oldschoolrc

iTrader: (1)

AND using them with an old school tekin tc 411p granted the speed controle can handle 20 nicads/nihms (24v)and even a 4c lipo(14.4v).....but it cant handle a 4c A123 pack(only 13.2v but can dump at 70amps)!!!! man it sucked when i saw a big cloud of smoke come from the back of my truck i had my spectrim transmitter throdle set to 30% only!

oh well...it ran for almost 10 min ....atleast the batteries are ok...not even warm

here is the carnage...enjoy!!



+



=








and me crying

Dave H

Hardly a surpise, the 411P is only rated for 11 cells, not 20. And that was in the nicad days, when cell voltages under load were lower than recent nimh.

The 420F is the 20 cell model.

InfiniteMotors

iTrader: (18)

Like I keep saying, A123 is no joke! Sorry about your meltdown haha

oldschoolrc

iTrader: (1)

snap!! your right (looked it up again )but why did it handle my 4c lipo till the motor went???

Duster_360

iTrader: (21)

I suspect they tended to over-engineer a bit back then. Why today's stuff is a little more touchy - its made with little allowance for more than its rated for.

Dave H

Are you suggesting that it should have been able to handle it, being over engineered as you say? That doesn't appear to be the case to me.

SpraydbySprague

iTrader: (64)

I noticed the use of high end car audio power wire for your batteries and ESC. The quality of the copper is not the problem with your wire, it's the PVC insulation on it. PVC type insulation on car audio wire can melt under the extreme temps in an RC vehicle. Look at the melted insulation near the Deans plug as an example.
Your best bet is to convert to some TQ racing silicone insulated wire. The silicone insulation has far greater resistance to melting. Less chance of melting means less chance of a short circuit in the car.

oldschoolrc

iTrader: (1)

that was from me tying to soder the wires on. i can never get them damn things to stay where i want them too so i end up heating up the wire to much to many times just so i can get it right... i have never had any problems with heat with the wires i have used...i just make shure that the wire is big enough to handle the currant....thicker wire=more currant handling

i use 12 gauge wire...i almost went to 10 just for giggles

Bugle

iTrader: (1)

Damn thats screwed..
You can upgrade those old speedos, there are now cheap to-220 package fets that'll do 170 amps continuous per fet. So 6 of them is going to handle anything.

kufman

iTrader: (6)

This not really. The fets can ONLY handle the current as long as their junction temperature stays at 25C. Even with large heatsinks this is almost impossible to do. Also, the to-220 package itself will limit the current to about 60 amps due to the lead wire size used. It is sad how almost all of the ESC companies use this data is totally wrong ways.

Dave H

Yep. Raw transistor ratings are one thing, what they can do in a circuit is just a tad different.

Plus you still have the little voltage issue.

Duster_360

iTrader: (21)

No, just the way things in general were back then, a tad overengineered. Safety factors, engineering cushions, whatever you want to call it, they were larger as part of the design process years back than currently.

How much time will you get trying that in the current equiv speedy?

Dave H

Not so sure, fudge factors are still alive and well in my experience, given rush to market pressures I frequently see a lot of overdesign, opposed to the slow trial and error of old. I suspect any surge in speedo problems recently are mostly due to the greatly increased complexity, with an ever increasing RC model size, rather than a conscious effort to cut it to the bone so to speak. The above example doesn’t seem to support substantially greater robustness levels in the day, the voltages mentioned aren’t all that much higher than the ratings. Perhaps a little less voltage sag from the batteries under load.

The 1/8 scale electric guys have a lot of experience with running speedos well over the ratings in recent years, oddly enough including Tekins before the RX8, plus the nitro guys running direct lipo on servos.

oldschoolrc

iTrader: (1)

what???befor you fry it?? most esc's of now adays can only handle a 3c lipo wich is like only 9 sub c's the esc i fried could handle 11 sub c's but the amp dump on sub c's doesnt compair to lipo's or a 123's

the tekin i fried also should have ben able to handle a 300amp dump...i think i dumped only around 280...it was an oldy but a goody though

im thinking about getting a nother