Li-po batteries are very good to supply large current. I just tested
"Tenergy 7.4V 900mAh, 25C High Power Lipo Pack"
on Nybble.
It seems that with its super power, the protection in NyBoard's step down chip will always be the bottleneck. So it's a must to bypass it as discussed in previous post.
It's also recommended to design a customized battery mount to replace the original one on the belly, to keep the center of mass low and symmetric.
Or you can remove the battery holder on the belly and fix the LiPo with Velcro strips, keeps the center of mass low and easy to fix and remove. I’m using a 1300mAh LiPo which is 30mm wide, a perfect fit.
Hi Steve,
Can you please let me know the make/model LiPo are you using, and also where you got it from?
Best regards
D L
I'm based in Switzerland so this link may not be useful to you, https://www.swaytronic.ch/LiPo-Akku---Swaytronic/LiPo-Akku-2S-7-4V/2S-7-4V---35C---70C/swaytronic-lipo-2s-7-4v-1300mah-35c-70c-jst.html, but the size and capacity should be available anywhere. The important dimension is the width. This LiPo is 30mm wide. I fix it more or less in the center of the belly and Nybble walks fine. What it won't do yet is recover from being on its back. I makes a brave attempt but ends up falling back, perhaps due to the additional weight of this battery, I need to play with the parameters.
I'm using these two:
https://hobbyking.com/en_us/turnigy-nano-tech-950mah-2s-25-50c-lipo-pack.html
https://hobbyking.com/en_us/turnigy-nano-tech-2000mah-2s1p-20-40c-lipo-receiver-pack.html
The 2000mah fits perfectly and ends on the side with the belly wood, but i haven't test center of mass during walking.
Had also the idea of fixing it with velcro stripes, works well, fast and easy!
Thanks guys, much appreciated.
Is it possible to use a 3.7v lipo w/o having to do the bypass mentioned above? I have several 3.7v adafruit batteries with various mAh ratings, such as this one (plus many others of higher and lower mAh ratings): https://www.adafruit.com/product/2011
My initial thought was to cut & strip the ends of a female JST and connect them to the + and - terminals on the board, then connect the male JST-out on the battery above to this wired-in female JST. This should allow to easily remove the connection & recharge the lipo w/the appropriate charger. I could probably just velcro the battery to the current AA holder to retain the ability to slide around the battery weight to adjust the center of Nybble, as needed. Would this work or I'm missing something? And while I'm wiring down there, is there something else I should consider adding, like an on-off switch like this: https://www.adafruit.com/product/3064 (I'd trim the wires to make in shorter, connecting one end directly to the terminals & leaving the female end for the LiPo). Apologies, I'm not a hw engineer, so I'm not completely comfortable w/power concepts.
Well, I tried the 3.7 lipo and it didn't work. Also made the mistake of thinking 14500 Li-SOCL2 were rechargeable - they ARE NOT. Caught them heating up in the charger before anything bad happened, but wanted to make sure others knew about this. Would love to hear best practice for getting the Deans / T connector on an RC lipo with specs like the ones above configured to fit into the terminal headers. Am thinking I'd take a female Dean to JST, trip off the JST end, then solder this to a two-pin header pin, shrinking up the wires and solder so there's no chance of a touch. This way I don't touch the battery wires & keep their integrity, just using a separate, modified cable for the adapter wire. Does that sound like it'd work?
@John Gallaugher Have you tried EBL 14500 battery that's available on Walmart.com? I've been using them when I was in the US.
When connecting batteries in serial, it’s very important to use same batteries to avoid unbalanced loads. To work with Nybble, the maximal discharging rate also matters. The battery should be able to handle >3.5A without shutting down the current. It’s ok the change the terminal plugs as long as the direction is correct.
So from some digging I expect these AA size EBL batteries are rated for ~1.0C or about 850mA max discharge in series (based on all the similar form factor datasheets I could find). I'm guessing things work because moves are a bit "bursty" on the current.
I was thinking I'd put of pair of Jauch 1.9Ah 3.7 with a 2C rating (e.g. Digikey 1908-1372-ND). This should then be good for 1.9A steady state (providing significantly more headroom) and essentially the same weight and physical envelope as the battery holder. Maybe instead the pack 1568-1876-ND, but it may be too wide and long. I'm only now starting to assemble so I don't have a good since of the true maximum.
@Rongzhong Li What are your thoughts on shimming the legs out a few millimeters (and what are the real maximum dimensions?
The EBL can supply larger current, with significant voltage drop. The capacitor on NyBoard is helping a little in buffering the power supply. The height of the servos is the obstacles for larger batteries. I’m going to live in a servo factory for several month to design some shorter servos. I’m also designing a 5C li-poly battery pack with charging circuit. I hope to provide it as an official accessory to solve all the powering issues.