# the answer to if ultracaps really help or not



## michaeljayclark (Apr 3, 2008)

http://www.labplan.ufsc.br/congressos/Powertech/papers/385.pdf

government funded research, finally they are putting our taxes to good use for once


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## PZigouras (Jun 5, 2010)

I like the part that says:

"[without capacitors] The resulting current surges in and out of the
battery tend to generate extensive heat inside the battery,
which leads to increased battery internal resistance – thus
lower efficiency and ultimately premature failure"

... and yet almost every EV that has ever pulled into my driveway had either no capacitor bank, or a very tiny one. Then they wonder why you have to change your pack every two years. Gee, maybe that's why?

- Paul


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## michaeljayclark (Apr 3, 2008)

I liked the idea of using caps when i first heard it almost 2 years ago. back then ultracaps where hundreds of dollars.

goldmine electronics has 2600 farad 2.5 volt maxwell caps for 20 dollars each. they are the older white label but cheap enough to put a nice pack in your car to help save battery life.


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## rmay635703 (Oct 23, 2008)

PZigouras said:


> I like the part that says:
> 
> "[without capacitors] The resulting current surges in and out of the
> battery tend to generate extensive heat inside the battery,
> ...


I wonder how much of an effect this really has, by the way that reads it should be beneficial for FLA in the winter?

Also $20 a pop for a 2.5volt cap would mean for me at least about $700 in caps for a slight margin of safety above my max bat pack voltage, that seems, well rather high, if my battery life doubled, I could see it but it would take a while for that to be recovered.

And my pack isn't even a HV pack.


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## EVfun (Mar 14, 2010)

Look at what these caps are being used for, filtering high speed ripple. That will only happen if the equivalent series resistance of the caps is very low. Most of the very high capacity caps have high equivalent series resistance. I would suggest looking toward capacitor used for for car stereo system. Not the overpriced offerings in the pretty packaging but the guts that makes up the inside of them.


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## michaeljayclark (Apr 3, 2008)

I am using boostcap 3000 farad maxwell 2.7vdc.

the DC ESR for these caps is .23 m ohms.

ill have 52 in series.. would the .23 ESR for each cap simply be added? 11.96 m ohms?


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## rmay635703 (Oct 23, 2008)

michaeljayclark said:


> I am using boostcap 3000 farad maxwell 2.7vdc.
> 
> ill have 52 in series.. would the .23 ESR for each cap simply be added? 11.96 m ohms?


52x30= $


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## GizmoEV (Nov 28, 2009)

Does any one know how much "energy" is in one ripple of the ripple current or how to calculate it? If the goal is to absorb the energy spikes from it and nothing more then this value could be used to calculate how large the capacitors would have to be.


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## T1 Terry (Jan 29, 2011)

Judging by the heading that paper is pre 2003 and most of the reference material is pre 1999, do you think it's relevant to present day battery technology? Maybe if the EV is using flooded cells but then the cost of ultra caps may be better spent off setting the cost of LiFeP04 batteries that can accept rapid charge and discharge. Will a paper dated more than 8 yrs ago help me make a valid decision regarding the use of ultracaps with lithium batteries? Not really.

T1 Terry


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## michaeljayclark (Apr 3, 2008)

considering that thundersky lipo is at about $1.25 an amp hour, a 160 amp hour cell would cost $200. 

for a 144 volt pack would be 54 cells.

thats $10800.

52 capos cost me $2000. 

I think its worth a try.


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## idarusskie (Feb 17, 2011)

Hi,I am new here so be gentle.

It would seem any transient on an electronic device will have an effect. How much can be debated.

The continued heating and cooling of the metal in the batteries has got to have an effect. Even in the newer batteries.
I like the idea that the caps are not affected by temperature. It may be worth it if they allow your batteries to age longer and they allow you to have fewer batteries.


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## Duncan (Dec 8, 2008)

Hi Michael

144v x 160Ah TS = $10,800 energy = 23Kwhrs

52 off 3000F capacitors 

at 144 v - energy = capacitance (3000/52) x 144v x 144v x 0.5 = 589,153 Joules
589,000 joules = 166whrs = 0.166Kwhrs

That is if you can use the power all the way down to zero volts - SAAAG!!!

If you use a second voltage booster you could use down to 100v

energy = 3000/52 x 144 x 44 x 0,5 /3600 = 50Whrs

23Kwhrs = $10,800 for TS = $469/Kwhr

50 whrs = $2,000 for caps = $40,000/Kwhr

Sounds a little more expensive to me!

Way back in 2003 the batteries available had much higher internal resistances most were only capable of a 0.5C discharge - a supercap pack stiffener was a good idea then

Now? No
An idea that is past its time


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## T1 Terry (Jan 29, 2011)

Duncan said:


> Hi Michael
> 
> 144v x 160Ah TS = $10,800 energy = 23Kwhrs
> 
> ...


Thanks for that Duncan, saved me having to ask how to convert capacitance to ah. Stuff must be meg a cheap in the states, 3000f Maxwell caps to buy here AU$2,123 for 26 units. At 48v not quite 0.5ah. With a motor looking for 650amp peak that's not much of a buffer.
AU$2,160 will buy another 16 100ah Thundersky cells. Min 200ah rate at 3C max charge/discharge = 600amps, another 100ah at 3C gives me 900amps, sounds far more logical to me. Am I missing something?

T1 Terry


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## Duncan (Dec 8, 2008)

Hi Ti

*AU$2,160 will buy another 16 100ah Thundersky cells. Min 200ah rate at 3C max charge/discharge = 600amps, another 100ah at 3C gives me 900amps, sounds far more logical to me. Am I missing something?*

I must be getting old - did not understand - can you explain a bit further what you are planning?


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## T1 Terry (Jan 29, 2011)

Duncan said:


> Hi Ti
> 
> *AU$2,160 will buy another 16 100ah Thundersky cells. Min 200ah rate at 3C max charge/discharge = 600amps, another 100ah at 3C gives me 900amps, sounds far more logical to me. Am I missing something?*
> 
> I must be getting old - did not understand - can you explain a bit further what you are planning?


The motor I'm looking at using at the moment is the 48v Green Motorsport that is matched to a 650amp controller. I plan to use this as a hybrid drive for my motorhome conversion so it's other function is regen braking, with the bus weighing around the 10 tonne mark there will be lots of regen. If the ultra caps could soften the impact the Thundersky batteries would cop from that amount of regen then they would be a viable proposition but simply adding an additional 100ah to the battery bank for around the same cost it looks to me to a better way to spend the money. If the ultracaps could absorb the regen load and release it slowly into the batteries I would get a better cycle life but they don't have the capacity to absorb more than a few seconds from what I can see. I may have got that all wrong, I'm very green at this stuff.

T1 Terry


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## michaeljayclark (Apr 3, 2008)

http://web.mit.edu/first/kart/everpres.pdf

this is a study by MIT in 2009. yes its a go-cart but Im sure the parts could be sized up because a dc to dc converter between the batteries and the motor controller would need to be 144 volt and 600 amps in the case with an ev. 

regen recapture by ultracaps is very acceptible and makes sense. when regen happens trying to put back into the batteries is fighting internal resistance of the batteries.

putting that regen power into ultracaps would be much more efficient.

lets remove the cost factor from this discussion. yes, ultracaps are expensive but the price is dropping. the case for showing a quick ROI would be a huge debate and thats not my intention. I am just trying to see how this would all work. the AFS trinity implements such a system. 

http://afstrinity.com/ 

they were issued a patent for their system using ultracapacitors to recapture regen in an AC system. 

regen is possible in a dc system buy placing a generator next to the motor with a clutch system where when the brakes are applied the clutch engages and regen is happening and the vehicle slows. 

yes these ideas have a pricetag but lets discuss it without dollars involved.


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## T1 Terry (Jan 29, 2011)

If $$ aren't in the equation then replacing the batteries with ultra caps would be the way to go, a million plus cycles with no BMS issues and unlimited charging speed.
In reality $$ need to be in the equation, not many could afford an ultracap only power pack and I thought the whole thread was about the prospect of using ultracaps to extend battery cell life and save frequent replacement $$.

T1 Terry


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## michaeljayclark (Apr 3, 2008)

this thread is meant to discuss how ultracapacitors can extend the life of batteries.

the afs trinity testing showed:

AFS Trinity claims a 150,000-mile useful life for its battery/ultracap system. What is this based on? The claimed 150,000 miles useful life is based on ten months of extensive and continuous physical testing by America's leading independent battery testing laboratory, Mobile Power Solutions of Beaverton, Oregon. This laboratory subjected AFS Trinity's dual energy storage system of lithium ion batteries and ultracapacitors to a demanding duty cycle simulating an urban/highway driving cycle with strong and frequent high current demands. Such a driving cycle was meant to subject the batteries to the kind of strong and frequent loads that the energy storage system would be subjected to by an aggressive driver— think New York or Paris cabby or your teenager. The AFS Trinity system delivered more than 3,800 duty cycles before the batteries reached end-of-life. Each cycle represents a full charge and discharge. Assuming that each charge can deliver sufficient power to propel a vehicle for 40 miles, this represents 152,000 miles, which we rounded down to 150,000.


