Hi guys
Ive been away from robotics fir a while so i could concentrate on another project. I have my hex built minus some tweaks but i never coukd figure out how to power it. I was trying to use a lipo with a high amperage and discharge rate. This worked while the hex was up in the air on its platform but as soon as you put it on the floor the battery goes dead instantly. It just cant hold itself up on those batteries.
After looking around on site i see that ni-cafs can be bought. But can i use AA battery packs? Or C battery packs? What kind of playtime is expected?
Hey,
Most unfortunate concerning your LiPo battery pack. Would you mind sharing the specifications for it (total capacity (mAh), nominal voltage (3.7, 7.4, 11.1, 14.8, etc.) and discharge rate (in “C” or A))?
As an example, for the Lynxmotion kit (2 DoF/leg; 12 servomotors and 3 DoF/leg; 18 servomotors) we typically recommend the following battery pack: [RB-Sta-08].
Such a pack is great since it can power the hexapod (when assembled properly and with proper servomotors) and also run just long enough that it is decent playtime but not too much to bring the servomotors into overheating / self-damage. Therefore, if you use a larger capacity battery pack do be mindful of leaving large enough rest for the servomotors to cool down between extended uses.
You can probably use AA or C, etc., but the main problem with primary cells like those is that you’ll need to buy new ones fairly regularly (every few uses due to the high current needed). Also, if using smaller cells like AA, you run the risk of the cells heating up if you put too much current through them (fire hazard), so do be mindful of that, too. This is true to for all batteries up to a point, but easier to happen with small primary cells since they are not meant for high current and you’d need to make your pack large enough to account for continuous current.
We hope this helps.
Sincerely,
The battery is a lion power 11.1v lipo with 1500mah and a 40c discharge rate thats been regulated to at 5.75 to 6.v on an adjustable regulator.
I was looking at the ssc-32 user manual pdf and on page 41 it days that lipos can be used but i dont understand why it drains so fast when its under its own weight. Not a big deal though and i understand why its not optimal for regular mg995 servos.
One more thing…
Can you explain why the botboarduino and the ssc-32 need 9volts to power the boards?
Because they are designed like that.
It’s to avoid any “brown-out” cause by spikes of current from the servos.
Hey,
Here are answers to your questions & comments:
As my colleague mentioned, this is related to the design of those boards. That being said, the BotBoarduino can easily run off only one 6 V DC stable power source (such as a NiMH 6 V DC battery pack) - as is typically done with Lynxmotion kits. Concerning the SSC-32, a VL source is greatly recommended to prevent brownout conditions, especially on setups with a large amount of servomotors (ex: hexapods, quadrupeds, humanoids, robotic arms) or large amount of current used. The SSC-32U has extra components to remove this limitation and can actually run off just one 6 V DC power source on VS1 and nothing else (no VL source required).
Oh, this raises a red flag here! Do you mean the adjustable regulator is part of the battery pack or a separate board/component? Also, how much current can the adjustable regulator provide reliably without dropping the voltage?
LiPo battery packs typically have too low a voltage (3.7 V DC nominal, 1S) or too high (7.4 V DC nominal, 2S, or higher) which therefore makes it not ideal for most RC servomotors that only support from 4.8-6.0 V DC. Of course, if your servomotors support up-to 7.4 V DC, than a 2S LiPo battery pack is a great choice (or a 3S like you have, if your servomotors accept up-to 12 V DC).
Did you actually confirm that the battery pack is drained when used with the robot? What you mention seems like symptom of the voltage being too low due to the current demand not being met.
Typical case: You have X amount of motors requiring current at a certain voltage (ex: 6.0 V DC). When powered, the power source circuit cannot provide enough current, therefore the effective voltage drops. If it drops low enough that the motor’s coils are not energized, you get limp motors (and a limp robot/robot joints, of course!). It seems likely that this is what you are experiencing.
Sincerely,
P.-S.: Sorry for the delay, I took a short vacation… 
