1
$\begingroup$

How to calculate the maximum charge of the battery that it can give from a fully charged state to a fully discharged one. I have been trying to solve this problem for 2 months. The drone itself is not. Maybe someone knows How to calculate the maximum charge of the battery? And sorry about my English. I don't know him well. Or some formulas for finding the electrical capacity of C?

New contributor
xCrane is a new contributor to this site. Take care in asking for clarification, commenting, and answering. Check out our Code of Conduct.
$\endgroup$
  • 1
    $\begingroup$ Welcome to Robotics:SE. What has your research shown you so far? You might find it helpful to review the site tour and Help Centre and, in particular, How to Ask. $\endgroup$ – sempaiscuba Jan 12 at 1:52
  • $\begingroup$ what will you do with the information? $\endgroup$ – jsotola Jan 12 at 2:43
0
$\begingroup$

If you want to learn about batteries and their characteristics, you should probably go to the BatteryUniversity to learn a few things before you start to do calculations, because if you miss interpret stated parameters as facts, you will get wrong results.

https://batteryuniversity.com/learn/

The specific mAh you can get from a battery depends on the voltage difference from charged to discharged state you are willing to use (carefull it can be dangerous or damaging to discharge to low or charge to high) and what you measure when you charge or discharge. Stated capacities on batteries are estimnates at best, depending on battery type it can be the most achivable mAh or the minimum value which is always achived ... check your datasheet of the battery for this(if your battery has no datasheet then good luck finding out by measuring).

There is some websites and youtube channels doing battery tests, only if you test a cell you can know exactly how it performs.

LIION:

https://lygte-info.dk/review/batteries2012/Common18650Summary%20UK.html http://www.dampfakkus.de/akku_liste-nach-groesse.php?size=18650

LIPO:

very difficult to find tests because the batches of batteries even from the same vendor have different performance characteristics. Find some here:

https://rightbattery.com/lipo-liion-life-batteries/

NiMH/NiCd

https://rightbattery.com/nicd-nimh-batteries/

theres are more resources but thats just what i found in a moderate time frame.

$\endgroup$
0
$\begingroup$

The mAh rating should be written on the battery. For Lipo batteries typically used in drones, the stated mAh is usually a fairly decent estimate of the actual, though that varies some depending on the brand and quality of the battery supplier. Even if there is no label on the battery, the mAh rating is typically printed on the side of the cells. If there is no label printed with mAh capacity, or you don't trust the stated mAh, you can discharge the battery till the resting voltage is about 3.7 volts per cell under no draw, and then charge it back. Your charger should tell you how many mAh were put back into the pack, and you can typically multiply this by about 1.2 to get an estimate of the total mAh available in the pack. It's not 100% accurate, but it's a safe ball-park. Regardless, the number you get will be a good value to use when estimating functional capacity for flight time estimates.

You typically won't want to draw your battery much below about 3.3-3.5v per cell under load, and it should recover to around 3.7v resting with no load. You don't want to use much more than about 80-85% of the overall mAh capcity of the battery. A resting voltage of 3.7v should get you right there, but if you have way of measuring mAh consumption via a current sensor, it will be much more reliable than relying on voltage alone, as voltage can fluctuate dramatically depending on the current draw load on the battery and the quality of the cells.

Another thing to be aware of is as your battery ages, the useful capacity of the cells, as well as the safe current draw, can reduce somewhat dramatically. You'll need to continually monitor the health of your packs throughout their life, and if you start to see a dramatic drop in performance, stop using them and replace them immediately.

Keep in mind this is true only for LiPo batteries we typically use. If you want to use Lithium Ion, the safe discharge voltage and discharge rates are very different, and the claimed mAh ratings can be dramatically off depending on the reliability of your source for the LiIon cells. Some 18650 style LiIon cells have been found to contain powder filler and a much smaller cell inside, so be aware of those caveats.

As far as identifying other characteristics of a battery, using a reliable "internal resistance" meter can tell you a lot about the battery performance and how much current you can safely draw from it. I use the Wayne Giles meter, and you can find a good discussion on the theory and how to use the meter here: https://www.rcgroups.com/forums/showthread.php?1323465-ESR-IR-Meter-fo-Lipos

New contributor
QuadMcFly is a new contributor to this site. Take care in asking for clarification, commenting, and answering. Check out our Code of Conduct.
$\endgroup$
  • $\begingroup$ be warned this is only true for LiPo-Batteries and some things in this post are missleading or half true. mAh stated can be way off (only if you test the batteries you can tell). $\endgroup$ – AnafiFlyer Jan 15 at 9:43
  • $\begingroup$ I've tested hundreds of lipo batteries and have never once found dramatic variation from the stated mAh. The Lipos we typically use for drones (which this question was referencing) are typically very close to stated. The ones where I've found variances have been slightly larger than stated, so going with the stated mAh is a very safe bet. $\endgroup$ – QuadMcFly yesterday

Your Answer

xCrane is a new contributor. Be nice, and check out our Code of Conduct.

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.