From reading some posts here (most from reviews by HKJ), I think it's mentioned that for Li-Ion cells (eg. 18650s), the charged capacity is usually equivalent to its discharging capacity (ie. if we drain the 18650 to its cut-off voltage, then say we don't have an "analyzing" charger but a charger that can show the charged capacity) then we could still use the "capacity charged" to indicate the capacity of that 18650. (this applies to "good/working" 18650s. Older 18650s that have very high resistance may have a much higher charging capacity that doesn't reflect its discharged capacity.
However, for NiMh batteries (eg. Eneloops), I recall reading that its charged capacity will usually be more than the discharged capacity, even for "good" cells. I can't remember how much percentage more the charged capacity over its discharged capacity.
I'm wondering how about for lead acid batteries -- eg. those 6v 4.5Ah sealed lead acid batteries that were previously popular for rechargeable lanterns (we have quite a number of them at home), or those 12v 7.2Ah sealed lead acid batteries for computer UPSes? It is noted that lead acid batteries are charged at a very slow rate (10C or usually 20C, ie. more than 10 hours up to 20 hours but at a low current). Is the charged capacity also more than the discharged capacity (let's say we're charging and discharging at the same rate of approximately C/10 or C/20 current)?
Also, how do we determine if the lead acid battery is almost fully charged (eg. at least 90% or 95% charged; since the 100% full will probably take a longer amount of time)?
Just like with any other battery, you use a charger that detects the max voltage.
And no you do not charge them at 10C, that would basically make them explode.
You can’t even charge most lipos at 10C.
You probably meant 0.1C, which would be 10 hours charge, or 0.05C which would be 20 hours charge.
Lead acid battery technology is pretty outdated. Only reason it still is widely mass produced is cost, plain and simple. Even if you use deep cycle types, discharging them under ≈50% state of charge can lead to damage. Heard cranking batteries start getting sulfated with just a mere (and relatively common) ≈10% discharge. All of this sells well, you know. :facepalm:
We are required to have an operating UPS on our family lottery sales office, however the propietary nature of the computer terminal which it backs up does away with any sort of possible UPS management, therefore its batteries die soon. Pb batteries suck.
Lead Acid batteries can actually be pretty sophisticated and usable, where the mass is tolerable, once you understand them and learn how to select the most appropriate, as well as cost effective. They are going to be around for many more years.
For example, modern AGM (absorbed glass mat) construction is very different from old fashioned flooded wet cells, in performance, durability, ease of maintenance, self-disharge and safety.
In answer to the OP’s question, the “efficiency” of charge vs. discharge of lead-acid cells has been understood for well over 100 years, and is applied in battery monitors in e.g. marine, standby power and recreational applications, which integrate charge and discharge currents, apply Peukert or proprietary algorithms, and display useful statistics.
