Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.



Now that you’ve cho­sen or built a frame, the next step is choos­ing the right pow­er­plant. Since most of the cur­rent drones are elec­tric, we will focus on gen­er­at­ing pure­ly elec­tric propul­sion through brush­less DC motors. The struc­ture of the pow­er plant includes motors, rotors (pro­pellers, abbr. props), ESC and bat­tery.

1. Motor

Which motors you use in your build will deter­mine the max­i­mum load the drone can lift, as well as how long it can stay in flight. The pow­er plant must nec­es­sar­i­ly con­sist of motors of the same brand and mod­el, this approach will ensure its bal­anced oper­a­tion. At the same time, it is worth not­ing that even absolute­ly iden­ti­cal (Brand/Model) motors can have a slight dif­fer­ence in speed, which is sub­se­quent­ly equal­ized by the flight con­troller.

brushed vs brushless

In brushed motors, the rotor with the wind­ing rotates inside the sta­tor, on which the mag­nets are fixed rigid­ly. In brush­less motors, every­thing is reversed; the wind­ing is attached rigid­ly to the inside of the sta­tor, and the mag­nets are mount­ed on the shaft and rotate. In most cas­es, you will only con­sid­er brush­less DC motors (BC). Motors of this type are wide­ly used in the ham radio indus­try to assem­ble prod­ucts rang­ing from heli­copters and air­planes to dri­ve sys­tems in cars and boats.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.

Pan­cake brush­less motors are larg­er in diam­e­ter, flat­ter and gen­er­al­ly have high­er torque and low­er KV (details below). Small UAVs (usu­al­ly palm-sized) often use small com­mu­ta­tor motors due to the low­er price and sim­ple two-wire con­troller. Even though brush­less motors come in dif­fer­ent sizes and have dif­fer­ent char­ac­ter­is­tics, choos­ing a small­er size does not mean that it will be cheap­er.

Inrunner vs Outrunner

There are sev­er­al types of brush­less DC motors:

  • Inrun­ner — inner rotor. The wind­ing is fixed on the sta­tor, the mag­nets are mount­ed on the rotor shaft which rotates (usu­al­ly used on RC boats, heli­copters and cars due to high KV).
  • Out­run­ner – out­er rotor. The mag­nets are fixed to the sta­tor, which rotates around a fixed wind­ing. The low­er part of the motor is fixed. (as a rule, motors of this type have more torque).
  • Hybrid Out­run­ner — tech­ni­cal­ly it is an “Out­run­ner”, but imple­ment­ed in an “Inrun­ner” pack­age. This approach made it pos­si­ble to com­bine in one type the torque of the “Out­run­ner” and the absence of exter­nal rotat­ing ele­ments as in the motors of the “Inrun­ner” type.


KV rat­ing — max. the num­ber of rev­o­lu­tions that a motor can devel­op with­out los­ing pow­er at a giv­en volt­age. For most mul­ti-rotor UAVs, a low KV val­ue (eg, 500 to 1000) is desir­able as this helps to ensure sta­bil­i­ty. While for acro­bat­ic flight a KV val­ue between 1000 and 1500 will be rel­e­vant, in tan­dem with small­er diam­e­ter rotors (pro­pellers). Let’s say the KV val­ue for a par­tic­u­lar motor is 650 rpm, then at 11.1V the motor will rotate at a speed of: 11.1 × 650 = 7215 rpm, and if you use the motor at a low­er volt­age (say 7.4V) , then the rota­tion­al speed will be: 7.4 × 650 = 4810 rpm. It is impor­tant to note, how­ev­er, that using a low­er volt­age gen­er­al­ly means that the cur­rent con­sump­tion will be high­er (Pow­er = Cur­rent × Volt­age).


