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Old Mar 03, 2011, 05:00 AM
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Joined Jan 2011
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Need new lipo to replace old nimh for aquajet boat

Hey guys,

so I have this old CEN Aquajet http://www.cenracing.com/boats/aqua.html


Actually, I got it from my uncle but it was originally nitro. So, he put his own motor in it (an old brushed style motor) with a modified motor axle (if thats what its called).


The boat has a motor that is almost 2.5 inches long and diameter is 1.5 inches. Im not sure but its probably size 500 or maybe more.


It had two Ni Mh 1000 mah batteries wired in parallel (so 2000 mah total). Each was a 7 cell battery, so 8.4 V when new.


I want to replace these NiMh with a single new lipo pack. Im not sure what to get. I need to take mah and C rating into account. How much does the old brushed systems draw anyway?


Also, what kind of motor could I get to replace the old fat brushed system? Preferably of similar power to a 550 size motor (maybe even 700 size motor) and thats 1.5 inch diameter (to save me having to modify the mount again).


Thanks for your feedback
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Last edited by short_circuit; Mar 03, 2011 at 05:12 AM.
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Old Mar 03, 2011, 11:01 AM
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EricJ320's Avatar
Knoxville, TN
Joined Dec 2005
1,502 Posts
I'm not sure how many answers you'll get about the amp draw of a stock boat system in the aircraft batteries and chargers forum.

Take a look at Hobbypartz.com, Gens Ace 2S 25C or higher packs should have something you need. Just remember, lipos of the same capacity are going to be significantly lighter, if balance on a boat is that important you might need to step up in capacity to help balance the boat. Besides, more run time is never a bad thing!

They would almost certainly also have a brushless motor to replace the brushed stock motor, but also remember that means you'll need a new brushless ESC as well. Google the boat name and brushless and I'm sure you'll find someone making suggestions for what you're looking for, and then look for what you would need from Hobbypartz, they have a ton of brushless motors and ESC's for this very thing.
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Old Mar 03, 2011, 12:45 PM
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ptglass's Avatar
USA, TX, Live Oak
Joined Oct 2002
679 Posts
Although 3 cell lipos work best for brushless motors, you can run a brushed motor on a 2 lipo cell pack. I have no experience with boats, but I am flying a 60" sailplane with a brushed motor with a gearbox that I used to fly on a 1100ma nicad pack. Even though the voltage is a little less with the 2 cell lipo pack, the lighter weight and consitent amperage easily makes up for that. Since I am using the original esc that was made before the advent of lipos, I carefully monitor cell voltage to prevent taking it too low. So far it's worked out fine. When the brushed motor finally wears out, I will replace it with a brushless motor and esc, but until then I will continue to fly it as is.
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Old Mar 03, 2011, 01:29 PM
NitroPlanes Sponsored Pilot
Joined Jul 2009
201 Posts
Although I don't have any experience with boats, I reccomend the GenAce or SkyLipo from HobbyParts.com. I can't even begin to tell you what C you will need, as I don't know how much a boat draws, but the 40C packs are now reasonable.
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