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I have 5 servo motors and I need to run them simultaneously. If I use two 18650 Li-ion rechargeable 3.7 V 1400 mAh batteries, will it be safe for the servos or not?

  • The total power of the batteries is 7.4 V and 2800 mAh
  • Servo type: Futaba S3003
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  • \$\begingroup\$ Some are, some are not. Look on Futaba website for the servo specifications. Actually, it's probably written on the box. \$\endgroup\$
    – DKNguyen
    Jun 27, 2022 at 14:15
  • \$\begingroup\$ If four 1.2V / 1.8Ah are placed in series, this totals 4.8V / 1.8Ah. If placed in parallel, it would be 1.2V / 7.2Ah. Note Ampere-hours means amps per hour, not peak instantaneous amps. So 1.8 Amperes for 1 hour then the battery is dead. Or 1.8*2A for half an hour, etc. \$\endgroup\$
    – rdtsc
    Jun 27, 2022 at 14:40
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    \$\begingroup\$ For future reference, in electrical units capitalization matters. Milli-amp-hours is abbreviated as mAh (as per JRE's edit). Your "MAH" would likely be expanded as Mega-Amp-Henries, which is not a particularly sensible unit to use for measuring a battery's capacity. \$\endgroup\$
    – brhans
    Jun 27, 2022 at 14:49

2 Answers 2

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it will be safe for servos?

The specs say that the maximum allowed voltage is 6V. So no, it will not.

The motor itself may survive but the servo section (i.e. controller board/sub-circuit) may not.

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  • \$\begingroup\$ What is the suitable battery to run it? can 3.7 volts does? \$\endgroup\$ Jun 27, 2022 at 14:18
  • \$\begingroup\$ @MohamedMohsen the specs are given for 4.8V and 6V. I'm not sure if it can work with 3.7V. \$\endgroup\$ Jun 27, 2022 at 14:19
  • \$\begingroup\$ I found on Amazon 1.2 volt and 1800 mah batteries if i used 4 of them the total power will be 4.8V and 7.2A, it's safe for servos if there is a high current "7.2A" ? \$\endgroup\$ Jun 27, 2022 at 14:27
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    \$\begingroup\$ The servos will only draw the current that they present as a load at the voltage you supply. The current draw most certainly varies with mechanical load on the servos and on the supplied voltage level. So in summary the supply could be 106A and the servos would take just what they will. \$\endgroup\$ Jun 27, 2022 at 14:37
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    \$\begingroup\$ @MohamedMohsen the total power will be 4.8V and 7.2A no, the total capacity will still be 1.8Ah because you are connecting them in series. The capacity has nothing to harm the servos. And I second what Michael says above. \$\endgroup\$ Jun 27, 2022 at 14:38
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A Lithium-ion or Li-PO battery cell averages 3.7V during a discharge. It is 4.2V when fully charged. It should be disconnected at about 3.0V.

A Ni-MH battery cell averages 1.25V during a discharge. It is 1.45V when fully charged. its voltage drops to about 0.9V when it produces almost no current.

If one cell has a capacity of 1800mAh then in series they also produce 1800mAh.

A servo or motor does not short-circuit all the mAh in a battery, the servo draws only as much current as it needs.

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