Electric Vehicle Travel Battery and Support Industry

1. OVEVIEW

ARPA-E Contact: None.
Technical Subcategory: 3.4 Chemical-Electrical
Funding Request: $500,000 Funding Request.
Project Duration: 12 Month Project Duration.
Project Abstract: Battery-Only Electric Vehicles (BOEV) tend to use energy more efficiently than fossil fuel based vehicles, however they are very limited in their travel distance due to the high cost of batteries. When traveling long distances, they are very inconvenient and time consuming to recharge, making them a very poor choice for general long distance travel, and making them non-competitive to fossil fuel vehicles. However, if cars are equipped with several travel battery slots, rental batteries could be inserted and replaced at various service stations along the travel route and make long distance travel almost as easy as fossil fuel vehicles.

2. IMPACT

Battery-Only Electric Vehicles (BOEV) have made some progress into helping the U.S. energy issues of being energy efficient, environmentally friendly, and reducing energy dependence on foreign sources. However, the vehicles are limited in driving range and cannot compete effectively with fossil fuel powered vehicles for the common action of traveling long distances.

This will enhance the economic and energy security of the U.S. by making long distance travel using BOEV more practical that will result in (i) reductions of foreign energy, since the more efficient BOEV can be used for long distance travel, reducing use of gas and diesel cars. (ii) Reductions in energy greenhouse gas emissions since the BOEV does not emit greenhouse gases and energy generation can focus on lower greenhouse emitting energy sources and battery charging stations can more effectively use the time varying power of the zero emission energy from solar and wind more effectively than the general grid power distribution. (iii) This improves the energy efficiency of the automobile industry and generation grid making BOEV usage more universally acceptable. This will ensure that the U.S. will maintain a technical lead in developing and deploying advanced energy technology since this will move towards better infrastructure for BOEV use.

3. STATE OF THE ART

The current BOEV solution has the vehicle sold with its target battery-pack size installed and all charging of the batteries is done within the car. The competing technologies are attempting to make better batteries that are smaller, have higher capacity, better charge cycle count, or better charging characteristics with the goal to sell a unique design to a high usage user, like a vehicle manufacturing company that only offers unique batteries for its production BOEVs. This is undesirable since the BOEV battery systems are diverted away from becoming a common commodity item that would have lower and more stable prices. This allows the car manufactures to sell special batteries at premium prices when selling new vehicles, as well as selling replacement batteries at premium prices. Since the battery cost is substantial, only smaller sized batteries can be put into the vehicles where economics of ownership is a strong consideration.

The BOEV cars are limited in driving range in the moderate cost vehicles of 60 to 120 miles, with only the very expensive electric, prestigious vehicles, have a range of 200 to 300 miles. The typical charge time can take 4 to 8 hours with a fast 30 minute charge, only gets to 80% capacity. Full charge to discharge cycles reduces capacity and also tends to reduce battery life and may need to be replaced 1 or more times during the life of BOEV. These limitations of electric vehicles make them only good for local use, poor as universal replacement of fossil fuel vehicles.

4. INNOVATION

The idea is to use a standard, quickly replaceable battery pack that can be retrofitted into several types of BOEVs.

This works for a person whom wants to use their electric vehicle for travel, they go to the local BOEV battery power energy service station, and rent pre-charged travel batteries. Each battery set/pack stores about 30 kWh of power good for about 100 miles of travel. Generally, a hand controlled electric install dolly, or in the future an automated robot, would be used to quickly remove and insert the heavy battery pack as one unit into one of several accessible battery slots under the front hood and/or back trunk. However, if a electric install dolly is not available, the battery pack is six 5 kWh battery units that can be unlatched from each other and being light-weight enough, can be independently inserted into the battery slots in a few minutes. With a battery weight of 243 Wh/kg using NCR18650B cells, a 5 kWh battery weight would be 20.6 kg. If the shell/enclosure and electronics was 5 kg, the unit weight would be around 25.6 kg or 56.4 lbs with full battery pack around 154 kg or 339 lbs. Future battery packs would probably hold more energy at lighter weights.

