Charge The Batteries

Safely ImplementProcess

Access BMS Port Access Voltage Source Apply Charge to BMSStop When BMS

indicates Full

Voltage Level Signal

Cut off Flow

Boolean Status Signal

Allowcurrent flow

Set Flow RateLocate J-1772 Locate Wall outlet

Plug cable in

Locate Plug

Plug in Cables

Master KeyTimer while

charging

E-Stop

Functional Decomposition Flowchart

Method 1 2 3 4 5

Power on button voice command clap/sound detection remote control signal from bike

Set rate dial potentiometer signal from bike buttons sliding potentiometer voice input

Detect charge from bike current sensor voltage detection temperature gauge coulomb counting

Stop flow of charge relays power transistors reactive decoupling robotic arm disconnect self termination

Emergency disconnect relays stop conducting reactive disconnect transistors software

Notify user when done audible alert visible alert both none

Prevent unauth. use pin code lock/key software password

Selection Criteria1. Safe to use2. Easy to use

3. Charges quickly4. Returns useful data

5. Portability

Legend1st choice2nd choice3rd choice

Morphological Chart & Concept Selection

Item Justification

Mechanical button powers on the charger A mechanical button is the easiest, cheapest and most reliable method of powering on the

charger. Other options involve significant time and resources to develop.

A dial potentiometer sets the charge rate A potentiometer is the most practical and user-friendly way of setting the charge rate, as the charge level can be adjusted in a continuous

manner (there aren’t discrete charge levels). A sliding potentiometer may also work; the choice of a dial potentiometer is a matter of personal

preference.

The charge on a battery pack is detected via coulomb counting

Coulomb counting is the method requested by EVT, as it is already implemented on their bike

and it offers the most accurate measurement of charge. Coulomb counting also only requires a wire with a resistance of 1 ohm and a voltage

sensor to implement, making it cost effective as well.

Power transistors are used in place of a transformer

Power transistors are far safer than a transformer, generate less heat, and have a much

smaller physical footprint.

Power transistors are used to stop the flow of charge

Since power transistors are being used in place of a transformer, they can also be used to stop the

flow of charge without needing extra components (like relays).

The user is notified via an audio-visual alert when the battery is finished charging

An audio-visual alert ensures that the user does not have to “guess” when the charging is complete. The visual alert also ensures an

optimal user experience for deaf/hard-of-hearing users.

A key must be inserted into the device in order for charging to initiate.

Requiring the use of a key to facilitate charging ensures that unauthorized use of the charger does not occur. This allows EVT to ensure that

every user is trained in using the charger before being able to use the charger.

Architecture

Control System

User Interface

Voltage regulation

Emergency Saftey Systems

CAN Communications

MSD Project Risk Assessment Template

ID Risk Item Effect Cause Like

liho

od

Seve

rity

Imp

ort

ance

Action to Minimize Risk Owner

Describe the risk briefly What is the effect on any or all of the project deliverables if the cause actually happens?

What are the possible cause(s) of this risk?

L*S What action(s) will you take (and by when) to prevent, reduce the impact of, or transfer the risk of this occurring?

Who is responsible for following through on mitigation?

1

J-1772 interface unobtainable

The charger will not be usable with J-1772 chargers unless an adapter is manufactured in house

IP restrictions/low demand or supply for the interface

1 6 6 Conduct proper research into the ability to purchase this interface

Team

2 Electrocution from arc flash

Damaged equipment, injured operator/bystander Battery failure 1 9 9

Researching and developing a safety mechanism that shuts down the charger and electrical system when failure is detected Team

3

Battery management system fails to cut off the charge

Batteries overcharge/lifecycle decreases

Microcontroller fails to detect a full battery/communication disconnect 3 7 21

Thorough debugging of code/firmware will be implemented, a microcontroller that can effectively communicate with the BMS will be researched and purchased. Use test equipment to ensure that the battery cells will not exceed or meet 100% capacity Team

4 Automatic switching system does not exist

Charger cannot automatically detect and switch between 120V and J-1772 charging

Unforeseen issues with the J-1772 protocol that prevent current switching 2 4 8

Researching J-1772 charging standard to ensure that automatic switching is possible, discuss alternate methods to implement current switching if a problem is found Team

5 Damage to charger

Must replace damaged equipment/increased cost due to replacement

Improper use, overheating, system design, short circuit 2 9 18

Implementation of redundant safety systems and procedures. Adequate research and testing to validate design Team

6 Design Over-Budget Not all components are obtainable

Lack of oversight, incorrect parts ordered, replacement to damaged parts 2 7 14

Keep a log of desired items/components, assign an estimate cost to each system, and minimize risk 5.

Team/Project Manager

7 Design behind schedule Project deliverables incomplete

Unforeseen design complications, Risk 5, Lack of communication between team 3 5 15

Team must update/adhere to schedule on a regular basis and maintain communication of any possible complications or FMEA’s

Project Manager/Team

8 System function fails test Function must be corrected

Inadequate components within system, not designed to interface with other functions 2 6 12

Adequate research will minimize risks. Having multiple concepts per subsystem/function will provide a backup in case system is proven to fail. Team

Likelihood scale Severity scale

1 - This cause is unlikely to happen 1 - The impact on the project is very minor. We will still meet deliverables on time and within budget, but it will cause extra work

2 - This cause could conceivably happen 4 - The impact on the project is noticeable. We will deliver reduced functionality, go over budget, or fail to meet some of our Engineering Specifications.

3 - This cause is very likely to happen 9 - The impact on the project is severe. We will not be able to deliver, or what we deliver will not meet the customer's needs.

“Importance Score” (Likelihood x Severity) – use this to guide your preference for a risk management strategy

Prevent Action will be taken to prevent the cause(s) from occurring in the first place.

Reduce Action will be taken to reduce the likelihood of the cause and/or the severity of the effect on the project, should the cause occur

Transfer Action will be taken to transfer the risk to something else. Insurance is an example of this. You purchase an insurance policy that contractually binds an insurance company to pay for your loss in the event of accident. This transfers the financial consequences of the accident to someone else. Your car is still a wreck, of course.

Accept Low importance risks may not justify any action at all. If they happen, you simply accept the consequences.

Test Plan ( First Cut )

1) Test AC/DC converter

a) Verify proper rectification of AC signal to DC

2) Test Voltage regulator

a) Verify proper control and accuracy of voltage regulator

3) Test User Interface

a) Verify Ease of use

4) Test Emergency systems

a) Verify proper reactions to error states

5) Test CAN Communication

a) Verify Communications to the BMS