Some man­u­fac­tur­ers of brush­less motors may indi­cate in the spec­i­fi­ca­tion infor­ma­tion about the max­i­mum pos­si­ble thrust (Thrust) gen­er­at­ed by the motor, cou­pled with the rec­om­mend­ed main rotor. The unit of thrust is usu­al­ly kilo­gram (Kg/Kg), pound (Lbs) or New­ton (N). For exam­ple, if you are build­ing a quad­copter and you know the thrust val­ue of a sin­gle motor = up to 0.5kg in com­bi­na­tion with an 11-inch main rotor, then four of these motors will be able to lift at max­i­mum thrust: 0.5kg × 4 = 2kg. Accord­ing­ly, if the total weight of your quad­copter is a lit­tle less than 2kg, then with such a pow­er plant it will take off only at max­i­mum speed (max. thrust). In this case, it will be rel­e­vant to either choose a more pow­er­ful “motor + main rotor” com­bi­na­tion, which will pro­vide greater trac­tion, or reduce the total weight of the drone. At max. thrust of the pow­er plant = 2kg, the weight of the drone should be no more than half of this val­ue (1kg, includ­ing the weight of the motors them­selves). A sim­i­lar cal­cu­la­tion can be made for any con­fig­u­ra­tion. Let’s assume that the weight of the hexa­copter (includ­ing the frame, motors, elec­tron­ics, acces­sories, etc.) is ‑2.5kg. So each engine for such an assem­bly should pro­vide (2.5kg ÷ 6 motors) × 2 = 0.83kg of thrust (or more). Now you know how to cal­cu­late the opti­mal thrust of motors based on the total weight, but before mak­ing a deci­sion, we sug­gest that you famil­iar­ize your­self with the sec­tions below.

Additional Considerations

  • Con­nec­tors: DC com­mu­ta­tor motors have two con­nec­tors “+” and “-”. Swap­ping wires in places changes the direc­tion of rota­tion of the motor.
  • Con­nec­tors: Brush­less DC motors have three con­nec­tors. To learn how to con­nect them, as well as how to change the direc­tion of rota­tion, refer to the “ESC” sec­tion below.
  • Wind­ings: wind­ings affect the KV of the motors. If you need the low­est pos­si­ble KV but pri­or­i­tize torque, Pan­cake brush­less DC motors are your best bet.
  • Mount­ing: most man­u­fac­tur­ers have a com­mon mount­ing scheme for BC DC motors, which allows frame com­pa­nies not to resort to mak­ing so-called adapters. The tem­plate is usu­al­ly met­ric, with two holes spaced 16mm apart, and two more holes spaced 19mm apart (at a 90° angle to the first).
  • Thread: The mount­ing thread used to mount the brush­less motor to the frame may vary. Com­mon met­ric screw sizes are M1, M2 and M3, impe­r­i­al sizes can be 2–56 and 4–40.

2. Main screws (Propellers)

The rotors (pro­pellers, abbr. props) for mul­ti-rotor UAVs orig­i­nate from the pro­pellers of radio-con­trolled air­craft. Many will ask: why not use heli­copter blades? Although this has already been done, imag­ine the size of a hexa­copter with heli­copter blades. It is also worth not­ing that the heli­copter sys­tem requires a change in the pitch of the blades, and this sig­nif­i­cant­ly com­pli­cates the design.

You may also ask why not use a tur­bo­jet, tur­bo­fan, tur­bo­prop, etc.? Of course, they are incred­i­bly good at pro­vid­ing a lot of thrust, but they also require a lot of ener­gy. If the pri­ma­ry pur­pose of the drone is to move very quick­ly, rather than hov­er­ing in tight spaces, one of the above motors might be a good option.

Blades and diameter

The rotors of most mul­ti-rotor UAVs have two or three blades. Pro­pellers with two blades are most wide­ly used. Don’t assume that adding more blades will auto­mat­i­cal­ly increase thrust; each blade works in the flow dis­turbed by the pre­vi­ous blade, reduc­ing the effi­cien­cy of the pro­peller. A small diam­e­ter rotor has less iner­tia and there­fore it is eas­i­er to accel­er­ate and decel­er­ate, which is impor­tant for acro­bat­ic flight.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.

