrfunnel@gmail.com

Hi, I have been looking for this information as well as my SmartSolar MPPTs 250/70 are operating daily at high temp, at times > 70-80 Deg.C. at the Heatsink. This is bad for power electronics devices or the internal micro electronics. It is due to the high density packaging of the MPPT. The thermal design could have been somewhat better engineered. It is commonly accepted in the electronics engineering field that every 10 o C rise in the integrated circuit temperature will reduce the average life expectancy of the ICs and electronics by 50% (refer to the Arrhenius equation).

To answer your question it seems that Victron do not make the MPPT temperature parameter available externally. I would be good if they did, then we could use this parameter for various things including trending and ideally for controlling the output relay. I base this on information from the Modbus TCP Register list - which matches your list almost 1:1. You can find it here: https://www.victronenergy.com/solar-charge-controllers/smartsolar-250-85-250-100#technical-information

Perhaps there is an Ethernet or VE.Can bus method to access the MPPT internal temperature parameter, but I haver not investigated this yet.

What I did recently - along similar lines of your thinking is to construct a cooling fan assembly using 2 x 80mm 24V fans and Aluminium Angle for a frame. This then sits on top of the MPPT with a rubber surround. It draws a lot of air, mainly through the heatsink and some around the enclosure. On average the MPPT temperature reading is at least 10Deg.C. less than without the fans and this is a good thing.

To prevent the Fans running all the time, what I do is use MPPT Relay Function 9 "Day Detection" which means that the fans run while the MPPT can transfer power from the PV array to the Batteries. At night time it switches off. You could also use an external Thermostat switch, such as a bi-metallic switch, in contact with the MPPT heatsink to provide you fan switching signal.

IMPORTANT: I would recommend do not connected external loads directly to the MPPT Relay - use an interposing relay which will draw less than 50mA through the MPPT Relay and you will be able to switch the higher Fan running currents through the interposing relay contacts. This will ensure a long electrical life of the MPPT relay contacts which is only rated at 4A up to 35V DC (or 1A up to 60V DC) and you do not want to damage the internal component.

I have two MPPTs which are now Synchronized for Charging state using VE.Smart Networking via Bluetooth - this helps to equalize the charging current and operating temperature between the units.

Below is a rough drawing of my circuit which I have not converted to CAD yet. The Interposing relay "K" which I use is an OMRON 24VDC coil (G2R-2-SN (s)) but many similar relays can do the job and are available with different coil voltages.

Below is my Dual Synchronized MPPT arrangement with Cooling Fan assemblies on top.
I can only fit them on top as wiring below the unit does not permit installation below. It is also easily removeable, all you have to do is cut a few cable ties and disconnect the wires at screw terminals.

I hope this has been of some help.

I also wish I could access the internal temperature, right now the only way to see it is by using the plug in optional display that plugs into the front of my 250/100's, exactly as shown in the photos above from Djino .... come on V, give us that data systematically some how please. :)