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If i am aware of the specs of electrical components in a project like for example in mine i am using 4 dc motors with the following specs for each:

  1. Operating Voltage Range: 3~7.5V
  2. Rated Voltage: 6V
  3. Max. No-load Current(3V): 140 mA
  4. Max. No-load Current(6V): 170 mA
  5. No-load Speed(3V): 90 rpm
  6. No-load Speed(6V): 160 rpm
  7. Max. Output Torque: 0.8 kgf.cm
  8. Max. Stall Current: 2.8 A

based on this information how would i calculate or find a suitable battery capacity or amphour delivery to power the four motors? What i mean is how would calculate the specs of a suitable battery that i can use.

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    \$\begingroup\$ 2 LiPo in series (2S1P) gives 7.4 to 6V depending on quality 1.5Ah to 3Ah typ Start current is 2.8A/motor so discharge time is short so get array of 2S4P using (8) cells for more energy. Consider 8A PTC per string for protection. \$\endgroup\$ – Tony Stewart EE75 Aug 9 '17 at 23:43
  • \$\begingroup\$ Does the battery pack have to be remove to charge? What is the max weight you allow for the batt? What capacity you're looking at? \$\endgroup\$ – Jason Han Aug 10 '17 at 4:18
  • \$\begingroup\$ 4xAA battery. seems like a good starting point, \$\endgroup\$ – Jasen Aug 10 '17 at 6:23
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You also need to consider the operate time and the normal run loading.

If the life time is short. 2 LiPo in series is OK. Start current = 2.8*4 = 11.2A is quite large? 18650 Lipo can support 20A.

2 Lipo in series supply max 8.4V which is over the operate voltage? Use PWM to drive.

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