Has anyone tried charging their i3 with a generator and lev-2 charger?

I don't own an i3... yet, as I've been trying to make the call between a BEV and REX. I know the REX gives shitty performance once the battery is depleted, and only recharges the battery minimally. So what about tossing a 3500 watt generator and a level 2 charger into the back of a BEV, so you can recharge at a decent rate (I figure 10-18 miles per hour) while having a picnic or catching a movie? I think I'd rather have the piece of mind of knowing when I need to, I can pack the generator and recharge anywhere (on those long trips with charging stations far between), rather than having to haul a clunky APU around all the time which doesn't have enough power to maintain highway speeds, and at least on US spec vehicles, cannot be activated on demand.

The REx can maintain city speeds and most legal highway speeds in the USA. It's just that most traffic exceeds the posted speed limits. You'll run into issues if your SOC is low and you then try to maintain high speeds up a long grade, or exceed the capacity of the REx to maintain (generally, a bit over 70mph). You may never have driven a vehicle with a 34Hp motor, but that's what you've got once your battery is low...if you're old enough, one of the original Bug's was in that range. Okay on the flat, but you definitely couldn't storm up a grade with one. At least on the REx, until the battery is on its last legs, you can draw from the battery's buffer to make up for the deficit. If you can get to the top, you can regain some of that energy on the way back down off of a long grade. High, extended speeds are like constantly climbing a grade...your battery buffer will gradually continue to be depleted. When I got into mine today...it said 69-miles to empty. I drove 14-miles, and when I got back, it said 67-miles to empty...how you drive, where you drive, and how fast you drive makes a big difference. This trip was mostly at 35-40mph, my previous trip was partly on the highway at 70mph...gives one pause to think about the impact of speed.

BMW could have made the REx engine larger, but for a car designed for use around the city, it's perfect (IMHO). When you try to use it for long-distance touring, it falls short, but it can still do it just like using pliers when a wrench would work better. Almost no other hybrid out there is a serial hybrid like the i3. Even the i8 is a parallel hybrid, as are all of the other, current BMW's that have batteries. The new x3 is reported to be a BEV, once it eventually shows up. With the slightly larger chassis, IMHO, it would be better with a parallel hybrid, but the infrastructure for DC fast charging may be expanding by the time it shows up.

As to a portable generator...I'm not sure how noisy electrically, the i3's power circuits can handle. NOt all generators put out a clean sinewave. Then, you'd have to have an EVSE rated for the available power, or your charging would be diminished. I'm not all that comfortable carrying around gasoline inside of a vehicle, either. I think you'd find that a 3.5K generator could provide about a max of 10-12 mph into the battery. Keep in mind that those delivered in the USA max out at 7.4Kw/hr and can take 3-4+ hours to fully recharge, depending on the battery...it would take at least double that with a 3.5Kw generator, IF you could load it at its maximum without issues, and the output waveform was acceptable to the vehicle. Many generators are rated at a peak, but also have a different value for constant loading that is lower.

Spacemanwill said:

and at least on US spec vehicles, cannot be activated on demand.

Click to expand...

Well...it can be activated on demand IF you code your car.
To answer your question, carrying a 3500w generator will probably work, but as Jim pointed out, it will take a while to charge. I'm not that patient on a long trip. I'd rather rent an ICE (or use my own ICE). And, like Jim, I'm not wild about keeping gasoline inside the car.
Edit: I've seen a photo of an i3 at a campground that was hooked up to a generator. So somebody has done it.

Not all generators are created equal...some of the cheap ones do stepped sine waves verses true ones. Some electronics don't fare well with lousy acv inputs. I have no insight on whether the i3 cares or not. It could be a really expensive experiment if it failed. Keep in mind that your EVSE would need to be matched to the generator output, as if the EVSE was rated at more than the generator can produce, the car could just overload it and cause it to trip. P=I*E, so if it was outputting 3500W and 240VAC, your EVSE couldn't report more than 3500/240*0.8 (the 0.8 is the maximum you can load a circuit when used constantly like charging a car) or less than 12A. But, since it's at 240vac, it still would be twice what the stock 120vac/12A EVSE that comes with the car. Keep in mind, on a dead battery, the stock EVSE that comes with it (in the USA, anyways), it can take over 20 hours to recharge the newer, larger capacity battery packs...you'd get twice the power with the 240 verses 120. Probably not worth the effort. See if you can find a 120vac plug, and just plug in the one in your trunk.

