Driven Electric Race Car – Heated Battery Boxes
For those of you who have been paying attention I have been working on a project called ‘Driven’ for the last 18months. ‘Driven’ is a single seat electric car project where myself and other Jaguar Land Rover graduates design and build a car to race in the Greenpower race series. On this project I had some help from Zoe and Will, graduates in the year below me on the scheme who will be taking over the project when I leave, thanks for the help guys!
The lead acid batteries we use in our electric car are heavy and the team needs an easy way of transporting them to races and storing in the workshop. Currently we use insulated battery boxes to store our batteries in, transport them to the race however, the boxes are too large and have no way of actively heating their contents. Since batteries are allowed in the rules to be heated to 25degC it makes sense for the team to always be running the batteries at this temperature: with lead acid the warmer the battery the more capacity we can get from it (within reason).
Solution: New battery boxes that incorporate a 12V heated seat pads from old car seats. These will allow us to both transport the batteries and warm them prior to a race simply by plugging in a spare car battery. By making the box just big enough there isn’t too much excess air in box that has to be heated up.
For this project I actually constructed a list of requirements before starting the build:
- 2 boxes should be constructed to hold 4 batteries each (4 batteries are used per car for race days and the team has 2 cars).
- Boxes should be easily moveable
- Boxes should be easy to strap in to the van for transport
- Boxes should use a Red SB50 anderson (12V) for power connection to the heated pad, this is the teams standard connector
- Boxes should be made from a wooden frame base with plywood cladding
- Boxes should look presentable, logos on side prefered.
- Lids should be removable and allow charging of batteries inside the box + battery access.
The bottom frame of the box is made from 2×4. This effectively transmits the weight of the batteries to the castors and gives space to insert a piece of insulation foam. A heated seat pad is re-purposed and simply pressed in to place using the piece of foam. Holes are drilled in the bottom of the plywood base for temperature sensors and to give an easy way to push the foam and pad out in case of maintenance. Castors are mounted so that the box can easily be pushed around the teams workshop.
With 2 bases completed Zoe cut up the plywood sides while Will and I glued and screwed them to the base. Extra timber is used inside the box to stiffen up the corners and give the insulation something to press up against. The 50mm insulation is easy to cut with a saw and simply presses in to place, it seems to hold any heat in very effectively.
A quick coat of paint and some securing handles later and we are finished. Another nice quick project that should help the team for many years to come. Now we just need some nice ‘Driven’ branded stickers to add the final touch.