Can you figure out battery health through storage charge measurements?

[lucidchaos]

I have two sky lipo 2200mah packs that I have been on average flying once per day. I haven't been bringing them to a storage charge but instead charging them after flights as I fly them nearly every day.

After reading the impact of leaving them charged at room temp I figured I would bring them down to a storage charge. This only took 660 out of the batteries to bring them from 4.2v per cell to 3.85v per cell.

I've read batteries are at storage charge at about half the cell's capacity - have I already wrecked these batteries? Can you determine battery health by analyzing storage voltage?

[Slyster]

Wrecked lipos don't usually lose capacity in my experience.. they lose 'punch'.. so they feel really weak/tired... can hit LV cutoff earlier.. puff up... and get hot and so on.

[The WoodCrafter]

If you are charging and discharging (using them) you are fine.
The problem is when you charge them and don't use them.
You are simply shortening the time span by flying too often.
How many cycles do you have on them?
How old are they?

[lucidchaos]

I bought them back in late October for my shiny new Blade 450 3D. Hard to tell how many cycles are on them - does everyone actually keep track of that sort of thing on a spreadsheet or something or do the better radios do it for you?

I would venture a guess that I have maybe 120 cycles on them, about 10-15 where I neglected to set the timer and went until I noticed a slight drop in HS.

[Slyster]

Congrats on getting over 100 cycles. I've yet to do that in 4 years and 40+ lipos. Time to buy new ones. Gens Ace are really good and $20 or so.

[Gregor99]

Originally Posted by Slyster

Congrats on getting over 100 cycles.

+1 That is unusual. However, I've done it. When I first started out I got 120 flights on one pack and 127 on the second one. The third puffed at 80. This was 2008 and packs were not near as good as they are today.

How did I do it? First off, I was mostly hoving and doing slow controlled forward flight. No flips, loops or climb outs. Second, I was using an ESC that did not have a functioning low voltage cut off. All my flights were timed and I only used 75%-80% of the pack.

When I upgraded to a better ESC with a functioning LVC, I was quite surprised when both packs hit LVC two minutes into the flights that were normally 6 minutes. Back then we didn't have an easy way to test or log pack's performance. As a test I bought a new pack and was in for a big surprise. With the new pack, the helicopter was transformed. Far more power and responsiveness. While that performance is not needed for early stages of learning, it sure was fun. The new pack made the full 6 minutes without hitting LVC. The old packs were retired at this point.

Long story short. Pack performance slowly degrades over time. If you don't have a decent LVC or means to test packs under load it can be difficult for pilot in the learning stages to detect this. One could argue that even if the pack is performing badly, but its still working well for the pilot's needs, should it be retired? Perhaps not. However, as packs reach near the end of of thier life, they are less stable and pose more of risk. The two retired packs eventually puffed on thier own while sitting in storage (at 3.85v per cell).