can someone explain batteries to me?

[twizm]

with the MaH (i think) rating, is a lower number meaning more current to the motor?

do the 10min+ runtime cells on the market have a higher or lower power output than stock tomy batteries? (as in, they run longer because they use less current)

thanks.

[betty.k]

to the best of my knowledge, mah means mili amp hours (spelling?). this kinda means how long it’ll give you a certain amount of power. that means how long it runs for before going flat. not sure about power output, but i have a couple of dual celled, 200mah nimh bits, and they run for 10 – 15 mins on a full charge, and seem to be delivering plenty of power:8ball:

[twizm]

i spose the question i should be asking is ‘do the standard tomy cells have a higher output than the 10-15min runtime batteries?’

[HACHI-RYOKU]

No, they have the same output. In fact I put this to the test recently. My dual “tomy” 50~60mah nicad batts go just as fast as the perfection nimh 200mah dual cell. The speed and acceleration was exactly the same. Higher mah batts just last longer, but you wont really notice the difference unless you can charge them fully. Nimh are known for their larger charge capacity and better durability, but it wont win you anything the nicads can’t win.

I do know that nimh could interfere with the steering magnet more than nicads though. Nimh will attract magnets more than nicads. So, if you dual cell a car and it tends to jerk at high speeds, then it may be the batts. I always try to keep the batts as far away from the steering compartment as I can. It’s better that way for weight distribution also.

[twizm]

its not really better for weight distribution, you want as much of the weight positioned in the middle as close to the ground as you can get it, which is why the internal dual cell is such a success, although the aesthetics of it would help

[trash]

Sorry guys, hadn’t noticed this thread.

The AMP HOUR rating is just a unit of capacity.
Sort of like saying I have a 20 litre fuel tank or a 50 litre fuel tank.

It simply means that the battery can supply
(example 800mAh) Can supply 800mA for one hour,
or 400mA for two hours, or 100mA for eight hours.

Of course it isn’t a perfect world, and you have to remember that the voltage of the battery is going to decline over that same period, this is going to effect how much current is going to be supplied.

You will definately want to have a look at the battery university.

http://www.batteryuniversity.com (I think that’s the correct URL).

Anyhow… one of the biggest factors you will want to consider is INTERNAL RESISTANCE of the battery. When this is the same as the resistance of the load (the motor) then you have MAXIMUM POWER TRANSFER. This means the battery is supplying as much current as physically possible
to the load. 100% it don’t get any better than that.

There are a few other things to look at like power to weight ratio’s etc.

[HACHI-RYOKU]

That is the way I distribute the weight, except, the batts are pushed back a little. I believe this is better because I have several different types of internal dual-celling, and the ones with the batts pushed back a little farther run better than the ones just conveniently put in the center. Here’s a couple pics of what I mean. Notice that the batts are very low. As low as I could get them.

http://community.webshots.com/s/image6/1/26/85/104512685GADIso_ph.jpg
http://community.webshots.com/s/image6/1/27/56/104512756Lwrjdc_ph.jpg
http://community.webshots.com/s/image6/1/27/91/104512791uPzBMm_ph.jpg

A couple extra
Look towards the bottum of the pics. There is a couple of good pics with a clear chassis so you can see it a little better.
http://community.webshots.com/album/104512105MRuimC

With the batts in the middle, there is more weight on the front wheels, witch without the aid of proportional steering, makes the car jerk a little too much at high speeds when trying to steer (as well as you might run into problems with the magnetic interference).
My style of dual celling is definately more work, but it’s well worth it. Trust me, I wouldn’t go through all that trouble to produce an inferior car.

Edited by – HACHI-RYOKU on 05 February 2004 16:38:59

[ph2t]

dude, can you redo your links please? the links assume you are the owner of the picture and therefore require you to login. Suggest you logout of webshots and then post the pic links as a normal user OR post the link to the album.

cheers,

ph2t.

[twizm]

would it be possible to get batteries for BCG that would have a higher output? this would help put more power into the motor.

[Ads]

You can get Li batts that work on a BCG. They are 3.7v so equivalent to a tricell car. They also only weigh 4g which is heaps less than NiMH batts. At 145mAh it is slightly less capacity than NiMH batts but you get the higher voltage. You just need to have a Li charger to charger the batt. Plus if you are on a budget the Li cell tend to cost a bit!

[twizm]

anyone else got some info on Li cells and chargers?

[Ads]

Looks like Plantraco have new batts since I lasted looked. They now have a 170mAh version at 5grams. They also have a charger there if you want.

[twizm]

and where do i get these in australia?

[Ads]

Not sure as I got mine from Plantraco! Nothing local stocks them or would get them in. Hard to find ones this small is the problem. Anyone else have these??

[twizm]

http://www.users.bigpond.com/uwhizz/page7.html

they sell some, but just not small enough to fit in a BCG by my measurements.

do you use yours in a BCG?

it looks like a bit of re wiring would be involved to get them to attach to the BCG PCB, either soldered directly or get a female adaptor to plug into on the PCB, which would be handy.

but jesus, a tricell mod at one third the weight of a single cell would be just madness, and i want every part in it i can have dammit!

youd probably end up spending the same amount on the cell as on replacing tyres and motors 😛

[Ads]

The top ones on that page are the ones I use. Yes in a BCG and my Bit char plane.

Yes the plug needs to be soldered to the board. It is a tight fit and with a bit of modification it can be done internally.

You spend a fair bit of time on your roof!! Once you get the handling down pat you get the hang of it. Works best with a booster car as you only use boost on straights. Would be a good option for those of you with monsters and want to use low gears for torque without loosing out on speed!

[twizm]

doesnt the tri-cell power rip the tits out of any motor you put in it though?

[Ads]

Thats why you put low gears on so there is little load on the motor! the higher the load the quicker you kill the motor.

[twizm]

with 3 times the normal power, i dont think the motor is going to have too much load on it at all really.

your car must be painfully fast. even moreso on top speed gears..

[Ads]

Fast as all hell! Hardest part is keeping it in a straight line when at full stick! With stacked FET’s, KIT racer gears and 3.8 motor I have pulled a 5m wheelstand. It almost runs out of range before hitting top speed!!

[jamiekulhanek]

twizm,

Its alot more than 3 times the power!!!

A dual cell car has around 4 times the power of a single cell.

A tri cell has around 6 times the power of a single cell car.

[betty.k]

Quote:

A dual cell car has around 4 times the power of a single cell.

A tri cell has around 6 times the power of a single cell car.

hey jamie, could you go into a little more detail about this?:8ball:

[HACHI-RYOKU]

Hey ADS, I got some questions. I’ve been reading about these a little. I was steering clear of them because I was finding info about it being bad to discharge the batts all the way. They come at 3.7volts, but some literature says not too discharge them below 2.5~3volts.

Do you ever run into problems with yours? Do you have a cut off system? If I got some of these, would I need any special equipment to protect the batts?

Also, here are some other sites that sell these little buggers;
Bob Selman Designs “users.joplin.com/nbselman”
FMA Direct
Skyborn Electronics “bktsi.com”

I’ve only checked the first 2. The last one I couldn’t access for some reason.

[Ads]

HR, you are correct on the 2.5v limit stuff (although it doesn’t completely kill the batt if you drop below this!) Since the batts hold a resonably flat discharge curve (same as NiMH) you can fairly easily tell when the voltage drops! As a rule of thumb as soon as the car drops speed you can recharge (doesn’t matter when you charge Li cells ie. part charge). Just make sure you have a decent charger! The cars are close to the limit for the max discharge rate so if you are running at full throttle the whole time you may run into some longetivity issues!

[Author]

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