This is 2021 model with 4 digit voltage display
Works on a 4way communication channel. When one battery is connected it displays value of the other 3 batteries-/+0.5mV. Correct value when you connect each battery.
When two or more batteries are connected in series or parallel, voltage differences begin to occur as the batteries charge and discharge. While some batteries may be overcharged,other will be undercharged. This causes battery sulfation and ultimately reduces the life span of your precious battery bank by about 2-3yrs
Once voltage difference of 2mv is detected, this energy transfer battery equalizer automatically begins to move current from higher to lower voltage battery until equilibrium is attained
specification
48v
1. 4 batteries in series
2. 8 batteries in series/parallel