ModeratedUser30082018

iTrader: (-1)

Excuse my ignorance but... from the fresh perspective of a racing noob - Mind you, I've played with 3.5t & 4.5t since 2005 with old & weak 6cell NimH technology (10C~15C rating tops)...
But why not just use an external battery to power the radio? Back in the day, nickel cell batteries were heavy, bulky, low current and low capacity and old AM/FM radios were glorified heaters. With the miniaturised lipo technology coupled with modern energy efficient radios and servos, for the tiny increase in weight (which you can mount anywhere on the chassis), I can't see an excuse not to ditch the BEC for the sake of safety and control. The only downside I can think of is that it would be slightly less convenient having to charge and monitor another battery... Though, seems like a small price to pay...?

bertrandsv87

iTrader: (2)

I think some racers started using these external radio batteries at some point, but it got banned...

ModeratedUser30082018

iTrader: (-1)

Banned? Why is everything always getting banned?

bertrandsv87

iTrader: (2)

That's the reality of rc racing: that's why so many racers have secrets....

DesertRat

iTrader: (2)

You can use a receiver pack, people do it all the time in onroad oval classes, and used to use them in 1/12 scale and other classes where maximum run time was the objective. It's fallen out of favor since. All ESC's can be powered in this way, just leave the ESC switch off and plug the receiver pack into the receiver.

gigaplex

iTrader: (2)

The single greatest piece of advice anyone can give you is to not pay much attention to what Bert says.

071crazy

iTrader: (8)

mid october of what year?

bertrandsv87

iTrader: (2)

Come on man, I know the Opioid crisis is big but you should be able to figure this out without any medical help.....lol....

Adamska27

iTrader: (2)

This is actually a very common misconception of the different chemistries.....

Nickel batteries never had or need a "C" rating. There is no limit to how fast you can discharge a nickel based battery cell (technically the internal resistance is the discharge limiting factor)

You can pull "infinite" amps from nickel batteries on a "surge" --- when lithium batteries came around we quickly realized they were incapable of such discharge currents, thus "C" ratings were invented

Brushed motors draw insano amounts of current for very short moments when those brushes arc, and nickel batteries, even 1300's, could fuel them, no problem, for some amount of time

Now lithium is superior in energy density and a better battery, but for a momentary surge, nickel or lead batteries can handle it better


---My thoughts on this thread

--- I wouldn't (not saying you can't, but I wouldn't) run my boosted 4.5 without my new LiHv packs ----- and here's why ---

We can argue about how misleading "C" ratings are, but let's pretend battery X really is a 50C battery ---- it's only 50C at a full charge, now I don't know all the maths involved here, but I puffed enough packs to realize that even good lithium when asked for high discharge rates will have issues at lower voltages, and in mod, if I ran too long of a practice run, the battery would get puffy, if I never ran the battery say past 8 minutes or so, it wouldn't puff, but if I had the track to myself and put in a good long practice run, bam, puffy lipos - now this was with the previous gen lithium chemistry to be honest, but that's all the more reason for me to use the good stuff. I buy new packs frequently and only buy the best, motiv usually, trinity, reedy on a good day, and fantom from what I have seen, get the good lipos, I really used to think all R/C lipos came out of the same Chinese plant, but even if they do, there is a real and obvious and widespread difference between the premium packs and the other brands, even names that used to be good, or we consider generally good


I would use my old pack for the stock motor car or something lower demand, and have good, flat stock racing/practice packs, and one brand new mod battery now, and another one every 6 months, my 3 year old packs just found their way into my starter box this summer, it's always nice to have good, older batteries, but if it's a hot day or something and you dip below whatever, then that old gen's ace gets puffy, and then it starts to make its way to the disposal facility, maybe not today, but sometime

DesertRat

iTrader: (2)

Sorry dude, but most of this is incorrect. Nickel batteries did not have a better burst current ability than LiPo, brushed motors did not have big jolts of power run through them even when they 'shorted', LiHV packs are not significantly different from normal and you cant use the LiHV feature anyway because of ROAR rules, and high discharge rates or deep cycling does not cause puffing of otherwise good batteries.


Nickel batteries could provide what at the time was good burst current, but at a loss of efficiency and generation of heat inside of the battery, and they were much less efficient, had much more voltage drop, and a greater internal resistance at high loads than LiPo.


Brushed motors with laydown brushes like those used in 27 turn stock could short the motor for a small percentage of the rotation of the armature. This would accelerate the wear on the comm and brushes, but generally was a small amount of the power used by the motor. Laydown brushes were used to ensure that the winds were energized for as much of the rotation of the motor as possible, which would increase torque, while Modified motors used stand-up brushes that couldn't arc.


LiPo batteries degrade over multiple uses, same as any battery, but the normal wearing out process and "puffing" are not the same mechanism. Normal degradation manifests as loss of charge capacity and increased internal resistance, puffing is chemical damage to the cell. To prevent puffing, don't store your batteries charged, and keep them in the fridge. Since I started storing batteries with 3.8v / cell or less, and in the fridge, they have not puffed a millimeter, and this includes a now year old 8000mah 1s battery that gets tortured in my mod 1/12 car, and it still has the good internal chemistry.


You can do what you like with your packs, but it's not the heavy draw use that kills them, its being left in the heat with a full charge inside.

ModeratedUser30082018

iTrader: (-1)

Quote: "You can pull "infinite" amps from nickel batteries"

Holy marsupial of Canberra!!!

On a more serious note - yes, you can draw large amps from nickel batteries, but that is only because V drop does not pose a massive safety risk or massively damages the cells as a result - but still damages Ni cells but to a lesser extent. *Edit* These are still puny amps by LiPo standards* Even if the voltage rebounds in a lipo from over current discharge, the damage is still done. Furthermore, Ni chemistry has significantly much higher internal resistance when compared with Li chemistries.

SouthFloridaApp

iTrader: (6)

This may be the best post ever on this forum.

071crazy

iTrader: (8)

I really can't figure it out, and neither can anyone else. So, enlighten us!

bertrandsv87

iTrader: (2)

I will know for sure what year after I fix my Jeep's timing chain....No way to run the rc cars before fixing the real car....Hopefully it will be this year, but who knows.....

nexxus

iTrader: (315)

You do know that when a timing chain or belt goes, the repair is often more than just replacing that part, I had a Timing belt go on a Kia once, one of the piston valves got halfway through the piston before it all seized up another two were bent and a 2nd piston had some pretty tell tale impact marks on the top of it as well.