A person travels on the freeway and when needing to, stops and gets the batteries swapped for batteries with a full charge. The use of power can be controlled in an ordered manner, using the energy from one travel battery before the next. When the person gets to their travel destination, and if planning to stay for more than several days, they stop at a service station and has the travel batteries removed.

The Travel Batteries are a higher voltage than the vehicle's primary battery set. When power is being used from the batteries, power is measured leaving the battery set into vehicle, and power from the Travel Batteries is pulse switched (very efficient) to the lower voltage into the circuit to equal the power being used. Power back from the vehicle's breaking or when going down a steep hill, is never fed back into the travel battery and only into the vehicle's primary battery. If the vehicles battery power level is down, the battery can be used to charge the vehicle's primary battery while driving, but the user would need to swap the Travel Battery sooner in the trip.

From the service station's point of view, they are a power and battery rent service. The discharged batteries are inserted into a large charging station that uses a computer to predict the car usage needs and consider power prices, solar and wind predications, etc., to try and get the batteries charged at the lowest power prices. When power conditions and prices are right, with extra charged batteries available, uses a local inverter and resells the power back from the stored batteries back into the power grid and make some money by short term grid power stabilization.

The batteries have a computer which monitors each of the cells voltage output during operation, keeps track of the amount of energy stored, and constantly displays the current energy in battery and how much power is used since the last charge. The vehicle has its own power usage measurement system and usage is expected to match within a small error. When plugged into the power charging station, the system can upload battery power usage, cycle information, etc., to cross check operation. Each cell could have an ID chip that allows the cells history and performance to be logged across its lifetime to match with other batteries. The batteries are built to allow the easy change out of a cell going bad, being replaced with a new or a cell with lifetime about the same level. Sometimes the full cell set might be replaced. Functional but aged cells can be kept as short term replacements. Bad cells are recycled since the value of chemicals is high.

No information about a universal BOEV travel battery concept can be found. This technology improvement is based on a new configuration of current technologies which will allow a BOEV to be used for long travel distances in a similar way to the established fossil fuel vehicles.

The new Travel Battery technology will advance the state-of-art of BOEV, by making them more acceptable by giving them the travel characteristics of the current fossil fuel vehicles when traveling main routes, for example, between Portland OR and entering LA California. Here we assume the vehicles are ready to go, energy full and/or Travel Batteries loaded, when starting.

Vehicle Range Travel Drive-hr Exit-hr Station-hr Stops Overhead-hr Total-hr
Gas 300 250 14.25 0.25 0.25 4 2 16.25
BOEV 100 70 14.25 0.25 0.5 14 10.5 24.75
BOEV + 2 TB 300 200 14.25 0.25 0.25 5 2.5 16.75

Figure 1: Vehicles Travel between Portland and Entering City North of LA

The BOEV is a standard car with a 30 kWh battery that has about a 100 mile range. The BOEV + 2 TB is same car type with two 30 kWh Travel Batteries installed. The gas vehicles tend to have a 300 mile range sized gas tank, but generally goes further when freeway driving, but you never want to run too low on gas, so you get gas about every 250 miles which requires 4 stops. The BOEV + 2 TB travel strategy is different, to prevent spending too much time at the service station. The vehicle would travel about 200 miles and only use the extra range of the primary batteries to get to a better service station stop. At the stop, the main battery quick charge is only done while the Travel Batteries are being changed. Without Travel Batteries, a stop distance that would allow the half hour 80% quick charge to work effectively, would be used to stay as short as possible. We will assume that we could effectively reach a station every 70 miles since we never run down to 0 power, which would be very costly to run out of power on the freeway. The stop time would be about 15 minutes off and on the freeway, but require a 30 minute quick charge for each stop. The gas only case would get us there in just over a 16 hr driver time, the BOEV with Travel Batteries would add about 1/2 hour more, with both of these having a low risk of running out of power. However the BOEV only car would take 8 extra hours and if missing the charge exit, has good a chance of running out of power and getting stranded.

