4 Weeks remaining: Small Scale Prototype

Wayside Power Small Scale Prototype:

 Update 4 Weeks remaining

Issues this week: 

Maxwell has still not gotten back to us, so we have begun to look for cheaper alternatives

1. If we create a supercap bank made up with many 2.7V cells in combination of series and parallel, we will be able to save money.
1. This does cause the charging time to increase to about 4 minuets, up from about 45 seconds, as each cell can only handle about 30A of current vs 2000A with the other more expensive modules.  
2. We will have to solder all of these together. 
3. We will have to create a casing to hold and easily assemble, dissemble. 
4. We can use SAB MOSFETS to balance our series stack and prevent overcharging instead of trying to match a mosfet of the shelf with our ucap modules, this is a good thing!
1. These are specifically designed to be a low cost and low power usage solution to balancing supercaps in series.
2. https://www.digikey.my/en/videos/a/advanced-linear-devices/using-mosfets-to-balance-supercapacitors-automatically   

We are also deciding whether or not we want wayside stations on both sides of the track or only on one side. Here are our thoughts on this:

1. Less expenses on supercaps to build wayside pickup on each end. Only have to design supercaps to work at constant velocity. Stations are designed to accelerate without using on-board supercaps.
2. Benefits of having one wayside station are less manufacturing and labor (This may actually cost more than adding supercaps)

We have also decided to use a regular MOSFET to control the charging of the solar and on-board supercaps to prevent over charging. We will be sending a PWM signal to a mosfet to charge rapidly initially and then slow to a stop when the supercaps are full. You can see in the above figure labeled "MOSFET".

1. The hard part will be to link the current going into the ucap with a % duty cycle to send to the MOSFET. 
1. It will mainly be a 100% duty cycle (fully open gate) up until 90% full to prevent over charging. After 90% the duty cycle will start to decrease until it reaches a point equal to the supercap leakage current to maintain a constant voltage and have no drop.