Wow guys lots of great questions! I'll try tackle these in order and post development pictures soon.
Are ultracaps safe? What are the limitations/compromises as far as being used for a vap?
Looking at the maxell pdf on these K2 series I see max rated Wh is only 3, which is about the capacity of a single AA Sanyo XX 2500ma Eneloop or 2700ma standard Sanyo NiMH AA...but with a huge size and weight difference! Have no idea how this translates into runtime, what parameters dictate that?
I guess, not understanding those parameters, if it heats up very quickly, then it would be more efficient than say the claimed 'one of the *world's most efficient* vaporizers' in that MFLB biggrin using said AA batteries above which have about the same stored energy, but only for a 0.2C discharge rate.
Yes safety is of the utmost importance. I'll spend some time to answer this question. While ultracapacitors have very high discharge currents, the voltage is very low (2.7v max, less than two AA batteries). It doesn't take much current to cause fibrillation of the heart, depending on what path the current takes. However with such a low voltage, diaelectric breakdown of the skin has essentially no chance of occurring (you would have to implant electrodes into your skin, to face any threat). Any voltage less than 200v will most likely cause burns due to heating from resistance. And voltage below 30v, no matter the current are generally considered safe. So to summarize, for electrical danger you need:
* Current (the higher the current, the more likely it is lethal)
* Voltage (the higher the voltage, the lower the resistance and the more likely dielectric breakdown occurs)
* Duration (the longer the duration, the more likely it is lethal safety switches may limit time of current flow)
* Pathway (if current flows through the heart muscle, it is more likely to be lethal)
So a tazer for instance operates at over 50,000 volts, yet is not considered dangerous because the current is small. This is the opposite, high current but not enough voltage. I've held both ends of the capacitors in my hands and was never in any danger, same as holding an AA battery in your hands.
Part 2 of safety, material safety of the capacitor. A capacitor, like a battery can fail or become damaged if overcharged. This capacitor is rated at 2.7v and overcharging it (well) beyond that would cause irreversible damage, and if this continued, the capacitor would fail, likely venting its contents. Again, this is a worst case scenario and is not possible with this unit. It is charged at 3.3v and charging cuts off at 2.62v. There is 2.7v zener diode, a "breakdown diode" that burns off voltage as heat if the microcontroller were to somehow fail and let charging go above 2.7v. Even if charging were to continue, without this diode I expect the worst that would happen would be a longterm decrease in energy capacity of the capacitor (as the internal insulating dielectric material between the two conductors allows more leakage over time)
Additionally, capacitors have a very long life, with little degradation over hundreds of thousands of charge cycles. Due to the capacitor's high number of charge-discharge cycles (millions or more compared to 200 to 1000 for most commercially available rechargeable batteries) it will last for the entire lifetime of most devices, which makes the device environmentally friendly. Rechargeable batteries wear out typically over a few years, and their highly reactive chemical electrolytes present a disposal and safety hazard. Capacitors have no toxic electrolytes and very low toxicity of materials (no cadmium, nickel, lithium, etc. as are found in rechargeable batteries)
Disadvantages of an ultracapacitor:
The amount of energy stored per unit weight is generally lower than that of an electrochemical battery (35 Wh/kg for an standard ultracapacitor, compared to 30-40 Wh/kg for a lead acid battery), and about 1/1,000th the volumetric energy density of gasoline. This capacitor can hold about 11,000 joules, a typical long life alkaline AA battery has about 9300 joules.
The next disadvantage is that capacitors have a linear discharge voltage which prevents use of the full energy spectrum. So a 1.2v AA NiMH battery might start out at 1.25v fully charged and end at 1.15v when "empty". an ultra capacitor would start at 2.7v then linearly lose voltage til 0.
If that doesn't makes sense, check out this graph.
How could one use these UC's for a portable battery powered vap like HD's Bud Toaster, which is already large enough, imho?
Concept is cool for sure, but not so sure about the current iteration of execution. Wondering how much could be done to reduce size?
A portable using one of these would have to be about the size of something like one of those plastic refillable water bottles. As for overall size of this unit, I don't see any way to reduce size without greatly compromising some vital function. The gray box is an "ATX" power supply, must give 12volts @ 12amps for aux ceramic heater, 5v (as well as standby 5v, even when the PS is off) for the microcontroller, and 3.3v @ 28amps to charge the cap.
