Protect Growatt from freezing

[Ronaldrwl]

I can't find a thread on protecting the equipment from freezing. Everything I find is about batteries while charging. I'm planning my next project with the equipment in our shed. Growatt says to keep it above freezing. What direction should I be looking for a solution? Thanks

 

[Ronaldrwl]

I'm looking at a temperature controller and heating pad?

https://www.amazon.com/gp/product/B01HXM5UAC/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

 

[iMakerShop]

How cold do you expect it to get?

 

[Ronaldrwl]

We have winters here. It can be <10f easy at night and <20f for a week. I plan on insulating and finishing out the shed. It's about 12'x10'.

 

[iMakerShop]

That's pretty cold. Here in Florida we don't see those temps ever so I don't have experience running equipment under those conditions. However, I do know my two systems generate their own heat during normal operations so would suspect that a system you put together in your shed would "self heat" from losses via normal operations. My Growatt 3k inverter document says the "no load power consumption" is <60W. That combined with the charge controller efficiency loss (1-95%=5%) and the inverter efficiency loss (1-90%=10%) the unit (in theory) would generate ~75W as heat powered on and idle. if the MPPT is pumping 200W of solar panel output into the battery, that 5% loss turns into another 10W of heat. If the inverter is powering a 200W load from battery (or solar), another 20W of heat gets added to the air surrounding the inverter. At 3.412BTUs/Watt that's 255 BTU's heating the shed/cabinet/box your system is enclosed in.

My 3k inverter is in at cargo compartment in my RV (with the battery). Here's a graph of the inverter temp (measured inside the inverter) from the last 24 hours:
Here's the power graph for the same period:

As you can see: Just charging the battery and powering the near constant 40W load in the RV (nothing's running) can produce useful heat.

I personally would have heater pads for the LiFePO4 batteries with a thermostat. I'm not sure how effective the heater pads are. As i recall they were in the 5-10W range so powering them from the inverter output should be fine though I don't know if a 5W heating pad is enough to keep things above freezing when its -20F. you can easily test it with a bucket of water sitting on you heater pad...
I think the main risk is the batteries draining, the system shutting down and then you have no heat to keep the batteries from freezing. If there's anyway to have a backup heating source (propane/kerosene heater or smudge pot around) around, I'd consider it.

Hope this helps.

 

[Brett V]

From the Growatt data sheet

 

[magnet creek]

My 10kW Growatt inverter shuts down every night; presumably because of Low temp. The last recorded temp on Solar Assistant is just below 2.5C I have the batteries on heating pads, but if the Inverter shuts down the power generation I lose the heating pads. I tried connecting the heating pads directly to the batteries but that created a fault with the batteries for whatever reason.
I'm going to try and insulate the inverter with some foam board to see if that helps.
It is all mounted in an uninsulated trailer, maybe I should just insulate the whole thing... More work in the snow. fun fun fun.