jdawg81

iTrader: (1)

I purchased a new Nano-Tech Ultimate 7500 Mah lipo battery and did a discharge/charge cycle on my iCharger to see if the battery will charge to the rated capacity. If I remember correctly the charger discharges to 3.1v per cell before starting the charging process. It only charged to 6700 Mah which is less than what i was expecting. Is this normal or should a new battery be able to charge close to it's rated capacity?

billdelong

iTrader: (33)

lots of variables to consider... but generally I think you have the right idea. Any chance the pack is a LiHV pack? Only reason I ask is because you might be shorting yourself some capacity if the pack was designed to be charged to 4.35V/cell instead. I've got a 6Ah shorty pack that is LiHV but I only charge to 4.2V/Cell... so I never get close to the rated capacity, but I'm okay with that, idea being that the pack should have a longer lifespan if not maxing out the cells to their rated capacity

ta_man

iTrader: (168)

Another factor is: The higher the discharge amp rate, the more the pack IR will depress the pack voltage resulting in stopping the discharge (at a given voltage cut-off) sooner with more capacity remaining in the battery.

In other words, if you discharge to 3.1V at 40 amps there will be more left in the pack than if you discharged to 3.1V at 5 amps.

malkiy

iTrader: (10)

Are you absolutely sure discharge was set to 3.1v? If I remember correctly I thought default was 3.35v? Depending on discharge voltage those batteries should charge to 7000-7100 after a full discharge.

jdawg81

iTrader: (1)

It is not a LiHV battery and I discharged at 2 amps. I have also confirmed that the charger was discharging to 3.1 volts and charging to 4.2 volts. I might do another cycle just to double check the result. If I get 7000 to 7100 then that would ok with me. If I'm still getting around 6700 then maybe this battery was sitting on the shelf for a long time before it got shipped to me.

I also emailed Hobbyking about the lower battery capacity and this is the response I got.

"LiPo batteries follow the 80/20 rule. You should NEVER completely discharge a lipo. 80% of a 7500mAh lipo is 6000mAh so that is all you should ever take out and put back in."

Is there any truth to this?

Xpress..

If you discharged it down to 0.00v then you will see roughly 7500mah. Things to consider: capacities are always an average of the cells inside, provided they took the time to match the cells. Unmatched packs likely will not meet the capacity specifications. Cycling your pack a handful of times can also aid in bringing the capacity numbers up. Discharging to 3.1v/cell is getting dangerously low and if you're seeing more than 80% of the capacity rating in that discharge then I'd say you're getting a lot out of that pack.