@Akshay Theertha The effect of series / parallel is to either increase the capacity or the voltage. This is how battery packs are made. Remember, the theory is different than reality since discharge is not always linear as the battery voltage drops.
I am deigning a tracking device using arduino uno and sim900 gprs shield. using two 3.7v 2200mah batteries in parallel … my device runs for 7hr . I am sending sms and to thingspeak 2 times i an hour. I want to minimize the current consuption so that my device will run for at least 24 hrs. What should I do… please hepl.
@ALEKOS DIGITAL Using GPS constantly consumes quite a bit of current - can you see if connecting to the GPS only when needed (twice per hour) helps? If not, you might just need a larger battery pack, or add three such packs in series.
I have a RC car with 4.8v NICd battery, can i use LiPo battery to increase power ?
@Mrityunjay This is hard to tell because the 4.8V may power electronics which are not 7.4V tolerant and would burn. The main motor may also not be 7.4V tolerant. You’d run quite a risk of damaging the system.
Hello, I have an arduino uno with five flexiforce sensors, five flex sensors, and five High Torque - Metal Gear Servo. Is it possible to operate them on one or two Lithium Ion Polymer Battery - 3.7v 2500mAh? if yes, how long will it last? Thank you
The Flexiforce sensors likely need to be connected to a voltage divider circuit operating at 5V, and the servos likely operate at between 4.8V to 6V. A 3.7V LiPo would need a 5V step-up regulator and then you should be fine. It’s really hard to determine how long a system will last (how long and how often will the servo be used for example?).
Hi sir,
I am making a humanoid robot .I plan on using 15 servos(60 kg servos) that have nominal voltage 7.4 V and consume 5 A at maximum load that would add up to 75 A totally.I want to use it for 30 minutes(Let’s assume all servos work at all times-Worst case scenario). Could you suggest a suitable Li ion battery/batteries that I can buy online?
Thanks in advance.
Also,I was thinking of using 3 2S 6000mah 25C Lipo Batteries connected in parallel so it would run
for about 20 minutes.Would this suffice?
You’re certain that you’ll be operating each and every motor at its maximum load, such that ALL 15 servos draw 5A each? Normally in a humanoid, the current draw is very different for different joints. If you use 3x 6Ah = 18Ah batteries, and you determine that you’re actually drawing 75A, it’ll last 18/75 = 0.24hs = ~14 minutes. This does not factor in inefficiencies of the battery, controller, motor etc. which can easily reduce it by 50%. You should take a look at each motor and see if you’ll actually be drawing a full 5A. You might need to calculate or estimate the torque at each joint under normal operation
Thank you for this excellent primer - very useful for this total novice!
I have a project that requires 16 digital micro servos (I’ve opted for the HiTec HS-503HD). This servo’s stall current draw is 360 mA and 8 mA at idle, operating at 4.8-6V. The servos would only be needed to operate for very short periods of time (~< 1 sec) only periodically (e.g. twice daily), either all together, independently, or in groups.
I also plan to add an Arduino to the mix (not sure which one yet), possibly attached to a lux meter, to automate the operations of the servos on a schedule or on input of variable data (e.g. open/close at dawn/dusk).
What battery would you recommend for this?
If you plan to operate them all at peak torque (which, according to you would require a current draw of 360mA?), you’d need a power supply of between 4.8V to 6V capable of providing 16 x 0.36A = 5.76A. A 4x AA pack will likely struggle with that current, so you might need something “beefier” like a 6V lead acid battery. Check the Arduino’s specs to see if the Vin pin can operate at ~6V and if so, you won’t need a second battery.
Suggest double-checking the 503HD specs to confirm the current draw is UNDER LOAD, since most small servos can consume pretty high current.
I have one stepper motor with 5V nominal voltage and i use 3xAAA 1.5 V battery to run it and it works
But my problem now is that i have to use 2 stepper motors
The motor requires 200mA and the battery capacity is 900mAh
Can I run both of them with the battery that i have? Should I use 2 separate power supply for the motors, each supply at 4.5V?
@Bianca It becomes less about the capacity and more about the battery’s maximum discharge current. Can you find that information about the battery you’re using? If not, do some research online and it’s a brand name battery, you might try to draw up to 2x 200mA = 400mA (napkin math) from those batteries. Ideally you’d use a higher capacity battery which tends to also provide a higher discharge rating. Using two battery packs is another option, but less “clean”.
The gear ratio, encoder and dimensions don’t affect the choice of battery.
You need to know the continuous current you’ll draw, and for how long, as well as the maximum peak / momentarycurrent.
This will help determine the battery’s maximum rate of discharge and the capacity.
You indicated one of the motors is 6V, whereas the other is 12V. An RC operates at 6V, whereas the MEGA operates at 12V.
You have two (evident) options: a dual battery setup with one 6V and one 12V battery, or a 12V and a decent spec voltage regulator.
Regarding the battery’s specs, it’s important to know the details above.
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@hamza87 Completely understand your question and you will agree that it’s unfortunate that most RC servo manufacturer’s don’t give that data, or at least some sort of current consumption. The best solution would be to measure the current consumption, but that requires setup etc. We can say normally that micro servos consume more current than standard sized servos since they need to produce decent torque in a small size. Ballpark estimate, a micro servo might consume 500mA continuously under load and even up to 1A under stall conditions.
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If you are considering this Feetech continuous rotation servo, the specs are in fact provided:
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The max height does not really have an impact on the choice of battery, nor does the Kv. You need to consider the total payload of this drone to know how much weight can be set aside for the battery. You also need to indicate the motor’s nominal voltage. If they consume 12.4A each (is this at maximum efficiency or maximum power?) that gives an indication of what the battery needs to be able to discharge continuously. The capacity will affect the battery’s weight and how long the drone will last before the battery is depleted.
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@hamza87 6S = 22.2V, which should correspond to nominal operating voltage of the motors you selected. 35C means it can provide a current of 35x4A = 140A, which is more than the 6x 12.4A = 74.4A you might need to power all motors (again, is this at max power or nominal?). The battery might last 4A x 60 minutes / 74.4A = 3.2 minutes at full drain.
Strongly suggest reading through 4. Battery in the following tutorial:
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great and detailed guide. Thanks for the work you’ve done!
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Great article!
i use esp32 (5v usb) + servo board pca9685 and sound MAX98357 and 3 servo fs90r (5-6v)
i calculate:
3 servo total max 1.5A (5V)
esp32 max 200mA (5V usb)
pca 100mA (5V esp32 pin)
max with 3W speacker 1A (3,3V esp32 pin)
to power both esp32 and servo at 5v is it best lipo 3.7v and stepup to 5v or lipo 7.4v and step down to 5v ?
thank you for help !
Leo
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