Dual 9volt works but not 18 volts.

[redline724]

Hey folks I came up with this idea since I tried it various times.
Do what you want with it.
Please bear
- 3 1.2 volt Ni MH rechargable batteries weigh equal to or greater than a single 9 volt.
- I tested using Alkaline. Radioshack sells 9V rechargables at ~ $12 each. You would have to find a charger or build your own.

To make this quick, at first I hooked up 3 additional AAA batteries totalling 7 and my Xmod was way too heavy and it would slide around too much as I had a 3 pack battery holder taped to the top of my chassis (fit snugly btw).

I moved on...

- I tested a stock motor with a 9volt battery... fast
- I tested same stock with 2 9 volts in series (18 volts total)....really fast..risk motor might burn out.
- I tested with 2 9 volts in parallel (9-18volts, have to verify) and I am suprised how it works slightly faster than 1 9volt battery and the life of the battery lasts longer. With this setup, I still have to test the voltage with my multimeter, have been lazy will do soon.
- I did tested 2 9 volts in parallel with my friends stage 2 camaro, evidently his is the faster car.

Note that because there are two batteries supplying the current rather than 1, they last much longer (something I learned in circuits class).

Let me explain how I wired the batteries up, so that you may try as well.
You will need:
- a soldering iron, they cost ~$11 for a decent one at Radioshack.
- solder ~ $2
- a bag (comes with 5) of 9volt terminal connectors that simply latch on to the 9v ~ $2

1) Grab two positive (red) ends of two different connectors and solder them together. Once they set, this is the tricky part, you will add a 3rd wire by melting the solder slightly so the 3rd wire is included. Think of a Y, the 2 positive terminals connected (soldered) to a single (3rd) wire. Allow enough roo
2) Repeat the same for the negative.
3) cut and strip the positive and negative that go INTO the circuit board, then remove the prehistoric AAA packs by unscrewing 1 screw and prying them off.
4) last, solder the Y connections made before to the right color.

I'm not sure what happens with this setup and a 3rd stage engine, that would be a sight to see. But I do know that 2 9vots are hard to squeeze in my 'stang chassis. My friend with a camaro did it fine. email me or pm if you'd like. Have fun. Later.

[broke ess supra]

interesting...i would never think to do this...i have tried an 8 cell design but it was to heavy and drifty.
i know that a 9 volt alone can't supply enough current to move these motors under load... but maybe this is true with the extra current of a parralel combination? Why don't you test to see how much current is coming out of this settup into a stage 2 motor without load?Also test under similar voltage situation with the aaa to see if the amount of current is the same? From what i heard about 9 volt setups the current is not sufficient? please prove me wrong!!

[Shelby_HEMI]

Question: How are you getting around the 8.4v voltage limit on the electronics?

[broke ess supra]

i have put 8 cells on the stock board with no problems really...i think it really just has to do with the luck of the quality board you get...plus i have heard about the 8.4 volt limit(7 cells under load)but i just decided to try it anywayz
-the real issue here is the discharge rate of the nimh 9 volt batteries...I've heard that they don't give enough current...but in parallel they might work?! regardless REDLINE724 hasn't answered this question and since i don't have the batts readily available i can't test the discharge rate.

[Horshu]

I damn near sound like a commercial praising this thing, but you can also get around the voltage limitation with a regulated external turbo, which can supply the motor with extremely high voltages (my AtomicMods v2.2 does 30V/30A sustained) while ensuring the ESC only ever sees a steady 5V. AM is the only one I know of that is regulated, although Woah Nelly was supposed to come out in a regulated version this year.

[Jshwaa]

Voltage isn't the most important component in making a more powerful xmod, mAh is. The truth is 9V batteries have 6 tiny cells in series inside them. Each of these cells have a relatively small mAh rating. Getting 9V out of such a small and light package might seem ideal, but you are starving your motor of the key component it needs to produce its electromechanical force.....CURRENT. 9V batteries are good for small electronics which need audio amplification, but for driving motors they are the worst choice.

