oldschool269

How hot do you guys let your lipos get during discharge ???

i see a lot on posts here of big head speeds and big teeth pinions ,

how hot do these lipos get when being run

my flight power packs can take it but how do the cheaper align packs hold up (12-18c ) ??
Cheers,

Jason

don_87

I have been reading a few complaints about the Align batteries losing power quickly.
Check out the TP 2070 they are supposed to be doing real well.
I'll find a link and put it here shortly.
Thunder Power Extreme, go here:
http://www.techmodelproducts.com/bat_charge.php

Don

walleye_gfa

The TP site has teh 2100 lipos as specifically for the trex... you can find tehm for about $65 if you look enough.

TP2100-3SPL
2100 mAh, 3 cells (11.1V), 16G wire, 4-pin balancer connector
Rating: 15C (31.5A) continuous, 24C (50A) burst
Dimension: 34mm x 100mm x 20mm

Weight: 142gm, for Trex


Thats what I use but am looking to see if I cant get a little more power if I accept a little more weight for non areobatic flight... if anyoone has any tried and true suggestions for more mAh let us know...

walleye_gfa

Ok stupid question...

The ones you linked to above have much higher amp rating, only what 20 or so grams heavier... so why do they recommend the one I referenced above for the rex ???

It would seem taht the one you mentioned above should be the hands down choice looking at the specs, am I missing something ???

Looking to buy a couple more batts for the rex soon so input is appreciated...

oldschool269

MY standard align packs have alot of problems once they have been abused a few times , my align lipos are rated at 18c 1800 ma, and they are rooted , it charges to 800 ma and gives me a 6 minuite flight ,

to compare the same setup with a "flight power' battery ,

this awsome battery gives me twice the head speed, and around 3 x 6minuite flights ,
(3500kv outrunner , 10 tooth ! 80% max head speed , CC25 speedy, and flight power 2150 batts )

the flight power pack weighs 185 grms and i add 24 grams of coins to the nose of the heli , it gives me a weight on the battery of 215 grams and the heli is much more stable in FFF, i can fly fast 1- 2 foot of the ground with the extra stability a little weight gives on the nose .

knowing this i believe a shift to a 215 gram lipo could be beneficial for flying in strong wind etc..


the align packs i have 1800 ma, are 143 grams and i bring them up to 185 grams with weight on the nose and they fly good , but dont last a jatz cracker.

i bought up this subject because i have always had to run 1 tooth down on recommended pinion count on my setups or it cooks stock lipos ,

the Cheap lipos cant take the current with just sport flying ...

does every one fly with just flight power or TP packs on the plannet or is there just alot of disatified TREX oweners who dont know their batts are holding them back ??

this is a question of heat , with the planes there is always a setup that works and comes back with stone cold batts and a long flight time ,
with the trexs i own the batts come back warm to hot , wich is not right for a lipo they like to be ice cold ...

so my batts come back stinking hot , is there others ?? ,speak up !
i know that its not binding as my bearings are all good and THE HELI FLYES GREAT !!

Jason

don_87

The 2070's are new I believe. the 2100 pro lites were the norm.
Only thing I can say for sure is that better batteries are on the way, customers are demading it.
When you try to do 3d manuevers, you get a higher amp draw (most generally run a 35 amp esc) when you get into heavier flying you will max out the amperage rating on your batteries, and even surpass the rating on the battery. Thus killing it.
With the higher amperage rating on the 2070, on most setups, you won't come anywhere near the rated amperage of the battery, thus less stress on it. The battery itself lasts longer, not to mention that the charge does too. People are reporting 10 minute flight times with these batteries.
You are right "hands down a better battery".


Don

shuohan

My Feedback: (3)

Don, if you are constantly pulling more current, or as you say "amperage", you will not get as long of a flight time. This should be intuitive as battery capacities are measured in milliamp hours. The greater current you pull the quicker you'll deplete the battery. I agree with you that battery should keep its original capacity longer because of the 50A or so max current rating it has. That way most people won't be going over the 15C on 2.1Ah packs during hard maneuvers overstressing the battery. Looks like a good pack.

You must note though, if a person buys this battery for its high current rating, he is probably going to be running higher current from the battery and as a result he'll get shorter flight times. If you're using this battery to its full ability you should expect about 4-5 minutes of hard 3D. If you somehow pull max current the whole time you'll get exactly two and a half minutes of flight before the 2070mA hours are completely drained. Conversely, if you did the same with a 2.1Ah 15C battery (31.5A max current), you'd get four whole minutes of flight. That's 60% more than the other battery. Obviously nobody runs at max draw for a full flight, but those figures show you the general trend of max current output vs flight time when capacity is roughly constant.

don_87

I'll try to explain it here the way I read it.
When you hit pitch and cyclic on your bird, you are going to concievably pull as much as 25 to 30 amps at one time. While it may onlty be a short burst, you have still gone over the amp rating of your 2100 battery. Which eqauls out to more of a drain on the battery itself , which in turn runs the battery down quicker. Thats where the higher amp rating of the 2070 comes in.

shuohan

My Feedback: (3)

Don,

I think you might have the letter C confused with A for amps. A "C" rating is a way for battery manufacturers to describe current relative to a battery's capacity. It does not specify current directly. If you have a battery rated at one C, it can move current fast enough to unload its entire capacity in one hour. To convert a C rating to current you multiply the C rating by the battery's capacity. The nice 2070 TP is rated at 25C. Its capacity is 2070mAh. You have 2070mA x 25C = 51.75A. That is its max current rating. For a typical TP 2100mAh battery with a 15C rating, you have 2100mAh x 15C = 31.5A max current. In a hard 3D maneuver you may pull more than 35 or 40A in a Trex. This is OK for a short time. If you are constantly in the 30A or more range you should use the 2070 TP with the 25C rating to save the battery.

