Batteries can weigh a ton- literally. The Pulsar that I acquired the parts from had 120 volts worth of 6V batteries. That's 20 batteries at 60 lbs each. OMG, that's a huge load for that little car to carry. When I tried putting 156V of 13 batteries at 50lbs each, there was a significant difference in acceleration but range suffered. Therein lies the problem every EV builder faces, do I design for speed or do I plan for range. You can't have both - or can you? Within the last couple years the newest technology became affordable - lithium batteries. Last year I put 48 LiFEPO4 batteries in my Sparrow. The results were amazing. Compared to the AGM batteries that were in there before, the sparrow was lighter, faster and the range more than doubled. And because I built a larger pack than what I use, they should last up to 10 years. I can easily say that I won't ever go back to AGM or Sealed Lead Acid batteries again.
The batteries in my Sparrow are in their second year and doing great, but a three wheel car has it's limitations, that's why I bought the Bradley. I'll take the batteries out of the Sparrow and transplant them into the Bradley. Yes, the Bradley will use a little more juice than the Sparrow but it will be nice to have that extra wheel and be able to take a passenger for a ride. Having given you a little background on the batteries let's look at the plan to arrange them in the Bradley.
This is the front battery box. It will connect to the front of the chassis and hang off the bumper steel poles. There will be 20 batteries, each at 7 lbs, so that makes about 140 lbs. This frame uses 1 inch box tube with 1 inch L brackets. With all that road stuff flying at the batteries, thery're going to need some protection - a box.
This is the first draft of the box, it's too tall. The original battery boxes were 14 inches tall for those heavy 6V batteries, and my LiFEPO4 batteries only need 10 inches. That's for the battery plus the battery Management System on top and the wire connections. This box will have a lid with a spy glass area so I can see if the batteries are equalized (a red light on the BMS).
If you're keeping count there's 28 more to go.
This box came form the backseat of the Pulsar. So this is where I saved some money. As you can see, I used to have a waterbed heater attached to keep the batteries warm. I'll get rid of that because the LiFEPO4s don't mind the cold at all. This will hold 2 6 packs and 4 4 packs. Think of this back box being split down the middle. The wiring will go from the left rear to the front then back to the right rear then to the magic box and controller.You can what I'm talking about by looking at the diagram I have created.
Here's the finished backseat box in place. After I trimmed it down and set it in the back. However, I'll have to lose the box so the batteries will fit. I could unstrap the two sixes to make 4X5 packs. The problem is when they strap these cells together it's very difficult to get them back in place. The cells are strapped to keep them from swelling. Swelling can happen from over charging and over discharging.
The back seat area batteries will be strapped down and the frame will be mounted through the fiberglass to either a plate something. The bars will help keep the batteries strapped and from tipping over.
The next problem is reinforcing the backseat area to withstand 200 lbs of weight? Do I add more fiberglass or reinforce with plywood and contact cement? Another Bradley converter used 100 AH AGM cells in the back seat - that was close to 400 lbs. I'm sure he did something to compensate.
Will that be too much weight on the back axle. Nope, the original gas engine weighed approx 200 lbs. The electric motor only weighs 80.
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