[Marius666]

If yu run your car on dual 9v you will fry it no matter how fast the dischargeis from the batteries. I have done it, now I have an xmod with a f***ed up electronics board.

in series, 18V will kill any board.... Some might get lucky to have good enough components to runs on 9V.... People do more research before modifying.

[83gt]

Originally posted by Jshwaa
Voltage isn't the most important component in making a more powerful xmod, mAh is. The truth is 9V batteries have 6 tiny cells in series inside them. Each of these cells have a relatively small mAh rating. Getting 9V out of such a small and light package might seem ideal, but you are starving your motor of the key component it needs to produce its electromechanical force.....CURRENT. 9V batteries are good for small electronics which need audio amplification, but for driving motors they are the worst choice.

What do you mean by this ? mAh has nothing to do with increasing power. Higer mAh = longer runtime, higher voltage and discharge rating = speed/torque/power. A 3000mAh cell will NOT give more power than a 500mAh cell unless the former has a higher discharge rating. You will allmost allways sacrifice mAh for discharge rating.

You are correct about 9v batteries having poor perfromance, but for the wrong reason. 9v batteries have a relatively low discharge rating (c rating). They are intended for low-draw devices, they last a long time, but that is because they do not discharge current as rapidly as the batteries we use in RC.

J.

[Jshwaa]

mAh has nothing to do with increasing power

You are wrong. The very definition of electrical power can be equated to current times voltage.

Higer mAh = longer runtime, higher voltage and discharge rating = speed/torque/power

How the heck does higher mAh amount to higher voltage? Also, you just contradicted yourself. You were quoted as stating that mAh has nothing to do with increasing power, and then quoted as saying it does. Make up your mind.

A 3000mAh cell will NOT give more power than a 500mAh cell unless the former has a higher discharge rating.

Ok, I challenge you to find 2 cells of the same chemistry(li-ion, nimh, nicd, etc.) with a higher mAh rating but lower discharge rating. You won't. Cell's discharges are rated in "C". The C is a multiplier. You multiply the C by the mAh rating to get the discharge rate. Therefore if a cell has higher mAh, it has higher discharge rate.

You are correct about 9v batteries having poor perfromance, but for the wrong reason. 9v batteries have a relatively low discharge rating (c rating).

Now what did I say? mAh of cells equates to discharge rates in that if you have a higher mAh rating, you have a higher discharge rate. The reason 9V have low discharge rates is because a 9V is composed of 6 tiny 1.5V cells in series. Each of these tiny cells have a very small mAh rating. The discharge rate of the 9V is dictated by the small mAh rating of the 6 small cells. Also, cells have an internal resistance. Putting cells in series puts the cells resistances in series, thus lowering the discharge rate even more.

I don't know who you are, but you're clueless in your attempt at saying I was wrong at anything. I would just give it up if I were you.

mAh = Milliamp hours, which is how long the battery can supply one milliamp. This is indeed how long the battery will run.

If you notice, he actually didn't say that mAh lead to more voltage since there is a comma in his sentence.

[83gt]

Originally posted by Jazz32
mAh = Milliamp hours, which is how long the battery can supply one milliamp. This is indeed how long the battery will run.

If you notice, he actually didn't say that mAh lead to more voltage since there is a comma in his sentance.

Thanks for that. At least someone can read!





I'm gonna have a hard time responding to Jshwaa's post as most of his statements don't even make sense.

I'll try to spell it out as simply as I can.

mAh, see excellent explanation provided by Jazz32 above!

To elaborate on mAh:

A milliampere hour (mAh) is 1000th of an ampere hour (Ah). Both measures are commonly used to describe the energy charge that a battery will hold and how long a device will run before the battery needs recharging.

Discharge rate - How quickly can a battery discharge it's stored energy.

