One of those things that make so much sense that you wonder “why didn’t I think of that?” That said, the Ego series of lawn care products is much the same. All batteries are physically the same size whether 2.5 amp/hrs or 10. The riding mowers can use the same batteries as a string trimmer, there’s just a minimum number of amp capacity to add to the battery bank and you’re good to go but like this, more AH will go longer.
Nice article Brian! I am of the suspicion that EVs do not pay the same penalty for weight that ICE vehicles do. With an ICE, you expend a bunch of energy to accelerate the mass of the car, then you throw it all away by using friction brakes or some other method to slow it down. With regenerative braking, you get a good proportion of that energy back again. It's not 100% (darn that entropy) but it's a whole lot more than 0%. Anyone who's driven an EV in one-pedal mode knows that you can often go without engaging the friction brakes at all, which means that a very high percentage of the acceleration energy gets recovered. Since the amount of energy involved to accelerate and the amount of energy available to harvest scale directly with the weight of the vehicle, the penalty for weight is not really very large. Where you DO pay a penalty for small batteries is their ability to deliver and store energy. There's a limit to how quickly a battery can transfer this power, and it's basically a percentage of total capacity. In other words, a big honkin' battery can deliver a lot of power in a hurry which is why the fastest EVs are also the ones with the longest range - both come from that big battery, despite the weight disadvantage. But it works the other way, a small battery can't take as much regenerated power so you end up throwing more of your energy away in braking. So your small battery car will likely end up being slower and less efficient. It'll be less expensive since you're leaving those big expensive batteries out, but then the concept of loading up "only what you need" means you have a significant investment sitting in the garage doing nothing. How do Palatov's plans compare to GM's planned modular battery line?
weight is always a penalty - in fact, somewhat hypocritically, Elon claims that the structural monolithic packs are to save weight. hypocritical is because he is adding hundreds of pounds of unnecessary weight to 'save' weight. yes EVs are more efficient with onboard energy, and yes regen helps a bit (not as much as you'd think due to roundtrip energy losses), but more weight will always take more energy to accelerate, decelerate and change direction. even rolling resistance of tires is higher with greater weight.
and you are correct that with current way of doing things, smaller battery is limited in its capacity to deliver energy - typically to 3C sustained and 5C max. in large part this is due to the fusible links necessary to interconnect cells in parallel - that is the only defense against uncontrolled current from adjacent cells if one were to short out. to fuse, the link has to get hot enough to melt. so you're running all interconnects hot, especially when battery is near max output, because otherwise they wouldn't work as fuses. energy loss in interconnect is typically higher than internal energy loss in cells. by only having series connections and having relays on each module we eliminate the need to fusible links and therefore can use very low impedance interconnects.
regular production 2170 cells, such as those from molycell that anyone can buy at retail, are capable of 15C max discharge. we're proven it on the dyno with our D2EV, drawing 1,000W (1,350hp) on the dyno continuously for 45 sec with minimal heat rise.
the other aspect is cooling, which our architecture optimizes far better than conventional approaches.
a 3KWh modbatt module built with molicell cells can deliver 30KW continuous and 45KW peak. not for long due to capacity, granted, but a 15KWh pack made of 5 modules, can deliver 150KW continuous and 225KW peak. plenty for a compact car.
the intent is to have your car configured for your typical daily use, like commuting. if you need more battery for a long trip, you go to a service station and lease more modules. they install them for you jiffy lube style. return when done. you can also have modules in your home, but they wouldn't be sitting idly in the garage - they would be in your powerwall, providing backup power, storing your solar system output, etc.
GM 'modularity' is in 50KWh increments which are way too big to handle manually. also they have parallel connections inside the packs, requiring fusible links and all the inefficiency that goes with those. plus, fusible links don't always prevent fires (and can actually contribute to them) - just ask GM about bolt batteries 😉
hope this answers the questions, but if not i would be happy to explain further.