I can compare the costs to how much it even costs to build an EV. Batteries are very expensive and will fall in price but in the meantime EVers still buy them even with the cost being so high. The production EVs are expensive, yet people still buy them. The ROI is WAY out for an EV right now. So the cost is a factor however under an early adopter label, the cost is high and ROI is low until the cost is low and the ROI high.

so, back to the discussion.......... 

as far as a balancing system there is already an active balancing system sold by maxwell for their caps. the kit costs 95 dollars for 5 circuit boards. 89 if you buy more than 5 kits.

I found an article laying out the diagram of this active balancing system. 

http://electronicdesign.com/article...racapacitor-strings-from-overvoltage-yet.aspx

I am wondering if I can have them made cheaper than buying them from maxwell distributors.

and.. can this active balancing circuit designed for 2.7 vdc be used for lipo 2.7 vdc cells?


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## Duncan (Dec 8, 2008)

Hi Ti

If you set up a voltage booster system so that you could get all of the power out of the ultracaps

589,000 joules at 144v and 650 amps is 6 seconds - not a lot!

2 x 100ah TS can be charged at 3C so 600amps - I don't think your controller can actually pump as much as 600 amps so you should be sweet

Hi Michael
Modern batteries have much lower internal resistances - as long as you are not exceeding their limits I don't see any way that the ultracaps can increase battery life


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## DJBecker (Nov 3, 2010)

I don't see a control here -- how would those same cells have done without the capacitor bank?

Several types of Lithium-chemistry cells, including most LiFePO cell structures, have significant charge storage (as opposed to only chemical potential energy as in lead-acid cells). Effectively they are already a combination of chemical battery and capacitor.


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## nimblemotors (Oct 1, 2010)

battery lifetimes are dramatically shortened when they are discharged at high rates. even the "continous" rating reduces their life, most cells specify their cycle lifetime at 1C rates.
But if you have a large enough pack, you can discharge at low rates and still have pretty high power. So the key is having a large battery pack. 
For 650amps, at 1C you need 650Ah battery, at 3C 216 AH. 
That is a very large pack. The larger the pack, the heavier the vehicle, and thus more power needed to get to 60mph.

Most just live with a slow EV and/or are killing their batteries.



DJBecker said:


> I don't see a control here -- how would those same cells have done without the capacitor bank?
> 
> Several types of Lithium-chemistry cells, including most LiFePO cell structures, have significant charge storage (as opposed to only chemical potential energy as in lead-acid cells). Effectively they are already a combination of chemical battery and capacitor.


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## T1 Terry (Jan 29, 2011)

The cycle life for CALB and Thundersky batteries of 3,000 to 5,000 cycle @ 70% DoD is at the nominated 0.3C charge/discharge rate, it says this quite clearly in the specs, how many people don't want to read that bit :lol: I have put the question to each of the battery companies (there is a lot of them producing LiFeP04 batteries now) asking what the cycle life is at the max rated discharge. Either I receive no reply or some obscure specs from a completely different type and capacity battery that doesn't answer the question at all. They try the "no understand question" tactic rather than giving an honest answer. 
Ultracaps could extend the cycle life but the number required relates to the max charge or discharge rate the motor will produce. At the max rated 650amps @ 48v in the case of my chosen motor would be a lot of caps, simply financially a non viable proposition. With a small light vehicle where minimal room for batteries is available and weight is everything but $$ are secondary then some gain could be achieved but I can't see it being enough to warrant the cost. A better deal $$ wise would be to sell the tired batteries at a reduced cost to someone looking for electrical energy storage generated via solar or wind or even using them yourself to make a solar home charging pack and using that value to offset the price of a new battery pack. With the cost of electricity continually rising and the cost of lithium batteries continually falling the self storage system makes a lot of sense and would save more $$ than cents 

T1 Terry


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## nimblemotors (Oct 1, 2010)

Thundersky only show .3C ? Scary how long they will last at 3C,
Someone needs to just simply test them and publish the results,
I'm probably going to build such a tester to truly find out.
For a 40AH, 24 cycles a day is 750 cycles a month, so it would take 3-6 months to truly find out, but I'd bet after 1 month you'd see some results.
I'd rather find out with one cell that a whole pack of them.

The caps don't have to supply all the current, if they can just reduce it by half during acceleration when the batteries are taxed, then it might double the life of the batteries, and for a $10k or $15k pack, that is a lot of cost savings. I'm more interested in building a really fast car using caps.



T1 Terry said:


> The cycle life for CALB and Thundersky batteries of 3,000 to 5,000 cycle @ 70% DoD is at the nominated 0.3C charge/discharge rate, it says this quite clearly in the specs, how many people don't want to read that bit :lol: I have put the question to each of the battery companies (there is a lot of them producing LiFeP04 batteries now) asking what the cycle life is at the max rated discharge. Either I receive no reply or some obscure specs from a completely different type and capacity battery that doesn't answer the question at all. They try the "no understand question" tactic rather than giving an honest answer.
> Ultracaps could extend the cycle life but the number required relates to the max charge or discharge rate the motor will produce. At the max rated 650amps @ 48v in the case of my chosen motor would be a lot of caps, simply financially a non viable proposition. With a small light vehicle where minimal room for batteries is available and weight is everything but $$ are secondary then some gain could be achieved but I can't see it being enough to warrant the cost. A better deal $$ wise would be to sell the tired batteries at a reduced cost to someone looking for electrical energy storage generated via solar or wind or even using them yourself to make a solar home charging pack and using that value to offset the price of a new battery pack. With the cost of electricity continually rising and the cost of lithium batteries continually falling the self storage system makes a lot of sense and would save more $$ than cents
> 
> T1 Terry


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## Duncan (Dec 8, 2008)

Hi Nimble

*battery lifetimes are dramatically shortened when they are discharged at high rates. even the "continous" rating reduces their life, most cells specify their cycle lifetime at 1C rates.

*

*Not* what the Carnegie guy said in his lecture - he talked about the amount (amp-hours) of charge and discharge and the temperature

As long as you keep within limits with cool cells - no big deal!

If you go over the limits and heat the cells -----


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## T1 Terry (Jan 29, 2011)

> I'm more interested in building a really fast car using caps.


Would ultracaps or headway cells be a better deal? Headways are cheap and rated at 10C. very high maintenance regularly checking for dead cells or high techo gadget dependant for cell checking but $$ wise? What a bout a bank of Headway cells buffering the main TS or CALB cells in place of the ultracaps?

T1 Terry


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## nimblemotors (Oct 1, 2010)

well that is just it, isn't it, at 3C, the batteries generate heat.
How much does 3C reduce life? I don't know, but if they won't tell you, the results can't be good. 



Duncan said:


> Hi Nimble
> 
> *battery lifetimes are dramatically shortened when they are discharged at high rates. even the "continous" rating reduces their life, most cells specify their cycle lifetime at 1C rates.*
> 
> ...


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## Duncan (Dec 8, 2008)

Hi Nimble

Range from lecture was 0.5 - 5 milliOhms

The only data I can find for TS says 1milliOhms internal resistance at 5C 
(TS 60Ah sag to 2.9v at 5C)

The resistance will be less at lower C ratings

so a 100Ah cell at 3C , 300A is 0.3v and 90 watts - so for a 45 cell pack you need to dissipate 4Kw and keep your temperatures below 60C
Does not sound too difficult to me - probably get more cooling that that simply by having the cells on the chassis of your car


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## idarusskie (Feb 17, 2011)

http://batteryuniversity.com/learn/article/modern_lead_battery_systems
according to this site 



> *EEStor*
> 
> This is the mystery battery/ultracapacitor that receives much media attention. The battery is based on modified barium titanate ceramic powder. EEStor claims that the battery has a specific energy of up to 280Wh/kg. The company is very secretive about their invention and only limited information is available. Financial Post, 26 June 2008 compares EEStor with specifications of NiMH and customary lead acid systems.


There are other batteries listed. which also use ultracapcitors. so it seems they do help but the battery manufacturers are starting to put them in their batteries


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## PZigouras (Jun 5, 2010)

idarusskie said:


> http://batteryuniversity.com/learn/article/modern_lead_battery_systems
> according to this site
> 
> There are other batteries listed. which also use ultracapcitors. so it seems they do help but the battery manufacturers are starting to put them in their batteries


That seems to be a lot of capacity, which makes a lot of people think that this may be a battery/capacitor hybrid, not just a supercap. Has anybody seen any proof that this is strictly a capacitor???

