Now that I've got the electric motor mounted in my 1967 VW Beetle, the conversion is picking up steam. I've got a used controller, and I'm ready to start mounting components. That leaves one key bit of equipment on the shopping list.
I picked up the Curis 1231C motor controller (pictured) on Tuesday from Kyle Dansie of ZEV Utah. He's been an invaluable resource as I've been making the switch from gasoline to electricity.
The motor controller takes input from the accelerator pedal and translates it into an appropriate amount of power to send to the motor. It is a critical part of the car for both efficiency and performance. The controller is a used one, but it's in good shape and a deal at $800. It'll handle up to 144 volts and 500 amps, leaving me with enough headroom to add more batteries to the 10 I've got planned for now.
The batteries are in a tidy pile in my garage, so all I need now is a battery charger. Companies like Russco and Quick Charge make some decent chargers that are relatively affordable at $500 to $1,000. That may seem like a hefty chunk of change, but you can easily drop a grand or more on high-end units from Zivans and Manzanitas. Even five bills is a lot for me to lay out at this point.
I knew going into this project I'd need to get creative to keep to my drum-tight budget. I've caught a few breaks on used batteries and I got a sweetheart deal on a Mars electric motor. But I've got less than $500 left in the piggy bank and a lot of odds and ends to buy.
That's got me thinking about a DIY charger.
I've heard of people building their own chargers and wondered how difficult, how safe and how expensive it might be. All a charger really does is apply direct current to a battery, right? How hard can it be? Building my own might get me rolling without breaking the budget.
I did a little digging and found some plans for a DIY charger. Doing it yourself is most tempting when your battery pack's voltage is close to the 110 in your house. No problem -- my Bug will be 120 volts. It's a relatively simple matter to convert AC to DC with a bridge rectifier and a few other parts. I can achieve small voltage modification with an inductor to bump the 110 volts to the 130 or so that is optimal for charging. I was pleasantly surprised to see how easy and cheap this would be to do.
That information tucked away, the next step was consulting my brothers, and a nephew, who happen to be electrical engineers or at least experienced with such things. They confirmed my plan would work and even suggested it wouldn't be hard to control the charger with a $30 open source programmable microcontroller. I figure I don't have too much to lose, since I got my batteries for $5 apiece. If I'd dropped a few grand on batteries, I might be leery of subjecting such an investment to an experimental charger.
There are some downsides, however. The main benefit of manufactured chargers is the managed charge. Not only do they shut off by themselves when the batteries are full, but most of them also have a multiphase charge profile, which is better for battery health and maximum charge. I can accomplish similar results, but it will take a lot of time, research and testing to program the microcontroller and get everything right -- and safe -- and I need a charger soon. The best I can do without a microcontroller is to use one of those household wind-up timers to make sure the charger shuts off before causing trouble.
Another option is using 10 individual chargers, one for each of the batteries in my bug. You can get them for $20 to $30 each. Getting 10 of them would be cheaper than buying a pack charger. Going this route allows me to manage each battery individually, but the penalty is the sloooooooow recharge time. It could take as long as 30 hours to recharge a dead pack. That's unacceptable for a car that will be a daily driver.
So here's my plan: Start with a very simple dumb charger. I'll put a GFI circuit breaker and basic timer in it and I'll consult the experts in my family for safety tips. If I have money in the budget, I'll also buy some individual chargers. The DIY charger can do the bulk charge, and the individual chargers will top off the batteries and keep them equalized. This should be good enough to get me rolling. Once I work out the kinks, I'll work on a second version controlled with the microcontroller.
Got any advice, suggestions or ideas for Matthew? Share ‘em with us! Follow his progress on Twitter @Wired_EV and here at Wired.com every week. He’s also launched a blog, evBeetle.com, to cover the conversion in microscopic detail.
*Photo: Matthew Redd / Wired.com
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