You can have a 2000mAh li-ion cell with a low discharge rate, say 1 or 2c. I don't care what you do to that cell, it's never going to put more power to your motor than a similar cell with a higher discharge rate, even if that cell is less than half the mAh of the previous cell. The lower mAh cell will simply drain faster and need recharging sooner.

As far as high mAh directly relating to high discharge rate, I don't even want to go there. That is pure falicy and should not be posted here. High mAh does not mean a cell will have high discharge. High discharge does not mean a cell will have high mAh.

Here's the answer to your "challenge". Not much of one since anyone could find that in less than a minute if they knew what they were looking for.

http://www.batteryspace.com/index.as...OD&ProdID=2158

Chemistry: High Current Polymer Li-Ion
Capacity: 1050mAh
Charging rate: 1050 mA Max.
Discharging Rate: 10 A Max. (10 C rated)

http://www.batteryspace.com/index.as...OD&ProdID=2157

Chemistry: High Current Polymer Li-Ion
Capacity: 1500mAh
Charging rate: 1.5 A Max.
Discharging Rate: 7 Amp Max. ( 5C rated)


Do some reading next time buddy. Preferably BEFORE you jump all over somone. Please feel free to explain the difference in the above listed cells by your "multiply "C" by "mAh" to get discharge rate" theory.

J.


Sorry for the thread jack. Back to the 9v idea, probably not the best batts you could use. But we're talking about a $40 car. Do what you want

[Jshwaa]

quote:
--------------------------------------------------------------------------------
Originally posted by Jazz32
mAh = Milliamp hours, which is how long the battery can supply one milliamp. This is indeed how long the battery will run.

If you notice, he actually didn't say that mAh lead to more voltage since there is a comma in his sentance.
--------------------------------------------------------------------------------



Thanks for that. At least someone can read!

Yea, I can read, but you just can't write. The comma should have been a PERIOD and TWO SEPERATE SENTENCES, sorry I wasn't a moron to think it was. Thank your buddy for having the same deficiency as you and helping you out with that. Why you bothered including his poor interpretation of "milliamp" is beyond me. I would have been influenced more by a quote from crusty the clown on some episode of the simpsons.

Now, on to your other short-comings......

What you say "doesn't make sense" is knowledge that comes from experience and a degree, thank you, so if you don't understand, don't even think that it's MY fault in the least bit, kid.

I know what the hell a milli-amp is, I know what a milli-amp-hour is. All you're doing is eluding the point with your little lecture on the issue. And why are you arguing the fact that I was right, but for the wrong reason, in the first place? Are you that much of a noob that you have to dig up an old post and nit-pick at it? Get a life!

As far as high mAh directly relating to high discharge rate, I don't even want to go there.

Of course you don't. Because you're dead wrong. mAh is a product of current and time, fool. If you have a 1000mAh cell, you can discharge it at a rate of 1A for an hour(in ideal conditions), OR you can discharge it at a rate of 500mA for 2 hours(ideally), OR you can discharge it at a rate of 250mA for 4 hours, etc. 1000mAh doesn't dictate current rate NOR time of discharge, BUT, if you have a higher mAh rating you CAN and DO have higher discharge rates available. Why the hell do you think higher current demanding devices have higher mAh rating cells in them? You think that is ONLY for higher amounts of discharge time?? NOOO! It's for higher current demand for ANY GIVEN AMOUNT of time as well. Which brings up your next ignorance. A cells "C" rating......

Get your mom's calculator and do a lil' excercise with me. Take the specs that YOU looked up if you would.

