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Running batteries in series or
parallel?
There are several advantages to
running two separate battery packs in a particular boat. One reason
is if you need 12 cells but have other hulls that use only 6 cells,
you will still be able to run these packs in the other hull at a
different time. Another reason is weight distributing. Some hulls
need weight moved around to help balance things off. Its easier to
do this with two small packs then one large one. The only downfall
is the added resistance from longer wires.
The bottom two graphs assume we are
running the average 7.2volt 2400mAh(milli amp hour) NiCad batteries.
The end result on what the motor gets for exact voltage and
mAh (milliAmp Hour) will
vary depending on many factors. Including but not limited to, wire &
electronic speed control resistance.
It is very important that in either of the two bottom
scenarios, that the two packs being used are both from the same
manufacturer, and the same mAh
rating. Both packs should also be peaked individually
within a few minutes of connecting them for use. If not serious
problems could occur including fire, and possible explosion.
Series Graph
This is what we run in most Fast
Electric setups. The output to the motor and ESC will see, will be
the combined voltage of each pack. So in the below example we have 2
x 7.2 volts packs totaling 14.2 volts and the mAh
will be 2400. You could also combine packs of different voltages,
but its important to use similar packs from the same manufacturer
with the same mAh rating. Both packs must be fully
peaked prior to running them. Also don't run the packs until they
totally dump, once the boat starts to slow down bring it right in,
just incase one pack has a bit higher mAh capacity
then the other. Also make sure the ratings of both the motor and the
ESC will handle the higher voltage, you don't want any premature
equipment loses.
Parallel Graph
Lots of scale or enduro boats will run this type of setup.
Its very important that both packs be the same voltage. If one pack
is stronger the the other, it will try to charge the weaker pack
when they are connected. The motor will see the same voltage as a
single pack but close to double the
mAh. Because of this you will see close to double the
runtime but slower speeds then the single pack due to the added
weight of the second pack. Take care to make sure all your
electronics is up to the task of double your normal runtime. Extra
heat will build up in motor & ESC. These should be water cooled.
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