What the hell is going on? How did it get like this?
As I work through finalizing the list of tests to perform on these LiPo battery packs, and how to best present the data, one thing has become very clear….most LiPo “C” ratings are complete fantasy.
Not just exaggerated but beyond comprehension as to how they could be set this high. They are obviously “pulse” ratings of some kind but even then they’re preposterous.
For example…
A very respected company has rated a pack in the 1800mAh range at 100C. That’s a rating of 180A. It has a DC internal resistance averaging of 42mOhms after break-in, very high. At 180A that means even when only pulsed, with a freshly charged 3S pack, the voltage drops from 12.6V to just over 5.0V instantly.
The minimum voltage is 9.0V for the pack. That 100C rating is utterly and completely useless and instantly brings each cell down to a level that can quickly damage it.
Another example of ratings silliness…
More than one of these 1800mAh packs has a C rating that results in a current rating above 117A. Why is that important? Because at 117A for more than a few seconds the 16AWG wire some packs use can melt…literally! Even if the current is pulsed the wires can reach VERY high temperatures, hundreds of degrees, at that current level. How can that possibly have been thought to be a rating, of any kind?
Another example…
The ThunderPower Rampage 70C pack (not in the table) has a continuous current rating of 126A, as listed on the Thunderpower web site. Even the 12AWG wire it uses will reach hundreds of degrees when used at that high a continuous current level and very high temperatures when pulsed. The voltage sag will be huge too. Just ridiculous.
Having said all this, the worst 1800mAh pack still outperforms the best pack we can make from 18650’s. I just want to inject a bit of sanity into the process of choosing a LiPo.
The table I’ve attached here shows the internal resistances of the 1800mAh packs I am testing. The names will be hidden until testing is done. You can see that two packs have very high internal resistance, a couple are fairly low, and the rest are in between. Interestingly, the lowest resistances do not belong to the packs with the best reputations. Quite the contrary in fact.
More info to come as the testing continues.
https://imgur.com/a/M6uZq
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