Running 7.2v servos off of 2s lipo

[#ARRMArcfanboy4life]

I am working on a robot project where I need to power 3 full size servos off of a raspberry pi pico, the pico can't handle running that much current through its 5v line, so I am going to buy an I2C breakout board to power the servos. Will the servos rated for 7.2v be able to handle a fully charged 2s lipo? The servos are some ebay servo (rated for 7.2v), and spektrum s665 and s652. I would can do a step down, but that adds complexity so I want to avoid that ideally. If I need a step down, how would you recommend doing that? I know I could just do coils of wire and the ratio of turns around the core to voltage is the same, but I want a better way of doing it.

 

[Tex Koder]

I am working on a robot project where I need to power 3 full size servos off of a raspberry pi pico, the pico can't handle running that much current through its 5v line, so I am going to buy an I2C breakout board to power the servos. Will the servos rated for 7.2v be able to handle a fully charged 2s lipo? The servos are some ebay servo (rated for 7.2v), and spektrum s665 and s652. I would can do a step down, but that adds complexity so I want to avoid that ideally. If I need a step down, how would you recommend doing that? I know I could just do coils of wire and the ratio of turns around the core to voltage is the same, but I want a better way of doing it.

They should be able to handle a stand alone 2S power source..

What will the servos be connected to..
expected to move/operate?

 

[Chapinb]

The amazon/eBay will handle it fine but expect them to fail sooner if they are under constant load. They arnt specced for the constant amp draw.

There are some cheap 8.4v rated servos available if its an option. I do have one of these being delivered for some testing.
For all I know they might be the same innards as every other amazon servo but with a heatsink case to handle the amp draw.

https://a.aliexpress.com/_mNQicJv

 

[#ARRMArcfanboy4life]

I already have the servos and don't have enough budget for this project to buy more.

I contacted spektrum and they said the servo needs to be rated for 8.4v for their servos to be operatable off of 2s directly. I might be doing voltage reduction.

 

[Chapinb]

I already have the servos and don't have enough budget for this project to buy more.

I contacted spektrum and they said the servo needs to be rated for 8.4v for their servos to be operatable off of 2s directly. I might be doing voltage reduction.

Spektrum is covering their rear. The servo isn't rated to 8.4 and they don't want to be liable if it let's out the magic smoke.
If you can work out a 7.2v solution, that will keep everyone happy, even if it's just not charging the lipo fully.
Otherwise give it 8.4.

 

[#ARRMArcfanboy4life]

That was my thought, but I wanted to make sure before just full sending it.

 

[#ARRMArcfanboy4life]

Dynamite had a 6 cell 900mah nimh battery for $3 on amazon, so I bought that. It is cheaper to use that than to risk it on a new servo or a voltage regulator (only rated for 3A).

 

[gotnitro]

Dynamite had a 6 cell 900mah nimh battery for $3 on amazon, so I bought that. It is cheaper to use that than to risk it on a new servo or a voltage regulator (only rated for 3A).

How much holding load will these servos have in a robot? 900 mah NiMh will sag farther than HIS boobs. Quickly too.

 

[RCbuzz]

In many/most cases overvolting the servo will significantly shorten it's life.

There are of course exceptions, but the only cases I have seen are where the internals are designed to have a higher voltage but the label was more conservative in its rating.

 

[#ARRMArcfanboy4life]

How much holding load will these servos have in a robot? 900 mah NiMh will sag farther than HIS boobs. Quickly too.

I have seen that picture before and didn't feel the need to see it again. Shouldn't have too much load the actual project I am basing this off of had a 5cell nimh which was around 2000mah and didn't have any battery problems.

In many/most cases overvolting the servo will significantly shorten it's life.

There are of course exceptions, but the only cases I have seen are where the internals are designed to have a higher voltage but the label was more conservative in its rating.

I figured there would be a shorter life, and I didn't want to make the bet that spektrum and nameless ebay gave more conservative ratings.