supercap

Battery Super-capacitor Hybrid power supply for vehicular and Standalone power supply.

I wroked as a research assistant in this NORAD and KU funded research project carried out at the Nepal Power Engineering Society, Lalitpur, Nepal. 

Project Description
The electric vehicles (called Safa Tempo) running in Kathmandu use Lead Acid Batteries and they are reporting very low battery life. (just a couple of years). One of the possible explanation is that huge currents surges during heavy acceleration and deccelaration are deteriorating​
the battery life. cycle life and rate

In the graph from http://www.mpoweruk.com/, we can see that as the Discharge current is increased, the life of battery gets decreased. If we could somehow limit the peak discharge current through the batter, then we can achive higher self life of the battery.

So the project aim is to divert the surge part of the battery current to a super capacitor and hence improve the battery life. In the process, any step change in the load current will be smoothened and only smooth current passes through the battery and the surge current is supplied by the super capacitor. This improvement in current waveform is postulated to improve the battery life. So, the project work mainly focusses on making the DC-DC convertor to interface supercapacitor into the system so that the surge part of the load current could be drawn from the supercapacitor and hence smooth out the battery current. Here is the basic project layout.

Simplified System Block DiagramA simulation Model has been developed to study the proposed system.

 
matlab model

Here is detailed view of the DC-DC convertor

 convertordetail

The simulation is result shows that the system succeeds in diverting the surge part of the load current through the ultracapacitor and only the steady-state part is consumed by the Battery.

Simulation Result1

The Supercapacitor Voltage Drops when it provides the surge current. But, the control loop soon restores its voltage by slow-charging it. Simulation Result2We have also started hardware fabrication of the project. Some of the hardware section were simulated in Proteus ISIS.

Partial Proteus SimulationHere is a quick-pic of the small hardware setup

smallhardware

Here is a a oscilloscope shot showing the rippling inductor current (measured as the voltage accross the resistor)

Inductor Current Ripple

 

Update:

We eventually changed the topoloy for various reasons. A paper on this project can be downloaded by clicking this link:
Battery Ultracapacitor Hybrid Power supply

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