Pitch/Angle of Attack/Efficiency/Thrust

The thrust gen­er­at­ed by the main rotor depends on the den­si­ty of the air, the num­ber of rev­o­lu­tions of the pro­peller, its diam­e­ter, the shape and area of ​​the blades, and also on its pitch. The effi­cien­cy of a pro­peller is relat­ed to the angle of attack, which is defined as the blade pitch minus the helix angle (the angle between the result­ing rel­a­tive speed and the direc­tion of rota­tion of the blade). Effi­cien­cy itself is the ratio of out­put pow­er to input pow­er. Most well-designed pro­pellers are over 80% effi­cient. The angle of attack is affect­ed by rel­a­tive speed, so the pro­peller will have dif­fer­ent effi­cien­cy at dif­fer­ent motor speeds. Effi­cien­cy is also great­ly affect­ed by the lead­ing edge of the main rotor blade, and it is very impor­tant that it be as smooth as pos­si­ble. While a vari­able pitch design would be best, the added com­plex­i­ty required over the inher­ent sim­plic­i­ty of mul­ti-rotor means that a vari­able pitch pro­peller is almost nev­er used.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.


The rotors are designed for clock­wise (CW) or coun­ter­clock­wise (CCW) rota­tion. The direc­tion of rota­tion is indi­cat­ed by the slope of the blade (look at the pro­peller from the end). If the right edge of the blade is high­er — CCW, if the left edge is CW. If your drone is designed with invert­ed motors (as is the case with the Vtail, Y6, X8 con­fig­u­ra­tions), be sure to change the direc­tion of rota­tion of the rotors so that the thrust is direct­ed down­wards. The front side of the main rotor should always be fac­ing the sky. The doc­u­men­ta­tion that comes with the flight con­troller usu­al­ly con­tains infor­ma­tion about the direc­tion of rota­tion of each pro­peller, for each mul­ti-motor con­fig­u­ra­tion sup­port­ed by the con­troller.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.

Execution materials

The material(s) used to make the rotors (pro­pellers) can have a mod­er­ate effect on flight per­for­mance, but safe­ty should be a top pri­or­i­ty, espe­cial­ly if you are new and inex­pe­ri­enced.

  • Plas­tic (ABS/Nylon, etc.) is the most pop­u­lar choice when it comes to mul­ti-engine UAVs. This is large­ly due to low cost, decent flight per­for­mance and exem­plary dura­bil­i­ty. Usu­al­ly in the event of a crash, at least one pro­peller is bro­ken, and as you mas­ter the drone and learn to fly, you will always have a lot of bro­ken props. The rigid­i­ty and impact resis­tance of a plas­tic pro­peller can be improved with car­bon fiber rein­force­ment, this approach max. effi­cient and not so expen­sive com­pared to a pro­peller ful­ly exe­cut­ed and car­bon fiber.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.

  • Fibre-rein­forced poly­mer (car­bon fiber, car­bon fiber rein­forced nylon, etc.) — is “advanced” tech­nol­o­gy in many respects. Car­bon fiber parts are still not very easy to man­u­fac­ture, and there­fore you pay more for them than for a reg­u­lar plas­tic screw with the same para­me­ters. A pro­peller made from car­bon fiber is hard­er to break or bend, and there­fore, if it crash­es, it will do more dam­age to any­thing it comes into con­tact with. At the same time, car­bon pro­pellers tend to be well made, stiffer (pro­vid­ing min­i­mal loss in effi­cien­cy), rarely need bal­anc­ing, and are lighter in weight than any oth­er mate­r­i­al. Such pro­pellers are rec­om­mend­ed to be con­sid­ered only after the user’s pilot­ing lev­el becomes com­fort­able.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.

  • Wood — a rarely used mate­r­i­al for the pro­duc­tion of rotors of mul­ti-rotor UAVs, since their man­u­fac­ture requires machin­ing, which sub­se­quent­ly makes wood­en pro­pellers more expen­sive than plas­tic ones. At the same time, the tree is quite strong and nev­er bends. Note that wood­en pro­pellers are still used on radio-con­trolled air­craft.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.


