Short run time?

bagmouse7 · #1 07-24-2002, 11:26 PM

I just got a DTM X4 and ran it for the first time today. While it is very quick, the battery life was incredably short. I have 2 of the stock 7.2v 110Ma batteries sold by Horizon hobbies. I charged both batteries with my smart charger and one took 87Ma and one took 89. So the batteries were definatly charged. I had installed a 180 size Team Orion Micro Elite Stock Motor in it. I set the ESC and the ran it. It FLEW for about 1 minute and then died. Hmmm....
I decided to put the stock motor in it to give it a try. I used the 14 tooth pinion gear on both motors. With the stock motor and the second battery it ran for about 3 minutes. I charded both batteries up and ran each again. About 3 minutes each time.
Is this normal? What kind of run times are you guys getting?
Thanks.

bagmouse7 · #2 07-24-2002, 11:44 PM

Also, the servo dosen't bind, and the gears mesh and turn nicely.
In fact, as a general comment, the car is REALLY well designed and it is a very nice model once it is all put together.
Really high quality parts and great fit and finish.

Here is a picture of the partually completed chassis next to a mouse for scale.

btlmr · #3 07-25-2002, 03:35 AM

Is 110Ma correct? You should have 10x that capacity I would have thought. I would expect a long run time from 110. Even the cheap AAA's I have for my mini-z are 550Ma.

bagmouse7 · #4 07-25-2002, 07:11 AM

110 Mah is indeed what is marked on the pack.
Here is the link for the battery from the Horizon Hobbies web site:
http://www.horizonhobby.com/products...t.asp?item=CPB

The battery I am using is the second on the page.
Thanks.

btlmr · #5 07-25-2002, 08:03 AM

Hmmm. I am surprised at that, but I can't really add anymore cos I don't have any Tiny RC's that run a similar setup.

I will be interested in the answer if someone else can help

The Thunderer · #6 07-25-2002, 08:37 AM

I've got a 7.2V 350mah which ran for OVER 30 minutes... I didn't check the charger settings or readings (I just listen for the "beep"), but this is what I get every time I take the car out. I'm running it on a stock Micro RS4 motor so that may be the difference.

btlmr · #7 07-25-2002, 09:11 AM

So if The Thunderer were running a 110 battery he would get under 10mins.

I wonder if any knows the current draw differences between the 2 motors. It maybe realistic to only expect a few minutes, but 1min is a bit short. Do any of the components of the car get hot?

Check the battery, ESC and Motor. I would expect the battery battery to get hot being discharged so fast...

I would expect longer from your stock motor too..

Ted theMechanic · #8 07-25-2002, 11:00 AM

The 110mAh is NiCd, right?
ABC also has a 250mAh NiMh for the X4.
Found it on a webpage somewhere...

MicroRCEngineering · #9 07-25-2002, 01:04 PM

That is normal. The only way you'll get decent run time is if you manage to put 6 AAA cells. Ive put 5 before, and it was alright.

4wd consumes more elec. due to the increased resistance suchs as extra gears, shaft, all this come into play.

Btman · #10 07-25-2002, 04:19 PM

If this car is anything like the 4wd mini-x, you may want to make sure the differentials and other drivetrain components are not binding and are adjusted properly. 5-10 minutes tops is what should be normal with a motor like that and a battery with that capacity. A set of bearings in the wheels will reduce friction as well. I am somewhat suprised that a 110 ma battery is available for a car like this, but I noticed that when these cars first became readily available. I guess the car was designed with 4-5 minute races in mind like 1/10 and 1/12 scale racing cars. Keep in mind that an HPI micro rs4 runs for about 60 minutes using 1600ma AA NIMH batteries and a stock motor. Your battery has about 1/15 the capacity. It may be time to invest in higher capacity batteries if you want to run more than 5-10 minutes per charge.

bagmouse7 · #11 07-25-2002, 05:45 PM

Here is the kicker...
I have a full set of bearings in the car, and there is no binding in the gears. The car is well put together (not to brag...) and there were no errors made when I put it together. The drivertrain is very smooth, and the diffs work correctly/ Also, nothing even gets warm when I run the car. I currently have the stock motor in it, so it will draw much less, but I will put the 180 motor in to tonight and see how well it runs.

I am going to do some serious testing tonight an I will post the results. I do have a Rc Hobbies 300mA Nimh battery on order, it is looking more and more like I will need it.
A couple of questions and answers...
The 110mA battery I have now is Nimh.
To The Thunderer, are you ruuning a DTM X4 or a SP?
Thanks guys and more to come.

The Thunderer · #12 07-25-2002, 07:08 PM

I'm running the SP version... sorry. BUT, if you want longer run times, I think you'll have to get a pack with a much higher mah. The one I have is 350 mah, but know that there are those that have an mah much higher (eg. the one I have for my micro is 1100mah -- no, I haven't put that on my DTM).

I wish that I had a DTMx4 so that I could be more helpful.

gertman · #13 08-12-2002, 01:05 PM

I have a DTM-X4 with full bearings, what I have done to combat the short run time problems is use NiMh cells.

I figured out that to fit 6 cells in an X4, you need to use 1/3 AA size batteries. I found a battery place on-line and I ordered NiMh cells rated at 230 mah. This is the SAME pack that ABC hobbies is just starting to sell. I paid them an extra few dollars and they even assembled it for me

.

BUT, for some reason when I WAS using electronics from ABC, the pack wouldn't work hardly at all. I have converted over to using REAL electronics

and the NiMh pack worse fine...................

BUT, unfortunately the discharge rate for NiMh cells is slower than for the NiCd's. To get the same low end punch out of the NiMh pack I have to gear up at least 2 teeth!!!!

Run time is 20min plus!!! Compared to a little over 7 with the NiCd pack. Keep in mind, I only use 180 size motors