# Can deep cycle batteries and ultracapacitors play nice together?



## bigwilly312 (Apr 10, 2008)

Ok I've been on here with crazy ideas before and have learned a lot but still love to think outside of the box. So, with that being said, can ultracapacitors be put in series with deep cycle batteries to increase the voltage output for at least a temporary power boost?

The vision is for a small lightweight reverse trike that can climb up to 60 mph. I have four 12V blue top Optimas and need somewhere around 60V to 72V. The weight and cost of these batteries is ridiculous so adding two more just seems like a bad idea. Like I said before I think outside of the box so I want to implement a permanent magnet generator tied to a flywheel and use pedal power to help charge the batteries and get some exercise at the same time. I have a 12 amp generator but might spring for a 30 amp generator if that would solve the riddle.

Is this possible? Could the pedal powered windmill generator be used to keep a charge in the ultracapacitors and thusly adding to my overall voltage output?


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## Karter2 (Nov 17, 2011)

Generally, for drive power , ultra capacitors are a waste of money, space, and weight. .
The controls required to integrate them into a battery/drive system are complex and the results disappointing. Use the money and space for extra batteries.
...you might consider a small LiPo pack instead
On board generator ??... Again, not generally a successful plan, the efficiency losses alone dictate you are better off just adding pedal power mechanically.
You do realise that a 12amp, 48 volt, generator will demand more power than you can produce for anything more than a few seconds ?
Even at 12 volts, it is beyond most human output for continuous operation.


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## arklan (Dec 10, 2012)

average human adults can continuously output between 100-200 watts
super fit adults like in the tour de france can do 300 watts continuously
there was a guy who pedalled a plane with a 90metre wing span accross the english channel and he did nearly 400 watts continuously, it nearly killed him
assuming you do 100 watts continuously, at 12v thats about 8amps
theres a motorbike guy on here who has pedals to help with speed and acceleration


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## PZigouras (Jun 5, 2010)

bigwilly312 said:


> can ultracapacitors be put in series with deep cycle batteries to increase the voltage output for at least a temporary power boost?
> 
> ?


 I think you mean in parallel, not series. I tried this on a motorcycle, in hopes of reducing the peak demand on the Pb batteries (hence, in theory, getting to use more of the available amp-hours in spite of the high discharge rate).

Well, it didn't work, mostly because the supercaps were too small. I had 6 in series (3500 F each), but that only came out to be about 8 W/hr total, if I remember correctly. Not a lot of power, and it was used up almost immediately on acceleration... which still put very high demand on the Pb's. 

I did not try it with a bigger cap bank, simply because I had no more room on the bike, and the super caps (or any other cap for that matter) were very large, and somewhat heavy.

So, I went with lithium instead. Then, all of a sudden, the discharge rate didn't affect cell capacity any more!


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## bigmotherwhale (Apr 15, 2011)

If you do put them in series with your batteries make sure you protect them from reverse voltage with a diode.

you probably could get a very short burst of energy out like this if you can find a way of charging them and your motor can deal with having its voltage doubled which most dc motors can for short periods and your controller can deal with the voltage and current surge. or are you using an ac controller?
i would use regenerative braking to feed them this is what they are best suited to and used for in trains, 
your system will probably get quite complicated quite quickly but it would be a fun project

using super capacitors in parallel is a total waste of time and capacitors this will achieve nothing that a dc link capacitor isnt already doing, albeit probably marginally better. capacitors can be used in their full range down to 0volts unlike batteries which is why they are usually coupled with some sort of bi directional boost controller so the energy can be put in rapidly and taken out slowly to charge batteries or used directly for propulsion.

good luck with your project, i have always wanted an excuse to buy an ultra capacitor module, there was one on ebay for a bargain price a little while back but i couldn't justify bidding on it before i had even made my car maybee in the future i might have a play with one.


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## Sunking (Aug 10, 2009)

It is a net loss in energy. There energy density is so low wh/Kg the added weight of the caps and equipment will take more energy to move them than they can store. 

In other words you spend your money, get nothing in return, lower vehicle efficiency, and more dead weight to carry around. .


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## bigwilly312 (Apr 10, 2008)

Thanks for your advice guys and thanks for your support bigmotherwhale. I've had this idea for years and years and gave up on it for a long while. Then I discovered the possibilities of a flywheel. I would highly recommend doing research on its infinite uses. This should make it much easier to get this generator turning at a fairly high rate of speed along with some wind power assistance (yes I said the crazy words wind power). 
Yes I want to maybe put some turbine blades on this puppy and channel just the right amount of wind in just the right area to flow through and also help keep me and my batteries cool. This is a windmill generator after all. I know the theories of wind resistance offsetting any gains but I think pedaling and flywheel and letting wind channel through working together has to quite possibly work great in theory. 
Ambitious as this goal is it has become my life long dream and I want to see it through. The problem is I just get completely lost when thinking of putting the electric drive system together. In a perfect world I would like to mostly bypass the need for batteries all together with the perfect generator. So working backwards from there, what is humanly possible from my fellow outside of the box thinkers? 
Please look up flywheel tech before judging me to harshly though is all I ask.


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## bigmotherwhale (Apr 15, 2011)

while this might be true in some applications, it is used in trains where weight isnt much of an issue. 

there is research going on into using them in cars - thats all you need to know.

ignore the naysayers and have a play with what you have got i say.