Fold­ing props have a cen­ter sec­tion that con­nects to two piv­ot­ing blades. When the hub (which is con­nect­ed to the out­put shaft of the motor) rotates, cen­trifu­gal forces act on the blades, push­ing them out­ward and essen­tial­ly mak­ing the pro­peller “stiff”, with the same effect as a clas­sic non-fold­ing pro­peller. Due to low demand and the large num­ber of parts required, fold­ing pro­pellers are less com­mon. The main advan­tage of fold­ing props is their com­pact­ness, and in com­bi­na­tion with a fold­ing frame, the trans­port dimen­sions of the drone can be sig­nif­i­cant­ly small­er than the flight dimen­sions. The accom­pa­ny­ing advan­tage of the fold­ing mech­a­nism is the absence of the need, in case of a crash, to change the entire screw, it will be enough to replace only the dam­aged blade.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.


Like UAVs, rotors can have a wide range of sizes. Thus, there are a num­ber of “stan­dard” motor shaft diam­e­ters in this indus­try. As a result, rotors are often sup­plied with a small set of adapter rings (they look like wash­ers with holes of dif­fer­ent diam­e­ters in the cen­ter) that are installed in the cen­tral mount­ing hole of the prop, in case the diam­e­ter of the main rotor hole turned out to be larg­er than the diam­e­ter of the shaft of the motor used. Since not all man­u­fac­tur­ers sup­ply props with a set of such adapter rings, it is rec­om­mend­ed to com­pare the diam­e­ter of the bore of the pur­chased props with the diam­e­ters of your motor shaft in advance.

The screw can be fixed on the motor based on which of the mount­ing meth­ods your motor sup­ports. If the motor shaft does not imply any mount­ing options (thread­ed con­nec­tion, var­i­ous mount­ing devices, etc.), then spe­cial adapters are used, such as prop­savers and col­let clamps.

  • prop­saver — is a sleeve with sym­met­ri­cal­ly arranged side holes into which screws are screwed. The bush­ing is put on the motor shaft and fixed with side screws. A pro­peller is installed on top of the sleeve, which, in turn, is fixed with a rub­ber ring that comes with the sleeve (usu­al­ly there are sev­er­al of them in the kit). Due to their unre­li­a­bil­i­ty, but at the same time, fast instal­la­tion, they are best suit­ed for short-term test flights dur­ing the drone assem­bly process.
  • Col­let clamp – com­pared to the prop­saver, it is a more bal­anced and reli­able adapter. The col­let clamp con­sists of a split cone-shaped sleeve with a thread­ed con­nec­tion (col­let), clamp­ing sleeve, wash­er and spin­ner nut. First, a col­let is put on the motor shaft, then a clamp­ing sleeve, then the main screw (pro­peller) with a wash­er goes, and the cook-nut clos­es the clamp design.

Brush­less motors with an exter­nal rotor (like “Out­run­ner”), as a rule, in its upper part, have sev­er­al thread­ed holes designed for installing var­i­ous adapters and mounts. An equal­ly pop­u­lar option for mount­ing the pro­peller on the motor shaft is a self-tight­en­ing nut. The shaft of such a motor has a thread at the end, the direc­tion of which is oppo­site to the direc­tion of rota­tion of the rotor. This approach elim­i­nates spon­ta­neous unscrew­ing of the fix­ing nut, ensur­ing the safe and reli­able oper­a­tion of the drone.

