Li-on Battery VS 9 Volt Battery

Madman

Madman

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So, in my seemingly never ending quest to perfect the weed whacker I made for my youngest grandson, I have run across a dilemma. It seems the 12 volt 3000Ah battery from China doesn't have what it takes to spin the motor. Yet when I attach a simple 9 volt battery to the motor it spins away. I
've been using these Li-on batteries to power some of my locos without any issues whatever. The motor I am using for the weed whacker is not much larger than a standard motor used by LGB in their locos.

I'm sure there is someone here smarter than I that can shed light on the problem.
 
Madman said:
So, in my seemingly never ending quest to perfect the weed whacker I made for my youngest grandson, I have run across a dilemma. It seems the 12 volt 3000Ah battery from China doesn't have what it takes to spin the motor. Yet when I attach a simple 9 volt battery to the motor it spins away. I
've been using these Li-on batteries to power some of my locos without any issues whatever. The motor I am using for the weed whacker is not much larger than a standard motor used by LGB in their locos.
I'm sure there is someone here smarter than I that can shed light on the problem.
Click to expand...

Can't find documentation, but I believe the discharge rate of LI-ION batteries is limited to prevent thermal runaway and fire. You may be able to bypass this at the risk of fire and explosion ;)
 
Sounds to me like this beast may be better using either a Lead Acid 12v job of a suitable size or perhaps a Radio Control Car one or perhaps 2 if the motor can take 14.4 volts. This would certainly give sufficient amps with a few Diodes to reduce the voltage to your chosen 12v. If you can find a couple of older batteries around or beg some you could test the concept before splashing the cash for new.
JonD
 
Greg Elmassian said:
Ummm... is the simple 9v battery the commonly called "transistor radio battery"?

about 1/2" by 1" x 2"?

if so, your liion battery is shot...

Measure the voltage of the battery while connected to the motor, I'll bet you it is almost zero.

Greg
Click to expand...


I'll have to try that Greg. I measured the voltage from the Li-on battery and it shows up as 12 +/- volts.
And yes, the 9 volt battery is your typical rectangular battery used in smoke detectors, etc, etc.
 
I originally tried a 6 volt Lead Acid battery, but it was a bit too heavy and little Enzo had trouble holding the weed whacker while pressing the on/off button. So my latest design uses 4 AA batteries.

Correct me if I am mistaken but four AA batteries equals 6 volts. If you had, for example, 6 AA batteries, cells to be politically correct, you would have a battery that puts out 9 volts. Shouldn't these six AAs last longer than a 9 volt battery ? Then shouldn't 6 D cells last even longer ? Basically, does battery size increase the longevity of the power output ? At least when I was a kid that's what I learned.
 
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You are correct Dan..

There is obviously 'something else' going on here??

I doubt a small motor is hitting the Lion battery so hard it is dropping to near-zero. - Can you measure the voltage when the switch is operated?
 
PhilP said:
You are correct Dan..

There is obviously 'something else' going on here??

I doubt a small motor is hitting the Lion battery so hard it is dropping to near-zero. - Can you measure the voltage when the switch is operated?
Click to expand...


Well, the deed is done. Forgetting that I said I was going to do just that, I dismantled the contraption and installed four AA batteries. Wait, I already said that, in post #6. So now little Enzo has a Weed Whacker that works, albeit at a lower speed. Which is probably good, since the zip tie i used for the business end can sting. So now my son wants me to change the zip tie to some sort of flexible ribbon. I have some braided strapping that is soft. That's tomorrow's project. It's a good thing I am not making this thing to sell. I would be way in the red before now.....:swear:
 
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