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Swapping Batteries · 3 September 05

Mike wrote the other day to suggest a setup where you have a couple battery packs. Instead of parking the EV to recharge you replace the drained pack with a charged one and the old pack recharges while you are away.

Service stations could offer charged battery packs for some nominal “fuel” fee, much like they do with propane tanks. This might be a little tough to institute: standard battery pack configuration is needed along with quick recharging and methods to qualify the packs (wouldn’t you hate to get someone’s abused, low-range batteries?).

The biggest challenge for a home conversion is that all of the batteries are seldom in one place. The reason we have batteries up front and the rest in the back is to ensure even weight distribution.

I’ve read of conversions where the batteries are rigged into an area under the passenger seating area of the chassis. This is ideal for weight distribution and keeping the center of gravity low. It’s tougher to fabricate and the batteries also need to be some sort of sealed cell since you can’t quickly access them and they may need to lie on their sides.

Maybe the batteries could be in a trailer instead, like the pusher hybrid mentioned yesterday? Someone sent an email wondering just that: can he make an electric pusher for his gas car, to help out around-town driving.

The existing gas vehicle wouldn’t need much, if any, conversion. Issues that come to mind include running the power steering and providing vacuum for the brakes.

It would lose a fair bit of efficiency and range from pushing around the extra weight of the gas engine, exhaust system, and fuel. If the majority of driving is within local, EV range, the pushing of “dead” weight every day adds to the wear and tear of the EV components and shortens the battery life.

All in all I think the gas pusher is a better approach for someone driving EV distances regularly. You only attach the gas engine pod on the days you need to make a longer trip.

Check out JB’s porsche pusher, AC Propulsion’s range extending trailer and the bike pusher.

Flow Battery Schematic

A totally different approach would be to replace the electrolyte instead of the batteries. There’s the flow battery, which allows the active material to be stored outside the battery. In a sense it operates much like a fuel cell as you can see in the diagram on this Redox Flow Battery page.

No idea on the price, availability, or how much electrolyte you’d need to tote around to get sufficient energy.

Reminds me of the phase-change heating packs. Click a little metal thing inside and the sodium acetate quickly turns from liquid to crystal and releases heat. Boil it again to “reset.”

After Gutenberg has an article on the latest happenings in the battery/power acronym biz of LMP, PLI, and I guess FCP.

Comments 1
  1. — DanP    Nov 05, 2008 08:30 AM    #

    Here is another nice one; The RAV4 Long Ranger.