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Current through two parallel connected same voltage batteries/voltage sources?

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Sarah1234

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Its obvious that connecting two voltage sources/batteries parallel will result in same output voltage as of one but what about current ? will be same as one or double? or else
 
Thanks, this is what I was guessing. So if there are two batteries of 3.7 volts , what is your guess how much current will they be drawing? I need no more than 3 to 4 amp current at output... what could be possible value of limiting resistance? 1k?
 
3.7V indicates a rechargeable lithium battery cell. Their voltage is about 3.2V when dead and is 4.20V when fully charged. Likely two will have different voltages and when they are connected in parallel then a very high current will flow between them possibly causing an explosion and fire.

We cannot guess about how much current unless we know the part number of the battery so we can look at its detailed datasheet. Some Lithium battery cells have a protection circuit inside that limits their maximum current to a safe amount.

Are you using 18650 lithium battery cells from China? Do they work or are they fakes? Some of the protection circuits are also fakes.
Here is one of many You Tube videos about fake Chinese Lithium battery cells:
 
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it is this battery. I couldn find out its current rating? could we have some idea from mAH?
 
As audioguru mentions, don't do it, unless there is some sort of current balancing scheme.
It can be as simple as adding a pair of low value resistors, one on each positive terminal, before tying both together.
But this wastes power, so the best would be an active current balancing circuit.
 
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it is this battery. I couldn find out its current rating? could we have some idea from mAH?

You mentioned earlier 3 to 4 Amps. That battery is a 130mAh battery or .130 AH (Amp Hour). Ten of those will get you maybe 1.3 AH. You will need more than two, way, way more than two. I suggest you start looking at 3.7 Volt 4,200 mAH LiPo batteries. I also suggest you start studying how these batteries work and are charged. AudioGuru's post was on target as really bad things can happen if these batteries are used incorrectly. The battery in your picture will be useless to you.

Ron
 
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It is this battery. I couldn't find out its current rating? could we have some idea from mAH?
Hyperion is one of the best small Li-Po batteries for radio controlled model airplanes and helicopters. Its tiny connector and wires on the connector limit its current. If shorted its wires burn off the insulation and glow red hot.
Here is a graph showing its 160mAh sister providing 2A for longer than 4 minutes. The purple line is a poor quality Chinese one from Hobby King. This 130mAh battery will have the same timing and voltage when its discharge current is about 1.6A.
But instead of paralleling two of these small ones why not use a larger 240mAh or 300mAh one?
 

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How long do you expect this battery to deliver current, he 3 to 4 Amps you mentioned?

Ron
 
well, this discussion has been helpful. I need to confirm you guys to have a look at this circuit diagram to ensure if connections are fine ? n if there is any short circuiting or break?
 

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It is not safe to connect two Li-Po batteries in parallel because their exact amount of charge probably will be a little different. Then an extremely high current will flow between them where one will discharge while charging the other. Their connectors and wires will probably be damaged by the extremely high current. Use one larger battery cell with a higher capacity instead.

These little Li-Po batteries work poorly in winter when they quickly get cold. Some people keep them warm in their pocket then put them in an insulating cover made of closed-cell foam rubber.
 
well, this discussion has been helpful. I need to confirm you guys to have a look at this circuit diagram to ensure if connections are fine ? n if there is any short circuiting or break?

You don't do this with LiPo batteries - you didn't make this clear at the beginning.

Assuming you want to parallel ANY batteries though, they should be identical, permanently paralleled, and charged like that - BOTH must have identical charges.

But Li is a special (and dangerous) case.
 
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