Ok lets talk voltage

[Adrenalynn]

but I prefer analog stuff when tinkering (Ham Operator KI4OZY). That wraps it up for me, I'm going home... Later guys (and gals LOL).

73's de K6JLR

 

[Scottbee]

Good catch. R_B should be 300 MILLIohm range. 320-360MILLIohm

There ya go!

 

[Adrenalynn]

Yeah, mea-culpa.

Not to make too many excuses, but I'm packing to move here, and I keep getting distracted sitting down at the forum(s) every couple hours and making just one or two fast posts and then bolting. I really should stop doing that, because I'm not doing a good job at either. Of course - here I am. Doing it again.

 

[Adrenalynn]

Hey, if you really want to do it right, you just need one of these: http://www.st.com/stonline/products/literature/ds/5686.pdf

A couple discreet components, and one of these: LiFePo4 Battery 12V/ 50Ah 12V50Ah lifepo4 battery CN;GUA products

That'll keep you smiling. Only about 11lbs, so you should be able to cart it around in a fanny pack just fine...

 

[Davo]

This post is about to get buried but I indicated I would measure and respond. Using a Fluke 77 digital multimeter I got 4.18~4.20 volts DC from the original auto standard V4L battery, right off the charger with no load. Then with the newer V4l battery, single logo (same 280 mah battery)... same results. After charging my XL 380 mah battery I got the exact same measurement. Soooooooooooo we are either dealing with a bad meter or poor scientific evaluations. Cool stuff!!!!!!!!!!!!!!!

 

[Scottbee]

To be honest with you... "right off the charger, no load" readings aren't really all that important. They're "surface charge" readings..... and they will degrade with time just due to the self-discharge of the cells (even though Li batteries have very low self-discharge rates).

$.02... no change required.

 

[Adrenalynn]

Agreed with Scott, and to further what he said - considering that the charger is putting the same voltage into the battery regardless of the current capacity of the cell, I'd be really surprised if you weren't reading the same thing.

Which is why, I believe it was in this thread, that I suggested sampling loaded conditions over the charge-life for the different cells. Assuming the atomizer is drawing a fairly consistent current you'll observe that a lower capacity cell will ramp down in voltage more quickly than a higher capacity cell.

Alas, that doesn't do much more than tell us that Ohm wasn't Lyin.

 

[~Gazoo~]

errr - I've gotta differ with you a bit.

mAh is the number of millamps that can be delivered for one hour before the cell is entirely dead. Alas, we can't drain them entirely, so the number is somewhat misleading, hence the need for "duty cycle". But if we figure a battery has a 50% duty cycle and 500mAh capacity, that means that it can deliver 250 milliamps continuously for one hour before it's no longer able to deliver adequate current to power the device. Or 500mA for 30mins. Or 125mA for two hours, and so on. Over that period, the voltage will ramp down, but far less for a Li* chemistry battery than for a lead acid or seal lead or nicad, etc.

Not to be confused with the battery's ability to deliver burst power, or it's maximum deliverable current which may be incredibly much higher. Even 30x or more. Although I believe these batteries are 2C max discharge.


So it IS, technically, how "powerful" it is. Noting that power = work/time, and the amount of power we can deliver into a circuit equates to how much work can be accomplished.

Edit to note: And this is the reason I suggest measuring the discharge cycle, because we're dealing with the internal resistance of the battery in this calculation - typically 320-360ohms in a LiIon cell

I looked up the 280ma battery before and I thought it had a 5 or 10C rating. But now I don't see it. Here is the Chinese to English google translation for the battery I think we are using:

Google Translate

The complete part number on the one I have is E08600LP16G11. The 16G11 could be a production code.

If these are the same I am surprised at the 2C rating since we are drawing at least 1 amp...and I think it's closer to 1.4 amps.

Here is a picture of it. It looks very similar to the one I have except mine is silver and does have the complete part number on it.

Google Translate

 

[~Gazoo~]

Assuming the atomizer is drawing a fairly consistent current you'll observe that a lower capacity cell will ramp down in voltage more quickly than a higher capacity cell.

Alas, that doesn't do much more than tell us that Ohm wasn't Lyin.

Speaking of constant current I built a box mod and am using a 1050ma AMC7135 board to regulate the current. These boards are common in LED flashlight mods. It's awesome but ugly...I haven't perfected it yet. Currently I am using 4 aaa sanyo eneloops to power it and they are attached to the outside of the box. I plan to convert to two LifePo4 batteries and mount them in the box. I like to tinker..

 

[Adrenalynn]

Great tinkering! I enjoy that too. I've just moved into a new house and everything is in boxes - my entire lab is buried under tons of karp I have no good place to put in this tiny house [sigh] - so it'll be a few weeks before I revisit.