- Paul


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## idarusskie (Feb 17, 2011)

http://www.tecategroup.com/white_papers/200904_WhitePaper_EngineColdStarting.pdf

Here are some white papers on the subject. Seems in cold starting they can cut the total batteries in half in an ICE required for cold weather starting. 

from another white paper
http://www.tecategroup.com/white_papers/200904_WhitePaper_AutomotiveElectronics_ASchneuwly.pdf


> Ultracapacitors are best suited to perform in those applications that require short bursts of power, interspersed with longer durations of low power requirements. Engineers continue to learn how to design systems that use two different components to achieve an optimal solution for both power and energy. One model is that of a cache of power; the ultracapacitor is sized for maximum peak power, while the primary energy storage is a large device sized for maximum continuous power (Figure 2). The primary energy storage can be a fuel engine, high-energy batteries, or a fuel cell. System designers size the ultracapacitor for the difference between maximum continuous and maximum peak power, to take full advantage of both components.


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## michaeljayclark (Apr 3, 2008)

speaking with the DEKA rep for the southeast he indicated that DEKA is designing a battery that has capacitors built into them... so the idea of how caps help bats I think is a yes.

the car stereo world is going to them... diesel truck battery companies are doing it. Ive seen a car stereo bat that was half caps and half bat.. a hybrid battery!

I have all 52 of my ultracaps in and I cannot wait to try them. As far as power only for 6 seconds? that is enough to get my jimmy up to 50 mph from a dead stop.

now I havent seen anyone talk about the peukert effect. regardless of what the china battery companies say they cannot beat the PE. The higher the C rate of discharge the lower the amp hours in the battery goes. discharge a lipo 160ah cell at the highest rated discharge C and you take away amp hours from the cell prematurely.

I will be happy to be the guinea pig here and put the system together and publish the results from real world testing. The test bed will be driving on US 19 between hudson, florida and st petersburg, fl. cant get any more real world than that. lots of stop and go track mixed in with a few miles of 55 mph semi-highway.

afterall, I am the one who stated this thread


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## Duncan (Dec 8, 2008)

Michael

*As far as power only for 6 seconds? that is enough to get my jimmy up to 50 mph from a dead stop.*

That was assuming that you could get all of the power from the ultracaps - if you are just using them to stiffen your pack you will get about5/144 of that 

0.2 seconds worth of power!
Still worth $2,000? - you must be a lot richer than I am!


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## T1 Terry (Jan 29, 2011)

Don't you hate it when half the post vanishes into the ether I'll try again.
Looking forward to the results. Not sure just how much regen you can expect from a Jimny, not much weight to keep the wheels turning. The Peukert’s factor with lithium batteries is only around 5% @ 3C going by the TS charts (if you can believe them) so if you plan to get a decent life out of the battery pack it wouldn't be pulled much below 80% DoD anyway so it doesn't seem to be a factor to me. In my case the discharge loads will be big and long as will the regen so to make any sort of an impact I think I'd need a lot of ultracaps, not $$ viable as I see it.

T1 Terry


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## michaeljayclark (Apr 3, 2008)

well, the whole idea of electric cars was too much money to begin with, yet we are here.

the volt was too expensive, yet they are selling..

the leaf is too expensive, yet there is a LLOONNGG list to get one.

overall ownership of an electric car is 3 cents per mile, a gas car is 25 cents just for gas then goes up from there...

yet people tell me $10,000 to build an EV is wwwaayyy too much...


I think $2000 for a cap back to make a smaller pack of batteries go further and last longer is worth it.. 

look at the long run here. not just the first initial cost.


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## T1 Terry (Jan 29, 2011)

We are going in circles here, I posted this back at no.13 last week


T1 Terry said:


> Thanks for that Duncan, saved me having to ask how to convert capacitance to ah. Stuff must be meg a cheap in the states, 3000f Maxwell caps to buy here AU$2,123 for 26 units. At 48v not quite 0.5ah. With a motor looking for 650amp peak that's not much of a buffer.
> AU$2,160 will buy another 16 100ah Thundersky cells. Min 200ah rate at 3C max charge/discharge = 600amps, another 100ah at 3C gives me 900amps, sounds far more logical to me. Am I missing something?
> 
> T1 Terry


The cost of ultracaps compared to the cost of more battery can't be justified as I see it, far better to spend those $$ in a larger capacity battery pack in the first place.

T1 Terry

 You can build an EV for $10,000 in the states, why are people still driving petrol guzzlers over there?


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## michaeljayclark (Apr 3, 2008)

when the peukart effect is considered, the ultracaps are worth the money. buying more battery just makes more peukart effect


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## GizmoEV (Nov 28, 2009)

michaeljayclark said:


> when the peukart effect is considered, the ultracaps are worth the money. buying more battery just makes more peukart effect


Actually the opposite is true. More batteries means less current for a given plate area so peukert doesn't come into play as much. When I went from 8V batteries to 6V batteries in my Gizmo and thus increased the weight from about 870lbs to 993lbs my efficiency actually went up. Same or higher currents but a significant increase in plate area.

With my LiFePO4 pack it makes no measurable difference whether I pull high current or low current from the pack. Understand that I'm using a 200Ah pack and can only momentarily pull 2C and spend more time around 0.6C or less so that may be why I don't see a difference.


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## T1 Terry (Jan 29, 2011)

As I said before, the Peukert’s factor with lithium batteries is only around 5% @ 3C going by the TS charts as far as I can tell so how does an ultracap pack with 0.5ah capacity if a special circuit to get it all out stack up against a lithium pack with 75ah allowing for Peukert's and a safe discharge level without any special circuitry needed? The cost for both is about the same. If there is a benefit I haven't seen please point it out.

T1 Terry


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## GizmoEV (Nov 28, 2009)

Terry,

The only thing I can think of for a typical road going EV to benefit from ultracaps is maybe the pulsing high current draws due to the PWM controllers. Sure most of them operate in the 15kHz range, but would a smoother drain on the batteries make them last longer? That is why I asked earlier about how to calculate how much energy one of the pulses from the controller would be. Size the ultracap bank to be just slightly bigger than that and maybe that would be enough.


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## nimblemotors (Oct 1, 2010)

But what if you are using Lead batteries? then caps can make a bigger difference, as lead is killed by high current. Lead is significantly cheaper than lithium. So you could make a case the caps last forever, and could increase the life of the cheap lead, so over the long-term it would cost less, replace a few lead packs over 100k miles, and perhaps even perform better with a small cap buffer.

To get the benefit you must use all the cap capacity, which isn't possible using just a parallel connection, a more complex controller is needed to use the full voltage range of the cap. 



GizmoEV said:


> Terry,
> 
> The only thing I can think of for a typical road going EV to benefit from ultracaps is maybe the pulsing high current draws due to the PWM controllers. Sure most of them operate in the 15kHz range, but would a smoother drain on the batteries make them last longer? That is why I asked earlier about how to calculate how much energy one of the pulses from the controller would be. Size the ultracap bank to be just slightly bigger than that and maybe that would be enough.


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## GizmoEV (Nov 28, 2009)

nimblemotors said:


> But what if you are using Lead batteries? then caps can make a bigger difference, as lead is killed by high current. Lead is significantly cheaper than lithium. So you could make a case the caps last forever, and could increase the life of the cheap lead, so over the long-term it would cost less, replace a few lead packs over 100k miles, and perhaps even perform better with a small cap buffer.
> 
> To get the benefit you must use all the cap capacity, which isn't possible using just a parallel connection, a more complex controller is needed to use the full voltage range of the cap.


The question then becomes why stay with lead? Drive once with LiFePO4 and you don't want to go back.

I heard a rumor of someone in Australia, I think, who made a lead pack last for 100,000 mi using a cap bank so there may be some merit to the idea.


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## T1 Terry (Jan 29, 2011)

GizmoEV said:


> Terry,
> 
> The only thing I can think of for a typical road going EV to benefit from ultracaps is maybe the pulsing high current draws due to the PWM controllers. Sure most of them operate in the 15kHz range, but would a smoother drain on the batteries make them last longer? That is why I asked earlier about how to calculate how much energy one of the pulses from the controller would be. Size the ultracap bank to be just slightly bigger than that and maybe that would be enough.


a quick look at the TS PDF and the impluse discharge current is 20C (is this the same as pulse current) so I'm not too sure if discharge pulsing would be an issue but they didn't mention anthing about impulse/pulse recharging. Does the DC regen current pulse on the output from an AC controller? 
As far as the lead acid, I guess if you already have a lead acid battery pack the an ultracap pack could help if it was big enough but wouldn't a lithium pack work better for the same $$? Life span is shorter but would the ultracaps limited capacity be enough to assist the heavy current draw issue over and above the capabilities of the lithium pack to make the cycle life of ultracaps a better value option?

