# super capacitors helping the batteries



## otp57 (Feb 7, 2012)

Have anyone use super capacitor with lead battires to help with the surge of current when a motor starts up.
I am thinking this would help the batteries.
I would like to see photos of setup THANKS


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## major (Apr 4, 2008)

otp57 said:


> Have anyone use super capacitor with lead battires to help with the surge of current when a motor starts up.
> I am thinking this would help the batteries.
> I would like to see photos of setup THANKS


Hi otp,

I have experience with ultracapacitors and have used them in conjunction with batteries. First realize that when a motor "starts up" it does command a high current but not from the battery. Battery current on a WOT launch is triangular with a peak at base speed. Peak battery current therefore occurs at base RPM on the motor and can happen at various times during the driving cycle.

These battery current peaks can be lowered by using an alternate energy storage system such as ultracapacitors. This requires a control system which can range from a simple parallel connection of the cap and battery to a buck/boost converter which is in effect about the complexity of an additional motor controller. The more sophisticated the control the better the utilization of the capacitor (meaning a smaller one can be used).

In a nutshell, for the money spent and added mass to the vehicle, you are almost certainly better off devoting the money and mass to better or more battery. And unless you have a propulsion system capable of regeneration, the capacitor recharges from the battery probably at inopportune times.

Regards,

major

ps....here is a thread which includes a photo. http://www.diyelectriccar.com/forums/showthread.php?t=25994&highlight=candy


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## otp57 (Feb 7, 2012)

major said:


> Hi otp,
> 
> I have experience with ultracapacitors and have used them in conjunction with batteries. First realize that when a motor "starts up" it does command a high current but not from the battery. Battery current on a WOT launch is triangular with a peak at base speed. Peak battery current therefore occurs at base RPM on the motor and can happen at various times during the driving cycle.
> 
> ...


I am going to use Electrolytic capacitors I have about .3f at 250v just as an example.


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## major (Apr 4, 2008)

otp57 said:


> I am going to use Electrolytic capacitors I have about .3f at 250v just as an example.


If you're really good, that might get you 10 hp for one second. Think that's worth it?


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## otp57 (Feb 7, 2012)

major said:


> If you're really good, that might get you 10 hp for one second. Think that's worth it?


10hp for 1sec how did you get the answer of 10hp and 1 sec
I would like to know how to do that thanks


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## major (Apr 4, 2008)

otp57 said:


> 10hp for 1sec how did you get the answer of 10hp and 1 sec
> I would like to know how to do that thanks


A lot of theory discussed in that linked thread. Stored energy: E = ½CV²


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## otp57 (Feb 7, 2012)

major said:


> A lot of theory discussed in that linked thread. Stored energy: E = ½CV²


 Ok thanks for the info.


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## kens0105 (Jul 30, 2012)

Is the super capacitor here the same as that of the i-ELOOP system? I just recently read it from an article of Mazda having an i-ELOOP system that have a super capacitor which is similar to a battery, in that it stores electricity, except it doesn’t retain it for long.


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## otp57 (Feb 7, 2012)

kens0105 said:


> Is the super capacitor here the same as that of the i-ELOOP system? I just recently read it from an article of Mazda having an i-ELOOP system that have a super capacitor which is similar to a battery, in that it stores electricity, except it doesn’t retain it for long.


 i will look into that thanks


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## kens0105 (Jul 30, 2012)

that will be great. thanks


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## otp57 (Feb 7, 2012)

kens0105 said:


> that will be great. thanks


 * Super capacitors helping the batteries* will help a small EV


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## major (Apr 4, 2008)

kens0105 said:


> Is the super capacitor here the same as that of the i-ELOOP system?


http://www.mazda.com/publicity/release/2011/201111/111125a.html



otp57 said:


> i will look into that thanks





otp57 said:


> * Super capacitors helping the batteries* will help a small EV


O.K. So how did you reach that conclusion  The original premise you laid out was: 


otp57 said:


> Have anyone use super capacitor with lead battires to help with the surge of current when a motor starts up.


