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New DuraBlue ultracaps from Maxwell increase shock and vibration tolerance, energy and power capacity

Maxwell_2.85 w DuraBlue cell
DuraBlue cell. Click to enlarge.

Maxwell Technologies, Inc. has introduced its new DuraBlue Shock and Vibration Technology with the latest addition to its K2 series of ultracapacitor cells. The new 2.85-volt, 3400-farad DuraBlue ultracapacitor cell increases the range of available specific power by 17% and stored energy by 23% in the industry-standard 60 mm cylindrical “K2” form factor. The new cells offer up to 1,000,000 duty cycles, with up to 18 kW/kg of specific power and up to 4.00 Wh of stored energy. The cells offer threaded terminals or laser-weldable posts.

The DuraBlue cell also increases vibrational resistance by approximately 300% and shock immunity by 400% when compared to ultracapacitor-based competitive offerings. This enhanced shock and vibration tolerance is particularly important in the transportation market—especially mass transit—and in developing markets in which the road infrastructure might not be quite as smooth as in more developed ones, noted Chad McDonald, director of product marketing.

In addition, McDonald observed, although the new DuraBlue cell carries about a 10% price premium compared to its predecessor (2.75V, 3000 farad), the increased energy density allows fewer cells to be used for equivalent performance, taking cost out of the large packs used in applications such as buses, in which packs can run upward of 300 cells. In other words, added Rick Roth, senior product manager, on an energy storage basis, the new cell offers a lower price per Wh.

The ultracapacitor industry is relatively young, and volumes in certain applications have just started to ramp over the last three to four years. One of the first industries where Maxwell has had substantial success is in the mass transit hybrid bus market. We have learned a lot as we ramped volumes. One of the things we learned in transportation, especially in mass transit, is that shock and vibration are big issues. The placement of the ultracapacitors in these buses exposes them to a vibration profile that exceeds what we had expected.

—Chad McDonald

Shock and vibration issues on truck applications are also high, noted Roth, not just in the cab, but also the body. DuraBlue is specifically designed to withstand those more rigorous requirements of different industries.

We have a good positon in the bus market, but are seeing more competition. Therefore, we think that this additional vibration tolerance will give us a very defensible position. With this technology, we are the only cell that mets these new shock and vibration tolerances. to support the bus industry.

—Chad McDonald

DuraBlue has two main elements. First is the cell fabrication process itself. Maxwell, unlike other vendors, uses a dry electrode process. One of the benefits of the dry process versus the wet process is the resulting durability and longevity of cells, McDonald said.

The second aspect has to do with the ways the cells are mechanically constructed and assembled. The new mechanical design enables the cell to be shaken and vibrated much more than its predecessors. Based on the analysis of points of failure in cells that did fail, Maxwell engineers devised a number of different proposals and solutions to address those, then went through design, testing and validation. The result, the details of which Maxwell is holding closely, enables the hightened shock and vibration tolerances as well as enhanced electrical performance.

Our new DuraBlue Advanced Shock and Vibration Technology combines Maxwell’s unique and patented dry electrode formation and manufacturing process with a robust proprietary cell structure design to meet or exceed the most demanding shock and vibration requirements of the growing number of power-hungry applications in global transportation markets.

—Franz Fink, Maxwell’s CEO

In addition to targeting deeper penetration of its existing markets with the more durable, higher power and energy cells, Maxwell thinks the new cell will open up new markets due to the lower cost of ownership. Grid energy storage is one such promising market in which the higher power and energy profile of the new cells could prove attractive, McDonald suggested.



Love this company, and the potential for microhybrids with ultracaps is awesome. But it has been a lumpy ride. In 2012, I thought MXWL would be a stand-out stock-out stock in the electrification universe. This is a classic case of "Faith", which is a great way to lose money. I have ridden this dog all the way down to about $5, and have watched all of their innovation gain little traction with the market. It's finally back to my buy price, so hurray for MXWL.