T1 Terry


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## michaeljayclark (Apr 3, 2008)

its all numbers really and to find the true answer it will have to take an experiment, yes an expensive experiment, but thats where the real numbers will come from.

to get all the energy from the caps they wouldnt be in parallel. the soliton controlle3r can operate down to 10 volts, this will be the test to see if it will use the current from the caps until they reach almost zero. when the speed stops increasing would be when 2nd gear if used..

hmm, maybe a simple shifter the driver would use to switch from the batteries from the caps? would simulate shifting gears. wow, back to a contactor controller lol


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## rmay635703 (Oct 23, 2008)

I doubt that 100k was because of the cap bank, more than likely was because of very light discharges coupled with HIGHLY CONTROLLED charging.

I think many here discount how far lead can go if it is taken care of and used for short distance travel.


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## GizmoEV (Nov 28, 2009)

Roland Wiench has a beautiful EV conversion he has been driving for something like 30 years. He uses lead acid batteries and drives very short distances, under 5 miles, IIRC. He gets at most 10 years out of a set of batteries. That is only 18k miles. Roland also highly controls the charging. If any one can keep a set of lead acid running for years he can. Either the 100k miles isn't true or there is definitely something else at work.


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## rmay635703 (Oct 23, 2008)

GizmoEV said:


> Roland Wiench has a beautiful EV conversion he has been driving for something like 30 years. He uses lead acid batteries and drives very short distances, under 5 miles, IIRC. He gets at most 10 years out of a set of batteries. That is only 18k miles. Roland also highly controls the charging. If any one can keep a set of lead acid running for years he can. Either the 100k miles isn't true or there is definitely something else at work.


Perhaps, I do know of a couple of 15yr plus battery packs still chugging around on the C-car group. One I believe was 20 years. There was also one guy with the old Atlas Lead Cobalt battery packs still operating after roughly 30 years in a different vehicle Mars comes to mind (all historic now though)

The guys with the old packs don't post much about it, I will have to see if I can do a poll again and find out who and how far (if they've kept track)
Most of the old packs were on Contactor drive cars which may add some truth to the effects of PWM. Or possibly older batteries were just made better.


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## idarusskie (Feb 17, 2011)

GizmoEV said:


> Roland Wiench has a beautiful EV conversion he has been driving for something like 30 years. He uses lead acid batteries and drives very short distances, under 5 miles, IIRC. He gets at most 10 years out of a set of batteries. That is only 18k miles. Roland also highly controls the charging. If any one can keep a set of lead acid running for years he can. Either the 100k miles isn't true or there is definitely something else at work.



The thing about batteries is they can age whether you use them or not. so the miles traveled is not always an indication of quality of the batteries. 10 years is pretty good.

The best return on your investment is to use them everyday.


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## GizmoEV (Nov 28, 2009)

idarusskie said:


> The best return on your investment is to use them everyday.


I believe that is why building a lead acid pack for 50%DOD on most drives is best. It is the point where most things balance out to get the most distance/$.


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## T1 Terry (Jan 29, 2011)

Lithium batteries have a very high impulse discharge rate, this is only a milisecond rate i'm told but would it be possible to charge ultracaps using this much higher figure and power the motor from the ultracaps? From what I've been told and read over on the AEVA forum lithium batteries suffer a much reduced cycle life if constant current is higher than the max 3C rating that CALB and TS batteries have. 

T1 Terry


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## michaeljayclark (Apr 3, 2008)

thats where caps will work, keep the batteries from seeing that major discharge. as far as charging that will be up to the vehicle owner to control that. when i asked nissan about fast charging they replied we dont recommend doing it everyday... 

i have been speaking with some EEs on other forums, they suggested using the caps IN SERIES with the batteries. so 54 ultracapacitors in series with 12 12 volt batts in series. a 288 volt pack as far as the total voltage is. the caps would be 145 volts and the batts 144. when charging a switch that isolates the batts. would have to make sure the caps are at the same voltage when reconnecting them with the batteries. Interesting concept...

the soliton controller can work with a 288 volt pack, just send 144 volts to the motor.


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## GizmoEV (Nov 28, 2009)

michaeljayclark said:


> i have been speaking with some EEs on other forums, they suggested using the caps IN SERIES with the batteries. so 54 ultracapacitors in series with 12 12 volt batts in series. a 288 volt pack as far as the total voltage is. the caps would be 145 volts and the batts 144. when charging a switch that isolates the batts. would have to make sure the caps are at the same voltage when reconnecting them with the batteries. Interesting concept...


So then what are you supposed to do when the caps drain in a very short time? Don't you mean in PARALLEL? If they are in series then it won't matter what their voltage is when reconnecting them. If it did, then you would have a hard time hooking up a regular set of batteries in series. Once you had two hooked up the third would be at best half the voltage of the first two combined.


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## T1 Terry (Jan 29, 2011)

michaeljayclark said:


> i have been speaking with some EEs on other forums, they suggested using the caps IN SERIES with the batteries. so 54 ultracapacitors in series with 12 12 volt batts in series. a 288 volt pack as far as the total voltage is. the caps would be 145 volts and the batts 144. when charging a switch that isolates the batts. would have to make sure the caps are at the same voltage when reconnecting them with the batteries. Interesting concept...
> 
> the soliton controller can work with a 288 volt pack, just send 144 volts to the motor.


 I understand the bit where the controllr will work down from the 288v total to the 144v batttery voltage but once the caps are discharged won't the 144v batteries have to go through the ultracaps creating a reverse charge or at least attempting to? I can't see this being a good thing.
How do you recharge the caps? How do you get the cap pack and battery pack balanced? 

T1 Terry


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## idarusskie (Feb 17, 2011)

http://www.ultracapacitors.org/index.php?option=com_fireboard&Itemid=97&catid=8&func=view&id=339

check out this site. There is a long thread which talks about making homebrew ultracaps.


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## michaeljayclark (Apr 3, 2008)

the series idea would work however wouldnt protect the batteries as planned.

just throwing ideas here no matter how far fetched. and if anyone else has these ideas they can search them here and see the answers.

Back to just parallel.

trying to avoid getting another controller to limit the flow of current from the batteries to the caps at 200 amps max.

that leads to the question what would be used to limit the flow of current from the batteries to the caps to 200 amps. resistors? the cap esr is total string resistance of .0145 ohms. just a set of lightbulbs? Ive seen that idea work before. then the flow would stop when the battery pack of 144 volts balances with the voltage in the capacitors.


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## nimblemotors (Oct 1, 2010)

Connecting them in series is a good idea, but it isn't so simple.
It would allow you to take all the power out of the caps, and if your controller can handle the high voltage its possible. 
But lots of issues. The caps could go to 0v very quickly and you'd need to remove them from the series before that happened, and then be able to recharge them again and reinsert them. Doing all this without drama could be a challenge.

Anytime doing something new and experimental, it is best to test it out on a small scale first. So like a go-cart, or an RC car was my plan.

Jack Murray
Nimble Motorsports



michaeljayclark said:


> the series idea would work however wouldnt protect the batteries as planned.
> 
> just throwing ideas here no matter how far fetched. and if anyone else has these ideas they can search them here and see the answers.
> 
> ...


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## michaeljayclark (Apr 3, 2008)

I wonder at what voltage the vehicle would just be slowing down for lack of voltage? would they reach zero? a test would see about that and that's going to be my first test is run them in a EV by themselves to see at what speed Id reach. when the vehicle starts to slow instead of accelerating at that point you would refer to the batteries.

a contactor that is controlled by a circuit that detects when speed is not going up as fast as it did at a certain point and then switches to the batteries.

seems just the same as having them in parallel, switched in by themselves, getting the vehicle up to speed and then switching to the battery string.

the batteries sustain the speed you wanted to be at and the caps get refilled by the batteries in this case while you are driving. just have to make the batteries only see a 200 amp load into the caps. if everything was in series?

the controller can handle the voltage.

I would think they would fill up pretty fast if 200 amps was sent into them with their low esr.

well, wouldnt the batteries help the caps from reaching zero? a lightbulb behind the caps in front of the batteries would slow the charge from the batteries into the caps. what type of resistor or a resistor acting device would slow the transfer of electrons from the batteries into the caps keeping it at 200 amps?


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## michaeljayclark (Apr 3, 2008)

tecate group has a nice ultracapitor sizing tool, a spreadsheet.

it is attached.