Chemistry: High Current Polymer Li-Ion
Capacity: 1050mAh
Charging rate: 1050 mA Max.
Discharging Rate: 10 A Max. (10 C rated)

Take the Discharging Rate and divide by the Capacity rating of the cell. I get 9.5238095. Now, do you think the engineers would have maybe rounded that number, and gave the cell a C rating 10?? WOW, what a stretch of the imagination that takes. This "theory" is fact! And if you think your links to websites proves anything, you need to get a hold of the webmaster of that site, because their specs listed and the actual pics of the cells are contradicting themselves, which leads me to believe that they and you need to take a walk. Don't even think that proves squat. There's no authority in a friggin' hobby website that supercedes experience and training. Most li-po cells I've encountered have a discharge of 10C, making a li-po cell with a mAh rating of 2000mAh have double the discharge current rate of li-po cell with a mAh rating of 1000mAh. It's simple math and deductive reasoning that accomplishes this understanding, not a website.

Do some reading next time buddy. Preferably BEFORE you jump all over somone.

You're the one who started it. Are you going to act like YOU'RE in the defense here? I mean, you're now bending and twisting the point in an attempt at sticking your chest out at someone and proving something. You've terribly failed. And then you bother to apologize about the big turd you laid on the thread? Take your $40 car, build a bench, and do some friggin' experimenting, AFTER you read up on some things, and BEFORE you even try to debate with me. Do you even have the slightest who you are in respect to who I am, when it comes to electronics, and especially pertaining to xmods? It wouldn't take anyone here long to realize that you don't. Why don't you do a search on some other forums? I've contributed more to the hobby, and done more with the hobby then you have websites to look up. So lock and load, buddy, there's more where this came from.

[83gt]

Oh don't worry, I've seen you around plenty. You've got alot of good knowledge and I won't argue that. My first point is that you're being a real ass. My second point is that a batteries discharge rate does not increase because it has a higher mAh. If you have a degree, and know as much as you say about electronics, you'd know that.

I don't know how much simpler I can make it.

mAh - the amount of energy a battery can hold.

discharge - how quickly same battery can release the stored energy.

You can find this in any textbook on the subject. You can argue till you're blue, and claim how much you know on the subject, but that won't change. I'll give you all the props you want on the subject of xmods, but on this one, you are WRONG. You are wrong because more mAh does not necessarily mean more power to the ground from your RC.

Last point, I am 30 years old with a degree in information science. I work for a software development and engineering company as a hardware specialist and systems engineer. I have 2 children and own my home. Watch who you call "kid". It's ok to be wrong once in a while man, even for someone like you. Just admit it instead of flaunting your xmod omnipotence to try and convince anyone reading that you're right. Dude, you could google for 5 minutes and find countless information to the contrary of what you're saying.

J.


I had to elaborate, I just could not resist. If you would like to continue this, lets try to keep it civil and knock off with the insults.

Most li-po cells I've encountered have a discharge of 10C, making a li-po cell with a mAh rating of 2000mAh have double the discharge current rate of li-po cell with a mAh rating of 1000mAh. It's simple math and deductive reasoning that accomplishes this understanding, not a website.

Most li-po cells used in RC will have discharge ratings of 10C. That's true. Most li-po's will not have a discharge rate of 10C. Alot are rated at 2C. There is no deductive reasoning involved unless you want to pick and choose cells that match your "deductive reasoning". It's science.

"C-Rate" is only a reference point that can be used to figure discharge rates. It is not C/aAh that gives you discharge.

A 1000mAh cell with a 1C rating will fully discharge in 1 hour IF it is discharged at 1C. That cell has a discharge rate of 1A. If a 1000mAh cell has a 1C rating, it can fully dump it's charge in .5 hours. That cell has a discharge rate of 2A.

You are abosuletly correct in that a 2000mAh cell with a 10C rating has double the discharge rate of a 1000mAh cell with a 10C rating. So, you are right if all cells were rated at 10C, but they are not. You can't take that "simple math" and apply it to all cells in the form of 1000/10 = 10, or 2000/10 = 20. It simply wont' work if you vary from 10C rating. There are plenty of cells out there with lower C ratings. If you'd look for 5 minutes you'd see that.

J.

[Jshwaa]

Blah Blah Blah. Read this thread over and over again, until something clicks. Hopefully you don't starve to death.