15 of these and you could store the energy of braking a 1500kg car from 30-0 mpg (which you often do), 60 and you could store the energy from 60-0 mph (which you rarely do).
Assuming you have a big enough generator and can do controlled braking.
Or you might use them with LiIon batteries in some kind of hybrid cap-bat system.
Really good regenerative braking would be a great boon.

I have heard that a Prius recovers 15% of the braking energy - can anyone confirm or deny this ?

Roger Pham

About 37 of these can store the energy of a 1500-kg car at 60mph, (~150 Wh) assuming no loss from friction and no loss in the motor/ generator/ inverter. Accounting for these losses and perhaps 30 of these can do the trick, but more may be needed depending on the lowest cut-off voltage that the inverter can handle.

Shock isolation can be done using a special suspension unit to mount these ultracaps, perhaps analogous to spring mattresses with foam padding.

I observe that on a Prius 3rd generation, 95% of braking can be done within the regen range of the generator/battery, and that very rarely that stronger braking would be needed outside the regen range. So, assuming 75% composite efficiency for generator/inverter/battery each way, over 50% braking energy can be recovered. With higher efficiency Lithium battery and more efficient SiC inverter, perhaps even higher efficiency regen braking would be possible, perhaps to 75%?


Imagine a replacement Prius battery with this cells. With 50 cells you would get 690 KJ (50 * 1/2 * 3400 * 2.85^2) or ~200 Wh capacity, this would translate to 3 bars of the Prius battery, more than enough buffer.

You gain:
- better charge/discharge efficiency (95%)
- more instant power to mask the delay of ICE revving to right rpm, before delivering power (throttle response)
- more recuperation power
- ICE can run more efficiently when it's only charging battery standing still (from current ~7 kW to ~15 kW)
- More life cycles
- Cells would weight 27 kg and could deliver 180 kW
- operating range from -40° to 65° C, no need for cooling

- 2 W leakage, meaning empty in 3 days, a normal 12V stater battery would have to power the starter motor.
- shelf life 4 years, 10 years at rated voltage, questionable longevity
- shock and vibration, don't know how big impact?


I see everyone has already done the power calculations.  What I don't see is any link to the specs on the unit (here's the datasheet).  Note that the rated maximum specific power is impedance-matched (load impedance equal to internal impedance); you'd want to run way, way below that.

The maximum storage temperature is well below automotive specs.  Most automotive electronics parts are rated -40°C to +105°C, or -40°C to +125°C for engine compartment applications.  A hot-soaked vehicle in the desert could easily put these caps beyond their specs just sitting there, voiding any warranty.

You'd want active cooling for these in hot climates, perhaps a solar-powered fan.  You'd have to limit the internal heat dissipation until the cooling system was working.  Other than that, at 4 Wh apiece, 60-odd of them (30-35 kg) would accelerate your typical passenger vehicle to 70 MPH.  They'd be a fine buffer for engine-off accessory operation in start-stop vehicles, and just dozen or so of them ought to be enough for launch assist.  What matters is cost.


I'm glad to see ANY improvements in supercaps or batteries. But this is underwhelming considering how long they've been at 6Wh/kg. To to up to 7.38Wh/kg is not what I was hoping for at all.

And as EP points out, the temp range is not in the right ball park either.

This further opens up applications for supercaps which is great news. But it's a baby step.


The temp range of NiMh is up to 50°C and it gets there mainly because of inefficiency (internal heating), Li-ion are hurting when they go over 30°C, see Leaf for example. IMHO containing this cells at 40° would be very easy.

Does Toyota TS040 use water cooling for their supercap?

50 cells with 180 kW rated on paper is overkill for Prius, Prius normally uses just around 8-12 kW (max 26 kW), these would have at least 14 kW (100A tested life cycle), with short burst of 50 kW easy. This means double the power.


Chevy said they could run the BAS Plus on super caps.

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