Have large battery, what to mod?
 

My wife and I are going to be driving to the west coast and back in 2 months and I have been thinking of ways I can utilize some of the stuff I already have to improve mpg.
Car - 2005 Ford Focus auto hatchback
I have been building ebikes and emotorcycles for years now. I do have, at my disposal, a 75v 60ah lithium pack I use on my motorcycle (Nissan Leaf cells). And also a 45v 45ah lithium pack which is in my wife's electric scooter (part of a Chevy Volt battery).
I also have numerous other small ebicycle sized lithium batteries.

I've thought of the 5th wheel drive, because I do have a powerful 10" scooter hub not in use. (from a Zapino scooter). But 98% of driving is going to be highway, so a lower power drive which would be okay for around town is not going to help much. Plus, a drive system is going to be quite complex and not able to integrate for max efficiency (can't just shut off the engine on the Focus on downhills, for example).

I personally want us to sell it and get a used Prius gen 2 or something. But she wants to keep her car until it's 'dead'. Even though it gets 34mpg at best. (not very good IMO)

So.... if I can get a powerful DC-DC step down converter for my 75v battery, I could then hook that up to the 12v system to reduce load on the engine. Maybe unhook the alternator? The battery is 4kwh, so it's got some energy in it.
The AC compressor is the biggest drain on the engine, so if I could power the AC with my battery that would be ideal. Maybe a stand alone AC unit running off my battery? We will be bringing our two dogs, so I know she won't want to be stingy with AC use. (I've driven cross country myself with a soaked tshirt to keep the AC use to a bare minimum. :)

I am going to crawl under the car and see what kind of smoothing I can do with coroplast sheets. My wife isn't going to be happy about any mods that are visible though :p

I just want to see what ideas you experts would consider the best, considering I do have 6kwh of free lithium batteries to use.

Or should I keep trying to convince her to swap over to a Prius? (which I loved driving a '13 model that we rented. I got 64mpg average with lots of highway use.)

The best thing you can do is just drive a slower speed on the highway.
No mods at all to the car. A/C does consume some energy, but not as much as you'd think once the car has been cooled down on a long drive.
Window screens can keep the sun from heating it back up.
Start driving early in the morning when its cool.

electric ac unit from a prius??
alt delete + headlights on battery??

Those are not easy mods. Follow your wife's advice. You'll be better off both money wise and Honey wise.

I think your best bet, considering you're looking at mostly highway cruising, is to minimize the load on your engine and skip any electrical drive or alternator delete mods. The car is proven in its current form, a long trip away from home is NOT the time or place to have a post-mod failure that didn't get found during the shakedown.

Tint your windows. Look at the local laws on the tinting limits, where I live you have to have a minimum of 35% visible light transmitted, and reflective films aren't allowed. Even so that can block a lot of heat coming in. If that works and the mod can be done, then you could consider pulley swaps that would slow down your AC.

Aside from that, I think that aero mods are the way to go. If something goes wrong you just tear them off, fold them up and stuff them into a convenient dumpster at the next potty stop, but the car will still be mechanically sound.

This is, to me, the least stress-inducing option, and vacations are about reducing stress.

Or as you suggested, rent another Prius. The money you save over the cost of gas in your regular car will cover at least part of the rental cost, and Prii are soooo quiet when cruising.

yep aero FTW

Agreed on the aeromods. Do a stealth / backside grill block, and an air dam. She probably won't notice. That'll get you a few percent right there.

Rather than modding the car, can you mod your trip? Much of the intermountain west gets cool to downright cold once the sun goes down, so if you can plan your trip to visit mountains/lakes/forests during the day (and let the dogs play!), and drive nights or early mornings, you won't have much need of A/C. Even further, if it's vacation and not going to a specific destination, driving through Colorado, Wyoming, and out to the Pacific Northwest is going to be a lot cooler (and have better scenery, IMHO) than taking I10 to LA.

I second modding the trip.

When my kids were small and before we had a minivan, we had a Hyundai Excel.

That name was not earned.

Among its many other faults the car's AC was not very powerful but in spite of its poor output, it had a marked effect on the car's performance on hills. To compensate we changed our long trips to take place mostly in the very early morning. To take trips from E. Tennessee to visit my parents in N. Virginia, we would set out at 4:00am. That put us arriving shortly after noon, just as it was starting to get too hot. We did about four trips that way and it was always a much, much better option than starting after sunrise.

Another realization that came out of one of those trips was when we took a detour across the bottom of the state to visit Colonial Williamsburg (hi, Old Mech!). Proceeding up I-95 was a nailbiting nightmare until I backed the cruise control just a couple of miles per hour slower than the vast majority of everything else. Then it became quite a relaxed trip and everyone simply flowed around me.

So: traveling earlier means less AC (and less traffic); slowing down, besides its other benefits noted in these pages, means less stress.

I like my grill block and air dam, although I need to make it prettier. However, people on here like to say that you only need the full grill pulling a trailer uphill through Death Valley in the middle of the summer.

Well, I do not live in Death Valley, the desert is cooler than the city, and you lose temperature when you gain elevation, but my Civic still starts overheating when I drive uphill during the day, but if I leave at 0400, everything is fine.

Do you think that I mind not driving a hot car?

No... :)