Battery safety grades table updated with wattages and coil resistances

[Mooch]

A common question asked here at ECF is "What is the best battery for my mod" or "How low can my coil build go with battery XXX" or "Is this battery safe to use in my XXX mod?". To help with answering these questions I have added wattages and coil resistances to my battery safety grades table.

For each of the current values (expanded to 40A) I have added the corresponding wattage based on a mod using a 3.2V cutoff. If the cutoff is higher, then there's a bit of a safety margin built in as the current level will be lower. I have also added the corresponding coil resistance for each current value. For 5A-20A I used a battery voltage of 3.9V. For 25A-40A I have used a battery voltage of 3.7V.

Here's an example using the HG2...

As you can see the HG2 can be used in a mod at up to about 64W. Or with a coil down to about 0.195 ohms. These correspond to 20A, the cell's limit before hitting my safety cutoff of 100°C when discharged continuously.

The temperatures of a battery during vaping is significantly lower than the temps reached in these tables though. Vaping with the HG2 at its Max Amps value of 20A results in temperatures no higher than using it continuously at about 50%-75% of its CDR. A good safety margin in my opinion. And even if the mod autofires continuously, the HG2 wouldn't dangerously overheat. For longest cell life though, I recommend a wattage/resistance/current level that keeps a cell in the green Pass zone.

I still have to update the instructions but wanted to post this in case anyone took a look at the table and wondered what the heck was going on.

Does everyone prefer the additional precision of having the coil resistances to the third decimal place? Or better to round them off to two digits? Thanks!

[edit] Oops...link to the safety grades table is in my signature.

 

[supertrunker]

Why the different voltages for different Amp batteries?

I've always been told to use the fully charged 4.2v worst case scenario. As for resistance values, i wish i could build coils to 3 decimal places!

T

 

[B2L]

Does everyone prefer the additional precision of having the coil resistances to the third decimal place? Or better to round them off to two digits? Thanks!

I prefer being able to read the thousandths (love my USA ohm meter) especially with lower builds. I'm not sure at what point the thousandths become necessary, maybe anything under .1 or .2, but having that info I find helpful.

Appreciate all you do!

 

[Mooch]

Why the different voltages for different Amp batteries?

I've always been told to use the fully charged 4.2v worst case scenario. As for resistance values, i wish i could build coils to 3 decimal places!

T

The initial voltage drop of the battery, due to its internal resistance and not from being discharged, varies depending on how much current is being drawn. At, let's say, 1A there is almost no voltage drop ("sag") and your discharge will start near 4.2V and slowly go down. But if discharging at 30A a fully charged battery immediately drops to a much lower voltage, near 3.7V, and then proceeds to drop more slowly as it discharges.

Using 4.2V is a great way to add an additional safety margin (ensures longer battery life too). Using two voltages for the calculations lets me get more accurate results though, based on what the batteries are actually doing. This lets each viewer of the table understand how the battery behaves and so they can set their own safety margin.

But, you can never go wrong by using 4.2V.

 

[edyle]

those batteries are supposedly good for a nominal 300 recharges.

testing batteries after 150 recharges would be tedious.

 

[Mooch]

those batteries are supposedly good for a nominal 300 recharges.

testing batteries after 150 recharges would be tedious.

To say the least.
Not sure I understand your post though.