Power problems

Lynxmotion Legged Robots
1

I’ve been making a hexapod using HS-85 MG servos. I’ve got a very nice laser cut design an everything, and it was all set to go, but when I first tried it, after pressing the start button on the PS2 controller, everything jolted and then everything died. I’m pretty sure I know whats going on, and I was hoping that you guys could confirm this and perhaps offer some suggestions:

My power situation is as follows:
2x Nokia BP-4L LiPo batteries 3.7v each, 1650 MaH
and to regulate the voltage I have a hobbywing.com/english/ArticleShow.asp?ArticleID=400
This takes the voltage from normal 2 Cell lipo range down to 6v which is compatible with the ARC 32 and HiTec servos I’m using.

The voltage regulator claims to have short circuit protection. Additionally it displays battery level in terms of a few LED’s on the front.
What I think is happening is that when I first start the robot, Phoenix tries to move everything to the starting position, which means all 18 servos at once, which either lowers the voltage to a point where the UBEC believes it is unsafe and completely gives up(which does not sound right… voltage shouldn’t change like that right?) or the short circuit protection on the UBEC cuts in and derails the whole thing.

As it is, I can inch towards the starting position by power cycling the system, since it jolts a tiny bit each time. Once it reaches the starting position, I can walk very slowly, but it will always die if I try going fast.

So, I’m fairly sure the issue is the UBEC, but I guess there’s a possibility it could be something to do with Nokia’s batteries? Possibly cell phone batteries are just not able to deal with this much current?

I’d like to continue using these batteries if possible; is there another voltage regulator that will work? do I need a voltage regulator? or will servos actually be able to handle the 7.2-8.4v that a 2 cell lipo system supplies?

if all else fails, what is a small and cheap battery system that would ‘just work’?

if you’re wondering, I’m using this system because I like the idea of having LiPo batteries, but chargers are kinda expensive, so I would just use my phone to charge the batteries…

Thanks

2

Believe me, it totally worths it to change to a RC LiPo system. The charger is not that high (you can find basic good ones for around 50$) ans the price of battery is really low (below 10$ for a 2200 mAh at 7.4V). More, the charging time is really low (around 30-40 minutes for this kind of Lipo)

Check there :

hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8935
Or these LiFePO4:
hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14063

3

You’d have to read the specs for the battery in question, but I’ll bet they’re not designed for delivering high current. That’s not what a cell phone needs.

The “Flying Pigeon” brand UBEC could also be the problem. Try only powering up half of the servos, and see if it handles it (use a real R/C battery). Maybe you can salvage the UBEC.

Try Hobby King for UBEC, battery.

hobbyking.com/hobbyking/store/index.rc

Alan KM6VV

4

Will I be able to use the lynxmotion.com/showproduct.a … ttery-pack ?

The voltage when fully charged is 7.2 volts, which is above the rating of the ARC-32, which is apparently 6 volts, and the servos are also not rated for 7.2 volts. However, it appears that the official lynxmotion electronics run off of these battery packs… so… anyone have any experience with this?

I would pick up a tenergy LiPo charger and battery pack except I don’t really want to have to stuff the voltage regulator into my tiny chassis which is already completely packed with excess wires.

Thanks

5

The spec Nominal Voltage needs a better label. The voltage listed is what the battery has right off the charger. So maybe Full Charge Voltage would be a better label. Truth is this voltage drops pretty quickly when in use. We will update the website. All boards will work with this pack.