I entered in the following values

working voltage: 145 vdc
minimum voltage: 1 vdc
current: 600 amps dc
time: 9 seconds


it gave me:

maxwell boostcap 3000 recommendation
number in series 54
number in parallel 1
total capacitance 55.6
total ESR 15.66 milliohms
weight 29,700 grams
volume(L) 21.5536
energy stored at working voltage 584,028 joules
energy stored between working voltage and minimum voltage: 584,000 joules
balancing resistor recommendation 52 ohm

if anything it shows these monsters store some incredible power!

as far as seconds being 9 does it mean it can deliver 584000 joules over 9 seconds?

if so, 200 watt hours per mile is common for conversions. 584000 joules is 162 watt hours. SO, the vehicle could drive over half a mile at a draw of 600 amps from these capacitors by themselves?


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## michaeljayclark (Apr 3, 2008)

spreadsheet sizing tool is attached here


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## GizmoEV (Nov 28, 2009)

Remember that to keep power constant that the current will have to increase as the voltage decreases so you won't likely be able to maintain 600A for the full duration of the discharge.


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## Duncan (Dec 8, 2008)

Hi Michael

_it gave me:

maxwell boostcap 3000 recommendation
number in series 54
number in parallel 1
total capacitance 55.6
total ESR 15.66 milliohms
weight 29,700 grams
volume(L) 21.5536
energy stored at working voltage 584,028 joules
energy stored between working voltage and minimum voltage: 584,000 joules
balancing resistor recommendation 52 ohm

if anything it shows these monsters store some incredible power!

as far as seconds being 9 does it mean it can deliver 584000 joules over 9 seconds?

if so, 200 watt hours per mile is common for conversions. 584000 joules is 162 watt hours. SO, the vehicle could drive over half a mile at a draw of 600 amps from these capacitors by themselves?
_

So 30Kg and $3000 = 162 Whrs

Thundersky 100Ah = 320 Whrs , 5Kg and $125


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## T1 Terry (Jan 29, 2011)

I just tried to see what 600amps for 3 min ranging from 96v down to 48v, basic useable parameters, remember mine is a 10 tonne motorhome and this is for a hybrid assist. I couldn't dial up the temp range found in the Aust outback of -5c to 50c in the same day but never mind that, the cap pack weight was 1,346.4kgs. Not quite sure how to convert that to US tons but it's rather heavy for a 3 min power burst or to absorb a 3 min decel considering the hills around here can take over 5 mins to come down and even longer to climb. Maybe not just yet, I might wait to see how lithium sulphur specs up first.

T1 Terry


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## michaeljayclark (Apr 3, 2008)

you could just add more caps. the sizing tool is very nice and gives alot of information. the graph was a gradual fall and at the end of 9 seconds it was at 20 volts. So not 0 even after 9 seconds of draw. impressive.

the 600 amps wouldnt be needed the entire time. even in the s-10 electric i have here, the amps do rise during acceleration but then fall a bit after the controller gets the vehicle moving and doesnt need as many amps to keep it going. Ill have to get these caps precharged and all in series to see how long the truck will move.

while the caps are all charged and in series I bet it would vaporize an aluminum can! I have been testing with just 6 caps in series and the aluminum just flashes and disappears.

I would need a graph simulating the 600 amps would fall slowly over the 9 second.

29,700 grams = 65.4772919 pounds

not too heavy at all for 54 ultracapacitors


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## GizmoEV (Nov 28, 2009)

T1 Terry said:


> ...the cap pack weight was 1,346.4kgs. Not quite sure how to convert that to US tons but it's rather heavy...


1,346.4kg * 2.2lbs/kg = 2962 lbs
2962lbs/(2000lbs/ton) = 1.48 tons or about 3.5 of my Gizmo's


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## GizmoEV (Nov 28, 2009)

michaeljayclark said:


> even in the s-10 electric i have here, the amps do rise during acceleration but then fall a bit after the controller gets the vehicle moving and doesnt need as many amps to keep it going.


Actually that is the back EMF from the motor spinning. If at the point the battery current starts to fall off you did a direct connect to your motor, bypassing the controller, you wouldn't notice any difference. Remember that as soon as the motor starts to turn it becomes a generator too. It "pushes" back against the batteries. Your power comes from the difference between the battery voltage and the motor voltage called back EMF (electromotive force).


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## GerhardRP (Nov 17, 2009)

GizmoEV said:


> Actually that is the back EMF from the motor spinning. If at the point the battery current starts to fall off you did a direct connect to your motor, bypassing the controller, you wouldn't notice any difference. Remember that as soon as the motor starts to turn it becomes a generator too. It "pushes" back against the batteries. Your power comes from the difference between the battery voltage and the motor voltage called back EMF (electromotive force).


The last sentence is not quite correct: The motor current comes from the (battery voltage minus BEMF minus brush voltage) / motor resistance. The power comes from the motor current times the BEMF.

Gerhard


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## GizmoEV (Nov 28, 2009)

GerhardRP said:


> The last sentence is not quite correct: The motor current comes from the (battery voltage minus BEMF minus brush voltage) / motor resistance.


Gerhard,

Could you explain/expound on the brush voltage? Maybe I'm thinking of it too simply but I was viewing BEMF as measured at the motor terminals so wouldn't this include everything, brushes and all?



> The power comes from the motor current times the BEMF.


I'm still trying to this out. The motor gets its energy externally, how can the power be a product of BEMF? What am I missing?


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## Duncan (Dec 8, 2008)

Hi Gizmo

The motor is turning the electrical power into mechanical power,

You have the -resistance- of the windings - this requires a voltage 
This voltage times the current is turned into heat - wasted!

The turning of the motor generates the back EMF - this voltage times the current is the power that is converted into mechanical work


If you keep the current constant you get ~constant torque
At low speed you are generating low mechanical power - Torque x speed
At low speed you are using low electrical power - current x back EMF (+resistive losses)

At high speed you are generating high mechanical power - torque x speed
At high speed you are using high electrical power - current x back EMF (+resistive losses)

Does that make sense?


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## michaeljayclark (Apr 3, 2008)

This would be when you are up to speed say 45 mph, let off the accelerator to stop and you see the volt meter go down slowly... is this energy produced by the motor as it slowly spins down? Its energy that isnt really created and put back into the battery pack, it just looks like voltage created.

am I understanding it correctly?


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## GerhardRP (Nov 17, 2009)

GizmoEV said:


> Gerhard,
> 
> Could you explain/expound on the brush voltage? Maybe I'm thinking of it too simply but I was viewing BEMF as measured at the motor terminals so wouldn't this include everything, brushes and all?


The voltage measured at the terminals is the sum of BEMF, ordinary resistance and brush voltage. Brush voltage is developed across the interface between the brush and the commutator. When the brushes are well seated and the comm has a good film, this voltage is one or two volts, independant of current. In an abuse situation where the comm overheats and the film is damaged, it will rise to maybe 10 or more. 



GizmoEV said:


> I'm still trying to this out. The motor gets its energy externally, how can the power be a product of BEMF? What am I missing?


See Duncan's reply.

Gerhard


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## ElectriCar (Jun 15, 2008)

GizmoEV said:


> Terry,
> 
> The only thing I can think of for a typical road going EV to benefit from ultracaps is maybe the pulsing high current draws due to the PWM controllers. Sure most of them operate in the 15kHz range, but would a smoother drain on the batteries make them last longer? That is why I asked earlier about how to calculate how much energy one of the pulses from the controller would be. Size the ultracap bank to be just slightly bigger than that and maybe that would be enough.


 You're on the same path as me on this!

Consider this guys. And expound on it as you can. 

It seems that most are viewing the application of a cap bank as if they will be charged up then begin discharging continuously once the controller comes on and that's just not the case most of the time. If you have a PWM controller as most of us do, unless you floor it you're not going to discharge the cap in that manner. Here's what you will have and I hope I can explain it well enough. I'm no PWM expert but understand PWM from an electronics background. 

Let's say you push the throttle to 50% for a normal acceleration. From what I've gathered from EV controller people, at 50% throttle, the controller turns on then off repeatedly based on the operating frequency of the controller. Mine operates at 10Khz so 10,000 times a second it's turning on and off. 

When I hit the throttle, it draws current off the pack for a fraction of a second then it shuts off and the cycle repeats 10000 times a second. It is during the off time of this cycle that the caps will begin to recharge until either pack voltage is reached or the control switches on again. 

As the motor begins to turn and back emf builds, the percent of time in each cycle the controller remains on versus off will increase. As the on time increases the off time must decrease, shortening the amount of time the caps have to recharge. 

This means that with no caps, when the control is on for a fraction of a millisecond, you have a surge of lets say 500A from the battery then nothing when it switches off, then 500A when it's on again. With a cap bank and assuming 500 amps is all the controller is needing, you'll draw part of that 500A from the battery and part from the caps. So your maximum draw from the battery may be 400 if the caps can put out 100A. If the caps can contribute 250A, you'll pull 250 from the battery. Now when the control switches off, you'll begin recharging the cap until it's back at pack voltage or the controller switches back on. If it reaches full charge at exactly the moment the control switches on, you've cut your pack amp draw from 500A half the time to 250A all the time, assuming the cap can recharge that fast of course. 

