RC18T Questions

[racer234]

Hi, I think I'm going to go the brushless route with my RC18T. So far my list includes:

Mamba 25 Competition (6800) $121.99
Aluminum Dogbones (for the rear) $8.59

I would also like to get some Li-Po's. I was looking at the Apogee packs, and found a 830mAh 2 cell for $30.00. I'm not sure how long 830mAh will last. I would also purchase the Apache 1-4 cell Li-Po charger for $50. What are you're thoughts? What batteried would you recommend? Oh, and what about the durability of the drivetrain, are CVD's needed for the front?

[TheSteve]

I don't really think 830ma cells are enough for a mamba system. It will work but the cells just won't last as many charge cycles as they should. I'm using the Mamba 6800 with a Polyquest/Irate 2S 1800ma pack. Its insanely awesome, tons of runtime and they fit without much rework. I moved the pack wires a little and nipped a little of the inner chassis away.
The Apache 2500 charger is great for the money.
So far I haven't destroyed anything in my RC18T with the mamba power but I'm sure it will happen. I'd watch the dogbones and outdrives and always ensure your gear mesh is good.
And I can honestly say you will *NOT* be disappointed in anyway with the setup. Its insanely awesome and with the latest software rev for the Mamba I can do a slow crawl(as slow as the stock DC system) with no signs of cogging and when I punch it I'm at almost 60kmh(stock gearing - gives 15 to 20 minutes runtime with the 1800ma cells)
All I can say is - do it, do it do it!!!

[racer234]

Thanks for the reply, where do you recommend buying Li-Po's? I'd prefer to buy them off of towe (I've had good experience with them) but I don't want to get some sucky packs if that's all they sell on Tower. Thanks again.

[glassdoctor]

I would recomend buying lipos from "lipo literate" places. I'm not sure what all Tower has, but things can change pretty wuick in the lithium market. Newer better cells are coming out all the time. Tower likely isnt' the first to catch the wave.

For example, there is a new cell from Tanic that would be awesome in a 18T, imo. It's a very narrow 2200 mah cell. Looks like a perfect fit... and it's the latest high-rate discharge of course.

I'll look for it and post a pic/ specs...

[glassdoctor]

Ok, I found the specs and compared to GP1100 cells. The Tanic 2200s are almost perfect. They are 12C, so rated for 26A+

GP1100 6 cell side by side pack: @ 28mm x 100mm x 16.5mm thick.
Tanic 2200 cell (3s 11.1 volts) : @ 35mm x 105mm x 16.5mm thick.

That's dimensions for 3 cells stacked... an actual 3s pack will be very close, but a mm or two bigger.

A 2s pack would be 11-12 mm thick.

weights:
6 cell 1100 4.6 oz
3s 2200 lipo 4.9 oz
2s 2200 lipo 3.3 oz

IMO, a 2s 2200 pack would be awesome in a 18T with a Mamba! Light weight, fast, and huge runtimes...

[racer234]

Hey I really appreciate all the effort you've put into your replies! Being a complete newbie at brushless and Li-Po's, can I ask you to recommend some places to purchase these cells? I'm interested in buying 2 cell's, maybe one 3, but mostly 2's to keep the power manageable. Thanks again.

[racer234]

I did a quick search and found the site! Thanks! :)

[Signats]

Without modification the battery tray in the RC18t is about 32mm wide, this means that unless you are planning to modify your chassis to accept a 35mm wide battery the Tannic 2200s won't fit flat in the battery tray. :eek:

[glassdoctor]

Sorry... tanicpacks.com is the main site for those. They are not the cheapest lipos, but they have a good rep. and the size of those makes them a great fit.

$50 for a 7.4V 2200mah sounds expensive, but it's cheaper than two matched GP1100 packs. :)

FYI... Polyquest 1800s would also be good, about the same exact size as the Tanics. Actually they are even closer to the size of a 6 cell nimh. They are a bit cheaper but less capacity than the 2200s.

