DC/DC converter 72v to 36v?

Hi

Have an 72V nominal (84V) batterypack I'm not using and was thinking of building a 36V "super-commuter". Do you guys know of any low loss DC/DC converter I could use to step down the voltage to 36V nominal (41V)?

Thanks in advance

//Nick

Why not just crack the battery in half and parralel it up?

Motor controllers are buck converters. If you don't want to "crack the battery in half," you can just use a 72V controller to buck the voltage down to your motor. You can even limit throttle to 50% or whatever throttle position corresponds to 36V (I believe most cheap controllers just map throttle position to PWM duty cycle).

Many 36V controllers will not appreciate being fed 84V from a full 72V pack. 63V rated capacitors are pretty common in them. Do some research first.

As for a DC converter, you're going to be looking at fairly large one to drive the bike, and efficiency will take a serious hit. Also you'll have one more thing to go wrong in the system, and unless you oversize and properly cool the converter, it's quite likely to fail.

I'd have a look at the battery and see about breaking it up (electrically, not physically) into 2 36V packs in parallel. Depending on the pack, it might be really easy and totally reversible if you ever need it.

If you're really determined to use a converter, you might look at wturber's wangdd boost converter thread; it might have info on a buck version.


But i don't see why you wouldn't just use a 72v controller and tone down your throttle use if speed is an issue, or use it's own speed limiting and/or power limiting functions, if it has them.


Or get fancy and use a Cycle Analyst to limit things for you.

dustNbone said:

Many 36V controllers will not appreciate being fed 84V from a full 72V pack. 63V rated capacitors are pretty common in them. Do some research first.
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I think you're talking to me here? That's why I said to use a 72V controller.

If you're talking about my last sentence, I guess I should clarify that the 50% throttle still needs to be on a 72V controller.