The cells database (CELLS.EDB) characterizes Nickel-Cadmium cells.
CELLS is a description of the selected cell (up to 20 characters). These cells are
mainly Sanyo. The most popular are the N-1700SCRC and RC2000 for sport flying,
and the KR-600AE and N-500AR for the smaller "Speed 400" models. This brand
has a proven track record. Cells with an 'R' in the suffix are especially suited
for the high charge and discharge rates needed for electric flight. Other cells
have a higher energy to weight ratio but at the expense of higher current
handling and/or charge rate
MAH is the typical milliampere-hour capacity of a cell. This basically means
that the cell can supply that many milliamps for one hour before the voltage drops
substantially. This is generally higher than the manufacturer's rating, but
will vary as a function of the charge method, discharge rate, and temperature.
This number is used to estimate the motor run time at the calculated battery
current. MAH is normally measured assuming a cutoff voltage of one volt or less.
With high cell-count packs you can't afford to let the pack get down this low per
cell without risking damage to the lower-capacity cells. You can expect the
capacity of a higher cell-count pack to appear less due to the higher probability
of a spread in cell capacities.
mOHM is the equivalent cell resistance in milliohms. The lowest resistance is
obtained with end-end soldered cells. Cell resistance should include the
resistance of the cell interconnections. The original data assumes minimal (end-end
soldered) resistance. Bars or heavy braid will be somewhat more (+0.5 milliohm)
and welded tabs could be substantially more (>1 milliohm). You can measure this
yourself with a good DVM, ammeter, and load. Basically you need to measure under
load and no-load voltage quickly so that chemical processes do not interfere.
Use at least a 10-amp load. Cell resistance is voltage difference divided by
load current divided by number of cells. See our web site for information on end-end packs.
DIA. & HGT. are cell dimensions in inches and are informational only.
WGT. is weight of the cell in ounces. This number is used in calculating the
plane weight. When the cell type is changed, the plane weight is adjusted
MAH/OZ. is informational. It is the capacity of the cell in MAH divided by the
weight in ounces. Use this to appreciate the capacity versus weight tradeoffs that
you must sometimes make.
COMMENTS are allowed at the end of the line.
PTR is a somewhat bizarre alphanumeric pointer assigned to this data entry for
reference by the PLANES database. There is a small chance that two entries will
have the same pointer and thus "confuse" the program into selecting the wrong
one. This can generally be fixed by making a slight change in the description.