With that example, you'll cut your voltage sag in half I believe due to halving the maximum current barring other factors that I may not be aware of. 

So you can see for all but extreme pedal to the metal acceleration, you don't need a megawatt of power stored in the caps, you don't even need 1 second worth of capacity. You only need enough to dump power for a fraction of a millisecond and recharge. I think therefore the most benefit you will get is during acceleration, whether full or part throttle. Full throttle of course will require a larger bank for more of an effect

Again I don't know all the ins, outs and calculations of all of this so I'm sure some of the current and voltage drop values won't be exactly as described. However my goal was to explain the basic idea of what is happening and why you don't need a humongous pack of caps to have an affect on the system. Hope this old head has spewed forth something of value to those contemplating adding a bank to their vehicles.


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## piotrsko (Dec 9, 2007)

i believe you are neglecting to account for battery current during the battery recharge of the CAPs, which according to my 50 year old electronic theory classes, could be as much or more than motor current.


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## TruEnergy (Apr 6, 2009)

I've spent a long time reading threads - this is my first time posting.

Current draw on the batteries can be controlled with a purpose-build DC/DC converter. In fact, using capacitors directly coupled to the batteries will result in approximately a 50% energy LOSS due to resistance. This is detrimental to vehicle range.

It is well known in the power supply industry that capacitor banks should be charged through a reactive element (a coil). This creates an LRC circuit and when properly switched with a free-wheel diode (read: purpose-built converter) it will have very high efficiency. Much better than the 50% seen with direct charging.

For more info, google "hybrid battery packs". There are some great white papers documenting this application. And its not free-energy BS either.

I am currently investigating this option for my own use.

I should clarify that the 50% loss will be in the energy used to recharge the cap bank - not 50% loss of all energy in the batteries.

The best "protection" for the batteries is to have them completely isolated from the motor controller. So the DC/DC converter will have to be large enough and switch fast enough to keep the caps charged during hard acceleration. During coasting or constant speed, the converter would adjust its output accordingly.

I don't know what the total losses in this complicated system would be. I have not seen anyone try it. However, we all know and agree that reducing sharp draws of high current from the batteries is a good thing. And extending battery life / range may offset the efficiency losses.


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## mizlplix (May 1, 2011)

TruEnergy, could you please introduce yourself? I am interested in your experience.

Ty, Miz


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## TruEnergy (Apr 6, 2009)

mizlplix said:


> TruEnergy, could you please introduce yourself? I am interested in your experience.


I quickly updated my profile - feel free to PM me if you have any specific questions not applicable to the thread, thanks!


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## bjfreeman (Dec 7, 2011)

GizmoEV said:


> I'm still trying to this out. The motor gets its energy externally, how can the power be a product of BEMF? What am I missing?


There seems to be a miss understanding of the Term BEMF.
BEMF is when the flux is raising from eternal Current being applied to an Inductance. Another term is Buck EMF.


When the motor is turning with no external current applied it become a Generator. the Motor is the Source. there 
the current and EFM created is from the rotor magnetic flux cutting the field coils.

There is a third condition which is the external current is removed and the Magnetic flux collapses, This is Called Reverse EMF


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## bjfreeman (Dec 7, 2011)

I am only familiar with Ultra Caps in Buses.
there are used for about 10 to 15 Sec to save draws on the Batteries for start and stops.
I found this PDF that does a good job explain
http://www.nrel.gov/vehiclesandfuels/energystorage/pdfs/45596.pdf


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## major (Apr 4, 2008)

bjfreeman said:


> There seems to be a miss understanding of the Term BEMF.
> BEMF is when the flux is raising from eternal Current being applied to an Inductance. Another term is Buck EMF.


Hello bj,

This is another example of you coming here telling us something which is contrary to convention and simply wrong. BEMF is Back EMF, or Back Electromotive Force. It is never referred to as "Buck EMF" when used in the context of electric motors and generators. Here is one definition: 


> BACK EMF
> What is the back _emf_? It's the voltage generated across the motor's terminals as the windings move through the motor's magnetic field. The back _emf_ actually opposes the drive voltage and is proportional to the motor's velocity
> _Vemf = Kemf ∙ __ω_​


from: http://www.ecircuitcenter.com/circuits/dc_motor_model/dcmotor_model.htm

It is also sometimes called CEMF with regards to motors and generators, Counter EMF.

Maybe in some other context, BEMF could mean what you say, but I saw no mention of Buck EMF in a brief web search or in any text or article which I recall.

Regards,

major


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## bjfreeman (Dec 7, 2011)

major said:


> Hello bj,
> 
> This is another example of you coming here telling us something which is contrary to convention and simply wrong. BEMF is Back EMF, or Back Electromotive Force. It is never referred to as "Buck EMF" when used in the context of electric motors and generators. Here is one definition:
> 
> ...


there you are. as many time I have shown what you say is not accurate you keep trying.
strange when other member agreed with me you did not jump in.
I know you think you are correcting things, but your only confusing things by put in your two cents.
also some of your links have misinformation.
BTW I am glad you finally recognize EMF now
so here is a quote from the pdf


> The signal can _bc obtained from a tachogencrator or from the _buck emf_ developed across the armature.


http://www.most.gov.mm/techuni/media/EcE_05031_10.pdf
Now lets follow this through.
when a current is applied to an inductor, the flux increases cutting the adjacent wires cause a EMF that is the opposite polarity than the Applied EMF that forces the current into the inductor.
Therefor this opposite EMF Bucks the Applied EMF
This is in every application using Inductor ie motors.
I can also go with Counter EMF, as long as the concept of the rising flux causes this.
as compared to the falling flux caused by the removal of current and Applied EMF.
Now I am willing to agree that those on this form have their own vocabulary. that does not mean that is the way the world sees it.


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## mizlplix (May 1, 2011)

A guy on EBay has one of these for sale. He sez it will fix all of my problems. I dont even need batteries either.

Do you guys think I should get it?

Miz


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## major (Apr 4, 2008)

bjfreeman said:


> so here is a quote from the pdf
> 
> 
> 
> ...


You need to get your eyes checked. It says "back". In that quoted sentence and 10 other places in the 8 pages in the pdf, it reads back emf, _b_a_c_k, back.


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## bjfreeman (Dec 7, 2011)

mizlplix said:


> A guy on EBay has one of these for sale. He sez it will fix all of my problems. I dont even need batteries either.
> 
> Do you guys think I should get it?
> 
> Miz


ah yes the flux capacitor. Only if you know street you can get 70 mph and can have lighting strike.
of course then you may end up in dinosaur area if you dont have the chronographs. (all tongue in cheek)


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## major (Apr 4, 2008)

bjfreeman said:


> ah yes the flux capacitor.


What was that movie, bj? Buck To The Future.


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## rwaudio (May 22, 2008)

major said:


> What was that movie, bj? Buck To The Future.




and I thought BJ had left us, we can all forever be exposed to his unique interpretation of electronics theory.


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## bjfreeman (Dec 7, 2011)

major said:


> What was that movie, bj? Buck To The Future.


LOL you confuse Capacitance reactantance with inductive reactantance .
some day you will get it correct.


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## Kerensky (Jul 8, 2011)

Time for my 2 cents. I believe electricar is on to something. If the pukert effect on the batteries is what we are trying to reduce, then placing a small ( say 3-5 farad 200v) cap bank in series with your Trojan T105's should definitely reduce the momentary drain on the battery pack caused by the Curtis 1231. ( I know ...I know very specific example!)
I use my own experience with large car stereo installs to reinforce my point. 2000 w car amp pushing 2/12 inch speakers will make your headlights dim every time the bass hits. ( equivalent momentary drain ). This consequence is removed entirely by placing a capacitor inline with the car amps power supply( it also provides somewhat improved fidelity though I lack the necessary experience to guess how that analagy might translate back to dc motor operation. Perhaps better throttle response. )
.... Ohhh and BJ it's 88 mph not 70 and u need to set your time circuit not the chronograph. Great Scot man this stuff isnt that heavy.


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## mizlplix (May 1, 2011)

You know what? After listening to all this, I think I,ll hold out for a "Mr. fusion" pack and not invest in antique lithiums .

Miz


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## Ziggythewiz (May 16, 2010)

Kerensky said:


> I use my own experience with large car stereo installs to reinforce my point. 2000 w car amp pushing 2/12 inch speakers will make your headlights dim every time the bass hits. ( equivalent momentary drain ).


Not much of a comparison. In audio you have hits of under a second, typically with well under 50% duty cycle. When an EV needs extra juice it will be for at least 5-10 seconds, at near 100% duty. The caps will be drained in the first second, with no time to recharge until approaching the next light.

For the same money you could have an A123 booster pack, that would provide actual power and some boost to range.


