27 E-Mobility Engineering | January/February 2026 That cuts the length, weight and cost of the high-voltage battery cables almost in half compared to packs that need to be run individually back to a single point.” Owing to the relatively small onboard energy capacity, BAE Systems chose not to incorporate the option for 800 A charging that it provides on other OEM applications with much higher 600– 800 kWh capacities. Fast charging is an option, but the baseline relies on CCS1 plug-in charging through a combo-plug, limited to 200 A and a target of 150 kW. “That’s typically the limit of most public chargers we’ve encountered,” explains Matthews. “The system is designed to follow Forsee-specified charge limits with each pack able to source 118 A continuous and 236 A peak. So, the system is almost always below a 1C discharge and, with 200 A of plug-in charge, it is at less than 0.6C when charging.” The cells used on the ZEN range are highly capacitive and low-current, so are less prone to overheating. Forsee’s mechanical and thermal engineers have developed an in-built liquid management system to keep temperatures in check, while the BAE Systems team has also integrated their own approach, within an optimised cooling system, to maximise safety. “There are currently two cooling loops on the vehicle: one for the batteries and one for everything else,” says Matthews. “On the battery, we monitor maximum temperatures across the pack, as well as inlet and outlet temperatures. We also perform rationality checks to ensure we are not seeing any cellspecific anomalies that would indicate a thermal event. “The motor, power electronics, MAPS, MPCS, cabin heating and liquidcooled accessories all share a common reservoir and radiator, with multiple pumps to circulate the different zones – but in the future, we plan to combine both cooling loops into a single system to make better use of the 3000 lbs of battery heat sink.” Customisation Perhaps the biggest innovation of all is the flexibility of the system’s specifications, which is delivered through what BAE Systems terms ‘modular slice technology’. At its highest level, this allows users to customise the set-up to best suit their needs by simply adding or subtracting functional ‘slices’ – or modules – of a MAPS or MPCS component. “There are many different ways you can customise the MAPS,” begins Matthews. “If you need more 24 V DC power than the 250 A that is provided by one slice, for example, you can simply add another. Likewise, if you want a 12 V DC and a 24 V DC bus, you can have one slice provide 12 V DC and another 24 V DC. “If you want to have a tandem e-axle configuration, you can simply put two inverter slices in the MPCS and the system will manage that. And if you need to combine four battery strings, you add one battery combiner slice; if you want eight strings, you just add another combiner slice. “Going a level deeper, we then have the ability to ‘flex’ inputs to be outputs and vice versa by changing the software configuration and the hardware options – for example, we can change the system set-up simply by modifying the fuse and contactor options, fuse sizing, and voltage and current sense options.” The demo vehicle only required two battery inputs and one charge port. So, the team configured it specifically for that set-up, with two high-rate opportunity ports becoming battery input ports on a charge slice, and the battery inputs and charge port connection combined within a single slice. The Modular Accessory Power System (MAPS) sits at the heart of the vehicle’s modularity approach The biggest innovation is the flexibility of the systems’ specifications, delivered through ‘modular slice technology’
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