willieboy

Hey all, I am fairly new to Hobby Grade RC vehicles. What a fantastic change from the toy store crap I fiddled with before.

I am currently running the basic 2wd brushed Stampede with a couple of minor changes (19/90 gears changed to 16/86 and I added the wheelie bar and rpm front bumper). I am absolute back yard/bmx track basher, with no intention of racing. I was thinking of going to LiPo for the extended run time and the slight edge in performance. However, I am not sure I fully understand the advantage. My current NiMH battery is fully charged @ ~9.45 volts. I play with it until the Titan 12T can't push it around anymore, and the battery is at ~8.4 volts. Now, as I understand it, the XL-5 ESC can handle 2s LiPo only. So, that means with my current setup I am going to be starting @ 8.4 volts and running to ~ 7.2 volts. Am I going to see a severe decrease in performance? Or is it more about the available Amps than the volts?

mkiiina

iTrader: (71)

You will see a drop in speed but you will have longer and more consistent run times. Lipos have a higher threshold for capacity than nimh and have less voltage droop as the pack discharges.

While the XL-5 can only do 2s the next upgrade to brushless will see that performance back, longer run times again, and you can get a esc that handles 3s.

I run 2s in my stampede and its pretty nuts with a 5700kv motor, I can only guess what 3s would be like. Welcome to the hobby!

Rock333

iTrader: (51)

Yeah with NiMh you have more volts but that starts to go down the min you start running. As you go through you get slower and slower. Now with a LiPo You will have less volts but you will have that same voltage the life of the charge. When a LiPo gets low its just flat out stops as appose to the NiMh you will be fast for the first 4-5 mins then its just average speeds. LiPo you get the same speed throughout the charge.

willieboy

The Titan 12T is notorious for overheating. I am adding a heatsink from Hobbyking. Can I go back to the stock gearing to try and get some speed back? I dropped gearing because the motor was getting hot (no exact temps, but it did not pass the finger test). Will the motor run cooler on LiPo since it is not having to work as hard to pull the amps? Will the heat sink help?

Thanks!

Rock333

iTrader: (51)

Heatsink will help but if you change gearing go with the 19/86 if speed is what you want. Larger pinion=more speed less torque. Smaller spur=more speed less torque.

trsills

With the longer, more consistent run time the motor will run hotter for a longer duration. Do yourself a favor and switch to brushless. I would religiously clean and maintain Jr's 12t after he ran it. Once we switched to LiPo we kept killing motors.

bowl806

Ps with the xl5 if/when you go to Lipo make sure you either watch your runtimes or get a Lipo cutoff. You'd be hurtin for certain if that Lipo voltage gets too low. Simply put, it'll run down to below 6.4v and you might have problems recharging. I'd suggest w/your Pede to go w/Trx. VXL motor/ESC. It has a built in LVC to protect your lipo.Also they don't run "as" hot.

Cpt.America

iTrader: (52)

Totally untrue.

TeamRCnal/Mike

A fully charged 2s LiPo pack will be at 8.5 volts. Also, LiPo packs have extended run times because or higher capacity thresholds, as already mentioned. Other perks are more consistant voltage while running, higher burst rates, and cooler running temps. Trust me back when I was a bashing junkie and was thinking about going LiPo, I diddn't understand why it was so much bettter either. It is just a dramatic performance upgrade. Period. I also thought I would never race. Now im at the track at least once a week, every week.

willieboy

Well, I took the LiPo plunge. Turnigy Accucell 6 50A charger and Turnigy 30-60C 5800mAh 2S LiPo cell. I also bought a hobbyking LiPo alarm that goes off at 3.3volt on either cell. The XL-5 in the brushed Pede has a built in LVC, but it cuts off at 3.0 volts, which seems pretty low.

Now for the next question: Is there any trick to breaking in a LiPo? I want this guy to last a while. I can certainly run it through some charge/discharge cycles on the charger, but I am not sure how hard I should charge or discharge it? The battery is rated for a 5C charge, but that seems excessive. I was thinking a 1C charge and a 0.1C discharge for a few cycles, and then let it rip? Any thoughts? I am over thinking this?

kaan

No need to break in a lipo.
Just balance charge and go

If you worry about battery life then you can prolong it by using the storage charge and keep them in a fridge when they are not in use.

willieboy

Charged it up, and WOW! What a difference from my NiMH. My concerns about being slower were misplaced, if anything it is faster. The Titan 12T certainly has a lot more power/torque as I had to adjust the slipper a bit (something I have never had to do with my NiMH). I am LiPo guy for sure here on out.

Dave H

Yep, you’ve discovered the big difference between nimh charge voltage and running/under load voltage. Much less difference with lipo, considerably lower internal resistance. Might even need to gear down a little, because of the voltage and run time.

I agree with your caution on using a slightly higher cut off voltage. Lipos dump quickly at the end so it won’t cost much run time either.

Perhaps the best part is typically you can charge them right back up too. As long as it’s not getting warm, which it shouldn’t if the setup is good.

Enjoy!

123nanez

keep the lipos in the fridge? is that safe? im new too.

justpoet

iTrader: (16)

Batteries make power, and degrade, via chemical reactions. Being colder in the fridge slows down those reactions, allowing the battery to last longer and be a little less volatile.

Don't follow that to the extreme though and think a freezer must be even better, that'll do damage to the cells.