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## ElectriCar (Jun 15, 2008)

Ziggythewiz said:


> Not much of a comparison. In audio you have hits of under a second, typically with well under 50% duty cycle. When an EV needs extra juice it will be for at least 5-10 seconds, at near 100% duty. The caps will be drained in the first second, with no time to recharge until approaching the next light.
> 
> For the same money you could have an A123 booster pack, that would provide actual power and some boost to range.


At 100% duty cycle you are correct. However who drives with their foot on the floor for 5-10 seconds? Well I suppose if you have a 5000lb vehicle with a 48V controller but for most who have a 500 or 1000A controller operating at 144V+ that's not the case. 

Personally I accelerate at no more than 15-25%. So 75-85% of that cycle the batteries are not discharging. It's during that off time the caps are able to recharge.


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## Kerensky (Jul 8, 2011)

.....and by placing the cap bank in series with the traction pack the capacitors are continuously charging from the batteries. The caps will in return reduce the momentary peak draw on the batts. It should have a "smoothing" effect and make the battery pack last longer. Arent lead batteries were designed for constant drain not pulse chopping ?
And besides at 100% duty cycle a Curtis doesn't pulse, thus removing the pukert effect we are trying to avoid. A capacitor bank placed inline will only be truly usefull during the first few seconds of acceleration when attempting to overcome stationary inertia. That is when the most extreme draw is placed on the traction pack, right ? So who cares if my cap bank is dead after 5 seconds I've already saved my $3k Trojan pack from the hardest work. It's not like the capacitor bank is gonna create a current restriction between the batts and the controller. 
I've picked up a 200vdc 3.5 farad cap bank to test my theory but I'm at least 3 -6 months till I can get my project to a place where I can perform said test due to massive repairs made necessary by the new jersey highschool autoshop class which originally made my truck. 
Has anyone in this conversation other than electric actually put a cap bank in their ev ? If so how did your ev behave with the caps installed? I think it's time for some "real world experience" as opposed to the theoretical discussion we've been engaging in.


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## ElectriCar (Jun 15, 2008)

A little confusion here. You can't put the caps in series with the pack. Series for example would be disconnecting one lead from the pack, inserting the cap bank between the two points you just disconnected. Caps don't allow continual DC current to flow. They must be connected across the pack leads, prefferably near the controller. Capicitors only allow AC currents to pass through them.


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## GizmoEV (Nov 28, 2009)

Kerensky said:


> .....and by placing the cap bank in series with the traction pack the capacitors are continuously charging from the batteries. The caps will in return reduce the momentary peak draw on the batts. It should have a "smoothing" effect and make the battery pack last longer. Arent lead batteries were designed for constant drain not pulse chopping ?
> And besides at 100% duty cycle a Curtis doesn't pulse, thus removing the pukert effect we are trying to avoid.


As for series caps see ElectriCar's response. And as far as Pukert effect, any discharge of any battery will display the Pukert effect. Lowering the current draw will lower the effect, not remove it.



> I've picked up a 200vdc 3.5 farad cap bank to test my theory but I'm at least 3 -6 months till I can get my project to a place where I can perform said test due to massive repairs made necessary by the new jersey highschool autoshop class which originally made my truck.
> Has anyone in this conversation other than electric actually put a cap bank in their ev ? If so how did your ev behave with the caps installed? I think it's time for some "real world experience" as opposed to the theoretical discussion we've been engaging in.


Then you need to check out http://www.metricmind.com/ac_honda/main2.htm specifically the Ultracaps section. The results weren't as great as hoped.


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## Ziggythewiz (May 16, 2010)

GizmoEV said:


> Then you need to check out http://www.metricmind.com/ac_honda/main2.htm specifically the Ultracaps section. The results weren't as great as hoped.


Where are the Ultracaps results at?


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## Kerensky (Jul 8, 2011)

GizmoEV said:


> As for series caps see ElectriCar's response. And as far as Pukert effect, any discharge of any battery will display the Pukert effect. Lowering the current draw will lower the effect, not remove it.


Yea .... Oops.... I usually only post at home and when I have time to read and check ma facts better. I spoke from my iPhone and made a fool of myself. Sorry 



GizmoEV said:


> Then you need to check out http://www.metricmind.com/ac_honda/main2.htm specifically the Ultracaps section. The results weren't as great as hoped.


 His cap bank is HUGE ! I thought something much smaller would do the job.


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## Ziggythewiz (May 16, 2010)

That's the main problem. You're spending nearly as much money, space, and weight as just getting a(nother?) lithium pack.


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## ElectriCar (Jun 15, 2008)

I'm just curious how much the caps would charge during the off periods. Don't know how you could calculate it but it would be very easy to see it with an o'scope. Fix the throttle, see the pack voltage display on the scope without the cap bank. Install it, repeat. Compare the cycle "off" voltage of the before and after. It should rise after the caps are in place.

Further use the 2nd channel of the scope to check across your amp meter shunt terminals at the same time. The voltage would indicate amps. A lower voltage on the shunt after adding the caps would confirm the caps are reducing your peukert effect due to the reduced battery current thereby extending your mileage. 

I have a cap bank, just no scope. Inquiring minds want to know...


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## bjfreeman (Dec 7, 2011)

Kerensky said:


> His cap bank is HUGE ! I thought something much smaller would do the job.


yes we are talking Farads not micro farads.
the Current Maxwell for 125 Volt 63 farad is about $10,000.
http://www.maxwell.com/products/ultracapacitors/docs/datasheet_bmod0063_1014696.pdf


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## bjfreeman (Dec 7, 2011)

ElectriCar said:


> I have a cap bank, just no scope. Inquiring minds want to know...


the Picoscope is neat. about $200-5,000, it works with a pc.


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## GizmoEV (Nov 28, 2009)

Ziggythewiz said:


> Where are the Ultracaps results at?


I'm trying to remember if I read it on his site or if I heard it from one of the OEVA members. I occasionally have attended the OEVA meetings in Portland, OR over the years and have spoken to Victor on various occasions. Sorry I just don't remember.


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## Ziggythewiz (May 16, 2010)

I guess sometimes we can be quick to publish our awesome ideas, especially the ones that pan out, but less positive results may be a little less urgent.


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## Kerensky (Jul 8, 2011)

Email request and link to this conversation sent.


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## GizmoEV (Nov 28, 2009)

Ziggythewiz said:


> I guess sometimes we can be quick to publish our awesome ideas, especially the ones that pan out, but less positive results may be a little less urgent.


And those less positive results are every bit if not more important!


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## Chad (Aug 1, 2008)

ElectriCar said:


> A little confusion here. . . .Caps don't allow continual DC current to flow. . . .


as a test, hook up your cap bank in series and step on the throttle, the amount of time the motor was under power is how long your caps will provide power to 100% discharge. Caps will only pass DC current until they have fully charged/discharged. (thats why they are used for simple timer circuits)

my 2 cents. . .

I have read through about 1/4 of this thread (pretty much all at the beginning) and I keep thinkiong about R/C boats - we build fast electrics and really punish LiPo batteries. We like to push them to the max, and use brushless DC motors that are current sucking hogs, but they put out the power too.

with respect to battery life, it is all about temperature, and C rating. First we decide what voltage a system we want to run, then decide how big a motor we want to stuff in the boat. Next we need to pick a controller (ESC) that can handle the current (and voltage) then, match a battery to supply the whole thing based on it's capacity and C rate. If a battery is only just enough, expect it to get hot, and fade away fast. If the C rating (discharge) is much higher than it needs to be, the pack will stay cooler, and hold voltage longer. ESC's all have caps on them, and an "upgrade" is to put bigger ones on. R/C (boat) speed junkies really punish batteries.

a 5ah 60C LiPo will put out 300 amps
a 10ah 30C LipPo will also put out 300 amps, but be twice the size.

In EV's the battery packs are so big, 100-200ah, that 1-3C is generally all you need to sufficiently supply the motor 70% of the time. Capacitors have a basic function, to "instantly" accept and give up a charge. I think the best they can do is smooth out small high frequincy changes in current draw. This is why they ARE effecive in large (car) stereos, but not likly for an EV.

That being said, the high charge and discharge capabilities of LiFePo4's make damage to the cells do to rapid charge or discharge unlikly. Just keep your temps in check.

As for Led Acid. . . they suck, what are you gonna do about it? They have a charge rate of about 0.4C

Maybe rather then trying to stick a capasitor bank in front of lead acid, you should try a LiPo bank with small LiFePo4's 

But maybe I am just crazy - wait I am, and thats why I am on a DIY Electric Car Forum


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## Kerensky (Jul 8, 2011)

results have arrived.. 











thanks to the owner of the crx for the data.... u rock !


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## Chad (Aug 1, 2008)

not trying to be a sceptic, the caps are definatly doing what they are designded to. But. . .


