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simalarion

My Experience with Nimh & Lipo

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2 hours ago, Losilancer said:

I guarantee if you put a healthy motor in a vice and run it at 7.2v it will last a great deal longer than 10 seconds before spitting out red hot brushes and smoke.

Feel like im going on repeat but


I think again you are missing out on some points here, you will never run a motor on 7,2 v at this point the Nimh is soon ready for Cutoff, that is just a standard volt for 2s (lipo) and 6 cell nimh, fully charged Nimh is up to 9.2 volt. Standard 540 motors have normal volt ti 7.2 and max 12v, so in between there is recomended ofc. 

If you are saying a free running 540 motor will run longer on full throtle on 3s compared to  lets say in a Agrios with a lot more resistance you must be wrong, as i tested this, its not correct. And if i was putting the 3s in my TGH and not in Agrios that motor would be burned right away.

Im not an expert (at all, and i wont oretend to be), but i already tested all this and that was the reason for writing the first post. Again Agrios have run just fine on 3s for some time on given setting, did not have issue with to hot motor or iffy smell, but shure as i wrote it will not last as long as it would on nimh

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53 minutes ago, simalarion said:

I think again you are missing out on some points here, you will never run a motor on 7,2 v at this point the Nimh is soon ready for Cutoff,

Not quite. A "7.2v" Nimh pack will spend the majority of time between 6-7v. It will be as much as 9v freshly charged but will instantly begin to plummet in voltage w9thin the first few seconds of use.

 

53 minutes ago, simalarion said:

Standard 540 motors have normal volt ti 7.2 and max 12v, so in between there is recomended ofc. 

Yes that is just manufacturer specifications and not usage specific. It doesn't mean the motor can be run at 12v in any scenario. The workload of the motor is incredibly important

 

53 minutes ago, simalarion said:

If you are saying a free running 540 motor will run longer on full throtle on 3s

I never said that. Please read again. 

I said a motor will wear out faster being overloaded and/or overvolted than it will running without a load at an appropriate voltage. RPM is not a significant enemy of brushed motors as long as they are operating within spec. Many domestic devices like hairdryers run at high RPM with very low workloads and last for decades.

53 minutes ago, simalarion said:

lets say in a Agrios with a lot more resistance you must be wrong, as i tested this, its not correct. And if i was putting the 3s in my TGH and not in Agrios that motor would be burned right away

As has already been explained, vehicles such a as the Argios have very low gearing which significantly reduces load put on the motor. You also said you have the throttle limited to 75% so for all intents and purposes, you are only running the motor on about 9.5v to start with.

But yes, a brushed motor running without load will last longer than one with a load, especially if it's overloaded and/or overvolted. Excessive current and voltage will quickly destroy the brushes and commutator.

Of course a motor running at full RPM will WEAR the brushes out at an accelerated rate but normal wear and arcing from overload and over voltage are not the same thing. 

53 minutes ago, simalarion said:

Again Agrios have run just fine on 3s for some time on given setting

And again, your Argios is an exception rather than a rule among Tamiya vehicles because it has incredibly low gearing AND has two motors sharing the load.

It is not comparable to a Tamiya TT-02 for example. And again, running on 3s but limiting throttle to 75% is not a valid 3s experience. 

 

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On 2/25/2021 at 6:58 AM, Exit13 said:

I’m sure the people that have Lipo’s and know how to maintain them it’s no big deal. But for me, I’m still an outsider getting in.  these last two months is the first time I touched RC in 30 years I’m steering clear Lipo. Seems like having a Lipo is like having a diesel car, it’s a lot more work I’ll stick with petrol 1:1 cars and NiMH in my RC. You know those people who win Lottery and blow all their money within a year? Yeah that would be me. So I’d probably burn my house down w/ Lipo.  As the season go by, I need to move from this hobby back into Bmx and then back into Modern and vintage Honda dirt bikes/duals sport and I can’t be worried about how I left off with RC, so I have time and I have money but I clumsy and sometimes careless,  I got to stick with simple-stupid  

 

Same same (20yrs for me). I won't forget about RC for the summer, but it'll definitely take a backburner to everything else (BMX mostly, besides ofc family stuff).

I want to add another vote for sticking with simple and bulletproof. My NiMHs have been perfectly fine, other than dropping volts when they got cold this winter (like any battery). But the maintenance is easy: I let them cool after a run, charge them up and leave them charged, then whenever I want to run again, throw one back on the charger to peak it, and it's ready to go. Same as NiCds except we fully discharge NiCds for storage. Definitely not the fastest, or lightest, or whatever, but I don't care as long as they keep working and allowing me to enjoy driving my old cars around (for far longer at a time than NiCds!!!). The charger and batteries just sit on a metal shelf in my office while they charge, and only get slightly warm to the touch when they're peaked. I've never had one "blow up" or even bulge, and this is with simple automatic peak chargers, nothing fancy.

They're robust too. The Traxxas NiMH used to be an 8-cell hump pack, but I cut the top 2 cells off and soldered new leads on the end... I think I got it in maybe 2012, and when I dug it out last year I wasn't sure it would even hold a charge, but after a little "conditioning" it sprung back to life and has been working solid ever since, through mud and snow and everything I can throw at it... even exposed in the ORV chassis! Although I wish the HW1060 ESC didn't have a low-voltage limp mode for NiMH because I want to drive my cars in all seasons!!! The batteries work perfectly fine, even when cold, with the Traxxas XL-5 ESC, which has no such cutoff.

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@Losilancer Seem that i agree more when you explain further, please note that i specified «at the given setting as i wrote in first post» , i think you did not quote me on that part.

And no, where i agree is i would not use 3s on any other Tamiya than Those in the same serie (txt-1 & 2 Clod), as i also wrote in first post i feel that it would not be ok for the motors to go abow 75% max forward.

So for the most part i think we are on the same page here

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Ran a bullhead on 3s with silver cans for a few years. No issues, but, you can't leave then flat out for long in those things, and they're geared low .

A silver can lasted quite a while in a boomerang on 3s, only giving up the ghost when doing,  have a go, exhibitions with the club, so it had done a good few packs back to back. 

Silver cans are only £4 , so ain't going to cry too much..

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