Thanks, jadnashuanh and theothertom. If I do get an i3 I'll probably do some recoding. Just curious, but how far can you drive in the generator-only mode? I imagine the top speed will continue to drop as the battery buffer is lost. I'm asking because I'm thinking of buying an i3 in Seattle, but I live 300 miles away in Idaho with the Cascade mountain range in between. I could have the car put on a flatbed, but that seems self defeating for such a "green" car, nor can I justify having my car towed immediately after buying it. The EV dealer there told me the trip could be done in a REx but I'd be crawling up the mountain at 30mph. Doesn't sound very safe to me, and driving on the shoulder you risk puncturing those expensive skinny tires. That's why I thought I should buy a BEV, but bring a portable generator and stop to charge up before the hill starts. The BEV has some advantages over the REx such as lighter weight, faster acceleration, a more efficient heat pump (the REx has resistive heating), no ICE maintenance, and no need to ever stop at a gas station. Isn't that the main reason for owning an EV?

It somewhat depends on if there are any charging stations along your route. All new ones have CCS (DC fast charging) capability (useless if you can't find a station, though!). Ideally, they would be along your route.

The logic won't start to limit things until your SOC drops below about 6% or so. It starts by reducing the HVAC, and then, the max acceleration rate, then finally, the maximum velocity. Note, some have indicated that the 2018 version gets a bit more power out of the REx than the earlier versions which may mean you can go a little faster without draining the battery. It's simple to recode the car, and you could do that in the parking lot in a few minutes. That would let you start the REx manually at anything less than 75% charge, rather than it waiting until 6%, where there's a lot less buffer. Note, when you shut off the car, whatever the SOC is, is the maximum the hold function will try to maintain. Some leave the car on and exit from the passenger's side so it will stay on to not reset that value. That can get you in trouble if the REx is still on, as all of the service stations really want the car to be not running when being refueled. The car will turn off if you open the driver's door if your seat belt is off.

If you ignore the warnings, then the drop from 'full' power to degraded mode can be quite dramatic from what I hear (I have a BEV). But, if you slow down a bit, you may never notice any issues at all. It might take 50mph at the steeper sections. You can get an idea of what's going on, and how much you need to adjust by monitoring the Kw output and the SOC percentage of full charge.

So, sort of depends. The dealer may be willing to include shipping to your home. One thing to consider is eventual service, but that may not be an issue if you're buying remote, but have a local dealer. Service at the purchasing dealership may get you a bit better response, though.

Spacemanwill said:

. . . . I'm asking because I'm thinking of buying an i3 in Seattle, but I live 300 miles away in Idaho with the Cascade mountain range in between. I could have the car put on a flatbed, but that seems self defeating for such a "green" car, nor can I justify having my car towed immediately after buying it. The EV dealer there told me the trip could be done in a REx but I'd be crawling up the mountain at 30mph. . . .

Click to expand...

Here is a summary of my purchase experience: https://priuschat.com/threads/why-the-bmw-i3-rex.165584/page-2#post-2356975

. . . I just arrived home with the BMW i3-REx:

• Left 5:53 PM, Arrived: 5:10 AM
• 9:31 - driving duration
• 462 miles - distance
• 4.6 mi/kWh
  
• 49.8 mph - speed
• Starting SOC: 100%, Ending 72%
• Fuelings
  • $5.10 - 1.75 gal
  • $4.35 - 1.50 gal
  • $3.29 - 1.45 gal
  • $3.65 - 1.48 gal
  • $3.89 - 1.53 gal
  • $3.70 - 1.55 gal
  • $3.88 - 1.58 gal
  • 10.84 gal - 462 miles -> 42.6 MPG
• @65 mph - 1.48 gal - 60 miles -> 40.5 MPG
• @55 mph - 1.584 gal - 70.3 miles -> 44.5 MPG
• dynamic cruise control tripped out three times, two driving into sunset and one at ~10 PM
• "Check Engine" light self-cleared within 10 miles
• Put car on free, public charger while eating supper, added ~7% SOC
• Commercial charger could not be made to work ... will check credit card for charges anyway

Still learning the car and systems. So far, no surprises. Taking a nap before trying Level 1 charging at home. Eventually, electrican for better home charger. Also test the Whole Foods and other chargers.

