As I believe Phaedrus to be an engineer and much more capable with relating the technicalities than me I'll reserve the technical side for him to explain. I'm more of the "meatball" type". For discussion purposes my explanation references a battery in perfect condition. Battery age and the manner they have been used widely impacts how they will perform with cell voltage and delivery of energy.
For ease of simple comparisons I'll say that mA can be likened to ounces of gas in a gallon. If we relate gallons to volts and ounces to mA we have a comparative starting point. Depending on how long or how fast you drove a number of time over the same distance with a 5 gallon (5v) gas tank the number of ounces or fractions of an ounce (mA
) of gas required to refill the tank would be different. If you drove with the pedal to the floor the vehicle would consume more fuel for the distance than if the vehicle was driven slow and gently. Taking that a little further, the number of ounces or fractions of an ounce required to fill the tank is dependent on the amount of fuel that was in the tank before you elected to fill it. At the end of the day you started with a 5 gallon gas tank and ended with a 5 gallon gas tank. Where total capacity in volts or amps is concerned nothing changed. What did change was the number of ounces, or fractions of an ounce (or mA for comparative reference) of gas you used and replenished.
Where our batteries are concerned mA capacity works in a similar fashion. We can effectively gauge % of capacity using mA counts. With a little practice we can establish where the voltage should be after using "X" number of mA. Inversely, we can (very roughly) estimate how many mA were consumed by looking at the displayed voltage level.
The mA count we see after charging a battery is what the charger is saying was received by the battery during the charging process. In theory, if you had a 5000mA battery that took 2500mA to charge it back to full state that battery was 50% discharged when you put it on the charger. That is not an accurate statement though as I've seen many batteries where the charger displayed a mA count higher than a battery's label capacity after a charge cycle was complete.
As I'm not an electrician or electrical engineer I lack the ability to get extremely technical but voltage and mA are directly related as voltage falls or rises as mA are consumed or added. The voltage level a battery is at when it is placed on a charger determines how many mA it will need to charge it back to full state. If we took two batteries of the same rated voltage and capacity and placed them side by side on a dual charger that had both been flown the same amount of time, more often than not the mA count to recharge them would be different as the voltage levels would have been slightly different when they were placed in the charge cycle. 1/100v difference between them at the start of the cycle causes a difference in mA input. The end voltage would be the same (+/- a couple 1/100's v/cell) but the number of mA required for them to achieve the final voltage would be different.
From my position, mA is the unit of measure used to determine how much energy was used or required to achieve a full charge. It's what I use to establish percentage of consumption as "X" mA consumed is pretty consistent in establishing voltage level. Some of the better DIY type flight controllers (Pixhawk, APM, Vector) provide mA consumption estimators in their telemetry displays. I love those things as they make things a lot easier when gauging remaining flight time. Battery bar graph displays do nothing for me as without any calibration documentation they cannot be trusted.
People that are good with Ohm's law and electrical calculations are probably very good at the math involved with the relationship of mA to voltage but I'm not in that group, using multiple flights of various times and charge cycles to learn battery percentages established through mA count, which also determines voltage, where voltage is what Yuneec employs for a user reference.
Your turn, Phaedrus
