Voltage Regulation of LA Batteries

Discussion in 'General Electronics Chat' started by stube40, Oct 14, 2010.

  1. stube40

    Thread Starter Member

    Feb 3, 2010
    I'm trying to drop the voltage of a 12V to approx 2V but allow many 100s of amps to be drawn, in order to provide power to an experimental DC motor.

    I've considered many options, of which the TPS40180EVM module is my favourite so far.

    However, I'm playing around with another option of turning the DC battery output into AC using a H-bridge to create a -12V / + 12V square wave then feeding this into a step-down transformer, then using rectification and filtering to create a 2V DC output (we can handle a bit of ripple in the motor). The advantage of this method is being able to handle the high currents with suitable choice of power transformer, rectification and filtering components.

    I just wondered if anyone had any thoughts on this idea, or if anyone had any better ideas?
  2. timrobbins

    Senior Member

    Aug 29, 2009
    Use a battery with fewer cells.
  3. sceadwian

    New Member

    Jun 1, 2009
    Of what possible even theoretical use could a low voltage ultra high current motor benefit anything?

    If you could define the specifications of your experimental situations I can guarantee someone would come up with a better idea.
  4. marshallf3

    Well-Known Member

    Jul 26, 2010
    Problem with the H bridge is that to get any efficiency from it you'd have to switch it as a square wave which would then induce losses from the transformer trying to deal with them.

    Seems to me you could make some sort of buck converter circuit that would be more efficient, but dealing with that amount of current is always going to present some interesting chalenges.
  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    You aren't looking hard enough. There are sources for LARGE single cell lead acid batteries out there. The need for 2V and the idea to use lead acid for large current supply was genius.

    Don't blow it trying to whimp out with a car battery. :(

    A single cell 2V lead acid battery that can deliver 1200 amp or even more can be purchased.


    Have you looked? These would be PERFECT for your stated needs. (and some 0000 cable and a rented hydralic crimping machine, for making the cables) :)
  6. stube40

    Thread Starter Member

    Feb 3, 2010
    Thanks - that battery is amazing!!! I've already contacted them to see if they ship to Australia and, if so, the ungodly price they'll charge to ship the beast!!

    The downside of this solution is that I am stuck with a fixed voltage. I dont know yet whether this is a problem - it may not be. Although, I had always targetted being able to fine tune the voltage up and down a notch or too. However, the general consensus would be that designing a buck converter to work at 500A or above would be a significant challange. In which case, the 2V LA battery is the obvious way forward............
  7. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    You might look at local battery supply shops.

    Electric Forklifts need their batteries rebuilt, and I bet there is a shop near you that handles them.

    They can provide a battery that will do what you want almost guaranteed.

    It would be a matter of taking a battery from an electric pallet handler I expect, and putting the cells in a set of shorter series configurations. You could use those smaller batteries in the body of the larger battery either in parallel or in sequence.

    The only problem will be that they shouldn't or won't want to set them up permanently connected in parallel. You would have a separate hookup for each battery created in the battery pack. That means extra sets of heavy wiring, or heavy diodes, relays, or transistors for switching them into a single set of power leads.