Hello to All,
> Mark Freidberg wrote:
>It seems to me these “modular battery packs” could enable EVs to
>really take hold in the mainstream.
Then, Lee Hart wrote:
> Sure; it’s done with electric forklifts all the time. The batteries are
> in big standardized packs that can be quickly swapped (with a forklift
> of course!
Yes, it’s done in the warehousing industry as a norm. Warehouses that run their lift trucks 24/7 ‘depend’ on battery swapping and have a battery room and gantry crane to do the job. It takes all of 5 minutes, from the moment the operator drives his tired forklift into the bay, until the time he’s rolling away with a freshly charged battery.
> The challenge is that when you convert a normal car, there is no place
> to put a normal quick-change forklift pack. They are in steel boxes
> about 1′ x 3′ x 2′ high, that weighs half a ton or more. Forklift packs
> are also usually 36-48v — lower than most people want.
Pallet jack industrial batteries are about the size Lee describes, are most always 24V, and weigh between 585-800 lbs. Stand-up rider type forklifts, like the ones you see at Costco and Winco stores, use 24V or 36V batteries that are larger at about 2′ x 3′ x 2.5′ and weigh 1800-2000 lbs. The typical electric sit-down forklift uses 24V, 36V, and 48V batteries that are about 2.5-3′ x 3′ x 2.5′ and weigh 2000-3500 lbs. The 24V battery is going away as used in sit-down type lift trucks, the 36V is now the most common, and the 48V is used in the larger, higher capacity trucks. Of course, with AC systems coming on line, 72V & 80V batteries are used as well, but these are not very common yet.
Forklift batteries are designed for relatively low currents that peak at around 500 amps and average in the 150-200 amp range. They actually want these batteries to remain heavy for ballast, so their 1/4 thick plate steel cases are perfect. The tubular type plates of a forklift battery are designed for deep discharges daily, and very long cycle life, at the expense of very low power density. For an on-road EV where weight is the enemy, a forklift battery would give low range, compared to the same weight in, say 6V golf car batteries. A forklift battery would also give substandard power performance. That said, you could pull a forklift battery down 80% every day, and have it last 5-7 years!
> A modular pack for a road-going EV would need a different configuration.
> Maybe something more like 2′ x 2′ x 1′ that weighs under 600 lbs and
> delivers 72v or more. Then you’d need to provide “hole” or other
> hatchway so a pallet jack or something similar could insert or remove
> the pack. You’d need to use 2 or more such packs to get higher voltages.
You’d need at least two of the 48V, 2600 lb. type batteries to get to 96V. A vehicle using two of these batteries would weigh 7000 lbs. at least, and at a safe max current of 500 amps, 45 kw or about 45 hp would be all you could wring out of them for accelerating a 3.5 ton vehicle…argghh!!! Once you got this monster up and rolling however, it’s range would be impressive. I suspect that on a flat long stretch of open highway at 55 mph, this beast of an EV would draw 200 amps continuously. These 48V, 2600 lb. batteries are rated at 1000 ahr @ C6, so they could easily deliver that 200 amps for 4 hours continuously without harming them at all. That’s 220 miles range….God help you though, if you ever have to accelerate out of another car’s way, or pull any kind of hill!
I suppose if one lived in Wyoming or eastern Idaho where long and lonely highways seem to stretch forever on the flat plains, a midsized pickup with a beefed up frame and suspension, fitted with twin 48V forklift batteries, might be just the ticket for your daily 100 mile commute Heck, if they had a crane at your work destination and a pair of industrial chargers on hand, and if you had the same setup at home, a 200+ mile commute would be quite feasible. Using the bed as the dual battery nesting area, you already have that ‘hole’ Lee mentions.
Back to reality….battery swapping would be practical with a compact 400 lb. LiIon battery that could be ejected and inserted like a fat CD in a big slot at the rear just under the trunk floor. With that kind of weight and size, a small metal dolly on rollers would be all one would need. On the other hand, using a 400 lb. advanced LiIon battery with 200 miles range per charge and a good fast charger, the need to swap out batteries would be minimized.
See Ya……John Wayland