7.2V battery packs and servos

[vmspionage]

Hello everyone! This is my first post so please be nice to me

My current project is a biped bot (scout kit) using 12x 5980SG servos and I have a question about the voltage. I know that these servos in particular are sensitive to anything over 7.2V, and I certainly don’t want undue wear and tear on my brushes, but is it possible to use a 6-cell 7.2V unregulated battery pack without harming the servos? Fresh off the charger it reads right around 8.4V which is a little out of range. I’ve considered using a voltage regulator however I’d rather not go that route as I’m sure that my pack doesn’t stay above 8V for very long.

So what I’m thinking is that if the pack doesn’t stay above 7.2V for maybe a couple of minutes, is this really a problem? Should I go with a 7 cell regulated or just drop down to a 5 cell?

Thanks!
Jeff

[adam-21]

Those are expensive servos. I personally would want them to last a while, so I would run a 5-cell pack.

[vmspionage]

@A-Bot

Those are expensive servos. I personally would want them to last a while, so I would run a 5-cell pack.

You sir pose a very convincing argument. I just ordered a couple of 5-cell packs.

[robotdude]

@vmspionage

Hello everyone! This is my first post so please be nice to me

We have one of the most polite and friendly forums around. Welcome!

@vmspionage

My current project is a biped bot (scout kit) using 12x 5980SG servos and I have a question about the voltage. I know that these servos in particular are sensitive to anything over 7.2V, and I certainly don’t want undue wear and tear on my brushes, but is it possible to use a 6-cell 7.2V unregulated battery pack without harming the servos? Fresh off the charger it reads close right around 8.4V which is a little out of range. I’ve considered using a voltage regulator however I’d rather not go that route as I’m sure that my pack doesn’t stay above 8V for very long.

So what I’m thinking is that if the pack doesn’t stay above 7.2V for maybe a couple of minutes, is this really a problem? Should I go with a 7 cell regulated or just drop down to a 5 cell?

This question has been bouncing around here for too long. I just emailed Tony with Hitec service about this. Here is what he said…

@Tony Ohm

Hi Jim,

It’s a battery specification and voltage allowed. I get this a lot on the RC emails also. The servos were designed with LiPo batteries in mind and even though the 2 cell LiPo batteries have a peak of over 8V, the peak will drop down fairly quickly when the servos are operated. So the higher voltage for a short time does not adversely affect the servo.

On the other hand, if the user is operating from a power supply, they should keep it at 7.4V or lower.

Thanks!

[vmspionage]

@Robot Dude

@vmspionage

Hello everyone! This is my first post so please be nice to me

We have one of the most polite and friendly forums around. Welcome!

This question has been bouncing around here for too long. I just emailed Tony with Hitec service about this. Here is what he said…

@Tony Ohm

Hi Jim,

It’s a battery specification and voltage allowed. I get this a lot on the RC emails also. The servos were designed with LiPo batteries in mind and even though the 2 cell LiPo batteries have a peak of over 8V, the peak will drop down fairly quickly when the servos are operated. So the higher voltage for a short time does not adversely affect the servo.

On the other hand, if the user is operating from a power supply, they should keep it at 7.4V or lower.

Thanks!

Wow, thanks for checking into that for me!!! When I wired it up to 8.4V I was thinking, “nah, this won’t hurt anything” but after reading a thread about fried 5995’s I was starting to get worried! I think I’m still going to switch to the dual 5-cells in parallel as I really have no reason to exploit the 7.2V power of the 5980s right now and there’s no doubt in my mind that a lower voltage is easier on the brushes. Plus there’s the thing about 5600mah from dual, cheap LM Ni-MH packs

Thanks again Robot Dude, see you around!

Jeff