BigTb17

I just installed a Novak Havok 8.5 brushless system in my Factory Team T4. I pulled the Novak 13.5 system out to put in a new truck I'm getting and dropped in the Havok 8.5 system.

I had been using cheap (Venom) 6 cell Ni-MH 3000 mAh batteries that I've had for a long time. They still take close to 3000mAh when charging and don't get hot or anything. They worked fine with the 13.5 (no problems, enough torque to pull wheelies), but I wondered how they would work with the 8.5 system.

I installed the system, dropped in a freshly charged pack and took it out into the freezing wind to try it out. I had crazy glitching issues. If I stayed within 20 feet or so it was ok, only occasional glitches. Beyond that distance it was almost un-driveable. I was afraid it was my batteries not supplying the requested amps and dropping voltage, but I didn't know for sure.

Today I got out my Fluke meter which has a setting that can capture voltage spikes or dips as short as 250mili-seconds. When not in Min/Peak capture it seemed like the voltage was staying above 6 volts when the throttle was blipped. However, once I put the meter into fast capture mode I found that when I blipped the throttle the voltage dipped to 2.9volts[X(]! That's definitely a problem. I didn't even have the wheels loaded, they were off the ground.

Looks like it's time for some new batteries. I'm glad I did this test because it was an eye opener. I figured the voltage was dropping (maybe even as low as 4-5 volts). But I never figured it was dropping below 3 volts. With a partially charged pack it actually dipped to 2.6 volts (again, with the tires off the ground).

Just thought I'd share my experience because I often read threads about glitching issues after installing Brushless sytems. I'm sure this isn't always the problem, but I thought it pointed out the importance of good batteries when running high power systems.

Lunchboxer

Time for some LiPo, eh?! ha!

BigTb17

Yeah, the batteries I have are pretty old and used. I would probably be ok with some decent Ni-MH batteries, but I don't know if it's worth it. I should probably just get a Li-Po or two.

BigTb17

I have a 2100mAh 2s Li-Po for another application. I don't want to over stress it (it's not really big enough for the truck), but I decided to put in in my T4 and just blip the throttle one time. It stood straight up in the blink of an eye and ended up standing against the wall on the other side of my appartment. Looks like I'm going to have to get some Li-Pos for it.

Evader ---> MGT

I don't know if you saw my thread from earlier, but [link=http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8357]these LiPo's[/link] look like an amazing deal. Zippy is a pretty reputable brand too!

jmcvicker

Big,
Did you change your pinion gear when you put in the new motor? Going from 13.5 to 8.5 on the same pinion gear is going to cause a big current-draw. Let's say the 13.5 had a 27T pinion on it. You should consider something like a 22T to start with (and then adjust accordingly) with the 8.5 motor.

BigTb17

I started with my smallest pinion (19 tooth). I would have actually started a bit smaller, but that was the smallest I had. The manual suggested to start with a 16-20 tooth and I fitured I would take it easy with the 19 tooth and monitor the temps. I didn't drive for very long (maybe five minutes) because of the glitching, but the motor and ESC weren't even warm afterwards.

I'm sure the batteries aren't up to the task either way. For the test the back of the truck was propped up and the tires were able to spin freely.

Thanks for the suggestion though. It is easy to forget things like that and chase your tail around trying to figure out what's wrong.