Is Lithium Battery Really Good !!!

[jerahteo]

I had two piece of Kokum 2 cell 8.4v Lithium battery. Bought less than 3 month and both are now as good as nothing.

I don;t understand why they behave that way ?

They say I could have discharge beyond the line !

Anybody got any solution ? To have good battery ! Or how not to over discharge ?

Really fixed

[HZM]

I had 5 etecs.... 3 x 2S1P and 2 x 3S1P..... the 2S is real long and those who know me knows i push my batts the hardest

Some far they still strong after 9mths tho not as punchy as new. They don fail....... Give mack a call for Etecs

Cheers


Mike

[Fit]

The number one cause of premature lipo death is overdischarging.
With Fixed Pitch Micros, they will continue to fly even when the pack voltage is below the minimum 3.6V per cell. Often the lipo pack is overdischarged by the time the heli falls into GE(Ground Effect).

Continuously overdischarging the cell will kill it very quickly. The rule for lipos is not to go below 3.6V per cell. In other words 7.2V for a 2S pack and 10.8V for a 3S pack.

There are ways to prevent overdischarging Lipos. One is to use an ESC with adjustable voltage cutoff like those from Castle Creations and some of the Jetis. Another way is to build or buy a low voltage warning device that beeps or lights up a LED when the voltage goes below 3.6V per cell.

And finally a crude but easy way to know that you should stop flying is to test the heli's climb out. Test the heli's climb out rate when the battery pack is fresh and take note of the rate of climb. Every 5 minutes do a climbout test. Once you find that the climb out rate is slow compared to the beginning of the pack, its time to stop. The heli will usually be able to hover fine but when you give full throttle, it would climb relatively slow as the battery's voltage drops substantially under load. Take note of the total flying time and take a minute off the time to keep it safe. This will then be your yardstick for all your flights.

By the way, which Kokams are you using? Generally the Kokam's lifespan and performance for heli usage is below average compared to other makes like the ETECS. Their pricing is also expensive compared to the ETECS that Mack is selling. I've been using Etecs HP from Mack and they're much much better in terms of voltage hold under load and lifespan. The pricing is also much cheaper than the Kokams. In any case my advice is to keep away from the 1200 Kokams. They're not good for anything above 3amps. The 1500's are okay but are considered older generation cells compared to the Etecs HP.

[Super-Hornet]

Hi jerahteo

U might read from other post that I mention that I have 3packs of 3Cells and 1pack of 2Cells of 1500mAH Kokam that dies around 1month plus.

With that, from now onwards, I stay away from Kokam (Suspect design fault). I now using E-Tec 1200HP. So far, one pack already 1 month old usage.

Super-Hornet

[waycool]

i thought the min volts per cell is 3v?

[jerahteo]

Lithium Battery Do's and Don't

Can you tell me which one is more reliable ESC or low voltage warning device and price wise which is more expensive and weight wise which is bulky or heavier. Where is Castle Creation and some of the Jetis ? Where to buy?

Who is Mack ? Is it a he or a shop selling this battery and how much for a Lipos of 8.4volt 2 cells 1200/1500/1800/2000.

Originally posted by Fit


There are ways to prevent overdischarging Lipos. One is to use an ESC with adjustable voltage cutoff like those from Castle Creations and some of the Jetis. Another way is to build or buy a low voltage warning device that beeps or lights up a LED when the voltage goes below 3.6V per cell.

And finally a crude but easy way to know that you should stop flying is to test the heli's climb out. Test the heli's climb out rate when the battery pack is fresh and take note of the rate of climb. Every 5 minutes do a climbout test. Once you find that the climb out rate is slow compared to the beginning of the pack, its time to stop. The heli will usually be able to hover fine but when you give full throttle, it would climb relatively slow as the battery's voltage drops substantially under load. Take note of the total flying time and take a minute off the time to keep it safe. This will then be your yardstick for all your flights.

By the way, which Kokams are you using? Generally the Kokam's lifespan and performance for heli usage is below average compared to other makes like the ETECS. Their pricing is also expensive compared to the ETECS that Mack is selling. I've been using Etecs HP from Mack and they're much much better in terms of voltage hold under load and lifespan. The pricing is also much cheaper than the Kokams. In any case my advice is to keep away from the 1200 Kokams. They're not good for anything above 3amps. The 1500's are okay but are considered older generation cells compared to the Etecs HP.

[Fit]

You either use one or the other. If you use an ESC with LVC adjustability then you do not need the warning device.
AFAIK, Castle Creations, TMM and some of the Jetis has LVC.

You can get Jetis and CC from Hobby Shack. TMM from Singapore Hobby and Jeti from Mack.
Mack is one of the forum members here. Do a search for his post to contact him.

The ESC's range around $50 to $70. For the Jetis not all has LVC, so you must check on the net the model number to see if it has LVC.

i thought the min volts per cell is 3v?

True 3V is the minimum, any lower and they're most likely permanently damaged. But I've had a pack gone down lower but managed to revive it by trickling them.
But its best to not go below 3.6V nominal per cell to prolong the cell's life.

[jerahteo]

Lithium Battery

I forgot to mention to you that I am flying the Humble Bee which everything is in one black box(Gyro,speed control, receiver etc) will the ESC work for me in this case ?

[jerahteo]

Battery

How do you do trickling can you teach me to revive my two Lthium Battery ?

Originally posted by Fit
But I've had a pack gone down lower but managed to revive it by trickling them.
But its best to not go below 3.6V nominal per cell to prolong the cell's life.

[PhiBeR]

Trickle charge ur Lipos, that's what it means..

Trickle charging is done by charging ur lipo cells at 0.1C..

So if ur cell capacity is 1200mah, u can trickle charge it at 0.12a

A 1C charge rate is 1.2A, 0.1C translate to 0.12A or 120ma..

If ur cell is 1500mah, then ur 1C rate will be 1.5A, etc..

[jason_ices]

DO NOT Trickle charge your Lithium Polymer cell. It will over charge and damage the cell. please read Lithium polymer user guide