"*The remaining capacity (criteria) display is based on voltage at no load. Since it may differ largely from
actual remaining capacity according to the battery type, use it as a criteria only.
*From the standpoint of the battery characteristics, immediately after charging and discharging, the
remaining capacity display will change until the battery stabilizes. The voltage stabilizes about 30
minutes after charging and discharging.
In addition, because of the different discharge characteristics, when the specified capacity was checked
after use, a remaining capacity lower than the actual remaining capacity may be displayed even for the
same type of battery. Judge the remaining capacity with the stable state value as a criteria.
*When the remaining capacity (criteria) display reaches 20% or less, recharge the battery.
*When the remaining capacity (criteria) display exceeds 95%, since the battery is almost fully charged,
refrain from charging it. Overcharging will cause the battery to deteriorate."
from the manual below
http://manuals.hobbico.com/fut/br3000-manual.pdf
if you download the manual, don't freak out because just the first half is in Japanese
