Lipo batteries are complexe!
 

Hey guy's, I' m all new to brushless systems and lipos, i need some help for charging them, this is my quetions: I just bought a set of maxamp 9000xl mah 2s pack. On the piece of instructions that came with them, it says I can charge the batts at 5c. If i'm wrong tell me, 1c is = to 4amps right, but my batts are only 9000 mah and they say I can charge them at 20 amps even if other people say that you should divide the amount of mah by 1000 an charge your batts at that amperage! please help me I am LOST IN THIS! NITRO IS MUCH SIMPLER BUT NOT AS FUN!! AAAARRGGGG:flaming:!

Thanks for helping.

1c= 1x a given battery's mah capacity. A 4000mah pack means 1c=4amps, 2c= 8amps, etc.. A 9000mah pack means 1c=9amps, 2c=18amps, etc..

While some batteries are "rated" to charge at 5c does not mean they should be. 1-2c is plenty fast, safer and attainable for most chargers.

Just to add to this as...

If you charge your Lipos at a lower C rating you are going to see a longer runtime and a longer overall life span, if you charge them at a higher C rating, you will see decreased runtime, and decresaed lifespan, but you will see a slight increase in power.

If you charge at 1-2c you shouldn't see a huge difference. Over 2c, yes I completely agree, sacrificing battery life for a faster charge time.

Even when the manufacture (TP in my case) says cycle life will not be affected?

Yes, even if they say they won't be affected. If your battery wears out faster they get to sell you another one sooner.

Everything you need to know about Lipos

http://www.tmenet.com/pdf/LithiumBatterySecrets.doc.pdf

:confused:

If charged to a given MAH at 2c, that battery will have the same runtime as a battery charged to the same MAH at 5c, or any other charge rate. Mah is Mah.

And all this hoopla over reduced service life when charging at higher rates has yet to be proven, IMO. There may be studies and theory, but in practice in the field I don't believe it. Any pack I own that allows for charging at greater than 1c gets at least a 2c charge. IR in every one of those packs is still low and they all still balance quickly and evenly, and they all are well over a year old now.

All you guys that are worried can enjoy wasting time at 1c. I'll stick to higher charge rates because nothing I've seen with this practice on my own packs has proven to be harmful.

And...for what it's worth, I store my packs on a wooden shelf, without a Lipo sack in sight, OMG. :eek:

:lol:

If you believe the little number on your charger's LCD, great. If you charge @ 5c you will shorten the cycle life of the pack. Like you pointed out, "there have been studies". What else is there to do to prove it?

To the OP, it's not that big a deal. Most racers don't keep their batteries until their last usable cycle, nor do they keep count of how many cycles they've charged anyway. If your race program moves so fast that shorter charging time is really important to you then it's fine to charge @ 2c. Even if it cost you 10% of your cycle life, you'd never miss it.

5c on a 9000 pack wow that is one hell of a charger that can pump out 45 amps and the power supply must be driven by a v8 gas engine. 20 amps is plenty. I have some 5200 packs that are 5c safe and I usually charge them at 10-12 amps. My charger maxes out at 20 amps per channel anyway.

Regardless of what my charger says, or what studies say, the best "proof" is what I see at the track regarding my own packs.

I agree with what you say about most racers not keeping their packs until their last usable cycle and never missing the last 10% of their cycle life. That is the other reason why I don't worry about charging at only 1c rates. To me, it's pointless to spend more time charging.

:nod:

There is no study lol, if anyone could see how fast a pack can suck MAH out when using a 4.5T 550 motor and 90C you would have no issue charging your packs at 20A. We could say drive slower because we wouldn't want to pull more than 1C out of the pack because it will shorten the life span. :lol:

Back to the original topic here. He did purchase a MAXAMPS lipo.... and if you guys know anything about them they have a 300 cycle guarntee. so if you want my opinion then charge it how ever you want to. charge at the highest possible c rating that maxamps suggests cause if it is true that it shortens the life span then guess what. you just got a brand new lipo for free. and if it is true that it does not affect the battery well then it was a good test and will prove the fact. either way its your battery do what you want with it. its the only battery on the market that will get replaced if it doesnt make it to 300 cycles.......

Here is a video I just took of some Eagle Tree data I logged yesterday when motor testing, look at the MAH. ;)

There is your study...

+ YouTube Video

I hope I don't really need to say this but here goes: Pulling current from the pack and putting it back in are two completely different things.