Whew! I musta missed your through reply.
I’ll do some further reading and research the chargers for a 4C before I do anything. I DO have a benchtop charger!
thanks!
Alan KM6VV
Sorry, I think I might have contributed to the wandering of the thread. You’ll have to pick a BEC, maybe like this one that’s been mentioned:
hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=4319
Then determine your average and total current draws. You might be able to multiply your average single servo (S2003?) current by 18(+?) to get the average draw of the 'bot. Then divide (in this case by the 3A) rating of the BEC.
Two BECs would give you 6A, which would allow some 330 mA per servo. Max current (peak) is 10A, which would allow for over 1/2 A per servo! That looks like it would cover it, but I’ll gladly defer to Eddie on this topic!
Alan KM6VV
P.S. With the S3003 servos, you want the minimum battery weight!
the CC BEC is rated 10A peak and 7A continuous with a 2S pack. Out of the package it comes programmed for 5.1V, but if you have a CC LINK you can adjust that from 4.8V to 9V in 0.1V steps.n They run around $22 on average but I’ve seen them for $20. I would recommend two of them, one on VS1 and one on VS2, if you plan on running 18-22 smaller servos.
That’s not the one I was looking at, or the Pack BEC, is it?
CC LINK? CC BEC??
Alan KM6VV
castle creations.
Their “normal” BEC is CC BEC 6S which is up to 6S, 10A peak, 7A continuous if VBAT < 12V and 5A continuous up to 6S Li pack.
If you need to change it from the default settings of 5.1V out then the Castle Link is used to program settings for all their products.
The park bec is something Mike linked earlier and would probably be too low a current output for anything bigger than a BRAT.
7A continuous would work! Thanks for the URL.
OK, so you need a programming dongle to set it up differently.
I noticed that the park BEC was a little light.
In one of Castle’s diagrams, they show an ESC connected to their motors, and the BEC powering the receiver. Must be big receiver! ESC I take it is some sort of a PWM motor controller?
Alan KM6VV
Great! thanx! Someone told me before that i needed about one for every servo. That’s why i asked… 
About the li-ion cells; The 2 cel 3200mA 7,2V pack, only weight’s 163 gramms or 0.36lbs.
And after adjusting my code my legs finally are using the calibration that i did in the ssc-32, and that helps a lot! It walks much better now. even though i have a bigger heavyer body then before.
It still amazes me that those little S3003 servos can carry all that!
Glad you’re getting there!
I too am getting a little closer to knowing how I went to set up my power for the 'quad I’m working on. Now if I can just get them to fit!
Alan KM6VV
Hi Guys,
I didn’t read through the whole post so I might have missed something.
I’ve never measured it but as far as I know a phoenix (18x645) at full speed draws about 10 to 12 amps. I’m aware that 18xS3003 servo’s wouldn’t draw as much as the phoenix does but this is just for information.
I’m using this 15A BEC in my phoenix and I’m very happy with it. I just got one extra for a new project I’m working on.
Mano,
What charger are you planning on? Li-on and Lipo batteries need a different charger. I’m using this charger. They are currently out of stock. Make sure you order the correct balance cables.
Hope it helps
Xan
How can it draw so much power? I’m sure there aren’t any batterypacks with those high currents.
my powersupply is 2.5A max. so it couldn’t draw more right?
Although your bot is walking, the servos are never really making it to the commanded position. They are off by some degree and their lack of torque will not correct for this. Your 2.5amp supply is probably pegged and the voltage is probably something less that 6vdc. When you power your robot from a battery its performance will improve, and the servos will draw more current. Yes there are small LiPo batteries capable of delivering tens of amps and much more.
Xan the Turnigy is a nice BEC too, higher peak output rating and continuous rating on 3S or less, and looks like is a couple USD cheaper. Personally I’m not comfortable with using my credit card with international retailers (hobbyking is HK based) I don’t know a lot about though so unless I had a reason to think the CC BEC wouldn’t do the job (no reason so far as I have a couple of them) I would just use them out of habit. I know you and Zenta have both had good luck with the Turnigy though too so I’m sure it is fine to use.
mano if you were to watch the output voltage of your 2.5A supply with an oscilloscope while you were walking you would see that as the servos ask for more power than it can deliver the output voltage drops until either the servos are drawing less amperage or the voltage gets low enough they just sort of fail. This is the major reason we encourage people not to power the VL inputs to the SSC-32 or BB2 from the same supply used for the servos… if the voltage drops too low it resets the microcontrollers and they stop sending servo signals. For the servos though, provided the controllers keep sending a valid signal to them, as voltage and current are available to them they will continue to try to reach the commanded position… sooner or later they arrive and the current requirement drops off, voltage comes back up, and so long as the reduction in their performance wasn’t obvious to the user (you) everybody is happy.