Now, as for your argument that a lower capacity battery, the 2070mAh TP would last longer in flight than the higher capacity battery, the 2100mAh let me explain why this is not correct. First of all, if you fly exactly the same, they will last just about the same time with the 2070 giving out just a few seconds earlier as 30mAh doesn'tmatter much. However, if you are using the 2070 to its 25C potential, you'll run it out much quicker because you're pulling greater current from roughly the same capacity. I hope this makes it a little bit clearer to you.

As a side note. Generally people running a battery in the 2100mAh range getting 10 minutes of flight are pulling an average of exactly 12.6A. This gives you guys an idea of how much over average 50A is.

don_87

I can't find the actual test that I was thinking about, but I think it was referring to batteries pooping out too soon also. I'll keep searching and post when I find it.


Don

shuohan

My Feedback: (3)

Obviously if you run batteries out of spec (higher than 15C and under 25C) the 15C ones will go bad quicker. That has nothing to do with flight time. Same wear on tear on both batteries, the higher current pack will be run down in less time.

credence

My Feedback: (2)

Just so you guys don't start panicking over temperatures too badly... Lithium batteries can be safely used at temperatures up to about 140F and still retain good cycle life. Obviously, the cooler they run the better, but don't forget that you're pulling alot of power from these relatively low capacity packs, so it's natural for them to get warm to hot during use, even at lower amp draws.

Generally speaking, 120F is the "OK" zone and you shouldn't suffer any pack problems (aslong as you use a balancer). 140F and you're coming to the threshold for safe operation and retaining cycle life. 160F is the MAX these packs should reach. If you're going as high as this or higher, you're damaging the cell structure and it will not only shorten the batteries life, but it's power output. (Not to mention the not too pleasent possibility of thermal runaway if you really kill the battery).

Also remember that just about every battery manufacturer grossly overstates the true discharge rating of their batteries. Most packs can't come close to their claimed discharge rating without suffering long-term damage. If a pack claims a 20C discharge, you can probably only realistically discharge it at about 12C or 15C (in the case of a good quality cell) without pushing the battery too hard. Sure, it'll discharge at 20C without blowing up, but I wouldn't count on the pack lasting at those discharge rates.

shuohan

My Feedback: (3)

Credence, I agree with you. If you are pulling current from a 2.1Ah battery at its advertised 15C rate it'll certainly get hot. The hope is if you pull that same 15C from the 2070mAh 25C rated pack that TP has the battery wont' get warm at all as you have so much current overhead and thus the battery will live longer.

credence

My Feedback: (2)

Indeed, it's better to go way over than what you'll need so that you don't stress your equipment as hard. The same applies for most ESC's on the market.

Most of them if you draw the current that they're physically rated at for extended periods of time, they'll end up cooking. Always get more than what you need so you have the overhead.

walleye_gfa

Pffft good discussion....

don_87

Thank you, that is the thought I was trying to convey.
I got some of my info from [link=http://www.helifreak.com/viewtopic.php?t=19718&start=0]here[/link] .

don_87

As far as "A" and "C", I promise to watch Sesame Street and reruns of Mister Rogers Neighborhood til I learn them.


Don

shuohan

My Feedback: (3)

Don, I just wanted to let people know pulling more current from a battery leads to shorter flight times, opposite what you said. That way people won't buy this battery looking to 3D for longer because they won't. Like I said, this should be intuitive if you think about it for a short while. As far as A & C, let me save you the trouble of watching the kids show. "A" stands for Amperes which is the measure of number of electrons moving past a certain point. C stands for the capacity of a battery.

don_87

I think you misunderstood what I was getting at, but we'll let it go there.


Don

shuohan

My Feedback: (3)

Maybe I misunderstood that statement as meaning you'll get longer flights. My mistake. Nothing to "let go" just making sure people aren't getting misinformed .

don_87

Ok, I'll explain a little better since you can't grasp the concept...........IT"S A FREAKIN JOKE!

don_87

And on this one, THEY ARE.........depends on motor, weight, headspeed, blades, pitch and throttle curves and a few other variables as we all know. Like looseness of the bird in question.
And with this post I'm done because you apparently are just looking for a fight.......I'm not participating!


Don

WhtBronco

To address the heat concern. Due to the specs reported by Thunder Power of 140 deg suggested max and 160 deg peak, I always figure if I can stand to hold the battery after a flight it’s not being damaged to much, if at all. I will say, though, that in my T-Rex the battery gets much, much hotter than in my planes. The li-po’s in my planes, well in 1 plane they get a bit warm and the other remains just above ambient temperature. In my Rex it’s almost to hot to hold at times and without a temp gun I suggest that this translates to 120-130 deg temp. IIRC, 120 deg is the temp at which we feel things as being hot.

shuohan

My Feedback: (3)

Don,

I'm sorry if I hurt your feelings. Please don't feel bad. I wasn't looking for a fight. Like I said, I didn't want people buying this more expensive battery planning on getting longer flight times. Thanks for the good discussion.

Shuohan

oldschool269

this is very good to hear, i have been looking at the outrunners there are some that peak at 12 a or hot motors that peak at 25 a or i might just have to go 14v+ to shead some amps , time will tell.

thanks guys
Jase