Recalibrating the BMS on a Delta 3 Plus
I have had my Delta 3+ for about 8 months now, and it has been used daily since I am mostly off-grid. On any given day, I can use between 400 to 800Wh, with my nightly loads taking the box from 100% to as low as 50% depending on how long I run the fans.I had read that around every 6 months, it is a good idea to do a couple of full discharge cycles to let the BMS recalibrate. I have had a couple of weeks where I was getting at best 4 hours of sun per day, and this led to the box being taken down to 20% and only charging back up to 60% or so.I noticed that the battery gauge on the app and box when connected to solar would at times seem to be going really fast, or would sit at a % for a long time before moving again, with roughly the same amount of solar coming in. Then one day it went from 75% to 100% in a blink of an eye.I am mostly off-grid, so if I want to do a few full discharge cycles, I would have to be very careful to plan it around the weather. The weatherman finally decided to work with me, and I have 3 days where I should be able to do 3 cycles. I drained down my older box to 20% so that I could use it as an extra load overnight.I was sitting at 40% and about 3 hours away from sun when I started to watch. The battery gauge was barely moving, even though I had a constant 100W draw on it. After 2 hours, I was down to 32%. I decided to speed it up and plugged the cooktop in, drawing 1.1kW, and took the box down to 5%. My thinking was that I really didn’t want to be hitting it with that high of a load when it hit 0%, so I unplugged the cooktop and went back to just that 100W load. It finally settled on 4% and then took another 40 minutes to drain to 0%. I will eventually level off with around 220W of solar which should take about 5 hours to get to 100%If the weather holds, I will attempt 3 full cycles and report back. I think it will be interesting to see the amount of solar it will take each time to go from 0% to 100% as the BMS is recalibrating.