Lithium battery in Lil Snoozy

[buff30]

Looks good Doug! I think your battery longevity will be much better with that second battery. .6C is a lot even for a LIFEPO4. Have you ever figured out what your Truck Fridge averages for current draw per day?

[dleverton]

Originally Posted by CarlD

Doug, I have a question regarding the 30A fuse in line with the solar panels. I also have a fuse in this location, but I installed it blindly because the manufacture recommended it. I may be missing something here, but what scenario will cause this fuse to blow? The solar panels have a current limit that, I assume, is less than fuse value, so there is no scenario there that could blow the fuse. Is there some kind of back feed mechanism in the MPPT charger that could feed battery current to the panels? Do you have any insight?

Your right that if the short circuit current of the panel is less than the fuse value...what’s the point? Two points: fuses are to protect the wire and the amp rating is chosen accordingly, and the manufacture recommended it because UL does, and it’s still a bit of a grey area.

[John in Santa Cruz]

Originally Posted by dleverton

Your right that if the short circuit current of the panel is less than the fuse value...what’s the point? Two points: fuses are to protect the wire and the amp rating is chosen accordingly, and the manufacture recommended it because UL does, and it’s still a bit of a grey area.

fuses are there to prevent fires. they do this by keeping the wiring from burning up. they can protect a power supply, but they are not there to protect the load.

[Air Doug]

Originally Posted by buff30

Have you ever figured out what your Truck Fridge averages for current draw per day?

I don't have a good number for the Truck Fridge draw. Obviously it is easy to measure while it is running. But how often it runs varies by ambient temperature outside and setting inside. Plus, the upper door hinge mount broke and the fridge door was slowly falling apart without us noticing it. It caused some abnormally high draws until we figured out that the door wasn't closing all the way (condensation at the door seal was the tipoff). After I get that fixed I may be able to get a good number at various fridge settings and outside temperatures, or maybe not. I really would like to not worry about it so that was another reason to get a second battery: I don't have to worry so much about the fridge power budget.

[buff30]

Thanks Doug,

I will eventually figure it out my self. I have my four 60 AH LIFEPO4 cells and my SBMS 120 battery management system. I just need to get it installed and figure out what my actual usage before I buy my full size cells.