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Anyone have any experience with HS-645MGs @ 7.2v?

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Posts: 333
Posted: 2008-01-29 17:15 
My J5 at this point has 6 HSR-5990TGs and the remaining servos are 645MGs... the 5990TGs are rated for up to 7.4v to get the full torque, so I'm wondering if anyone has had any luck running 645MGs @ 7.2v as well?

Would be nice to replace the 6v pack I have with a 7.2v and run it in parallel with my other 7.2v pack that is connected to the gearhead motors. A 7.2v battery pack w/ 10ah total would be sweet :D

Andrew Alter
Trossen Robotics
Hardware Dude
Join the Robotic Competition Revolution @ mech-warfare.com

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Posts: 557
Posted: 2008-01-29 22:07 
When I initially built up my biped scout with 12 HS645s, I didn't have a "6.0V" packs (note the quotation mark because at open circuit, the battery will have a higher potential/voltage between the terminals at full charge). So I opted to use my matched Sub-C 6-cell packs to test out biped.

Well, sub-C are "1.2V" each and *6 since stacked gives you "7.2V" (it's about 9V open circuit when fully charged). My HS-645 gave a crap load of torque, not to mention the increase in transit speed as well.

However, I do not recommend running it that long because even with minimal load on it, the servos were heating up rapidly because of the increase in power dissipation through each servo.

If you plan on running it for less then 5 minutes with minimal load, you wouldn't have that much of a problem, but aggressively monitor your servo's temperature and if it even gets slightly warm, I would shut it down to not risk a meltdown...

Eventually, you'll probably want to save up and invest in some more 5990 TGs to make them all "7.4V compliant"

7.4V is the maximum rating of the 5990TGs, so if I were you, I wouldn't even run it at that level, I'd run a 5xAA cells or 5xSub-C cells...


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