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Tommygunn

What spec of Lipo for a stock Tamiya Monster Beetle?

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Currently, I'm restoring my Monster Beetle which has the stock 540 motor and Tamiya mechanical speedo. However, before I go all out, i.e. brushless and ESC, I want to get it rolling with the bare minimum.

What I need to know is what spec of Lipo do I require?

I'm not going to go over 7.4V but what do I require in terms of C rating? I have three Turnigy Nanotechs which are specced at 15/25C. Is that sufficient or do I need something with a bit more heft?

Cheers,
Tom.

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Welcome to TC! :)

Any 2s (7.4V) LiPo should be fine with the plain silvercan motor, as long as you make sure their dimensions fit the Monster Beetle (Frog) chassis battery compartment. Remember to use a device that warns you before the LiPo battery runs dry (e.g. LiPo warner or LiPo cutoff), to avoid permanent deep-discharge damage of the LiPo.

Before using any other more powerful motors, modifications of the gearbox are highly recommended (look out for Oldfrogshot's diff mod). Otherwise be prepared for excessive wear on the differential gears. This is a general design flaw of this chassis' gearbox.

See also this thread for more information about what LiPo fits in what chassis type:

http://www.tamiyaclub.com/forum/index.php?showtopic=67706

If you like to, feel free to share pics of your restoration process. :) The MB is a lovely car with lots of character.

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Greg,

Thanks for the welcome and the advice. No problem with other aspects of the Lipos as I am into Quads and Helis and I have several alarms.

I've been reading up on the diff problem and as you say I might go for the mod. Mind you, my Beetle has been pretty well bashed around in it's life and the geabox is in perfect condition.

I'll be keeping the Beetle stock, as far as the motor goes, and use my Losi LST2 for going mad.

Cheers,

Tom.

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More milliamps means more runtime. I like to calculate value of a battery by dividing dollars by milliamps. This gives a good comparison of how much you are paying per milliamp. Sometimes it's cheaper to by two lower milliamp packs rather than one big one. It's hard to beat paying less money for more total amps. Plus the versatility of having multiple packs.

The C rating you need will depend on what motor/ESC you are running. If you have a 120amp ESC, it would be ideal to purchase a C rating high enough that the lipo can provide at least 120amps continuous power (even more is better). Here is how to calculate this:

- convert battery milliamps to amps:

5000mah / 1000 = 5amps

- calculate required C rating:

120amp ESC / 5amp battery = 24C. That means with this combo you need at least a 25C rating or higher.

- convert battery milliamps to amps:

3200mah / 1000 = 3.2amps

- calculate required C rating:

120amp ESC / 3.2amp battery = 37.5C. This means you need at least a 40C rating or higher to safely run a 3200mah pack.

Now those calculations are based on the ESC's rating which means you could run ANY motor rated for that ESC without blowing up the battery. But if you are running a hot ESC with a very slow motor, you "could" get away with a much lower C-rated battery. In this case you would take the motors peak rated amps instead of the ESC's.

- convert battery milliamps to amps:

3200mah / 1000 = 3.2amps

- calculate required C rating:

60amp Motor / 3.2amp battery = 18.75C. This means you would only need a 20C pack to run with your selected low-power motor. But if you switch to a hotter motor, you better be weary of your packs low rating.

In reality it's the motor that demands the current, so it will dictate how much power is pulled from the battery. The ESC is just a gateway. So if you absolutely must use low c-rated batteries, you should match them to each of your motors.

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94eg,

Thanks for the reply. However, I'm running a stock Monster Beetle with a Mabuchi 540 motor and mechanical speed controller.

The only improvement to this spec is the likelihood of getting a Hobbyking X-Car 45A Brushed ESC at some point in the future.

Tom.

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Personally I wouldn't go any hotter than a Sport Tuned in, especially running on LiPo. Even after the OldFrogShot mod the gearbox just can't cope with big power due to the monster truck wheels.

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Sorry that was really bad English, it should have read: I wouldn't go any hotter than putting a Sport Tuned motor in.

The Tamiya Sport Tuned motor is the most popular motor upgrade for Tamiya fans offering a reasonable (and noticeable) speed and torque increase without breaking the bank (or your car). They look good too, coming painted in black with the immortal words 'Sport Tuned' in big silver letters.

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Even better, the speed will probably be about right when coupled with a LiPo

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