EV 'spare gas can'

REQUIREMENTS

• Charging EV without a charging network.
• Electric power when parked anywhere.

MARKET RESEARCH

I have been shopping for a portable generator (aka., EV equivalent of a spare gas can) that could be independent of any charging network and found:

• Sportsman Gasoline 4,000W Portable Generator
  • Sustained 3,500W
  • 1,750 W, 10 hrs, 3.6 gallons = 17.5 kWh
  • 70 mi ~= 4 mi/kWh * 17.5 kWh (@4 mi/kWh)
    • ~20 mi/gal = 70 mi / 3.6 gal
• 23" x 20" x 18"
• 101 lbs
• 120 VAC NEMA TT-30 (3.6 kW)
  • ~14 mi range per hour (4 mi/kWh)
• ~$300 purchase
• Air cooled

OPERATIONAL SCENARIO

Both of my EVs, a 2019 Tesla Model 3 and 2017 BMW i3-REx, have a 2" receiver hitch and one shared, removable, 2" rear carrier platform. Mount the generator on platform with folding, adjustable legs so only 50 lbs has to be raised at a time.

The 2017 BMW i3-REx has a range extender with ~88 mi gas range. But it does not have a range extender engine mode with power outlets when parked. Once parked, It has a limited, 150 W, inverter on a very small 12 V battery.

My 2019 Tesla Model 3 Std Rng has a 48 kWh, traction battery with no power outlets. There is a 150 W, 12 V source from a very small battery.

Bob Wilson

 

My Tesla requires a minimum of 6 A and the requirement may occur when there is insufficient solar flux. This is a 'spare can' solution which means 24x7. There are solar-to-battery systems that have much lower kWh capacity, heavier, and cost a lot more.

You are asking the right question.

I had considered higher energy density cells like those used in missiles. These primary cells often use a chemical 'fire' to melt the electrolyte and generate a great deal of energy in a short time. The light weight and high energy solve the problem BUT they are expensive and one-time only use.

Bob Wilson

 

Can you provide a product URL so I can check?

The portable energy storage batteries I've seen reviewed are heavier for less energy. Weight and power are critical requirements.

Bob Wilson

 

Thanks!

Specs from the web page:

• Capacity - 2048Wh
  • two DELTA 2 Max Smart Extra Batteries
  • AC Output - 2400W total
  • (Surge 4800W)
  • X-Boost 3400 W
• Dimensions - 497 × 242 × 305 mm /19.6 × 9.5 × 12 in
• Net weight - 50 lbs (23kg)
• Cost - $1,749

Capacity 2 kWh versus 17 kWh. Weight 50 lbs vs 101 lbs. Cost $1,749 vs $300.

So it has half the weight for 1/8th the capacity for 5 times the cost. You're right, impractical for an 'EV spare gas can.'

Bob Wilson

 

No problem. We have different requirements.

Bob Wilson

 

If not, I’ll return it. Can you share the voltage waveform from that generator?

Bob Wilson

 

I had looked at RC-sized, turbine engines because of small size and low weight. But costing over $2,000, made them an expensive choice. Furthermore, I would have to come up with a generator and inverter. See XICOY X45 Micro Turboprop.

There are some interesting Wankel generators also smaller and lower weight. But so far, I'm only seeing manufactured units output 72 VDC or lower. Prices are just double the unit I'm looking at. I did see one 120 VAC, 3 kW unit on Ebay that is is no longer in production.

A Google survey suggests ~$300 in the 3-4kW range is the optimum price-performance range. Lower priced, ~$250, are in the 2kW range, half the power.

Bob Wilson

 

Two weeks later, I bought a 2017 BMW i3-REx which is a great, urban car. The short wheel base, BMW suspension, and battery lowered center of gravity, it is a pocket rocket around town. But the short wheel base makes it 'rocking horse' on many Interstates at speed. It lacks Autopilot/Full Self Driving driver assistance. So I have two EVs:

• 2019 Model 3 Standard Range Plus - cheapest to drive, a great cross country car, and mostly well behaved. But at 115,000 miles and 4+ years, I have begun to doubt the "reserve range" claims of early reviewers. I've bought instrumentation to find out but doing the 'forbidden' experiment requires the 'EV spare gas tank.' Furthermore, 'hotel Tesla' lacks off-grid power.
• 2017 BMW i3-REx - slightly more expensive to drive and manual driving with dumb cruise control, a hoot in traffic. At 56,000 miles, there is about a year of battery warranty left but it looks to have ~27 kWh from the new 28 kWh. A recent benchmark showed 106 mi EV range at 65 mph on a Standard day. Like the Tesla, 'hotel BMW' lacks off-grid power.

Having two EVs, I can tackle multi-day repairs on one and still have a working EV to get tools, parts, and live normally (well what I call normal.) This reduces my total cost of ownership and provides intellectual amusements for this retired, 73 year old, engineer. <GRINS>

My EV projects list:

• Tesla front suspension link - a latent design defect lets rain water drip on the front, upper ball joint. This leads to a squeak that can be temporarily resolved by disconnecting the ball joint and manipulating the residual grease on the joint. But it will come back. So I have a pair of after market links that 'shelter' the ball joint from rain water. Each will require a long day to remove the old links and install the new.
• "Hotel Tesla and BMW" - rework or replace the passenger seat and rear bench cushions so both have a fully reclined, single bed. I did this with my 2003 Prius gaining not only a place to cat-nap but also handle larger, longer loads. In effect, 2x4 boards from the passenger footwell out the open trunk.
• Complete Tesla silvered cabin cover - a work in progress for the Tesla, I'm adding additional side cords to handle winds better. The current one reduces the outside and inside temperatures to 5 F in the midday sun. Tenting will be independent as the Tesla is too low to support standup, door tenting.
• Combined BMW cabin cover and tent - planned, it will achieve Tesla temperature management but also provide a stand-up tent when camping or traveling. Designed for Spring, Summer, and Fall, it supports comfortable camping even in moderate rain.
• Tesla aerodynamic tuning - underbody air dams, wheel covers, front air inlet covers, removable side mirrors, anti-bloom side camera covers.
• Tesla steering with self driving spoofing - cut the upper steering section to make it into a yoke. The steering spoof supports hands-free driving.
• Identify failing sensor - a puzzle with just one mechanic, me.
• BMW and Tesla trailer wiring - I want a universal solution for both vehicles that uses a trailer electric supply.
• Transformer trailer - low profile, aerodynamic, crank-up, with no drag motor and regenerative braking. Works from a blizzard to Death Valley. Tented, bug-resistant cooking, out side galley. It might look a lot like a BMW i3-REx.

That is my short list.

Bob Wilson