2s 1800 pack 34mm x 98mm x 14mm
rated 20+ amps @$45

Polyquests distributor site is www.rclipos.com also sold at places like www.starluckrc.com www.battlepack.com www.maxamps.com .....

[racer234]

After researching Li-Po's all night, I am soo confused :p Well not that bad. I think that I am gonna go with a Poly Quest 2S 1800mAh. I found them for about $40, which is pretty good. It's so hard comparing amps, C's (whatever they are, like 1.xx amps or something?), mAh, size, and price! :eek: But I really appreciate the helpful people on this board.

[glassdoctor]

:) lipos vs. nimh are a whole different ballgame.... just like brushless vs. brushed.

I didn't know exactly how wide the battery tray was on the 18T. But there were others running lipo packs wider than these.

Don't forget to compare the weight also!!! ;)

[ducati777]

@racer ugh, I know exactly what you mean. I really want to get the mamba, and then I'd like to go lipo... but sheesh, new packs and new charger required...

[racer234]

Yeah, now what I've decided is to just get the 8000, and run some 6 cell Ni-Mh's, and then I'll have the option of gettin Li-Po's, but it should be fast enough without, well maybe not fast enough.... :p Thanks for all the help.

[johnrobholmes]

why are you wanting such a high rpm motor? you could get cooler running with a 3 cell lipo and a slower motor like the mamba 5000 (i think thats the Kv rating i have). same power, just more volts to get there. more volts for the same power means less amps, less heat, same speed, and more runtime. even on a 2 cell the 5000 is very fast.

[racer234]

Well if I can get the 8000 for $10 more, and it's just as fast as a 5000 w/ Li-Po's, it's saving me a lot of money :p Li-Po's are about $40 each, and a charger is $50, so I'm saving $80.

[TheSteve]

It may get you similar performance, but not the same as. Higher voltage/less current will give higher efficiency of course. Lithium Polymer weighs much less, which makes a huge difference in something the size/weight of the rc18t - compare the weight of the truck/radio/motor to the weight of the stock NiMH battery pack.
That said, there is nothing wrong with starting with NiMh cells, but once you want the best acceleration, highest top speed and longest runtime, Lithium Polymer it is...

[johnrobholmes]

i would suggest the 5000 over the 8000 just for the usability. even on 6 cells the 5000 is very very fast. if you are ONLY going to race, then you could use the 8000 on 7.2 volts. but it heats up so quick even in the mini-t. if you are going to do ANY bashing get a slower spinning (Kv) motor. you will get longer runtimes too- even with the same top speed and power. you dont have to use lipoly. as TheSteve said, there is nothing wrong with NiMH cells at all.

the output wattage should be the same between the 5000 and 8000, its just that they get there by different means. the 8000 uses amps and the 5000 uses volts. it is always better to use more volts unless the extra weight of the batts causes other problems.

[standard_63]

Tanic 2200 cell (3s 11.1 volts) : @ 35mm x 105mm x 16.5mm thick

I couldn't get the tanic packs to fit in my 18T. :( They are about 2-3mm too long. Even cutting the battery posts they won't fit. Any other suggestions for a good pack for the 18T? I guess I can use the tanic in my 1/10th car...

[ElectricThunder]

Duct tape is your best bet....lol!

[glassdoctor]

The Polyquest 1800 packs would work then. They are 98mm... 1mm less than a 6 cell pack.

[TheSteve]

I use a Polyquest 1800 pack in mine.The cells themselves fit just fine, with the wires they are a little wide for the stock chassis. You can either cut a little chassis away or just cut the shrink on the pack, move the wires to the top and reshrink it.

[glassdoctor]

Steve, you have the Irate branded pack, right?

In case others didn't know... PQ and Irate are the same...

[TheSteve]

Yep, they are the same - although mine isn't branded anymore since I changed it to black shrink when I reworked the wiring.