No one got anywhere by listening to anyone about what isn't possible. 

"Scientists at the Argonne National Laboratory have demonstrated that an integrated system combining batteries with ultracapacitors dramatically improve braking energy recuperation efficiency and eliminate the need for battery over-sizing, reducing the weight and cost of the entire system."

someone with more funding agrees


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## bigwilly312 (Apr 10, 2008)

bigmotherwhale said:


> while this might be true in some applications, it is used in trains where weight isnt much of an issue.
> 
> there is research going on into using them in cars - thats all you need to know.
> 
> ...


 Thanks man. I'm a little confused about the comments about the weight of supercapacitors or ultracapacitors. the ones I've seen weigh way less than any lead acid battery for sure. Much less any deep cycle battery out there.


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## Sunking (Aug 10, 2009)

bigwilly312 said:


> Thanks man. I'm a little confused about the comments about the weight of supercapacitors or ultracapacitors. the ones I've seen weigh way less than any lead acid battery for sure. Much less any deep cycle battery out there.


It has to do with Energy Density and Specific Energy Density of the storage medium or fuel. 

Energy Density is a given amount of energy for a specified volume of space. Expressed as Watt-Hours/Liter or wh/l 

Specific Energy Density is a give amount of energy specified for a measure of weight. Expressed as Watt-Hours/Kilogram of wh/Kg

Lithium batteries are on top of the density in the battery world. Depending on which chemistry we are talking about _Energy Density_ *250 - 650 wh/l* and _Specific Energy Density_ of *80 to 275 wh/Kg*

Lead acid batteries not so great at 60 to 110 wh/l and 35 to 45 wh/Kg.

Super capacitors are pathetic. *5-8 wh/l* and *.5 - 5 wh/Kg*

That means a Super capacitor would have to be 90 times larger in volume, and 100 times heavier than a lithium battery for a given amount of energy. Or it means Super Capacitors would have to be 20 times larger in volume and 20 times heavier than lead-acid batteries. Take your pick

What they can be used for is regen braking to act as a buffer to slow down the charge to the batteries during braking. 

As someone stated; put some bike pedals on the EV so you can pedal to make electricity. It would be both more cost effective and generate more power.


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## bigwilly312 (Apr 10, 2008)

Okay thanks SunKing. So supercapacitors are a bad idea. The problem is I'm stuck with this big purchase of deep cycle batteries that will top me out at 48v to 52v max. I would love nothing more than to sell them and start fresh with some lithium. Have you ever heard of saltwater batteries? With the right size anodes and diodes and wiring could they ever achieve enough amperage? Crazy question I know. But you never know unless you ask.


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## Karter2 (Nov 17, 2011)

> .....What they can be used for is regen braking to act as a buffer to slow down the charge to the batteries during braking.


 Yes...but unfortunately lightweight EVs produce very little regen power, certainly not enough to need serious buffering.

If you are serious about having an efficient power generating system to add power, remember the most efficient portable generator available is the human body !
Anything you put between it and the drive wheel ( alternator, flywheel, or even just a chain and sprockets !). is just going to waste energy and reduce efficiency. 
The biggest improvement to your system efficiency that you could make, would be to replace those lead batteries with a much lighter lithium pack.
It will eliminate your voltage issues, improve the performance and range, as well as saving you money in the longer term !


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## bigwilly312 (Apr 10, 2008)

Okay one more question: Given the advice I have received I am looking at a 72V 40AH LiFePo4 Lithium Ion Battery and a 5000W motorcycle hub motor that tops out at 96V and would go up to 77 mph. Now ignoring my generator dreams, could this be connected to 2 of my Optima batteries in a way to where they would only be in a connected series when I flip a switch I would call overdrive? Otherwise just the 72V would be in use for the motor and the two deep cycle batteries would run accessories and possibly an invertor for random purposes. So the big question is there such a connection that can safely and easily be switched on or off? Or have I delved into a subject for another forum?


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## Karter2 (Nov 17, 2011)

It would not be impossible to switch in extra batteries ( but tricky, with several issues to consider), however, finding a motor controller that would be happy working with such a voltage range, may not be so simple.


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## bigwilly312 (Apr 10, 2008)

Ok I've been doing some more studying and hope to continue this discussion just a little further. So I'm thinking my original idea of going with an ETEK style brushed motor is the best idea to simplify things and avoid any motor controller issues. Now I just need to come up with the best utilization of the pedal power concept.
So what's possible? The obvious answer is get some lithium and go baby go. But I have one more out of the box question before I just fall in line and do whatever everyone else is doing: What if I took one or two of my heavy duty Opimas and put it in series with a high output pma generator? So battery then pedal powered generator then brushed motor with a blocking diode and/or a voltage regulator before the motor. My obvious thought is that the battery would just turn the generator into more of a motor than a generator. But I implore to any experts for one more bit of patient knowledge and advice.

Thanks


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## bigwilly312 (Apr 10, 2008)

I have either reached the end of your patience or just nobody is seeing this question. I think its an interesting question of physics and energy dynamics colliding.


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## karmann eclectric (Mar 26, 2008)

Perhaps due to the inconsistent logic in your questions. You talk about simplification, and then want to add Rube Goldberg inefficiencies. Build a simple single-motor EV, possibly with a direct link to pedal power, and then there will be time to play and learn.


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