Hi there, wow, look at the start date of this post lol.
Though id let you know how it all went, I managed to get an A on my folder and A for my prototype model and this thread has undoubtably helped me to achieve that. So your probably wondering what the solution was......
Well, after countless hours of researching into Li and lead acid batteries it was evidently clear that they were not small enough to get the overall purpose of the prototype (to reduce the size dramatically). I researched further into transformers and the problem lay with the amps as oppose to the volts like you guys claimed from the start. I really couldnt comprehend how much power a standard calcium car battery puts out.
Then randomly i stumbled across a Japanese designers website, who had development sketches for a 'Mini Max 900' jump starter, in association with a company called GP Batteries. I was slightly annoyed that someone had the same design goals as me and had already fully developed it, but thats life. I found they were using a new technology called TMF batteries (Thin Metal Film), and these batteries were easily pushing out 900 amperes at 12-14volts (6 in a battery pack).
I ordered one of these online, they were incredibly hard to find in the uk. And the unit was so small as the main GRP shell only housed a pcb, 9 aa batteries and the TMF battery pack composing of 6 individual lead acid batteries.
Obviously A level projects dont't require you to invent new technologies lol, so i stripped the unit apart, and used the TMF battery unit which was secured to two copper plated clamps as the basis for my design. I then managed to encorporate this into my new grp shell and created a new circuit board which contained the same safety features but got rid of the need for the backup AA batteries which were wired in, which saved a lot of space. This allowed me to reduce the size of the product by 40% for my final prototype. Then using CAD/CAM i manufactured the external shell, created necessary fixtures for the DC charger input and thought i would spice the design up a bit by running two 4000mcd LED's off the power supply, which wasnt exactly cheap.
The overall effect i think was really well made and fully functional, it was able to jump a near dead battery 4 times before needing charging. The TMF batteries can also self charge from the primary car battery once the car is running. I think its an incredible technology and its now being widely used in other applications, the company leading the way are called BolderTech. They didnt have a fully working website so finding more information on them was damn near impossible.
Once again thanks for setting me on the right lines with power outputs etc, i valued every suggestion. Its a shame i wont be using my design skills again as im going onto Computer Science at Durham Uni. This really has been the hardest project ive done yet, ill get up pictures as soon as i get the model back from the exam board.
For those interested, here's some info on the SecureStart - jump starters:
**broken link removed**
Cheers
Dan