by Stefan Vorkoetter
At KRC'98, I purchased an 8-cell Sanyo 1100AAU pack to use in my JR XP642
transmitter. Since I use this transmitter for most of my planes, it gets
a lot of use during a day of flying, so I wanted more capacity than the
600mAh provided by the factory pack.
A few months ago, I saw that East Coast Model Center was advertising
individual 1100AAU cells for Cdn $5.99 (about US $4.00) each. I decided
I'd give these a try as a power source for my Sydney's Special
a Speed 400 sport plane I've been flying with 7x600AA packs for about a
year now. Flights with this 37in span, 270 sq.in, 17.5oz (94cm, 17.4dm2
500g) plane have been around the 6 to 7 minute mark, mostly at half
throttle. Flying at full throttle, Sydney
can just finish a 4-minute
EMFSO Speed 400 sport pylon race.
I ordered a set of seven 1100AAU cells, and assembled them into a hexagonal
pack (one cell in the middle, six around it), using the same assembly techniques,
wire, and connectors as on my 600AA packs. The photo below shows, from
left to right, 7x600AA, 7x600AE, and 7x1100AAU (I ran out of clear heat-shrink).
I cycled the pack on my computer controlled battery analyzer (some day
I'll have to write about that) until the capacity stopped increasing. After
four cycles, the capacity levelled of at 1.099Ah when discharged at 1.2A
The first test flight was phenomenal! Sydney
climbed out with
her usual authority, and after a few seconds of climbing, I throttled back
to half throttle and started flying figure eights. Occasionally I'd get
too high and do a few loops (from a slight dive, still at half throttle).
My ESC has a gradual motor cut-off instead of a sudden one, so I bumped
the throttle from time to time to see if it could still provide full power.
When it no longer could, I landed and looked at the clock: 14 minutes
of cruising flight with mild aerobatics
. After returning home, I discharged
the pack to determine how much capacity I'd used. There was 88mAh left,
indicating I'd used just over 1Ah.
Being a technically minded person, I also did some tests using my battery
analyzer to compare the performance of 600AA, 600AE, and 1100AAU packs.
For the 600AA and 600AE packs, I used the results from my best packs. For
the 1100AAU, I used the results from my one and only pack.
Each pack was cycled at 1.2A until its capacity no longer increased.
Here's the executive summary:
|7 x 600AA
|7 x 600AE
|7 x 1100AAU
Notice that the 600AA pack delivers significantly less that 0.6Ah, and
the 600AE pack a bit less than 0.6Ah. The 1100AAU pack lives up to its
name, giving almost 1.1Ah. Furthermore, the average voltage delivered by
the 1100AAU pack is higher, indicating a lower internal resistance, and
further increasing the total energy output of the pack. The 1100AAU pack
can deliver over twice the total amount of energy as the 600AA pack, and
almost twice the total energy of the 600AE pack.
The 1100AAU pack is only 0.4oz (12g) heavier than the the same-sized
600AA pack, and thus can be used as a direct replacement, as I did in my
The following three graphs are from the last cycle done on each pack. First
is the 600AA pack. Notice that even after the initial drop, the discharge
curve is quite steep, dropping from about 8.8V at the 6 minute mark, to
about 8.3V at 18 minutes. Click the image to enlarge.
Next is the 600AE pack. The discharge curve is about as steep as the
one for the 600AA pack (it doesn't look that way because the scales of
the graphs are different). The overall capacity is a bit higher. Click the image to enlarge.
Finally, here's the graph for the 1100AAU pack. Notice that the discharge
curve is very flat, much more like an AR type cell. The voltage drops from
about 8.8V at 13 minutes to about 8.5V at 39 minutes, and then starts to
drop more rapidly after that. This alone makes the 1100AAU more suitable
to electric flight than either the 600AA or 600AE. And of course, the capacity
is nearly doubled. Click the image to enlarge.
That the Sanyo 1100AAU cells haven't been talked about more is a mystery
to me. This cells is ideal for Speed 400 flying, providing about twice
the capacity of 600mAh cells at a very modest increase in weight (only
7% heavier than 600AA, or 29% heavier than 600AE). The discharge curve
is nice and flat, giving consistent power levels throughout a flight. Only
time will tell how well these cells hold up under use, but so far, they