Lipo Midpoint

[RelaxC]

Hey all,

Question about lipos that has me curious. Every lipo I’ve ever had of various brands, seems to be fairly linear in terms of voltage and respective capacity. If I store them at 3.85v it takes almost exactly half the battery capacity to get them there, and another half capacity to full charge.

The latest lipos that I bought, seem to have their midpoint voltage closer to full capacity. They will take well over half to storage charge from empty, and well under half to charge up to full. I assumed that their capacity simply wasn’t what is stated on them, but if you fully charge them from LVC, they take about their stated capacity.

This seems weird…….

 

[RC-Dude]

Midpoint is not really the benchmark. If you discharge a 5000mAH lipo from 4,2volt down to 3,8 volt and then recharge you charge less compared to bringing up a pretty empty lipo to 3,8 Volt and then charging it. First case you might charge 2000mAh to full and second case you will probably chare around 3000mAh to full.

 

[RelaxC]

Okay, I’ll keep and eye on them.
Thanks!

 

[Hector_Fisher]

Your observations are correct. Each lipo model/brand has a different chemistry which affects voltage/discharge curves, capability, and overall long-term reliability. I've had some lipos with most of their mah's below 3.9v per cell, and some with most of their mah's above 3.9v per cell. I have a set of lipos that, under discharge, hold strong at 3.6v per cell for a long time and then finally drop down to LVC. Ironically, those are some of my most reliable batteries.

This is all normal from my experience, just depends on the batteries you get. Generally speaking, i think you could argue that the lipos with the higher "midpoint" are better, but as long as it doesn't hit LVC prematurely and you get the stated capacity, i think it's fine.