That is a huge capacitor 16.5F
Why is this test in very different conditions?

the first test without caps seems to be from a stop, and has greater acceleration/power output peakes
The second test seems to be from rolling and does not have as many or as long of power demands

I would like to see the graph include throttle input, or at least done through a similar drive. Where did the pic come from? Is there more info?


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## bjfreeman (Dec 7, 2011)

Chad said:


> not trying to be a sceptic, the caps are definatly doing what they are designded to. But. . .
> 
> 
> That is a huge capacitor 16.5F


http://www.diyelectriccar.com/forums/showpost.php?p=291104&postcount=96
ten seconds of of charge is about 260 F for about 300KW @ 125 volts(rough estimate)


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## ElectriCar (Jun 15, 2008)

Freeman, the thing is I'm not looking for caps to run the car for 10 seconds. I don't think it's clear what some of us are thinking and I'll explain. The whole purpose to me was to reduce the peak amp draw off the pack.

When you accelerate like normal, you don't give the controller 100% throttle. I probably only give it 15-25% throttle. If my understanding of PWM controllers is correct, 75-85% of the 10 second accel time the controller will be OFF. So during that time the caps are recharging.

Controllers turn the pack voltage on and off to the motor 8,000 times in a second or more. For explanation purposes lets say 1 second is considered one cycle of the controller which means in one second of time, the controller turns on for part of that second and the remainder of that second it's off. 

The controller doesn't deliver a percentage of the pack voltage to the motor depending on the throttle level of input, it applys full pack voltage to the motor but only for a fraction of a second. If you give the controller 10% throttle, during that one second the controller is on for only 10% of that second, the remaining 90% of that one second the controller is off. If you apply 50% throttle, the controller is on for 50% of one second and off the other 50% of the second. With a cap bank the caps recharge whenever the controller is off. 

So at 50% throttle, the controller is off half the time and on half the time. *My idea for the cap bank is this. If you are needing 200 amps from the pack for half a second* *with no caps, in a perfect system you will draw only 100 amps from the pack for the entire second as the caps will dump 100 amps along with the battery when the control comes on. 200 amps for half a second is the same as 100 amps for one second. 

*


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## Chad (Aug 1, 2008)

ElectriCar, you are on the right track, and this is how caps can smooth out the "pulsing" as it is. How ever, the pulsing of the PWM is so fast that it is more of a vibration then a pulse. Small caps could smooth this over very easily.

I think the pack damage is coming from the "on-off-on-off" of the throttle. Both from non-smooth driving to the force inputs on the vehicle (wind gusts, bumps, being cut off, etc.)

These larger on-off demands are what are hard on the battery pack. the goal is to smooth out current draw, think of it like this;

You have a large pool of water, and to empty it you have a few people with different sized buckets, some large some small. In order to have a steady flow of water coming out of the pool, you have it drain at a regulated, steady rate via a hose and valve into a large garbage can. The people then remove the water from the garbage can in varying amounts.

This way the pool (large battery) has a smooth steady release of water (watts) and does not get damaged by waves (power surge)

The garbage can (capacitors) is able to take the abuse of of the waves (power surge) and can even deliver the water (watts) faster.

The buckets are comparable to the demand for water (watts) being small (coasting) or large (accelerating, hills, etc)

The question remains, how big (Ah) is big enough? And is it cost effective?

There is no doubt it is effective. But is it too costly in weight and money? As well, if Lithium batteries have the ability to provide the power demands, is it necessary?


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## ElectriCar (Jun 15, 2008)

Someone with a scope will hopefully see this and do a test as I suggested. That will show the effect.


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## bjfreeman (Dec 7, 2011)

ElectriCar said:


> Freeman, the thing is I'm not looking for caps to run the car for 10 seconds. I don't think it's clear what some of us are thinking and I'll explain. The whole purpose to me was to reduce the peak amp draw off the pack.


I agree, however I think you bring up a good point about whether someone is talking about a street car or a racing car.
Also those that drive on all level ground and those like myself that drive on hills. you can not drive 5 miles in any direction and not encounter a hill, at least a block long.


> When you accelerate like normal, you don't give the controller 100% throttle. I probably only give it 15-25% throttle. If my understanding of PWM controllers is correct, 75-85% of the 10 second accel time the controller will be OFF. So during that time the caps are recharging.


for flat land driving I agree. As I mentioned above you press the throttle a lot more than if on flat land.
What your looking at is the change in the current demand when the PWM changes to provide higher frequency (AC) or more Voltage (DC).
During this time there is a average higher demand on the Batteries. This is where the Caps come in. There is no way with more demand that the average charge in Caps can recharge.


> Controllers turn the pack voltage on and off to the motor 8,000 times in a second or more. For explanation purposes lets say 1 second is considered one cycle of the controller which means in one second of time, the controller turns on for part of that second and the remainder of that second it's off.


It is not the constant PWM but the change in the PWM that causes more/or less demand on the batteries. 


> The controller doesn't deliver a percentage of the pack voltage to the motor depending on the throttle level of input, it applys full pack voltage to the motor but only for a fraction of a second.


Not all controllers work that way. an AC Motor the Voltage is applied when the PMW starts to have a Frequency. No frequency, No voltage.


> If you give the controller 10% throttle, during that one second the controller is on for only 10% of that second, the remaining 90% of that one second the controller is off. If you apply 50% throttle, the controller is on for 50% of one second and off the other 50% of the second. With a cap bank the caps recharge whenever the controller is off.
> 
> So at 50% throttle, the controller is off half the time and on half the time. *My idea for the cap bank is this. If you are needing 200 amps from the pack for half a second* *with no caps, in a perfect system you will draw only 100 amps from the pack for the entire second as the caps will dump 100 amps along with the battery when the control comes on. 200 amps for half a second is the same as 100 amps for one second.
> 
> *


In a perfect system you would not need Cap to fill in because the Batteries would have no internal resistance. and if you wired to reduce the inductance of the wiring, from the Batteries to the controller.
So the only other use of the caps would be to in a regen system where you reduce the number of charge and discharge, in a hilly environment that there are many start stops.

so I agree in environment that is basically flat you have a different requirement. but I did not see where the thread was about flat land driving or DC motors only.

BTW that graph is from a AC controller and MetricMind site is about AC system.


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## Ziggythewiz (May 16, 2010)

ElectriCar said:


> Someone with a scope will hopefully see this and do a test as I suggested. That will show the effect.


And not just a couple tests, but lots!

If the full bank includes parallel strings, you could test with one fewer string each time to see the result at each capacity level.

It's undisputable that infinite capacitance will have a great effect, while 0 capacitance will have no effect. The question is how far up the capacity ($$$) chain do you have to go to get enough of an effect to be worth the effort. And then what would be the effect of that much $$$ in high C lithium.


Course, I prefer to drive with the throttle full on all the time, so...?


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## ElectriCar (Jun 15, 2008)

bjfreeman said:


> I agree, however I think you bring up a good point about whether someone is talking about a street car or a racing car.
> Also those that drive on all level ground and those like myself that drive on hills. you can not drive 5 miles in any direction and not encounter a hill, at least a block long.
> for flat land driving I agree. As I mentioned above you press the throttle a lot more than if on flat land.
> What your looking at is the change in the current demand when the PWM changes to provide higher frequency (AC) or more Voltage (DC).
> ...


I live at the base of the Appalachian mountains so there's lots of hills here but I still never push the throttle much. My truck isn't heavy like it was with lead plus with a 165V pack, it doesn't strain at all to acellerate nor climb hills. That said, I honestly don't think I ever give it more than 25% throttle unless I'm in a hurry. 

I'm pretty convinced it will lower the peak amp draw thus peukert effect, depending on the capacity of the bank. Again, someone with a scope can answer a lot of questions if they do it right.


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## mizlplix (May 1, 2011)

Excuse me if this was previously discussed, But...

Does not the controller/inverter perform the voltage and current spike regulation when on Regen (in an AC system)?


I guess this requires a recording monitor on my pack to answer. 

Miz


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## major (Apr 4, 2008)

mizlplix said:


> Does not the controller/inverter perform the voltage and current spike regulation when on Regen (in an AC system)?


Always has for me, both with AC and DC. 

I am considering a "spike" to be a fraction of a second, maybe milli or micro seconds. I mean during a hard regen you will see a high peak current usually triangular in shape and lasting for seconds. Battery voltage is limited by the controller by automatically reducing braking torque. This requires the ability to blend regen torque with the service brake friction torque. Works nicely when controller is in a torque control mode.

You can also set controllers to limit the magnitude of the peak regen current which, like the regen voltage limit, will reduce the regen torque to accomplish that.

That does let kinetic energy go to waste in the friction brakes. You have to decide for yourself if extra energy storage means are of value to be able to capture those peaks.


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