Battery Charger Feasability

Discussion in 'The Projects Forum' started by Nicholas K. Heinrich, Feb 27, 2012.

  1. Nicholas K. Heinrich

    Thread Starter Active Member

    Feb 25, 2012
    This is all hypothetical (for now at least), but I was wondering if this just too crazy to work! It would be charging a battery bank connected in series to make 240vdc, and would be around 2000 amp hours. I would be using some seriously high powered car alternators to keep this charged up. Question is, how do I take the 12vdc output and step it up to 240vdc? And here is the kicker, the charge rate needs to be close to the drain rate, so around 35kw.
    Thank You,
    Nicholas K. Heinrich
  2. jimkeith

    Well-Known Member

    Oct 26, 2011
    Investigate running automotive alternators at full field--they are designed to put out 14 volts over a 10:1 speed range, so at full field and full RPM, they can put out perhaps 140V at the rated current. This is probably still insufficient voltage, but if the rectifiers are removed and/or converted to voltage doubler types, 240V is perhaps feasible. Another approach would be to transform the voltage further via 3phase transformers--if custom designed, the size would be small due to the high frequency.

    In any of these approaches, the voltage may still be adjusted dynamically via a regulator that tweaks the field current to prevent over-current and over-voltage.
    Nicholas K. Heinrich likes this.
  3. radiohead

    Distinguished Member

    May 28, 2009
    maybe a step-up transformer would work
  4. Nicholas K. Heinrich

    Thread Starter Active Member

    Feb 25, 2012
    I am unfamiliar with 3phase tranformers, but like the idea, as for running them at full field and full rpm, that would be a problem because I need them to charge even at low rpm, such as idle. More or less this is a power supply-with a battery buffer, (a very large one, but still one none the less)
  5. crutschow


    Mar 14, 2008
    No standard automotive alternator will give you anywhere near 35kW. They top out at perhaps 5kW. 35kW is a large alternator. And that requires at least a 30HP engine to drive.

    Sounds like you are trying to make a Chevy Volt.
  6. Nicholas K. Heinrich

    Thread Starter Active Member

    Feb 25, 2012
    I am aware of that, and have not found an alternator for anything that puts out 35kw. Which is why I planned on using 10.