51 Fellten Charge Qube | EVD E-Mobility Engineering | March/April 2025 The Qube I was shown in mid-January was fitted with a pair of Tesla Model 3 packs for a capacity of 150 kWh. The packs were supported by a steel framework and stacked one on top of the other. They had space above them for more pairs, doubling or tripling capacity to 300 kWh or 450 kWh. Andre says it is possible to install eight packs for a capacity of 600 kWh. Qube is not limited to packs from any one manufacturer, so Fellten can make the most of whatever is available. Today, Tesla packs are plentiful, and the company anticipates also using units from Kia and BYD. The structure of Qube is made from half a 20 ft-long ISO container by conversion specialist Titan Containers. It arrives at Fellten’s premises near Bristol, UK, fully painted with the cutouts for the charge ports and heat exchanger, plus all the internal bracketry and support structure, so it is ready for Fellten to install the battery packs, power electronics, thermal management and control equipment. Empty, the container weighs 1.2 t, Andre says. With each battery pack at 400 kg, total container weights will range from 2.5 t to 4 t, well under the maximum allowable gross weight of a 10 ft container. Other than the change in length, no structural modifications are made to the container, as the openings for the charge ports are made in the wall panels. It therefore retains its original strength, so it can be stacked several high, which provides additional benefits. Power electronics At the heart of the AC charging system is an off-the-shelf inverter that was the subject of a long and thorough search, which enabled Fellten to go ahead with Qube’s development, as Hazell explains: “We designed the Charge Qube five years ago, but then found we had to buy so much power electronics to get it to do what we wanted it to that it was never going to be financially viable. “Everything back then was 48 V, so it just wasn’t efficient, and it wasn’t until new inverters came out that can do phase-balancing and tie into the grid, as well as running off-grid in one unit, that it became viable,” he says. “The fact that we are using second-life components but others are not makes it more cost-effective for us to build, and allows us to sell it for less. There’s also a major benefit for bigger companies because the environmental impact is lower and the carbon offset is a lot better,” he says. The battery packs in Qube are not (as may be expected) ones that have degraded to 80% of their original capacity. Fellten also converts classic cars to electric power, and it has years of experience dismantling and reworking battery packs from many manufacturers, including Tesla, Volkswagen, Jaguar Land Rover (JLR) and Kia. “The whole industry has realised that batteries last way longer than anticipated,” says Jerome Andre, EV advocate and consultant for Fellten. “We’ve seen early Tesla Model S cars run with their original battery packs to 400,000 miles with no issues whatsoever.” “It’s very rare to find a lithium-ion EV battery that has degraded as far as to have only 80% of its original capacity left,” Hazell notes. He recalls that when working on a contract for JLR about three years ago, for which Fellten was dismantling iPace batteries for secondlife applications, they never found one with less than 88% of its original capacity. “These were packs from prototypes and vehicles used in the iPace race series. Those packs were still surprisingly good, even though they’d just been absolutely abused. “What you tend to find is there’s a degradation curve, and once you get down near the 80% it flattens out. What we’re expecting with these is that, keeping them between 20-80% charge, they’ll slowly get down to 80% capacity and stay there for a long period of time. Looking at current reports we’re seeing 25 years life expectancy for a lithiumion battery.” Instead, the packs used by Fellten are undamaged, healthy units, taken from vehicles written off after minor accidents. Internal layout, revealing battery packs, power electronics, cooling pipework and heat exchangers, based on car radiators. Wheels aren’t normally fitted (Image courtesy of Peter Donaldson)
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