Maxwell Ultra-Cap's/Lithium cells hybrid pack - RC-Monster Forums

Serum · 12.04.2006, 12:35 PM

:031: what happened to the 480 gramms you talked about in your opening post.?

zeropointbug · 12.04.2006, 12:42 PM

HAHA, here we go again Serum. 480 grams was a larger bank, which is unnecessary large. The 140 Farads would do it, prob the 120 Farads too.

BrianG · 12.04.2006, 03:48 PM

OK, I think I'm going to order several of these caps and make a "2s2p" bank for a total of 11v and 1F and install it on my Jato for giggles. All I need is an Eagletree to take some readings on voltage drop. I guess I could strap my Fluke meter on top and set it to record min/max/average voltages...

zeropointbug · 12.04.2006, 03:59 PM

Brian, i really don't think 1 Farad will do the job, that would only be 60 Joules, even if you used 1/4 of that on a burst you are down to 3/4 the voltage, prob higher than your batts in the first place. It might have too high resistance/impedance you think? I don't think they will help it. You could try it though, they're only $3.50...

BrianG · 12.04.2006, 05:49 PM

I see what you are saying, but I know how much difference a 1.2F cap makes with my 800w (conservative rms) car stereo when pushed. Without it, the headlights dim quite badly. With it, the dimming is hardly noticeable. Of course, more capacitance would obviously be better, but 4 of those small caps won't weigh much at all or take up much room and will at least help somewhat. They will be going to go in the rear battery compartment of the Jato. If I can fit two more in there (1.5F), I might try running 2s1p since the pulse load on the battery will be less.

BrianG · 12.04.2006, 11:03 PM

Quote:

Originally Posted by BrianG

OK, I think I'm going to order several of these caps and make a "2s2p" bank for a total of 11v and 1F and install it on my Jato for giggles. All I need is an Eagletree to take some readings on voltage drop. I guess I could strap my Fluke meter on top and set it to record min/max/average voltages...

Well, scratch that idea. After looking at those caps a little more closely, I started to wonder if the terminals and internal conductors could pass the kind of current I'm looking for. So, I finally found a datasheet and found that the rated continuous current is so low that it would be all but useless. They are designed for long, very low current discharge (in the mA range).

zeropointbug · 12.05.2006, 12:27 AM

Really? I would have thought that they would do fine as far as current.

Maxwell Technologies haven't replied yet on the email about the 120,140,310,and 350 Farad medium size cells. Im starting to think that the smallest cell, the 120 Farad cell should be enough. Enough to keep the voltage of my pack at least 16.0 volts (16.5volts nom.) under normal driving, which is bashing for me. But you know what, it would be so cool, cuz if you let the truck sit a couple seconds you would be able to bring the system up to no load voltage, which would be 17.25 volts (around 3.45 volts/cell), and then get a huge burst of NOS. :026:

I just hope the caps are around 20-25 dollars a cell.

BrianG · 12.05.2006, 12:49 AM

Quote:

Originally Posted by zeropointbug

Really? I would have thought that they would do fine as far as current.

Yeah, and it makes sense really. Look at the caps used for car audio. They are only 1-1.5F typical and rated for 20v, and they are huge and heavy. Well, the connections and the internal plates are designed to pass heavy amounts of current. The small caps I was looking at are WAYYYY smaller and lighter even discounting the voltage rating. This is due to the thinner conductors used internally. High burst current was compromised in favor of small size and weight. Makes sense since these are designed for memory backup applications. This datasheet is what I was looking at (page 2, table at the bottom headed by "Standard Ratings").

zeropointbug · 12.05.2006, 02:15 AM

Well, what are you saying? That a few mA isn't enough to throw around your Jato?
LOL

I really want to try this, it appears so promising for my setup. The A123's cells will last and last, they will run super cool and low discharge; this would allow them to easily reach over 3000 cycles. At 25 degrees, after 1000 cycles at 100% DOD they are still at 95% capacity retention, and they say the internal cell resistance goes down over use!