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current amplifier

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BigJay

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hello i need the schematics for a circuits that amplifies dc 12v 50amp to dc 12v 100amp and dc 12v 50amp to dc 24v 100amp. for example using a car battery as input source.
 

Sceadwian

Banned
That doesn't make sense. You can't just create power out of thin air. What exactly are you trying to do?
 

BigJay

New Member
ok i have an air pump that runs on dc power 12v i need to run it on a 12v 50amp battery. but it's killing the battery quickly so i need to add the current so it will last longer. now i once found a circuit that does it but using capacitors. but i lost the schematics.
 

Sceadwian

Banned
Buy a bigger battery there is no circuit you can add that will increase the run duration that would violate the laws of physics =)
 
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BigJay

New Member
aha ok. i'm very beginner to electronics thx for ur quick response. just one more question how do i calculate (if possible) the running time of an device plugged to a battery like the pump has a 3 amp max current and the battery has a 50amp so is there any formula or i dont understand the concept?!
 

Sceadwian

Banned
The capacity of the battery isn't measured in amps, it's measured in amphours so watch your terminology =) A 50AH battery is rated for 50 amps of current draw for one hour fully charged. The trick is the 50AH rating is usually based on how much current you can draw over a 20 hour period. So 50/20 is 2.5amps for about 16 hours. You're drawing 3 amps which should be pretty close if that's what's actually being drawn, so your battery when fully charged should be lasting 15 hours or so. It will slow down towards the end of the discharge, and if this is a car battery it's probably not a good idea to discharge it all the way, you'll need deep cycle marine batteries. How long do you need to run the pump for?
 

BigJay

New Member
i just need it for 4 to 5 hours but i tested my pump it lasted for 1hour and a half so i'm guessing i have a problem with my battery (it's used by the way not a new one) so i just need to change my battery.
 

Sceadwian

Banned
Yeah, sounds like a tired battery. Make sure you purchase a marine or deep cycle battery. Regular car batteries don't last very long when you drain them all the way down. Even then you should not drain the battery all the way to the point where the pump doesn't function, so if you can afford it buy a larger capacity battery even if you don't need the extended run time so there is some extra capacity. The battery will last much longer that way.
 

Hero999

Banned
The capacity of the battery isn't measured in amps, it's measured in amphours so watch your terminology =) A 50AH battery is rated for 50 amps of current draw for one hour fully charged. The trick is the 50AH rating is usually based on how much current you can draw over a 20 hour period. So 50/20 is 2.5amps for about 16 hours. You're drawing 3 amps which should be pretty close if that's what's actually being drawn, so your battery when fully charged should be lasting 15 hours or so. It will slow down towards the end of the discharge, and if this is a car battery it's probably not a good idea to discharge it all the way, you'll need deep cycle marine batteries. How long do you need to run the pump for?
It's not that simple, you get less amp-hours from larger loads than you do from smaller loads.

Here's a datsheet that illustrates this.
http://www.onestonesoup.org/ProjectSolar/battery-1.pdf
 

Sceadwian

Banned
That's exactly what I said Hero. Your PDF shows the proper way to calculate it though.
 
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