Charging voltage versus battery voltage

moatasim23

Why during charging a battery the terminal Potential Difference becomes greater than the EMF?

Drakkith

I believe it has to in order to reverse the chemical reaction that produces the EMF in the first place.

moatasim23

Well to be more specified.I wanted to ask HOW..

Drakkith

How what? Please be specific when posting questions, or you will confuse people, and more importantly you will confuse me!

moatasim23

Sorry for inconvenience...I wanted to ask:
How the potential difference becomes greater than EMF?

Drakkith

I think the charger is simply set up to apply a greater voltage than the battery produces.

Bobbywhy

There are many types of batteries. Charging each type uses a different method. Read up on the types batteries and charging methods at:
http://batteryuniversity.com/learn/a...d_acid_battery

Once you select the type of battery you are asking about you may discover the detailed voltage/current necessary.

faizanejaz

Hi moatasim:)...IN the start you can't roughly say t.p.d will be greater than emf during charging.when u begin charging, the terminal p.d simply increases coz of the incoming positive charges from other source.charge accumulation leads to greater increase in potential difference(as Q is directly related to V). when charge accumulation goes on increasing then incoming positive charge from external source towards negative plate of cell(under charge) will be attracted towards it more strongly and when it reaches negative plate then it is pushed towards positive plate due to increasingly potential difference.as emf is the push of positive charge from negative to positive terminal,then with da increase in time this push becomes more and more ease and less emf though will be due to a p.d cloud.NOW,as you know emf exists even theres no current in circuit and p.d dont exist if theres no current.In start when charging begins,p.d goes on increasing but still be less than emf already present.SO in begining and till to a particular time t.p.d will be less than emf. MATHEMATICALLY FOR DISCHARGING
t.p.d = E - Ir
V= E - Ir ( E is the electromotive force)
or E=V + Ir ( V is t.p.d)
FOR CHARGING
v = E + Ir (as for charging respective electrodes are alike)
E= V-Ir SO you can clearly see emf decreses by a function of time Q/t.( Ir=Q/t*r) with the passage of time E goes on decreasing and consequently V goes on increasing..I hope you will get it:)

faizanejaz

Hi moatasim:)...IN the start you can't roughly say t.p.d will be greater than emf during charging.when u begin charging, the terminal p.d simply increases coz of the incoming positive charges from other source.charge accumulation leads to greater increase in potential difference(as Q is directly related to V). when charge accumulation goes on increasing then incoming positive charge from external source towards negative plate of cell(under charge) will be attracted towards it more strongly and when it reaches negative plate then it is pushed towards positive plate due to increasingly potential difference.as emf is the push of positive charge from negative to positive terminal,then with da increase in time this push becomes more and more ease and less emf though will be due to a p.d cloud.NOW,as you know emf exists even theres no current in circuit and p.d dont exist if theres no current.In start when charging begins,p.d goes on increasing but still be less than emf already present.SO in begining and till to a particular time t.p.d will be less than emf. MATHEMATICALLY FOR DISCHARGING
t.p.d = E - Ir
V= E - Ir ( E is the electromotive force)
or E=V + Ir ( V is t.p.d)
FOR CHARGING
v = E + Ir (as for charging respective electrodes are alike)
E= V-Ir SO you can clearly see emf decreses by a function of time Q/t.( Ir=Q/t*r) with the passage of time E goes on decreasing and consequently V goes on increasing..I hope you will get it:)

NascentOxygen

The model for most batteries is of an "ideal" voltage source in series with a resistor. It's that resistor that you need to consider.

* ideal means whatever you need it to, here.

Naty1

Batteries produce power via chemical reactions...charging reverses those...the higher the charge voltage the higher the current flow and the faster the reverse chemical reaction.

BUT higher currents [via higher charge voltages] mean more heat and that can ruin batteries...so charge voltages must be limited....

An AGM battery can be charged at it full rated amp hour capacity because it has very low internal resistance, so not much heat is generated during charging, not so for a traditional wet cell lead acid battery which is limited to about 25%. These mean for a battery rated at, say, 100 amp hours, you can safely charge an AGM at 100 amps but a conventional battery at only about 25 amps. In a conventional wet cell lead acid battery about a quarter of the charge power is lost thru heating, only 1 or 2% is lost to heat in an AGM type battery. .