Maxwell Ultra-Cap's/Lithium cells hybrid pack

[BrianG]

Believe me, I'm not trying to argue against using them, I'm just trying to see if there is a feasible way to use them.

That said, you said you can charge with your bench power supply at whatever current you set. OK, that's constant current mode. However batteries are constant voltage sources. So, if I charge the cap up and then install it in my R/C, great, all will work fine. But once the batts finally dump, the batts and the cap will have a lower voltage. So, you stick a new pack in there and connect them and BAM! Those poor Deans will have a nice black mark where the arc hit. I guess I'm thinking more in terms of Mr R/C Joe who just hooks stuff up and goes. I don't think he'll be bringing along a multi-thousand dollar P/S. :)

A way to get around this would be to permanently wire one of those caps to each pack. That way, they are charged at the same time and discharged at the same time, so there will never be a difference in potential. The only time you'll have to be careful is the initial hookup when you build the pack/cap combo.

This would certainly help battery life! All you would need is a battery that can supply the average current required by your setup since all spikes would be all but nonexistant!

Also, no more worries about max C, pulsed C, etc - only the constant draw would be the issue, which is quite low. For example, my Revo with 14XGP3300 cells gets about 13-14 minutes of runtime. I'm sure it pulls 100A bursts (or more), but the average draw is only ~14A. That means a lot more batteries can be used where they couldn't before due to their low max discharge performance, even though their capacity was great (like GP4300's).

Oh, and I like my Spektrum a lot. The receiver is small and fits anywhere. No glitches ever. I only wish the transmitter would have more model memories. If I had to do it over again, I'd get a Nomadio and still use the Spektrum receivers where small size is needed (the Nomadio receivers are kinda big IMO) simply because it can store more models.

[zeropointbug]

Yeah, i sooo want to try this. About the setup, ya if you have more than one pack, the deans connector would disappear if using A123 cells, and would be very dangerous using LiPo's. But, i only have one pack, that can be charged in 25 minutes ;) (the BK power supply is $330) So, for me i would have the pack and caps permanently hooked together, well not really, just a deans but they would never be disconnected.

So, would you know the duration of the 100+ amp bursts in a brushless setup like Quark and an XL motor? Just so i can do more calcs.

This would be a kick in the face for the motor! :)

[zeropointbug]

Also, the self discharge of the 120 farad cap is .15mA which is VERY low, no worries about it discharging the battery pack anytime soon...

[BrianG]

Yeah, if you are set up for that kind of thing and understand the possible risks if not done right, it should work great. Doesn't seem to be something that will be available for the masses anytime soon though.

The bursts doen't last very long; basically however long it takes for the motor to reach the rpm of the signal it's being fed, which is mostly on take-off out of the hole, and any hard acceleration. I'm sure there are a couple graphs of an EagleTree plot around here somewhere.

150uA delf discharge; not bad. According to my calculations, it would take about 3.5 years to totally drain a 4.6Ah pack not including the self-discharge of the battery itself.