Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

can a capacitor put charge into a battery?
can a capacitor put charge into a battery?
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 20th August 2008, 06:05 AM   #1
Clipped is offline Clipped  Thailand
diyAudio Member
Join Date: Mar 2005
Location: home
Send a message via MSN to Clipped
Default can a capacitor put charge into a battery?

if you have a very large bank of capacitors, fully charged at around 24 volts...

and connect it to a battery which is discharged to around 11 volts
can the charge from the caps bring the batteries charge back up?
to the nominal 12.6-12.8 volts?

this question doesnt have anything to do with caps in a stereo system...or the charging system in a car.

just a simpe transfer of energy question.

  Reply With Quote
Old 20th August 2008, 06:12 AM   #2
jan.didden is offline jan.didden  Europe
diyAudio Member
jan.didden's Avatar
Join Date: May 2002
Location: The great city of Turnhout, BE
Yes of course, there will be a current from the caps into the battery. But the total amount of energy transferred will not be very great. Very quickly, the capacitors will discharge to the same voltage as the battery and then the current stops. So, the battery does receive some charge but it is only a fraction of what batteries normally need, so as a battery charger this is not useable.

Jan Didden
Cable: a potential source of trouble interconnecting two other potential sources of trouble - Erik Margan
Linear Audio pubs and articles . The SilentSwitcher now at diyaudio store SilentSwitcher. Keeping in touch with SY.
  Reply With Quote
Old 25th August 2008, 03:10 AM   #3
Clipped is offline Clipped  Thailand
diyAudio Member
Join Date: Mar 2005
Location: home
Send a message via MSN to Clipped
thanks Jan, sorry for my slow reply...about how much current is stored ina 1 farad capacitor?

and if there was a 100 farad bank of capacitors, about how much current could be transferred to a standard SLA battery?

  Reply With Quote
Old 25th August 2008, 03:43 AM   #4
Eva is offline Eva  Spain
diyAudio Member
Eva's Avatar
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
An electronic circuit is required for efficient transfer of energy from a capacitor to a battery. Direct connection results in a theoretical maximum 50% efficiency and destructive peak currents.

The problem has to be analyzed in terms of energy, not in terms of current.

A 1F capacitor charged to 24V stores:

E = .5*C*V^2 = 288 Joules

The energy delivered to a battery while charging is:

E = I*V*T
288 = I*13.8*T
I*T = 288/13.8 = 20.87 amperes second

Or 2.09 A during 10 seconds, which translates into:

2.09*10/3600 = 0.0058 amperes hour (Ah)

Note that not all the energy delivered into the battery is actually stored, there are losses in the battery and in the transfer circuit (that must be a switching converter to be efficient).

Thus a 100F capacitor bank charged to 24V can theoretically deliver 0.58Ah to a 12V battery (more likely 0.52Ah after 10% losses are accounted for).

In general, the advantage of capacitors over batteries is very low AC impedance at the expense of low energy storage density, while the advantage of batteries over capacitors is high energy storage density at the expense of high and non linear (hysteretic) AC impedance.

In other words, a battery with an electronic transfer circuit becomes a much more convenient way to transfer energy to another battery.
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote


can a capacitor put charge into a battery?Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
how do i charge a capacitor? Infinity_Addict Car Audio 18 30th August 2010 08:26 AM
multi cell battery charge limit circuit ideas sss Power Supplies 29 20th August 2009 08:53 AM
Charge controller for 12V battery and wind to fuel inverter jacquesl Power Supplies 0 20th January 2007 06:34 AM
What voltage must supply to charge a 1.2 battery? lagoausente Power Supplies 20 30th November 2006 05:58 PM

New To Site? Need Help?

All times are GMT. The time now is 10:22 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio