What Does The Advertised "C" Rating Say?
Nothing you should trust! From what I can tell, 30C just means that if you discharge that pack at 30C, it'll last 20 cycles - not what most people want.
Other than that, you can multiply the C Rating by the mAh of the pack to get the Amps the pack is advertised to give without blowing up (at least for the 1st 20 cycles or so). So a 30C 2300mAh pack gives 30 times 2.3A. That equals to 69amps. For those that didn't catch it, it's 2.3A because 1000 mAh = 1A.
What Does Cell Voltages Say
2.8v - Dangerously low, charge with caution (i.e. Slowly... and stop if the pack starts heating up!)
3.4v - The lowest you want to get when flying around.
3.7v - Nominal voltage, 25% capacity left - Good voltage to stop flying at.
3.9v - Whoa... we're half way there... whoa-oh! Living on a prayer!
4.1v - 85% Capacity - Good voltage to charge up to for fast charge.
4.2v - 100% Capacity - Takes a lot more time to charge up to compared to 4.1v!
What Does Pack Temperatures Say (In Celsius)
30 to 50 degrees - Good, batteries will last at least 100 cycles or more.
51 to 60 degrees - Cookin it a little, it'll last 50 to 100 cycles...
61 to 70 degrees - Fryin it now..., with luck you'll get 20 to 40 cycles...
> 71 degrees - Are you nuts?
When I say last, that means the pack isn't bloating/puffing/inflating dangerously and you have at least 75% of the advertised mAh when you charge to 4.2 volts (full charge) and discharge to 2.8v.
Why Does My Lipos Heat Up When Used?
In short, because of Internal Resistance (IR). IR is what makes your packs less "powerful" because more power is converted to heat than useful motion (i.e. Turning your motor). The lower the IR of a pack, the higher a discharge rate it can handle without overheating and without the voltage dropping too much.
Heat Kills Li-Po
So arrange for as much airflow as you can over your batteries during flight, and/or keep your flight times less, so batteries don't heat up too much over time. You can also try changing your propeller (for airplanes) and main gear ratio (for helicopters) to something that has less load on the power system. That usually means smaller less pitch props and less head-speed respectively.
Batteries Get Soft Without Use
Batteries are like human muscles... if you don't exercise them they get sloppy, but if you over work them, they get burnt out... however unlike humans, batteries don't regenerate after some rest... (i.e. once their internal resistance (IR) gets raised from over discharge/over temperature, they stay raised, high resistance = less power, more heat, less capacity)
More About Internal Resistance (IR)
The most obvious sign that your batteries IR got higher due to damage is bloating, however, IR also get's higher the more cycles you put on the battery and for that, if it's a good battery, you won't find any bloat even though the IR gets higher!
I Wanna Charge At 2C (Or Higher)!
Sure! But the last time I tried that, my packs lifespan seemed to get halved. They could hold less than 75% of capacity after 50 cycles... When in doubt, 1C is nice.
About Deans & Bullet Connectors
High amps have a habit of de-soldering connectors off batteries in flight!
Up to 55amps - Deans Connectors
> 55amps - Use 4mm, 5.5mm or 5mm bullet connectors please!
Note that if your soldering sucks, it doesn't matter what connector you use... get it soldered properly!
Why do my Lipos Puff/Bloat/Inflate
3 Main Reasons:
- Over discharge - Used to much mAh and/or discharged at too high amps, heat build-up
- Over charge - Put in too much mAh during charging
- Defective Pack - Usually means impurities are present in the batteries chemistry
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