Testing lithium batteries and solar

System

This discussion was created from comments split from: Post up some shots of your T@B set-up at the camp site! #3.

techietab

Denny16 said:

@techietab the campsite looks grand, and has a nice open feel to it.  How did the test go?  Did the solar keep the battery back charged back up from the night time useage?  Do have the 2-way, AC/DC fridge?

Cheers 

The campsite was indeed quite a bit larger than I expected. Could have comfortably parked 2, maybe 3 (if you wanted to get cozy) T@bs on the site, not that it would be allowed. 

The solar + electric testing went well, and confirmed my fears that my 2 suitcase panels + the stock Sunflare are not sufficient to fully top-up the battery given 1.) mediocre late summer/early fall sunlight conditions and 2.) steady extra power draw from add-on devices I've wired into the 12v system (Peplink UBR LTE modem/router + Peplink 42G roof-mounted antenna array, SensorPush wifi gateway for environmental sensors, and a Raspberry Pi 4b that serves both as a Kodi media center frontend and as a Netmaker mesh VPN gateway that ties my home, leased servers, and mobile devices together. During daylight hours, more or less broke even on the energy produced vs used, and plowed through ~50% of the battery bank capacity overnight. I have the 2-way fridge, which I had set to the coldest setting, which probably was a big contributor to the high draw. I intentionally avoided cooler use on this trip to simulate a worst-case refrigeration scenario.

I have another couple trips planned without access to shore power before the end of the season. Planning to rely heavily on my Yeti + Cooler Insert for refrigeration those trips.

Denny16

Good test outing then, we found our overnight use ran the battery down about 20%, with fridge set to 3 it kept food at the correct temp (40F) to keep food safe.

Turning your fridge up past 3.5 is a waste of energy.  In 100 degree weather, our 2-way stayed at 38-40F set to 3.5.  Running it at max will get the fridge too cold, and will freeze leaf type vegetables.  Setting it at max, just causes the compressor to cycle more often also, wasting battery power.  You should never have to turn it up that high in actual use.  Get a fridge thermometer to set the fridge temp to correct safe food temp you prefer.
 Cheers 

techietab

I have a SensorPush device inside my fridge - the wifi gateway for that is part of the reason my 'idle' power draw is so high. Running at 'max' constantly, my fridge has struggled to maintain ~40 degrees in sub-100 degree temps here in northern VA, with or without having a decent amount of stuff inside to help with thermal inertia. On the very hottest days (obvious below) I've even cracked a window and turned the vent fan on to lower the cabin temps.
The only time I've noticing it freezing a vegetable was on this most recent outing, where on the second day it ruined a head of lettuce, but the other vegetables (tomatoes, bell peppers, asparagus) were fine.



Admittedly, I've never actually tried running the fridge at a lower setting. It might be cycling too often with diminishing returns that don't justify it.

Denny16

Give it a try, set the fridge at 3 and see what temp it will cool to.  You may be surprised by the results.  I did say leafy veggies, like lettuce, tom’s and regular veggies can take lower temps OK.
 Cheers 

tomtek

I had my fridge set to 3.5 and it froze everything and it was over 90 degrees ambient that weekend.  I run at 3 now and I think its still a bit high.

techietab

Moved the fridge dial to approximately 3.5 this morning. Seems to be stabilizing around 39 F with ambient temp outdoors in the high 70s. Ambient temps inside the camper are in the low 70s (I have the Air 8 cycling in dehumidify mode currently). It is probably ~20% full with some relatively stable items that stay there between trips.