DC voltage & current booster

[johny_ulau]

hi all,

anyone know how to boost dc current from 6V to 12V with current limit is 25A..?

 

[xaccto]

your question does not make alot of sense.
You cannot boost both the voltage and current.

For example

If your 6V supply is capable of delivering 25AMPS - that is 150 Watts
Power = Volts X Current

if you boost the said voltage to 12V, assuming 100% efficiency! the current available will only be 12.5AMPS.
In practice it is possible to get a voltage converter of ~95% efficient at a specified load,$$$, though more common efficiency would be 50-60% for less $

search "DCDC converters" for more information


Perhaps you should explain what your trying to do?

 

[johny_ulau]

tQ for ur ans..

let me explain it.

i am try to use dc motor to charge the car battery 12V.
when the motor rotates, its supply 6V & 1AMPS..
so is it possible to step-up the voltage and current?

 

[karesz]

Hi Johny,
As Xaccto wrote, you can boost voltage or current tto, but not at same time becouse you can not produce through boosting more energie!
Typical DC/DC converter has an efficiency of ~70-80%, means if you double the voltage _your corrent cant more as 50%multiplyed with 0.75 (efficiency) the 1A (at6V),also your 12 V current wiil be maximum 0.35-0.4A!!
K.

 

[johny_ulau]

tQ for answer..

so does it's mean that if i gain voltage, the current will step-down?

but if i step-up only the current, does it will step-down the voltage?

 

[karesz]

Exactly, tha the "product" UxI=constant! (& of course minus efficiency), also power/=(UxI)xη ...
η=0.7--0.9 (in best cases).
K.

 

[johny_ulau]

tQ 4 ans,

but what is "U" mean for?

 

[karesz]

Your welcome.
Energie/power input = voltage in(U) x current in(I) , after converting;
Energie/power output= voltage out(U) x current out(I) but Input power is not more & not equal with output power!
You have to calculate with conversion efficiency(η) too, where (η) is garanted less as 1! Means, after some conversion, you will have still less energie/power product ...
K.

 

[johny_ulau]

owh!..

example; let say i has a car alternator, charge 12V 45A.
if i boost a voltage to 24V, the current will be 20.25A. am i right?

 

[karesz]

Yes, maybe at 20A or less...
regards
K.

 

[johny_ulau]

owh!

tQ..

i am try to convert 12V 6A to 24V... so i will get less than 3A. am i right?

erm, if i want only step-up the current, what circuit i need?

 

[karesz]

Jea, step up the current means: you can have only a "(voltage)step-down"-converter :-(... Its life.
K.

 

[johny_ulau]

Jea, step up the current means: you can have only a "(voltage)step-down"-converter Sad... Its life.
K.

owh!

tQ

erm,, does its same like voltage converter?
lets say i has battery 12V 12A, if i step-up current double, does its step-down voltage double? so its result be 6V 24A?

 

[karesz]

So is it; tels us the equation from "10 Mar 2010 17:27" too...Dont forget to calculate with conversion efficiency(η), what is never=1 (100%), as said typically at 0.7--0.9 (70-90%), but can be lower too :-(...
K.

 

[johny_ulau]

ok.

erm..
could you tell me where to find simple circuit of current step-up or how to make its circuit?

thank you..

 

[karesz]

Search pls for step down voltage regulators!
As detailed explained, their are the (from you) so called Current Step-Up Converters...
K.

 

[johny_ulau]

ok.

thanks. u help me lot.