Instead of very technical and confusing Delivered Wh (Watt-hour) performance numbers for each cell I will now be using E-Scores (Energy Scores) in my ratings tables and the ratings graphic for each cell. The higher the E-Score, the longer the cell will run.
E-Scores do not take cycle life (overall cell life) into account! Additional testing will have to be done to see which cells last the longest overall.
Using E-Scores is easy…
Choose the right size cells with a high enough current rating for what you will use them for. Then choose the ones with the highest E-Score at the current/power levels you run at. Those cells are the ones that will run for the longest. Capacity ratings are pretty useless, you can ignore that rating if the cell has an E-Score.
Other changes…
The Puff Counts will be removed from each cell’s ratings graphic as they are just the Wh numbers formatted differently.
The safety documentation section was removed from the ratings tables. It was becoming practically a full time job trying to get those documents from the cell wrapping companies and authenticating them. I just don’t have the time. If a company uses an unknown cell then we just won’t know if it was safety tested or not.
The ratings tables now include a section on how to choose a battery based on the E-Scores.
The DC Internal Resistance will still be measured.
The new ratings tables have already been posted (links below). The new ratings graphic will be used as I post each new cell’s test report.
Tech stuff…
E-Scores are the exact same performance number I was using before, the delivered Wh at the stated current level down to 3.2V. They can still be directly used as Wh by more technical cell users. These numbers are a great measure of how a cell actually performs and E-Scores are an attempt to make them easier to use.
Not at all. The data is subject to change at any time though.
Please include the two links to the tables so they can always get the original data and any updates I have made to the tables.
Isn’t it a bit misleading to write the equivalent power draw, when in reality there is no equivalent power draw since the voltage changes as the cell is discharged at a constant current?
I kinda wish the numbers were based on constant power discharge, because I think that would be more useful of a metric… Then again current is easier to work with for our application.
The CDR and the P42A’s all-around performance. The BAK is a good performing 10A energy cell. The P42A is a great performing power cell…different uses.
Being my best all-around choice means the P42A might not be the best at anything, just the best all-around compromise if you need a cell that can perform well at any level. Like any all-around choice though that means it’s probably not the best at everything.
The BAK is slightly better at lower power levels than the P42A, as seen by its E-Score. But it’s not a big difference and the P42A will outperform the BAK at higher power levels and run cooler doing so.
That helps make the P42A my all-around choice for anyone who only wants to use one cell at different power levels or who just wants the “best cell” and doesn’t want to deal with looking at any data (the vast majority of people).
At lower power levels the higher capacity of the BAK means longer running time. The reduced voltage sag you get with the P42A doesn’t make much of a difference at lower current levels so it’s up to the capacity to determine run time.
At higher power levels the P42A would easily outperform the BAK, running for longer and at a higher voltage.
Misleading? I don’t think so.Changed my mind…see post below.
Though I fully accept that some would feel that number can’t be used and I would recommend that they only use the current level instead.
The power does indeed change though as the discharge proceeds. I use the approximate power level that most applications would see near the end of the discharge but that might not be exactly what someone needs to see. It is the standard I use though and still provides a method to directly compare the performance of one cell against another.
If someone has a constant-power application and they need to calculate actual run time then they should do a constant-power test and get the actual numbers they need. They can still use my data to choose the best cells for their testing though.
Constant-current (CC) discharges are the standard and still provide a method to directly compare cell performance. It is in between how hard a constant-resistance discharge (less current as the discharge proceeds) stresses the cell and how hard a constant-power discharge (more current as the discharge proceeds) stresses the cell. A good all-around method to measure cell performance. Not the best way for everything, just a good way to get the data that can be of most use to the largest number of people.
CC discharges are also needed to get an estimate of the cell’s true current rating and how hard a cell can be run before it reaches its max surface temp rating.
I would love to see someone do constant-power testing though! I’d be happy help in any way I could with that.
I am torn about using the power level number though. It really helps some cell users but can confuse others. We’ll see how it all plays out.
I changed my mind. My one-power-level-for-all-cell-voltages can be confusing for some and that means the number can be misleading.
Thank you for bringing this up. In my drive to change over all the tables and switch to E-Scores it is easy to ignore little things. It’s feedback like yours that focuses me back on those things and that helps to make the table a better and easier to use resource. Thank you.
I am going to keep the single wattage number since it is very useful for the vaping community but I am going to tag the number and add a footnote saying that the wattage number represents the highest wattage a vaper can use the cell at before exceeding the matching current level for a typical vaping device that cuts off at 3.2V.
Moochscore?
