Another 18650 mod
- Thread starter Gummy Bear
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That's right. Power in = power out + losses. So, using 90% efficiency and 8W output as an example, input power is 8W/.9 or 8.9W. If battery voltage is 3.7V, that would be 2.4 amps input. However, battery voltage can drop lower than 3.7V and you have to assume worst case. So if the battery is replaced (or the circuit shuts down) when battery voltage is 3.2V, then peak battery current would be 2.8 Amps.
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One quick question though. Seeing as the native output is 5V, if vaping at 4.4V, through the use of a diode, should these AMP/watts calculations actually be calculated at 5V?
Well, in that case, you would have to consider power lost in the diode as a drop in efficiency. You can actually measure efficiency pretty easily on the bench with a voltmeter and ammeter. You don't have to calculate it part by part. That can be involved and doesn't always give you an accurate result due to smaller neglected losses like those in the wiring and PCB.
Diodes are quite lossy at higher currents and a Schottky rectifier can result in as much as a 10% decrease in efficiency, almost double that with a standard diode. That's why, in my latest mod, I went to a lot of trouble to go from an asynchronous to a synchronous boost controller (asynchronous uses a diode rectifier, synchronous uses a MOSFET rectifier). Though, I did lose the ability to run below battery voltage, but I wanted the increased efficiency for longer run times and I always vape at batt voltage and above anyway.
Diodes are quite lossy at higher currents and a Schottky rectifier can result in as much as a 10% decrease in efficiency, almost double that with a standard diode. That's why, in my latest mod, I went to a lot of trouble to go from an asynchronous to a synchronous boost controller (asynchronous uses a diode rectifier, synchronous uses a MOSFET rectifier). Though, I did lose the ability to run below battery voltage, but I wanted the increased efficiency for longer run times and I always vape at batt voltage and above anyway.
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To whom may know the answer (HEY GUMMY!)
using an 82.5k resistor on pins 1&3? the table (table 2-14) in the spec sheet says the output should fall between 5.2v and 5.4v with that resistor. The data sheets says minimum power output is 0.5v over input, and they assume 4.5v in many places, so I've inferred the use of 4.5v input for that set point resistor. Is it pulling 4.4v with a 82.5k resistor because the input is 3.6v instead of 4.5v?
I just ordered my "samples", and will be using one or more in the very near future! Thanks ya'll!
using an 82.5k resistor on pins 1&3? the table (table 2-14) in the spec sheet says the output should fall between 5.2v and 5.4v with that resistor. The data sheets says minimum power output is 0.5v over input, and they assume 4.5v in many places, so I've inferred the use of 4.5v input for that set point resistor. Is it pulling 4.4v with a 82.5k resistor because the input is 3.6v instead of 4.5v?
I just ordered my "samples", and will be using one or more in the very near future! Thanks ya'll!
It's hard to say and you won't find that way mentioned in the datasheet.
It was first used by RjG, one of the first modders on these forums to use the TI Booster. Nuck mentions RjG and credits him for all his help in his Fistpack guide. He was a bit of a maverick though. He also made a 5V mod that used a 3.7V Li-ion and a 1.2V NiMH in series. Claimed it worked well with a protected Li-ion.
As to your first question the booster regulates the voltage, it will remain constant as the cell drains.
With no resistors, just using the diode Nuck uses (right before the atty connector) should give you about 4.4V.
I don't know why it works, but it does! Gummy told me to do it that way, said he didn't remember where he got it from, I'll take Willy B's word for it since he's been around here longer than me. I'm using the chip, as Gummy says "nekkid" no caps or diode with an IMR 26650 and it takes a couple of days for the batt to get down to 3.5v. I'm very happy with it.
Robert
Robert
I'm not questioning that it works to cut the native voltage. I'm just saying it's not listed in the datasheet.
As far as nekkid, the official, LOW ESR caps that TI recommends are dirt cheap. I'd use them. At least one on the input side.
EEU-FC1E181 Panasonic Electronic Components Aluminum Electrolytic Capacitors - Leaded
Hey willy!
I've already got 10 of these sitting in front of me. 100uF,16v, radial, aluminum, dk blue in color, through hole. it also says 85°, VX(M), and the numbers 89851. Got'm from digikey a while back for...God knows what. don't know how to id them exactly, but they look pretty darn close to the other ones i've seen attached to the 04050 board....
I've already got 10 of these sitting in front of me. 100uF,16v, radial, aluminum, dk blue in color, through hole. it also says 85°, VX(M), and the numbers 89851. Got'm from digikey a while back for...God knows what. don't know how to id them exactly, but they look pretty darn close to the other ones i've seen attached to the 04050 board....
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If you could do the skins on the inside of the tube it would really look sweet with the added depth. Plexi also does some cool stuff with LED's. You can etch it and it will light up like crazy when the LED comes on.
a little easier is like old school Easter eggs. draw on it with hot wax, and then etch the surface (you can even just use super glue vapor!), clean it up, and viola!
I should have said engrave rather than etch. Any scratch will show the light very bright. I've done images and logos that light up really sweet. You can also lightly scuff or sand to diffuse the lighting. Lots of optiions once you begin messing around.
kinda wished you hadn't said anything; it was on my list to wow peeps here with ;D
oh well, it'll still be cool!
oh well, it'll still be cool!
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