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What's the best way to increase the power on my son's electric motor bike? Answered

I bought a riding toy for my son and it's cool, but it doesn't have enough power sometimes.  It's fast enough in the house, but it gets stuck outside.  The plastic wheels tend to slip on rough surfaces and inclines, but I can address that issue at the wheels/tires to some degree.  However, the battery that came with it is a 6V4.5AH/20HR sealed lead-acid rechargeable battery (It has F1 contacts, so unless I change or adapt the wires/connectors, I think I need to stick with a battery that has these).  The AC-DC adapter has 6V DC 500mA output, but I think I could get a UNIVERSAL AC DC ADAPTER {1.5V 3V 4.5V 6V 9V 12V 500mA} that would work with a new battery.

I'm hoping that I can increase the power noticeably but safely.  One constraint is the width of the battery area inside the "engine" compartment.  It fits the present battery (1.75 x 2.75 x 4), but I'll have to mod the compartment to fit a replacement that's more than slightly bigger.

I've seen some 12V4.5AH batteries online, but most are larger in every dimension.

Am I even on the right track thinking a higher voltage battery is what I need?
Could I use an NiMH or Li battery/batteries instead?

What's the easiest, safest, cheapest route for this mod?


5 Replies

liquidhandwash (author)2013-04-24

Have you thought about using a cordless drill? you get a charger, battery, controller with reverse and a motor. If it were me I would use the battery and controller and wire it up to the cars motor. If you burn the motor out then replace it with the drills motor. it probably only has to last a year or so, kids grow up too fast.

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frollard (author)2013-04-22

The motor in the bike is rated for about 6 volts, if you feed it 12 volts it will consume 2x as much power, go 2x faster (not necessarily with 2x as much torque) -- but it will get a LOT hotter and under continuous use will die a horrible death, not counting the electronics in the throttle probably starting on fire because of overvoltage.

Reason: The equivalent resistance (reactance) of the coils in the motor is fixed, and if the voltage doubles, the current through the motor doubles...
the power disspated goes up with the square;
P = I^2*R
R is constant, so the current (I) going up double means 4x as much power, which essentially translates to 4x as much heat.

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danhorowitz (author)frollard2013-04-22

Thanks, frollard! I'll avoid that route then. Barring a battery that doubles voltage, what's a better alternate course to pursue considering my objective (short of buying a different bike -- this one, despite the humorous translations in the user guide, is very cool and was worthy woot), Inside it's fine, but it struggles up the driveway and isn't apt for uneven terrain... so torque is probably a better consideration.... perhaps a different electric motor?

I'm not opposed to thinking deeper under the hood, but I'm trying to maximize my efforts or rather the effectiveness thereof.

Bottom line... battery with more volts out? if so, then what other variables can/should I consider?

thanks again for the input!

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frollard (author)danhorowitz2013-04-22

Per my first response:

It's a chicken/egg problem.

Battery with more volts = cooked electronics and motor
Bigger motor = battery dies faster, electronics may or may not support more current, drive train may not be able to handle extra torque (slippery wheels, etc)
Bigger controller = might burn out existing motor and battery will die faster;

So - if you want it more powerful, you need to upgrade all three reasonably; batteries, controller, and motor/drivetrain - going that overkill makes a person think its a better idea to just get a bigger bike.

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rickharris (author)frollard2013-04-22

Your real problem is the plastic wheel - This has little traction on ground such as grass.
The toy is really intended for inside.

You could glue on a rubber tire tread this will give a lot more grip. Cut up an old bike tire.

To get more torque you need to change the gearing. BUT this will lower the top speed as well.

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