I agree on the powersupply. It will not draw more amps then it’s rated at. But batterypacks can give more power then rated. If you check out a Lipo you’ll see a number like 2000mAh 15C. This means that the battery pack can deliver 2A for one full hour. The 15C means that it can deliver 15 times his nominal rating without a problem. This batterypack can give 30A without a problem. It will be empty in 4 minutes though 
This is why Jim mentioned that the bot will perform better on a battery.
I totally understand about not being comfortable about using your creditcard with international retailers. But buying stuff in the USA or in HK is the same for the guys who live in Europe (incl me) 
And it’s fun to receive a packedge full with unreadable characters from time to time
Xan
For the lipo packs, I find using the Ni-MH packs work well and are safe. My 6v Ni-MH pack runs my brat for around 30 min or more. Plenty of time. Now I realize hex bots draw more power because there are more servos moving at the same time under load verses my brat. All the Lynxmotion videos of the hex bots walking are using regular Ni-MH packs without any problems that I can see. Lipos are great but they scare me. 
Ha! And people criticize me for not wanting to accept international credit cards. lol
Yes I can verify we are using NiMH batteries on all of the hexapod videos we have provided. Some have a 6vdc or 9vdc battery powering VL but most do not. Powering everything from a single battery does reduce the run time a bit. But it’s normally just a minute or two. The one fun side effect for the powerpod controlled hexapods is when the battery gets low enough for the SSC-32 to reset, the bot goes limp and drops to the floor, then the battery recovers, the bot powers up and stands up, then the battery gives in again… It’s sort of funny. 
Hi Jeroen,
I noticed that your UBEC is marked LIpo. I can’t see why it wouldn’t work with NMIH; is there a reason? Looks like a good choice. Otherwise a pair of BECs as mentioned might be my choice.
I like the charger as well (handles everything!). But where are the balance cables you speak of?
New project? Spill!
Alan KM6VV
Just a WAG on my behalf, but BECs and ESCs that are LiPO-aware usually have provisions for a cut-off voltage. Typically they look at the voltage range and make a determination of how many cells are in the string and then set the threshold at somewhere between 2.8 and 3V per cell. I suppose, if you can’t adjust or disable this feature, it is possible to pick a NiMH cell string length that has a voltage close to a cutoff voltage such that a BEC might prematurely shut off its output even though the NiMH cells have plenty of charge left (i.e. cell voltage > 0.9V/cell).
Hi Eddie,
Sounds like a pretty good guess! Not sure how they would know how many cells in the string, 'tho. Are there any characterizing features of the discharge curve that could tip them off as to the proper time to disconnect the battery?
Alan KM6VV
I would guess just by measuring the string voltage. Li-ion cells should be between 2.8V and 4.1V per cell right? So say 2S = 5.6 to 8.2V, 3S = 8.4 to 12.3V. Seems like there could be some overlap on cell counts higher than 3S… dunno how the CC-BEC or CC-BEC-PRO does it… but they probably have a microcontroller in there so they could be looking over time at more than just the initial string voltage.
Hi Alan and Eddie,
I think you’re pretty right about the cutoff voltage for the Lipo. Good point! Didn’t thought of that since I’m using it for a Lipo. The number of cells can be determent by measuring the voltage indeed. The balance leeds are only used to balance the voltage between the cells when charging in a special program. The charger works in the same way, it measures the voltage and shows the number of cells even without having the balance wires connected.
So no idea how this BEC will work with a NiMh battery connected.
About the balance cables; the balance connectors are not universal. There are some brands that use different connectors. Check the small plug in those 2 batteries.
Polyquest Lipo
Turnigy Lipo
So you’ll need this kind of cables
Xan