I've used this type for various projects, and it worked very well for me with 3S battery. I've seen some others on here use it too. Totally quiet and very strong. Rated torque at ~30kg/cm and stall torque at up to 87.5kg/cm for the ~15 RPM versions. Lots of RPM versions available.
There are at least two alternative vendors for this form factor:
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GW31ZY-14 12VDC 14RPM 30kg/cm
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TSINY TS-40GZ495-1216 12VDC 16RPM
Specs for the TSINY version:
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http://www.tsinymotor.com/Products/W...4/0513/16.html
Best regards,
Stein :-)