TEBerg

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I have spent a bit of time searching and reading to try and figure out how I will be charging, balancing and running my first Lipoly batteries...

Now – I am not an expert, just a newbie to lithium polymer who had questions...

So, I looked up things like:

Minimum “safe” voltage per cell
Maximum voltage per cell
Discharge limits
The “80% Rule” and what it means.
Battery Care
Charging at 1C
Conditioning the Battery
Balanced LiPoly Cells and what voltage is “balanced”
Storing batteries
And a bit about “C Rating”.

So, I put together a Cheat Sheet that I will have in the box with my balancing battery charger – and I’m posting it here. I also did a little calculation (back of the napkin type of calcs) just to have a starting idea about using my 4S Lipoly packs…

OK – Please feel free to take a look and comment if you like... If I’m completely wrong (meaning unsafe) with something let me know and I can make changes. If I’m not even close I’m sure people looking here may still want to hear the correct information so let us know.

For other newbs like me – please feel free to print this out and use it as a starting point…

Edited to upload JPG - I posted a JPG because that is what the site will take.

TEBerg

My Feedback: (1)

Well - That didn't work at all, so here it is:

LiPoly Battery Information

Voltages:

Base: 3.7v per cell
Max: 4.2v per cell
Discharge/Minimum: 3.3v per cell
Damage at: 3.0 volt possible.
Note: Charge to 4.1v per cell can extend battery life.

80% Rule:

Approximately 3.5 volt per cell will be about 80% discharged. This can also read back up to 3.7 volts “resting” after 5 to 10 minutes.

Milliamps – leave 20% in pack/ 80% used or “put back” during charge.

Battery Care…

Charging = 1C
Condition the battery, charge = 0.5C
Balanced Cells = 0.03v max difference for a Charged Pack. No difference or 0.01v is best. Note: Partially discharged pack can have larger differences between cells (0.1v)
Balanced cell voltage measured in fresh charged pack!!
Do not Discharge to balance, it may over-discharge and damage cells.
Storage = 3.85v (1/2 between 3.7v-4.0v resting)
Note: A drop of 0.1v from a cell in 1 day may indicate a bad cell/pack.

C Rating…

“Capacity” in milliamps times “C” rating = discharge capacity.

Example: 2200ma/1000 mA/A X 15 “C” = 33 Amps

4S, 14.8v, 2200 mAh, 15C battery…

Max Voltage: 16.8 volts
Minimum Voltage: 13.2 volts

Target 80%
= 13.44 voltage reading
= 1760 milliamps “put back”; 440 milliamps discharge remaining.
Note: 2200 mAh discharged at 33 amps = 4 minutes.
However, @ 80% => 1760 mA at 33 amps = 3 minutes 15 seconds.
Also, 80% flown at 80% throttle => 1760 mA at 26.4 amps = 4 minutes.

Therefore: 4 minute flight good starting point!!

yahman1254

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the jpg works fine. good help btw. gonna buy my first lipos later.

huck1199

C Rating…

“Capacity” in milliamps times “C” rating = discharge capacity.

Example: 2200ma/1000 mA/A X 15 “C” = 33 Amps

Your example qouted above is confusing.

TEBerg

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Huck,

You are right, it is a bit "short hand" for me also...

I understand the "C" rating is the discharge capacity of the pack. This is a combination of the amps available (or milliamps) and the 'rate' at which the power can be delivered.

So: my pack it 2200 milliamps and has a rating of 15C

2200milliamps/1000 milliamps per amp = 2.2 amps of power

My battery has a 15C rating so: 2.2 amps X 15C = 33 amps;...

So this setup can deliver 33 amps of power to the speed control/motor... Now if you need something like 45 amps you will either need to get a bigger pack (more millamps) or a better C rating...

This is what I have gleaned from several sources including; RCGroups guide to Lithium polymer batteries, Battery University, and the thread here from Aeajr (EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT)...

There is a lot better detail at these sources and others...