LiPo ideas needed

[Ducman82]

so i am in the process of building my brushless conversion, and was wondering what everyone used for lipos? i take it the 3s, and 6s etc, mean the number of "cells"?

I'm leaning towards SMC... toughts?

duc

 

[frddyj]

so i am in the process of building my brushless conversion, and was wondering what everyone used for lipos?

here is a thread that a few of the b/l members hit https://www.hpisavageforum.com/forums/showthread.php?t=11750

i take it the 3s, and 6s etc, mean the number of "cells"?

yep. the "s" means how many cells are being run "in series" in that pack.

on the stock flux you run 2 packs in series so you count all cells in both packs.

for example, when you hear a guy with flux (2 packs) say "i run 6s," he's saying that he runs 2 x 3s LiPo batteries in series for a total of 6 cells in series (or 6s).

if you run only a single battery pack then you have the option of running 2s to 6s in a single pack. pack will be bigger 4s-6s ($$)

I'm leaning towards SMC... toughts?

SMC packs get great reviews. Bryan, aka Snuffleupagus on here works for SMC and is a great guy. Check out his interview on this week's podcast.

 

[Larsenracing]

SMC is one of the highest on my list of brands to recommend. There are lots of great packs out there though.

Also great work Frddyj.

 

[HOLLYW00D]

apologies if i step on any toes, but it sort of relates and may help us new guys out:

2s, 3s, 4s, etc. all refer to the number of cells in series when talking about LiPo. a single LiPo cell is rated at 3.7 volts and you don't want to discharge below 3.0v. my question is, what do people mean when they say they charge at "1C" or "2C"? what exactly is "C" (current?) and how do you know how many "C's" you should charge a given pack at? also, how many amps does "1C" equate to? i've read 5.5 amps, but can't grasp how "C's" relate to amps. thanks in advance.

 

[whipnet]

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[HOLLYW00D]

ah, i see. so if i had an 8ah pack, 1c would equal 8 amps and 2c would equal 16?

 

[whipnet]

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[Ducman82]

hummmm so how do you not discharge a LiPo to much?

 

[whipnet]

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[MikeK1981]

I don't know if they will catch on fire during discharge, but they will be ruined. I think fires are usually caused by overcharge.

 

[whipnet]

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[88gtanotchback]

I agree with whip on the auto LiPo cut off however i would set it lower. ive heard of guys having issues having it set at 3.0 or 3.1 from voltage spikes. ive set mine at 3.5 from advise from the Heli forums i was snooping around in. i figure the little bit of run time i loose is worth it to protect the packs.

 

[frddyj]

my question is, what do people mean when they say they charge at "1C" or "2C"? what exactly is "C" (current?) and also,how many amps does "1C" equate to? i've read 5.5 amps, but can't grasp how "C's" relate to amps. thanks in advance.

Your correct "C" is short for current which is measured in Amps.

Mah = 1/1000 of an Amp hour & is the standard rating for a packs capacity.
so a 6500 Mah LiPo can deliver 6.5Amps of power for 1 hour at full charge.

"C" as relates to charging batteries, - refers to the current rating to charge your pack & you determine it by dividing your Mah by 1000. For example lets say you have a 6500 Mah pack:

1c = 6500 Mah / 1000 = 6.5 Amps (set charger rate to 6.5A)
2c = 6500 Mah / 1000 = 6.5 x 2 = 13 Amps or 2c (charge 13A)
3c = 6500 Mah / 1000 = 6.5 x 3 = 19.5 Amps or 3c (charge 19.5a)

we'll stop there caz ive yet to see a common everyday charger that has a charge rate higher than 20 Amps.

how do you know how many "C's" you should charge a given pack at?

This question is best answered by the mfg of the pack. Heat is a by-product of charging and the enemy of any battery. Charging at higher currents produces more heat which can shorten the life expectancy of the pack.

Most will prob recommend charging at 1c or 2c maximum.

I most hear peeps say to charge at 1c to maximize the life of your pack.

Hyperion claims that their new Vx line-up can be safely charged at up to 5c. But, as you can see from the example above, based on the packs that you can realistically run in a savage, most peeps chargers are going to limit them to 3c max (based on the notion that you wanna run a pack around 5000 Mah at a minimum).

Hope this helps.

 

[whipnet]

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[Larsenracing]

Your rigs ESC's should all have an auto-cutoff.

This is not true in all ESC's. There are actually only a select few that that built in cut-offs. Many of the low end ESC's have nothing for protection against low voltage. If the case you have no cut off there are devices out there that do this for you that you just add in-line. There are also things that you can plug into your balance plug that will beep when a certain cell reaches 3.0V some will have a volt meter on them and some will just beep and some will have Led Lights, Etc.

 

[whipnet]

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[Larsenracing]

LOL, sorry I never cought that. My bad.

 

[whipnet]

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[Ducman82]

thanks for all the info guys. its been a great help. still lots to process, but it gives me some great ideas.

 

[frddyj]

20C battery should be able to supply 20 amps continuously without damage.
30C battery should be able to supply 30 amps continuously without damage.

my question is, what do people mean when they say they charge at "1C" or "2C"?

Yep. To avoid any confusion, "C" rating is used to rate current in 2 ways:
in Whips example: C rating is describing the packs Discharge Rate:so if you had a 40C 5000 Mah LiPo, it means that the pack is rated for 200amps of continuous discharge (5000/1000 x 40).

In Hollywood's question, the C rating is describing the charging current from the charger into the pack as described earlier.

how many amps does "1C" equate to? i've read 5.5 amps, but can't grasp how "C's" relate to amps. thanks in advance.

in its simplest terms, 1C = 1/1000 of the packs total Mah (capacity)

 

[whipnet]

I think you wrapped it up Frddy, nice job.

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[wrenchman]

If your ESC doesn't have a LiPo cut-off, here is an example of a cutoff that you can add in-line, as Larsen had mentioned...

http://www.teamnovak.com/products/lipo_cutoff_module/index.html

 

[Bankrupter]

thanks for all the info guys. its been a great help. still lots to process, but it gives me some great ideas.

Back on pac ideas. If you want to go 5S SMC cant help you unless you go single pack. This forced me to go to Hyperion G3 packs 35 C 6500 MAh fair price and very hi quality.

 

[whipnet]

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[frddyj]

Sorry to dig up an old thread, but I wanted to make sure that the fact that discharging a LiPo too far is as dangerous as charging it too much.

BY discharging too much (leaving them plugged into the esc for example) will cause to the batteries to puff up and possibly explode.

So maybe no fire, but still a dangerous situation.

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great post whip +1

 

[whipnet]

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[Ducman82]

so here is a question for everyone. if you have an old LiPo, what should you do with it? take it to a special battery recycle place? how do you "old timers" do it?

 

[whipnet]

so here is a question for everyone. if you have an old LiPo, what should you do with it? take it to a special battery recycle place? how do you "old timers" do it?

I was just thinking that because I have one. I was going to ask my LHS today.

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[wrenchman]

This is what I've heard of to dispose of LiPo Packs...

http://www.rctoys.com/pr/2007/07/06/safely-dispose-of-lithium-polymer-LiPo-lipoly-battery-packs/

 

[frddyj]

This is what I've heard of to dispose of LiPo Packs...

http://www.rctoys.com/pr/2007/07/06/safely-dispose-of-lithium-polymer-LiPo-lipoly-battery-packs/

sounds good. wonder if the salt water becomes poisonous ?