 This iELOOP system is for an internal combustion engine car which has no electric drive motor and no propulsion battery. It is simply a wimpy KERS system using a capacitor to store a very small charge delivered by the alternator during deceleration and then used for auxiliary electrical loads. At 24V such a system could not effectively recover but a small percentage of the vehicles kinetic energy without huge current which I am sure the alternator would not support.

The iELOOP system has nothing to do with EVs. Or helping batteries.


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## otp57 (Feb 7, 2012)

major said:


> http://www.mazda.com/publicity/release/2011/201111/111125a.html
> 
> 
> 
> ...


Thinks for the info.


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## PStechPaul (May 1, 2012)

A quick way to estimate how long a capacitor will provide a certain anount of power is to use the RC time constant. So if you have a 100 volt system and 10HP it's 13000W or 130A and 0.77 ohms. So 0.7F is 0.54 sec. You might not even get that much because the TC is to 37% of peak voltage which is just 37V. The maximum sag of lead-acid batteries is probably to 50% and more reasonably to 70%. So you might only get 1/2 TC. 

One way that might work better is to use a DC-DC converter or switching supply that can handle the full capacitor voltage at maximum and work down to about 33%, like a universal supply that works on 85-264 VAC. It could give your battery pack a boost of, say, 24 VDC on top of the 100V nominal. But it would have to be capable of full load current so that was just a brain fart. 

Adding a small LiPo pack may be better, especially if it can handle 30-40C. There was another thread on that...


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## otp57 (Feb 7, 2012)

PStechPaul said:


> A quick way to estimate how long a capacitor will provide a certain anount of power is to use the RC time constant. So if you have a 100 volt system and 10HP it's 13000W or 130A and 0.77 ohms. So 0.7F is 0.54 sec. You might not even get that much because the TC is to 37% of peak voltage which is just 37V. The maximum sag of lead-acid batteries is probably to 50% and more reasonably to 70%. So you might only get 1/2 TC.
> 
> One way that might work better is to use a DC-DC converter or switching supply that can handle the full capacitor voltage at maximum and work down to about 33%, like a universal supply that works on 85-264 VAC. It could give your battery pack a boost of, say, 24 VDC on top of the 100V nominal. But it would have to be capable of full load current so that was just a brain fart.
> 
> Adding a small LiPo pack may be better, especially if it can handle 30-40C. There was another thread on that...


Thanks for your info.


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## mizlplix (May 1, 2011)

I am using a small pack of 10AH Headway cells in parallel with my DC/DC converter to be my Aux power supply.

I am running my lights, 3 air blowers, 3 liquid pumps and a 1/3HP 16" Spal fan on my radiator.

The headlights would flicker when idling and the pumps cut in and out.

I installed 2- 3000MFD/300VDC caps in parallel. It stopped the flickering. The cap-self discharge rate does not seem to be a problem as yet. It seems to be small.

But my alternative is to place a contactor between the caps and the cells to stop the discharge. But even that has a complication, a current in-rush every time I turned on the key. That calls for a precharge resistor, that requires a delay relay to operate the contactor to provide a precharge jnterval....Sheesh....

So, for now, I live with the small parasite.

Miz


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## otp57 (Feb 7, 2012)

major said:


> http://www.mazda.com/publicity/release/2011/201111/111125a.html
> 
> 
> 
> ...


I found this information and that is how I reach that conclusion !
http://spectrum.ieee.org/green-tech/advanced-cars/a-batterycapacitor-hybridfor-hybrids


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## PStechPaul (May 1, 2012)

Note that the article is from 2008 and refers to using lead-acid or NiMH batteries in a hybrid. It mentions Lithium batteries as "experimental". I think there is no question that ultracapacitors may help batteries with high ESR for short bursts of power, as well as for regeneration, but with advanced Lithium batteries the old limits to discharge and charge have been largely eliminated.


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