Voltage and Ohms Law

[Spooky Mulder]

So I just want to make sure I've got this right.

Ohm's Law Calculator

Are all batteries 4.2 Volts on a full charge?
So say I wanted to do a 0.5 ohm build on a mech. So I enter 4.2 for Voltage and 0.5 on Resistance?
Which would come out to 8.4 amps and 35.28 watts right?

So if I want to calculate for a mech mod on a fully charged battery it will always be 4.2? And whatever the ohms of the build in addition to that will always give me the Amps and Watts?

I hope that's right...lol.

 

[Ryedan]

So I just want to make sure I've got this right.

Ohm's Law Calculator

Are all batteries 4.2 Volts on a full charge?

The spec is 4.2+-0.05v. It depends on the charger. My Xtar MPII leaves them at 4.19 right after charge and they go down to 4.18 after a few hours. I don't worry about the 0.02v in Ohm's law calcs.

So say I wanted to do a 0.5 ohm build on a mech. So I enter 4.2 for Voltage and 0.5 on Resistance?
Which would come out to 8.4 amps and 35.28 watts right?

Correct. You're actually going to have some voltage drop from the battery so you will not see all 35 watts in the atty, but the battery will have all of the 8.4A drawn from it.

So if I want to calculate for a mech mod on a fully charged battery it will always be 4.2? And whatever the ohms of the build in addition to that will always give me the Amps and Watts?

I hope that's right...lol.

That is correct

 

[Spooky Mulder]

The spec is 4.2+-0.05v. It depends on the charger. My Xtar MPII leaves them at 4.19 right after charge and they go down to 4.18 after a few hours. I don't worry about the 0.02v in Ohm's law calcs.

Correct. You're actually going to have some voltage drop from the battery so you will not see all 35 watts in the atty, but the battery will have all of the 8.4A drawn from it.

That is correct

Ok thanks. I was hoping it was right. I was a little confused because some batteries say like a 3.7 V or some other number on the specs?

I also was going to ask about Voltage Drop? I'm guessing I'm going to need a multimeter too? Or one of those round voltage things I see reviewers use sometimes that goes between the mech and the atty to measure it?

Although I don't plan going below like 0.4 at the very lowest.

 

[Ryedan]

With mech mods at the least you need a way to check atty ohms and battery volts. I have a DMM, a black box ohm checker and I also have an inline voltmeter that makes checking voltage drop under load easy. Using a dripper that you can take the cap off of and a mod where it's relatively easy to activate the button, you can put the pos DMM lead on the positive post of the RDA and the neg lead on a negative post, hit the switch and you'll see the voltage under load. That's not hard and I did it that way for a long time, but you do need somewhat nimble fingers.

The voltage drop under load that you see with a clean mod will be almost all from the battery's internal resistance. It goes up with lower ohm attys. I check that when I get new batteries so I know the V drop at a given resistance (always 0.5 ohms for me) with new batts. As they age I check again and the V drop will go up as the internal resistance goes up. I find this a good way to tell how healthy the batteries are over time.

You don't have to do this, but if you do you'll have a better feel for how well your batteries are doing.

 

[Spooky Mulder]

With mech mods at the least you need a way to check atty ohms and battery volts. I have a DMM, a black box ohm checker and I also have an inline voltmeter that makes checking voltage drop under load easy. Using a dripper that you can take the cap off of and a mod where it's relatively easy to activate the button, you can put the pos DMM lead on the positive post of the RDA and the neg lead on a negative post, hit the switch and you'll see the voltage under load. That's not hard and I did it that way for a long time, but you do need somewhat nimble fingers.

The voltage drop under load that you see with a clean mod will be almost all from the battery's internal resistance. It goes up with lower ohm attys. I check that when I get new batteries so I know the V drop at a given resistance (always 0.5 ohms for me) with new batts. As they age I check again and the V drop will go up as the internal resistance goes up. I find this a good way to tell how healthy the batteries are over time.

You don't have to do this, but if you do you'll have a better feel for how well your batteries are doing.

Ok thanks for all the good info. I have an ohms checker box. I'll definitely invest in an inline voltmeter soon and a multimeter too.
I haven't even bought the mech yet..lol. I just want to make sure I know everything first to be safe about it. Thanks again.

 

[bigdaddybrink1]

you can buy an in line volt meter there are several others.

Or this may have no baring on what your lookin for......