5. RISKS AND CHALLENGES

A challenge is that each car company produces different batteries with different voltages and different trunk spaces, making it difficult to create a universal Travel Battery, which could be retrofitted into most of the types of BOEVs. Since car companies want to sell more items, including batteries, they may change the design of future battery systems, and storage space, so that a universal Travel Battery cannot be easily put into them. Also a Lithium Ion cell has a large output voltage operational range of <3 to >4 volts depending on the charge state, current draw, and temperature. High voltage is achieved by putting these in series, however, the voltage swing across the series set during discharge is still > 25%. At the same time, the characteristics of the vehicle's battery has the same operational voltage range issue. It will be challenging to design a battery system to provide the power as needed, possibly charge the primary battery, at the same time operate with whatever state the primary battery is in. Voltage pumps from lower to higher voltage are inefficient, however, the down voltage pulse switching is much more efficient. The system will monitor the voltage and the current currently leaving the battery system and match the power coming out of the Travel Battery system when selected. Any power coming back from the brakes or going downhill will be stored in the primary battery, not the Travel Battery. The goal is renting the battery and selling portable power, charging the Travel Battery in the car or adding the battery as a primary battery is not.

This approach does not require any new innovations to be successful. However Lithium Ion, 18650B cells, used in Tesla vehicles degrade moderately fast when cycled between full and discharged levels, with a predicted life of only 500 cycles. This small cycle count greatly increases the cost of using the battery across its lifetime. The charge cycle life count can be greatly increased by using less than the full charge-discharge cycles. Large cycle counts are very important. Some battery companies claim large cycle counts, but it would need to be evaluated.

BOEV batteries are extremely expensive, making is too costly to sell vehicles at price points competitive to gas vehicles. However, the vehicle is not used continuously, allowing a battery used just a short period and then returned for recharging would cost less than a the cost of ownership. The fee would include the daily battery rent, charge for the energy used, and since the charging cycle can currently affect life of the battery, a charge cycle degrade cost (depending on how the person decided to use it), charged % of battery pickup, and the returned charge level. Currently, a 30 kWh battery would cost about $18 for each cycle for only a 500 cycle count, which is much higher than the energy value and probably higher than the rent. Hopefully, over time, this small cycle count will greatly improve and this will disappear into the daily rental cost.

Initially, a custom battery pack socket would be installed in each car and only in cars that have physical space to do so. When the need for universal Travel Battery slots become obvious, car companies would probably start adding them, since people owning the cars would see a strong need for them. After the first production BOEV with Travel Battery slots starts getting sold, all the others would probably need to follow suit or disappear.

6. PROJECT PLAN

The major tasks to accomplish include: A study of how a BOEV Travel Battery industry can evolve. Research of the different voltage and storage characteristics of BOEV batteries used in current BOEV to determine a good architecture with the goal of a modular 30 kWh battery and base battery slot design, vehicle specific install slot, charging station, travel battery evolution and timeline study, and business plan to match the evolution and timeline.

The work on a BOEV Travel Battery industry includes evolution study and creation of a business plan from the study. Research of the different characteristics of a group of BOEV batteries to determine the characteristics of batteries that can be used in the vehicles. Design and build a Lithium Ion Travel Battery prototype that can be used (probably based on the 18650B cells). Design charging station for the battery set. Stretch goal is to test prototype battery in a BOEV.

7. TEAM

The project will be managed and developed by Mike Polehn, 30 years engineering experience, BS of Computer and Electrical Engineering, OSU (Oregon). We will hire ME and EE college students locally from WSU (Vancouver) part time or paid interns to enhance their education.