# Pyle Capabat, bad math or bad pyle?



## piotrsko (Dec 9, 2007)

lousy advertising:

from their PDF download they are a 22ah battery with a whatever farad capacitor paralleled to it in a fancy box with LED indicators. Nice for low duration current peaks like during a sub-woofer solo.


Your Calcs look correct on my napkin


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## gmijackso (Sep 30, 2008)

Yeah, that's kinda what I got out of the whole thing too. I was looking into a method of using caps to store regenerative braking power. In theory it would make regen a little more efficient and remove the need to run the regen through a voltage converter. The problem I'm having is the amount of capacitance it takes to store a useful amount of energy is hard to come by at pack voltages (cheaply anyway).

What is the average amount of energy obtained from a single application of a regen system, i.e. one stop? Basically, how much storage space would I need to supply to capure the energy created by a single stop utilizing regen?


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## TX_Dj (Jul 25, 2008)

Maybe things have changed. It's been ~ 15 years since I started noticing my hearing was going, and that's the last time I really had a "big loud" stereo in my car...

But my opinion back then was anything made by Pyle was a pile. Could be it still holds true today.


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## gmijackso (Sep 30, 2008)

I think pyle is still in fact a pile (I still have a loud stereo system... it's just always parked in the garage now). Just stumbled on this by accident and the claims got me interested.


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## gmijackso (Sep 30, 2008)

gmijackso said:


> What is the average amount of energy obtained from a single application of a regen system, i.e. one stop? Basically, how much storage space would I need to supply to capure the energy created by a single stop utilizing regen?


It appears I've thought long enough to figure out the answer to my own question. 
E=(m(v^2))/2
Assume a mass of 1000 lbs(454 kg) that's light for most of your EVs
Assume a max velocity of around 75 mph (120 kph or 33.5 m/s) fast for most EVs
E=(454(33.5^2))/2
E=254750.75 joules for a single high speed stop

Assuming you're probably only going to ever recapture 80% of that energy at best, 203800.6 joules (about 56 watt hours) would be the goal amount to recapture.

I'm sure nobody cares... but you never know when it might be important to know. For the record, on my 48V system, it would take about 175 Farads to recapture the energy I think. Not likely.


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## piotrsko (Dec 9, 2007)

napkin again: it ought to take about 1/2 hour to get them 175 farads up to 66% charge. kind of a long down hill run unless you can really dump current into them.


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## gmijackso (Sep 30, 2008)

It's just all very interesting to me. I see all this "news" about supercaps and ultracaps being the "new" power source for EVs, but it has to be nearly impossible. 

My original idea was to capture regen braking into a cap. The cap would start with zero charge every time you brake and charge as you brake. This would give a uniformity to every braking experience as you're no longer storing the energy into the batteries which are constantly changing states as you drive. It should also prolong battery life, and make regen more efficient since a cap is much better at taking fast doses of high current than a battery. Add to it that you should no longer need to regulate regen braking voltage since the cap is going to take it as pure current and it seems like a winner.

All this got the calculations going, and with my wimpy 48V system I need the 175F of caps to store a brake session. Maxwell seems to make some of the largest ultracaps available. 3000F @2.5V The 2.5V rating means I should probably use 24 caps in series to obtain 60V working voltage just to be safe. The 24 series caps now only have a capacitance of 125F which isn't enough.

So to work the problem backwards, knowing now that it is going to take parallel set of a series of 24 caps, each set needs to supply 88F. So we need to be in the neighborhood of 2400F caps at 2.5V and need 48 of them.

All that aside, I'm not even sure the ultracaps can handle that much current, AND all of that is to capture a few Watt Hours of energy at a LOW pack voltage. As the pack voltage increases the number of caps quickly multiply to hold the same number of joules. How is it realistic to get a couple dozen kilowatt hours with a pack voltage in the 120 area?


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## gmijackso (Sep 30, 2008)

So I just found this. Maxwell has made a "125 Volt Heavy Duty Transportation Module". It is apparently what is supposed to be the big thing for EV. But... here are the stats.

125V Nominal, 130V Max, 135V Surge... Probably fine for most EV
63F of Capacitance, we'll need to see how much that stores.
101.7 Watt Hours, no even close for most EVs
150 A Max Continuous current, Some could get away with this I suppose.
750 A Max current for 5 sec 10% duty cycle, also probably fine

So, even these beasts are going to need to be paralleled up to provide enough current and storage.  dashed hopes...


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## TX_Dj (Jul 25, 2008)

I like the way you think, though... 

If you want your hopes dashed more, look for the pricetag on those maxwell ultracaps.


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## gmijackso (Sep 30, 2008)

Yeah... I looked around a little for them and mostly only found stories of their use in mass transit and decided that I probably didn't want to know anyway. The price tag is why I was considering the car audio caps for my low pack voltage, somebody has a 30F @ 21V working for about $100 ea. That would take 3 to get 63V working @ 10F which seemed like plenty until I did the math.

Seemed like an ingenious idea until the caps weren't big enough. So now I'm mulling the idea of adding a comparator to monitor the cap. Start braking with an empty cap isolated from the batteries, once the cap is approaching full charge, parallel the batteries to take the rest of the current. Stay paralleled until the caps are near empty after the next acceleration, then isolate and start over.

I just don't know how much gain there is at that point. It seemed pretty obvious with a 100% capacitive regen capture, but it's much harder to figure with say a 10% capacitive regen 90% battery. Especially since it's working backwards to the way you'd like. You're capacitive capturing the full pack voltage braking then switching in the batteries as the vehicle is slowing and your regen voltage is dropping. In a perfect world that is when you want to use the caps.


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## TX_Dj (Jul 25, 2008)

Granted I have no real-world experience with regen (closest has been dynamic braking to stop things from spinning quickly) but it's my understanding that after efficiency losses and the fact that more energy goes into moving the vehicle than can actually be regenerated, you only see about a 5-10% range increase overall.

In my mind, 2-4 miles extra range on something that gets 40 miles that typically don't get used fully anyhow, just isn't a good thing to sink money into anyhow.

If the system has regen inherently, it makes sense to use it... but because of this I've never been so interested in it for my applications.

In fact, on my scooter, I opted for freewheel sprockets instead of regen, because I believe that with the reduced friction from disconnecting the drivetrain during coasting when coupled with copious use of coasting when appropriate, one can see better than 5-10% range increase. :shrug:


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## gmijackso (Sep 30, 2008)

Yeah, the 5-10% range is pretty exact and can actually be calculated. It's all about the number of joules captured per stop and the average number of stops in a given trip.

I kinda agree with the thought that you're generally not using all the miles available anyway so why care about regen. But, the same can be said for an ICE and the fuel tank. Who cares if it only get 5 MPG, with a 16 gallon tank, that's 80 miles, I can make it from gas station to home to work to gas station in 80 miles. 

I think we should make every attempt to get every mile we can out of it. Maybe with regen we can get an extra 10% range, add an amp or of solar and get some more range, especially if parked in sunlight at work. Add the option to disable regen (freewheel) for coasing and only regen when brakes are applied, or "hill switch" is enabled and maybe get another 10%. Maybe that's the best use of my MagnaDrive from my other ill-fated thread (to enable disable the drive train in 100%, 0% options for regen). Do all those things and maybe you've increased range by 25% right? So now you don't need as much battery capacity (not to mention less kwh from the plug), which reduces weight which gets you another %. 

I really see this as a method of obtaining the most efficient vehicle possible. Maybe I'm overly optomistic about it but I think every little bit helps. Maybe it doesn't make much sense to fill the salt shaker one grain at a time, but it's better than leaving it empty. And eventually it'll be full.


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