24 V Battery with step down transformer

Discussion in 'General Technical Questions and Answers' started by WM5TS, Aug 10, 2020.

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  1. WM5TS

    WM5TS XML Subscriber QRZ Page

    Does anyone here use a 24VDC battery and a step down transformer for your Go Kit? IF so what are the pro and cons of this set up? Just wondering if this is an alternative.

    Thanks
     
  2. KM3F

    KM3F Ham Member QRZ Page

    Clear this up please!
    A reduction in DC is done through a regulated series resistance not a transformer.
    Only time a transformer would be used is if the 24 v was driving a switching circuit generating AC then rectified to DC and regulated to 13.6 volts +/-.
    To use 24 vdc, build a series regulator and have it over with.
    All the linear power supplies do that as a normal function off the 120 ac line.
    You could take a linear power supply, remove the heavy power transformer and connect 24vdc to the same point the original power supply connected to the regulator circuit and should end up with the same 13 volt out put. You would have to consider current and power rating capability of the regulator and cooling if needed and fuse protection.
     
  3. W6MK

    W6MK Ham Member QRZ Page

    Lots of people seem to use them (step down converters, not transformers) for powering 12v devices from solar, marine and other systems which operate at voltages from 15V to 48V.

    The caution seems to be to obtain a converter with at least twice the ampere rating that you will require at converter output. As with many consumer items, ratings can be misleading.

    Not my personal experience. Just based on my reading of reviews of people using such converters. As with other things, get a high-quality converter with headroom.

    Output of most inexpensive consumer units seems to be 12V unadjustable. If your gear works better at 13.8V this might be worth consideration.
     
    K0UO likes this.
  4. KF5LJW

    KF5LJW Ham Member QRZ Page

    Geez another CB radio operator who does not know a transformer from a hole in the ground. No such thing as a DC transformer.
     
    W4HWD and K4VLF like this.
  5. KF5LJW

    KF5LJW Ham Member QRZ Page

    Immediately you lose 50% of your power burned off as waste heat. If device uses 100 watts, takes 200 watts to run turning your series regulator into a space heater.

    Linear power supplies and series regulators are just like incandescent light bulbs. Just a matyter of time the Green Mafia comes and takes it away, and bankrupts any manufactures who fails to comply with their wishes. You are next on the hit list to be terminated. :)
     
  6. N7EKU

    N7EKU Ham Member QRZ Page

    Ah,

    Come on, isn't it possible the guy just typed the wrong word? Anyway, some DC-DC converters use the SMPS method and those often use transformers anyway. Looking at his QRZ bio, he doesn't look anything like a greenhorn CB operator :)

    73
     
  7. WM5TS

    WM5TS XML Subscriber QRZ Page

    Stuck in the AC world and used the wrong term. Good to know there are so many people who just can't wait to point out mistakes. Thanks for the honest help to those who sent it in. If anyone can tell me how to edit it I'll be happy to do so or eliminate it.
     
  8. WA9SVD

    WA9SVD Ham Member QRZ Page

    I will take your word that your request is legitimate.

    It will depend upon the current requirements of your "Go-Kit." A simple linear regulator to reduce your 24 Volts to 13.8 Volts (preferable to a simple 12 Volts) can be made easily with "off the shelf" parts from places like Mouser, DigiKey, Jameco etc. The DISadvantage is it WILL be inefficient, and require a substantial heatsink, (think significant added weight) especially if you need more than an Ampere or two. Anything more, and you will have to use (or consider) a switching type step-down supply. Generic plans are available form various places, but you will have to be sure adequate filtering and/or shielding is provided to reduce or eliminate interference to your equipment. The advantage of a switching supply is small(er) size, and (usually much) lighter weight than a linear system, the disadvantage being circuit complexity and often higher cost. Commercially available units may be available for your needs, but may require additional filtering and bypassing of leads to be "radio friendly."
     
  9. KE5MC

    KE5MC Premium Subscriber QRZ Page

    Using Google and the search term "buck converter module" will supply the information you are looking for at least in regard to hardware.

    1. Current draw will be limited to what module is rated for and priced accordingly.
    2. Efficiency is less than 100%, but much better than a linear regulator.
    3. Switching noise in the converter could be a problem for the radio.
    4. Some converters have adjustable output and can have a wide range input.
    5. I'm thinking a 24V battery setup might be bigger and heavier than 12V, but have the advantage of "buck operation" down to battery discharge voltage.

    Likely other points I missed. Interesting project concept, good luck.
    Mike
     
  10. N3HGB

    N3HGB Ham Member QRZ Page

    Is it really necessary to lead off with unfounded personal attacks and "must be a CBer" every time someone uses a poor choice of words? This is exactly what drives people away from this hobby, there is a lot to learn and no one wants to be insulted every time they ask a question.
    We all know transformers don't work at DC and we also know the 1001 varieties of power supplies sometimes just get called transformers generically or maybe the guy was just typing fast and not picking the best words.
    Anyway - for the OP - there are plenty of DC-DC converters around. For one example, 24 volt boats and airplanes sometimes need to run 12 volt radios and 12 volt boat and airplanes sometimes need to run 24 volt radios at the high price and and eBay is full of cheap converters. Some of them run hot and some of them have horrendous RFI. Is there a reason you want 24 volt batteries?
     
    WA7ARK, W2ASC, WR2E and 3 others like this.

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