RE: lipo [TANKS]

["Gene Burbeck" <gburb-at-advantagecs.com>]

Size the battery right and they should do just fine. What voltage do you run the drills at from SLAs? 12V? 24V? Choose a Lipo pack with voltage less than or equal to the voltage you have found to work well on the drill motors. Capacity is where things get expensive. Normal SLAs will not deliver thier entire capacity when you have high current spikes like doing skid turns. Lipos on the other hand will deliver all the current you draw...until they catch on fire :)  It is absolutely nessesary to size your Lipo battery pack so this does not happen.

 

Do you have a good ammeter (clamp on prefferably)? If I were converting a tank to Lipo power that's where I'd start. Measure the total current drawn by the motors while doing the most stressfull driving you'll ever do - spin the tank in place most likely. If you size the lipo to deliver that current EASILY you should be fine. For example, if the motors draw about 75 amps total at stall/hard driving you'll want a lipo that will handle that current without exceeding 5 to 10 C. C is the number you multiply by the pack's capacity in AH to get current output. A battery draining at an average of 1C will be discharged after one hour. So for our example, a Lipo pack with 7.5 AH capacity will drain at 10C while skid-steering the tank. Good Lipo packs will handle 10C continuously and short pulses up to 30C or so. From this data, I conclude that a pack sized to last one hour with normal battle driving will have an average current low enough not to have any problems with peak currents. Use a fuse that blows at 15C to 20C.

 

A final note: Lipos are a waste of money unless the rest of the tank is built of light and strong materials, the motors are efficient and powerful, and the drivetrain is geared right. Lipo batteries save major weight, therefore the total tank weight is less; consequently less battery capacity is nessesary to last through a battle.

 

Enough rambling...I'm using NiMH batteries, they're good enough for me at the moment AND they fit my budget. I would be thrilled to see a Lipo powered tank...build a fast tank and build safe!

 

 

Gene

 

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From: tanks-admin-at-rctankcombat.com [mailto:tanks-admin-at-rctankcombat.com] On Behalf Of Chrysanthos Kanellopoulos
Sent: Sunday, September 30, 2007 9:52 AM
To: tanks-at-rctankcombat.com
Subject: lipo [TANKS]

Talk of which, what happens to our motors if we run them on Lipo batteries?  I have drills' motors, I have heard that they'll perform great, but they'll wear out very very fast.

 

Chrys

 

If you want a super-fast tank that runs for a minute or two, use CO2 and air
motors....If you want a super-fast tank that runs for an hour use Lipo
batteries...If you want a super-fast tank that runs all day, use a gas or nitro
engine.

Gene