Rotor protection

Rotor pro­tec­tion — designed to exclude direct con­tact of the UAV pow­er plant with an oncom­ing object, there­by main­tain­ing its integri­ty and per­for­mance, and also to pre­vent injury from rapid­ly rotat­ing pro­pellers as a result of a col­li­sion with peo­ple and ani­mals. The pro­peller guard is attached to the main frame. Depend­ing on the ver­sion, it can either par­tial­ly over­lap the work­ing area of ​​the pow­er plant, or com­plete­ly (ring pro­tec­tion). Screw pro­tec­tion is most often used on small (toy) UAVs. The use of pro­tec­tion ele­ments in the assem­bly also brings a num­ber of com­pro­mis­es, includ­ing:

  • May cause exces­sive vibra­tion.
  • It usu­al­ly does­n’t take a lot of hits.
  • Can reduce thrust if too many mount­ing posts are placed under the pro­peller.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.


Unsat­is­fac­to­ry bal­anc­ing occurs with most inex­pen­sive pro­pellers. To make sure of this, you don’t have to go far, just insert a pen­cil into the cen­tral mount­ing hole of the screw (as a rule, in case of imbal­ance, one side will be heav­ier than the oth­er). There­fore, it is strong­ly rec­om­mend­ed to bal­ance your props before installing them on the motors. An unbal­anced pro­peller will cause exces­sive vibra­tions, which in turn will neg­a­tive­ly affect the oper­a­tion of the flight con­troller (man­i­fest­ed in the drone’s incor­rect behav­ior in flight), not to men­tion increased noise, increased wear of the pow­er plant ele­ments and dete­ri­o­ra­tion in the qual­i­ty of shoot­ing of the sus­pend­ed cam­era.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.

A pro­peller can be bal­anced in a num­ber of ways, but if you’re build­ing a drone from scratch, you should def­i­nite­ly have an inex­pen­sive pro­peller bal­ancer in your arse­nal of tools that makes it easy and sim­ple to deter­mine the weight imbal­ance in the pro­peller. To equal­ize the weight, you can either sand the heav­i­est part of the prop (even­ly grind the cen­tral part of the blade, and in no case cut off part of the pro­peller), you can also bal­ance by stick­ing a piece of adhe­sive tape (thin) on a lighter blade (add pieces even­ly up to those until a bal­ance is reached). Please note that the far­ther from the cen­ter you make a bal­anc­ing upgrade (grind­ing or adding tape) to the pro­peller, the greater the effect based on the torque prin­ci­ple will be.


ESC (Eng­lish Elec­tron­ic Speed ​​Con­troller; Russ­ian elec­tron­ic speed con­troller) — allows the flight con­troller to con­trol the speed and direc­tion of rota­tion of the motor. With the cor­rect volt­age, the ESC should be able to han­dle max. the cur­rent that the motor can con­sume, as well as lim­it the cur­rent pass­ing through the phase dur­ing switch­ing. Most hob­by drone ESCs only allow the motor to rotate in one direc­tion, but with the right firmware, they can work in both direc­tions.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.


Ini­tial­ly, the ESC can be con­fus­ing, because there are sev­er­al wires / pins / con­nec­tors avail­able from two sides to con­nect it (ESC can come with or with­out sol­dered con­nec­tors).

  • Pow­er sup­ply: two thick wires (usu­al­ly black and red) are pro­vid­ed to sup­ply pow­er from the dis­tri­b­u­tion board/wiring har­ness to which pow­er comes direct­ly from the main bat­tery of the air­craft.
  • 3 con­nec­tors: Three con­nec­tors are avail­able on the oppo­site side of the con­troller, designed to con­nect to the three bul­let con­nec­tors (usu­al­ly includ­ed with the motors) on the brush­less motor. The use of con­nec­tors when con­nect­ing the ESC allows, if nec­es­sary (in case of fail­ure), to quick­ly change the con­troller with­out using a sol­der­ing iron. It hap­pens that the bul­let-shaped con­nec­tors that come with the motor do not match the con­nec­tors on the reg­u­la­tor, in this case, just replace with the right ones. Which of the three is plus and which is minus? The land­mark is sim­ple, the incom­ing pos­i­tive wire from the bat­tery goes into pos­i­tive on ESC, sim­i­lar­ly with a minus.
  • 3‑pin R/C ser­vo con­nec­tor with thin wires: through which the pro­cess­ing of the sig­nal com­ing from the receiv­er is car­ried out, of which one wire is sig­nal (trans­mis­sion of a gas sig­nal to the ESC or input), the sec­ond “minus” (or ground), and a pos­i­tive wire (not used if there is no built-in BEC; with built-in BEC is 5V pow­er out­put, which can lat­er be used to pow­er on-board elec­tron­ics).


