For the SKY, I recommend you follow what I did in my post here: Easy SKY+SPA battery expansion (unofficial). If you have a DC power supply you can charge the SPA by connecting directly to the pogo pins. I note the polarity in the referenced post. I recommend that you also disable the cold temperature protection in the SPA. Also, make sure all the batteries are charged to the same voltage when you put things together. I have found that my mod has been working just fine and it may help yours make it through the winter.
2 Likes