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Capacitor vs. battery, elec. engineer type of ? #3071098
08/24/22 01:51 PM
08/24/22 01:51 PM
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roadrunninMark Offline OP
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This is a general question about using capacitors vs. batteries (in an EV, mainly) and is just for my curiosity to learn. Since Dodge is coming out with the Daytona Banshee and batteries are not really recyclable (at this time). They are also expense, heavy, use rare minerals, etc., etc., I was thinking why not the use of capacitors to store electrical energy? I briefly did some searching on what a capacitor is, looks like it takes DC energy and stores it as AC energy(?). It seems these are less complex and costly than a battery. I assume a lot cheaper and easier to make and sound like they could be more recyclable too? So why not use a bunch of capacitors in place of a large number of batteries? Do they not store nearly as much energy as a battery, even if using a high voltage unit? Would they charge slower or faster and would they last longer? Are they not as safe as a battery? I can understand not wanting to store a lot of AC for safety sake, so I am assuming that could be a good reason.

Last edited by roadrunninMark; 08/24/22 01:54 PM.
Re: Capacitor vs. battery, elec. engineer type of ? [Re: roadrunninMark] #3071130
08/24/22 03:32 PM
08/24/22 03:32 PM
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Capacitors store DC not AC.

Energy density is the issue. Caps are great for short bursts of high energy, not long term supply. Batteries are great for long term supply, not as great as caps for short term high energy bursts.

Recycleability is moot as far as either goes. Can they be? Yes, not cost effective right now.

Re: Capacitor vs. battery, elec. engineer type of ? [Re: roadrunninMark] #3071364
08/25/22 12:01 PM
08/25/22 12:01 PM
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Capacitors cannot make electricity; batteries do and store it also up work

Last edited by Cab_Burge; 08/25/22 12:03 PM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Capacitor vs. battery, elec. engineer type of ? [Re: Cab_Burge] #3073741
09/03/22 03:52 AM
09/03/22 03:52 AM
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CokeBottleKid Offline
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Originally Posted by Cab_Burge
Capacitors cannot make electricity; batteries do and store it also up work


No, they're both storage devices Cab

Re: Capacitor vs. battery, elec. engineer type of ? [Re: CokeBottleKid] #3073851
09/03/22 12:01 PM
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Ground, discharge, a capacitor and wait for it to make itself charge up again whistling scope
Do you know how long that will take grin You will be dead a long time before that will happen shruggy
Discharge a new battery and wait for it to make more electricity and see how long that will take scope
Batteries make and store electricity grin

Last edited by Cab_Burge; 09/03/22 12:03 PM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Capacitor vs. battery, elec. engineer type of ? [Re: Cab_Burge] #3073898
09/03/22 01:32 PM
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Originally Posted by Cab_Burge
Ground, discharge, a capacitor and wait for it to make itself charge up again whistling scope
Do you know how long that will take grin You will be dead a long time before that will happen shruggy
Discharge a new battery and wait for it to make more electricity and see how long that will take scope
Batteries make and store electricity grin


Guess I can go out and toss my alternator then eyes

You really need to stop.

Batteries do not make electricity, they store it. They can handle a long term drain a lot better than a cap but they are nothing more than storage devices. They do go flat if you leave them hooked up long enough.

Re: Capacitor vs. battery, elec. engineer type of ? [Re: Sniper] #3073901
09/03/22 01:38 PM
09/03/22 01:38 PM
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Like they say, Ignorance is Bliss!

Re: Capacitor vs. battery, elec. engineer type of ? [Re: Sniper] #3074016
09/03/22 08:00 PM
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Originally Posted by Sniper
Originally Posted by Cab_Burge
Ground, discharge, a capacitor and wait for it to make itself charge up again whistling scope
Do you know how long that will take grin You will be dead a long time before that will happen shruggy
Discharge a new battery and wait for it to make more electricity and see how long that will take scope
Batteries make and store electricity grin


Guess I can go out and toss my alternator then eyes

You really need to stop.

Batteries do not make electricity, They do go flat if you leave them hooked up long enough.

It is evident you have never filled up a new dry battery with new acid, HUH shruggy
Batteries make electricity through chemical reactions when they are built, DUH.
How long will a dry cell battery live stored on your shelf with nothing hooked up to them? 1 year? 5years? 10 years probably: up:
Alternatosr do not, cannot, make electricity unless they have a voltage feed from a battery or some other source to feed them: scope:
Generator do make electricity. I've rode in more than one old car that had a completely dead battery that you could push start and drive with a generator, not possible with any newer car with an alternator twocents scope
Do your homework on theory before making any more false statements please, especially on here devil stirthepot hammer grin


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Capacitor vs. battery, elec. engineer type of ? [Re: Cab_Burge] #3074187
09/04/22 11:46 AM
09/04/22 11:46 AM
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DrCharles Offline
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Step back and take a deep breath, boys... you're both right in places. smile

Capacitors store energy in the form of electrical charge, but batteries store energy in chemical reactions. Putting a load across a capacitor causes a flow of electrons (current). The chemical reaction during battery discharge liberates electrons (also collected as current flow).

Keep in mind that some of the previous argument ignored that there are two kinds of batteries. A primary battery is used once and discarded (carbon-zinc which has been mostly replaced by alkaline, for example). A secondary battery is the kind we put in our Mopars, and is recharged with electrical energy that is stored as chemical energy...

A lead-acid battery is indeed charged when the electrolyte is added, because the chemicals have been placed in the high-energy state at the factory! Used to be called "dry-charged". The positive plate is lead oxide, and the negative plate is lead. As it discharges, the plates bothturn into lead sulfate, and electrical charge is liberated from the negative plate. That's why the electrolyte is sulfuric acid - you need that sulfate ion.
See, for example, https://www.pveducation.org/pvcdrom/batteries/lead-acid-batteries for more than you probably wanted to know whistling

Once the lead-acid battery has been discharged, you cannot get more energy out of it except by forcing current into it and reversing the chemical reactions (back to lead and lead oxide). Yes, it will recover a bit if it hasn't been 100% totally killed flat dead. Let it sit discharged long enough and the lead sulfate crystals grow to a point where they can't be easily removed, if at all. Then you recycle it.

There is even more to it, of course, but that should be plenty for now work
Hope that helped.
-Charles
(EE since 1981).







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