If you don't mind, what expertise do you have with ultracap designs or usage? With such high current capability, I don't want to just take someone's word on this, these are not toys. Given it's being "made in the USA" do you plan on getting a UL cert, so we can feel it's reasonably designed for safety?
If you're asking if I am an electrical engineer, I am not. I have a medical background and am self taught in electronics. Ultracapacitors are a relatively new technology and I have spent months researching everything I can possibly find on them. The power supply is already UL certified and I have done no electrical modification to it. However the unit as a whole will not be UL certified.
Let me get this straight, the 200a dual MOSFET's is the power supply for charging the ultracap? Did not see those in the pictures, can you point them out? You mention the MOSFET discharge rate, I did not know transistors were considered an energy storage device that 'discharges'. Do they need to be 200A & large fan cooled? Could you get away with 100A MOSFET's instead, and a smaller fan, or passive heat dissipation with a heat sink?
What is the tiny fan on top off the unit for?
Sorry if that was confusing, but the MOSFETs act as a solid state electrical switch, or gate, to govern flow rate from capacitor to heating element. This is done by switching them on and off hundreds of times a second in a method called pulse width modulation (PWM). The 200amp number is their max rating. The MOSFETs are not directly visible, but they sit under the top mounted gold heatsink/fan. Like I mentioned early this is very overengineered, so for production I will probably move to one 300amp or similar MOSFET. They don't necessarily need to be fan cooled but this allows me to use a smaller heatsink. The MOSFETs are most efficient when cool. I was also thinking of moving the fan/heatsink to the side or maybe even internalizing it into the power supply for production units.
I believe I see the 10w resistors (white rectangles) on the side with lots of red wires coming out of them. Is there some other configuration that might be more tidy, efficient? a PCB set of mounted resistors?
Yes there is a more tidy way
(I kind of like the look but if others don't it can be easily changed) Again, this is overengineered offering 100watts of power dissipation. I'll probably use less than 50watts for production. Either 5 (or fewer) of those ceramic ones, or one of
these aluminum ones.
PS "auto" over-voltage & SC protection? How well is that engineered? Off the shelf parts, or custom design? Reason I ask is some batteries with protection circuits, those cheapy Chinese made models (not the better quality ones) have very poor quality protection circuits.
Yes you are right, this is quite difficult to achieve, and would have cost hundreds if not thousands of dollars to design. This is why I went with the ATX power supply which has already had many smart engineers work all that out for me
What would happen, if say, the safety sensor failed???
The safety sensor is just there so the heater can't be activated if the bowl is not in place and sitting correctly. If this were to somehow happen it would most likely mean the heater wouldn't turn on. But it could be possible that it would mean that the heater would turn on if the bowl is not in place. Not too big a deal as long as you don't stick your finger in there.
Alright under idea conditions it can discharge at very high currents for very brief periods, but in your vap, what kind of limitations are there on the actual currents being discharged
Yes this is where PWM and the MOSFETs comes into play, they control electrical current. They are a combined 400 amps so that would be the max but, I am operating it about 200 amps to maximize efficiency.
As I'm sure you know, 120v x 15A is a lot more energy than you *appear* to be trying to make it out to be, as most new circuit breakers are 20A. When you compare only 2.7v & max peak current of 2200A 2.7v x2200A = 5940 watts energy for 1sec. compared to typical home outlet potential 120v x 20A = 2400watts. Typical electric range in a home running 240v, can have same potential wattage as that ultracap. It's still impressive for the size, however.
Sorry, I was not trying to deceive or mislead I was only trying to offer an everyday example for people not familiar with electrical laws to compare to.
so do you have an idea what the beta test units are going to cost? And how limited will the production run be?
Beta units will not cost more than $490 max. Limited quantities means I have budgeted for 30 units.
Is the airpath truly all glass? Many products claim all glass, or 100% glass airpaths, but are not. Some feel that since so many others make this claim it is alright for them to also make the claim (everybody else is doin' it...). Is there absolutely no other material except glass in the airpath?
The airpath runs through all glass, meaning it doesn't go through plastics or over electronics and such, but the heater components are not glass. Aux heater is ceramic, and primary heater is stainless steel and copper (same as MFLB)
. Had hoped he knew a bit more about ultracaps though.
using said AA batteries above which have about the same stored energy, but only for a 0.2C discharge rate.
I'm working on making retail price as low as I can and I feel it definitely competes with the other vaporizers in this price range and even those that are more costly.
I'm just lol at the match game going on here!