At the time of the birth of air­craft mod­el­ing, an inter­nal com­bus­tion engine was used as a pow­er plant, and on-board elec­tron­ics were pow­ered by a small bat­tery. With the advent of elec­tric trac­tion and reg­u­la­tors (ESC), the lat­ter began to include the so-called bat­tery elim­i­na­tion cir­cuit — BEC (in Eng­lish Bat­tery Elim­i­na­tor Cir­cuit; or on-board pow­er con­vert­er; as a rule, pro­vides an addi­tion­al source of cur­rent with a volt­age of 5V at a cur­rent strength of 1A, or above). In oth­er words, this is a volt­age con­vert­er used in the LiPo assem­bly to volt­age for pow­er­ing the on-board elec­tron­ics of the drone.

When assem­bling a mul­ti-rotor, you need to con­nect all the ESCs to the flight con­troller, but only one BEC is required, oth­er­wise there may be prob­lems with sup­ply­ing pow­er to the same lines. Since there is usu­al­ly no way to dis­able BEC on an ESC, your best bet is to remove the red (+) wire and wrap it with duct tape for all but one of the ESCs. It is also impor­tant to leave the black wire (ground) for the com­mon ground.


Not all ESCs on the mar­ket are equal­ly good for mul­ti-rotor appli­ca­tions. It is impor­tant to under­stand that before the advent of mul­ti-engine UAVs, brush­less motors were used pri­mar­i­ly as a pow­er plant for radio-con­trolled cars, air­planes and heli­copters. Most of them do not require fast response times or updates. SimonK or BLHe­li built-in ESCs are able to respond very quick­ly to incom­ing changes, which gen­er­al­ly makes the dif­fer­ence between a sta­ble flight or a crash.

Power distribution

Since each ESC is pow­ered by the main bat­tery, the main bat­tery con­nec­tor must some­how be divid­ed into four ESCs. This is done using a pow­er dis­tri­b­u­tion board or a pow­er dis­tri­b­u­tion har­ness. This board (or cable) splits the pos­i­tive and neg­a­tive ter­mi­nals of the main bat­tery into four. It’s impor­tant to note that the types of con­nec­tors used on the bat­tery, ESC, and back­plane may not match, so it’s best to choose a “stan­dard” con­nec­tor when­ev­er pos­si­ble (eg Deans), which is used every­where. Many inex­pen­sive boards may require sol­der­ing, in this case the user decides which par­tic­u­lar con­nec­tor to use in the assem­bly. The sim­plest pow­er dis­trib­u­tor might include two input ter­mi­nal blocks, or sol­der all the pos­i­tive con­nec­tions togeth­er and then all the neg­a­tive con­nec­tions togeth­er…

4. Battery

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.


Bat­ter­ies used in drones are now exclu­sive­ly Lithi­um Poly­mer (LiPo), with some of the com­po­si­tions being quite exot­ic, such as Lithi­um-Man­ganese or oth­er lithi­um vari­ants. Lead acid is sim­ply not suit­able, and NiMh/NiCd is still too heavy for its capac­i­ty and often fails to pro­vide the required high dis­charge rates. LiPo offers high per­for­mance and dis­charge rate at a light weight. The dis­ad­van­tages are their rel­a­tive­ly high cost and con­stant safe­ty prob­lems (fire haz­ard).