Bob Wilson

Interesting, so the REx gets lower fuel efficiency than a Prius on long trips. But I know, where the i3 shines is in city driving, on battery power only, charged at night when the rates are lower, and preferably from a utility that generates renewable energy. The ICE generator is only a stopgap until a better charging infrastructure is in place. Personally, I'd like to see in-road inductive charging. Someone just needs to build a truck that digs a trench, lays a cable, then patches the road as it goes. Maybe Musk has already thought of that. Alternatively, inductive charging could be integrated into prefab road tiles that also incorporate solar panels, but that's still a long ways off. Maybe before that ever happens, we'll all be flying electric quadcopters instead.

Spacemanwill said:

Just curious, but how far can you drive in the generator-only mode? I imagine the top speed will continue to drop as the battery buffer is lost.
The EV dealer there told me the trip could be done in a REx but I'd be crawling up the mountain at 30mph.

Click to expand...

My guess-o-meter (GOM) says about 80 miles range on the REx. Top speed doesn't drop until you hit around 5-6% state of charge. State of charge will drop with the REx on if you drive much over 60 mph. That's why you need to code the car to turn on the REx around 75% so you can continue to drive at highway speeds and keep the state of charge "up".
Get the plugshare app (free) for you phone so you can see where the charging stations are along your route and in your local area.

Everything you say about the REx vs BEV is true. Long term, if you'd rather have a BEV, that's what I would get and flatbed it to your home. Otherwise get the REx and drive it home but code it before you leave Seattle. Search for experiences with Bimmercode app. That seems to be the most convenient way to code your car.

Spacemanwill said:

Interesting, so the REx gets lower fuel efficiency than a Prius on long trips. . . .

Click to expand...

I find long trips are 10-15% of our total miles. The 40-42 MPG is for us, acceptable.

Good luck,
Bob Wilson

The REx will run at different speeds, somewhat unrelated to your actual road speed...it adjusts to try to balance the generator to the actual power use of the vehicle. So, if you're not driving fast, the engine won't run as fast to maintain your SOC. Running fast enough to require full speed on the REx will drop your efficiency. Things like your HVAC setting, headlight use, seat heaters, rear window defogger, etc. will all vary how much power is needed, and force the REx to try to compensate. This is one reason why the ECO modes help...they limit the use of some of those functions. The active cruise control is much more steady on the throttle than a human can be the vast majority of the time, accelerating and decelerating smoother (and slower) than most people would, which helps as well. Pushing the REx at high speed, running in comfort mode without regard for efficiency, you can figure closer to the mid-30's mpg...IOW, it's not that great in the ICE scheme of things for similarly sized vehicles. Given that it was designed as an emergency backup, that lower efficiency was acceptable to the designers. When used as intended, the REx would rarely be used, and it's mostly a mute point. My ICE can achieve over 30mpg, running 70mph, and do it for 500-miles or so without stopping...it is my longer-distance ride. I wouldn't use the i3 REx as a long-distance ride unless it was my only choice or under special circumstances, like maybe getting it from the dealership to home - IOW, a very rare occurrence.

Thanks, guys! I really appreciate all your help. If I have any more questions regarding REx vs. BEV, I'll post em here.

I gotta say, all it took was one test drive of the i3 with its smooth silent acceleration, high seating position, and one pedal driving, and I was sold! Never thought I'd give up stick shift driving, but like the ICE, they'll soon be relics of the past. And that's a good thing! Happy EV'ing.

It had crossed my mind of the possibility of fitting a wood burning stove in the back of my i3 for the winter. If fitted with a big Peltier device it could help charge the batteries and any residual heat could be used to warm the batteries and cabin.
I already found out that the i3 boot (trunk) is just wide enough to fit a wooden pallet which I burn in my stove at home.

Surely, you're joking.

Spacemanwill said:

Surely, you're joking.

Click to expand...

BMW are already developing a 500W TEG (Thermal Electric Generator) to extract waste heat from an ICE exhaust, so I could use a couple of those.
A small stove should be able to push out 3KW equivalent of heat. If I can then harness 1KW as electric and the other 2KW to keep the cabin and batteries warm.
I'm sure the extra weight of a small stove is equivalent to that of the Range Extender.

(I was joking by the way, but the numbers do actually stack up!)

Kristian

Within half a mile from picking up the car, I had it coded for 75% enable. Within 12 miles, I enabled the REx and drove 465 miles home over a mountain pass.

A former Prius owner, driving 63 mph or following a semi-trailer truck and you'll get closer to 65-75 miles per tank, ~1:15 (hh:mm.) It remains our backup for our SR+ Model 3.

Bob Wilson