I guess the main thing to keep in mind is to not exceed the battery manufacturer's recommended rate for that battery.

This. Charging at a max of 1C is old skool and not in a good way. Cheap TX packs, maybe, but better packs usually support at least 5C. I charge almost all my packs at 20A (max my charger can supply).

How long does it take to charge a 5000mAH battery at 20A?

I am looking at the TrakPower VR-1 charger and one of the ports charges at 20A so if this is OK and doesn't kill batteries I would like to do it. Do you guys by the cheap chinese batteries or good solid known batteries for racing?

20 amps is going to be about 15 minutes or more. It may help to realize that 20 amps = 20 ah (in an hr) , but of course most users don;t get the set point for 100% of the charge. I use almost ALL cheap packs and rarely over a 25C rated pack and charge them at around 30 amps.

Balancing, storage, cut off voltage are more important factors than charging at 1 or 3C as soon as lipo is 5C capable.

If you charge fast you'll need less lipos to run constantly. So even if you use high grade lios, it will cost you less. I just use 3 lipos and already did an endurance race of 12 hours with 4 lipos only..

find that hard to believe. the faster you charge the shorter life you are going to get as the packs will get hot whilst charging. if you want to save your investment......then just charge at 1c if you are not in a hurry

Want to ask a silly question and see if there is an answer.
How to verify the number of c on the battery label?

We've been talking about constant charge "c" and you will need to clarify what part of that you'd like to verify. I'm not even sure if anyone has a std for charge C , I used to use actual constant discharge "C" divided by 10. You can easily set a charge for that value that is on the label and start the charge. If you are happy with what you see then it is verified?

For discharging "c" the battery can be discharged at the "c" rating to see if you can tolerate the temp rise and/or volt drop. It can also be tested thru IR and estimated fairly close.

as a new player in ep, my question to what i tried to ask previously is how to counter check or by what means i can see the battery i am buying is the number of "c" claimed on the label. on the market, the higher the c, the higher the price is.
and which brand sells more true "c" as label?
thanks!

I see, you want to verify the constant discharge rate before purchase?

Only way I know is to scour the web/databases for the specific pack and hope that others have already purchased it and posted test results. If it's a popular brand then others probably have an idea even without testing.

You gotta be careful when reading reports because there's a difference between an accurate label and a "good" pack. (two different things) It's also easy to fall prey to reports that "battery A" works perfect in my app so it is assumed the label is correct. This is a "race" forum so many of these guys know what "wins"

You got a specific brand or pack in mind? Perhaps someone already has experience with it. Two hot topics right now seem to be haiyin and chinaonline packs.

yes, you got my thinking.
as a customer, i want to buy something really meant to what it wrote on the package, a label is just a printing and the manufacturer can print whatever "c" they like to, especially those china made non famous brand. i know all lipo packs were made in china nowaday,......but, there are still non famous brands that we should try or trust, having said that, how to test or calibrate the "c" that bought from a shop?

The IR can be tested within close temp controlled conditions with an IR meter (from Wayne) or many chargers now have the IR test function. The i-chargers are very popular units for testing IR accurately. This is only half of the equation and trusts the capacity on the label.

Beyond IR testing many chargers can run discharge tests at various currents to verify both capacity AND "c" rating. A CBA from westmountainradio is an excellent device for doing nice graphs.

thanks so much, i learnt so much!
have a nice day!

Not many chargers can determine C rate. Not enough discharge power. WestMountain would be the only way

As for IR non of the RC chargers do it accuratly. They only measure DC IR across a pack and this is not IR of a cell which is measured via ac IR at 1khz.
So to use your charger to compare packs you must...
1. Use the same charger all the time at the same temperature
2. You can't compare a 4S pack to a 6S pack for example
3. All your wires and leads must be the same. 50% of your IR measurement is in the leads, this different packs will show your different results especially sinceyou are trying to measure a 1 - 5mohm value with chargers that have component tolerances as wide as 10%.....very hard to do accurately and repeatedly

question for the experienced lipo users.I accidently left my battery plugged in and car on for 4 days before realizing it and ran the battery down to 2.5v total.It is a dynamite 2s 4200 30c($50.00) so not an expensive battery.The question i have is should i pitch it or is there a way to bring it back? thanks for input