Musashi Seimitsu ($7220.T) Supercap Note

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Ok kicking myself for forgetting this one in the recent SiC/GaN post.

One very useful component is the supercapacitor, a giant capacitor. Mainly for energy storage as a rapid response alternative to batteries. These things are not for traditional capacitor uses (filtering/de-cap). Separate niche. I know the ESR is high, go away.

Exponentially growing niche lol.

I own some shares from like a year ago in one of the long only accounts and sort of forgotten about them. Position was down like 25% at one point but is now up 57% even after I bought some more this week.

Honestly don’t own nearly enough. Want to double position but no free cash.

Anyway I am super busy so this post has a 1 hour time limit. Last year I did a detailed analysis of 10+ supercapacitor companies (for myself, did not publish it) and concluded that $7220.T vaporizes everyone else. So will only include second place here in the interest of time.

This is an uber monopoly of a rapidly growing, mission-critical niche that has massive technical/engineering moat. Cant resist have to drop everything and write this up ASAP.

Datasheets are public. This is very clean thesis. IDK how the fuck this random Japanese company made this thing but its way WAY better than anything else on the market.

The keys specs are energy density. Particularly volumetric energy density. Musashi way ahead. Higher rated voltage means you need fewer of these in series simplifying control and circuit design. Will get to that shortly.

Big drawback of Musashi solution is very high ESR. (parasitic resistance)

Again, for this application, density is by far the most important metric.

As an aside, these capacitors are extremely dangerous. Can easily kill a human.

To show why density is so important, let’s look at an appliance Musashi offers that is built around their supercapacitors.

The datasheet advertises backup time but this thing has so much more value than that. Smooths out power and load spikes.

Some of you may be wondering how capacitors rated for 3.8V can be built into a product that supports hundreds of Volts.

Let’s look at a nice TI application note I found.

Oversimplified, a control circuit needs to step down the voltage and charge a mixture of batteries and supercaps. The supercaps can be stacked in series to improve rated voltage at the cost of capacitance and efficiency due to higher ESR.

Here is another example for an ADI application note.

Efficiency of this circuit is not good because you have to step down the voltage then boost it back up. Thus, ESR of the supercaps themselves is not the most important spec. DENSITY DENSITY DENSITY. The point of these things is to have a dense energy buffer, at the cost of some efficiency.

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See you this weekend for memory/DRAM/HBM project.