In prac­tice, you will only need one bat­tery for your UAV. The volt­age of this bat­tery must match the motors you choose. Almost all bat­ter­ies in use today are lithi­um-based and con­tain sev­er­al cells (cans) of 3.7V each, where 3.7V = 1S (i.e. one cell bat­tery; 2S two cell, etc.). There­fore, a bat­tery labeled 4S will like­ly have a nom­i­nal val­ue of 4 x 3.7V = 14.8V. Also the num­ber of cans will help you deter­mine which charg­er to use. Note that a high-capac­i­ty sin­gle-cell bat­tery may phys­i­cal­ly look like a low-capac­i­ty mul­ti-cell bat­tery.


Bat­tery capac­i­ty is mea­sured in ampere-hours (Ah). Small size bat­ter­ies can be as low as 0.1Ah (100mAh), medi­um sized UAV bat­ter­ies can range from 2–3Ah (2000mAh — 3000mAh). The high­er the capac­i­ty, the longer the flight time, and, accord­ing­ly, the heav­ier the bat­tery. The flight time of a con­ven­tion­al UAV can be in the range of 10–20 min­utes, which may seem short, but you must under­stand that the UAV con­stant­ly fights grav­i­ty dur­ing the flight, and unlike an air­plane, it does not have sur­faces (wings) that pro­vide assis­tance in the form of opti­mum lift.

Discharge rate

The dis­charge rate from a lithi­um bat­tery is mea­sured in “C”, where 1C is the capac­i­ty of the bat­tery (usu­al­ly in amp-hours, unless you’re con­sid­er­ing a palm-sized drone). Most LiPo bat­ter­ies have a dis­charge rate of at least 5C (five times the capac­i­ty), but since most motors used in mul­ti-rotor UAVs draw high cur­rent, the bat­tery must be able to dis­charge at an incred­i­bly high cur­rent, which is typ­i­cal­ly about 30A or more.


LiPo bat­ter­ies are not entire­ly safe as they con­tain pres­sur­ized hydro­gen gas and tend to burn and/or explode when some­thing goes wrong. Thus, if you have any doubts about the per­for­mance of the bat­tery, in no case, do not con­nect it to the drone or even to the charg­er — con­sid­er it “decom­mis­sioned” and dis­pose of it prop­er­ly. The tell-tale signs that some­thing is wrong with the bat­tery are dents or bulges (i.e. gas leaks). When charg­ing a LiPo bat­tery, it is best to use a LiPo safe box. Bat­tery stor­age is also best done in these box­es. In the event of a crash, the first thing you need to do is unplug and check the bat­tery. A boxed bat­tery can add weight, but will real­ly help pro­tect the bat­tery in a crash. Some man­u­fac­tur­ers sell bat­ter­ies with and with­out a hard case.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.


Most LiPo bat­ter­ies have two con­nec­tors: one is designed to be used as the main “dis­charge” wires capa­ble of han­dling high cur­rent, and the oth­er, usu­al­ly small­er and short­er, is the charg­ing con­nec­tor (usu­al­ly a white JST con­nec­tor), in which one pin cor­re­sponds to ground­ing, and the rest, the num­ber of bat­tery cans. You con­nect it to the charg­er, through which the charg­ing (and bal­anc­ing) of each cell of the bat­tery is car­ried out. The charg­er must be sure to report when charg­ing is com­plete, and be aware of the safe­ty con­cerns asso­ci­at­ed with lithi­um poly­mer bat­ter­ies. After the end of the charg­ing process, it is best to imme­di­ate­ly dis­con­nect the bat­tery from the charg­er.

Do-it-yourself drone: Lesson 3. Power plant.Do-it-yourself drone: Lesson 3. Power plant.


The bat­tery is the heav­i­est ele­ment of the drone, so it should be installed at the cen­ter dead cen­ter to ensure the same load on the motors. The bat­tery does not require any spe­cial mount­ing (espe­cial­ly self-tap­ping screws, which can dam­age the LiPo and cause a fire), so some of the mount­ing meth­ods used today include Vel­cro straps, rub­ber, plas­tic com­part­ments, and oth­ers. The most com­mon bat­tery mount­ing option is to hang the bat­tery under the frame using a Vel­cro strap.


By Yara