using a power supply to charge a battery.

Discussion in 'General Technical Questions and Answers' started by KC9NEQ, Oct 28, 2008.

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  1. KC9NEQ

    KC9NEQ Ham Member QRZ Page

    i have a mfj-4035mv regulated power supply.
    can i use this power supply to charge a 12v deep cycle marine battery or a regular 12 car battery?
    if so, will i need any type of additional hardware or attachment to use it?
  2. WB7DMX

    WB7DMX Guest

    if you can set the output voltage to 15 to 16 volts yes you can as long as you watch the amps and the voltage, you may need to manually adjust the voltage to keep things working.
    also you may need to install a diode with the neccessary currant rateing to prevent any voltage feed back to the regulator circuit of the power supply.

    if you can't do any of the above, then your answere would be a definate NO.
  3. K7JEM

    K7JEM Ham Member QRZ Page

    Actually, it should work OK. Turn the supply on, and adjust the supply to near the battery voltage. Then connect the supply to the battery. Then crank up the voltage to 14v or so, making sure the current doesn't exceed whatever rate you want the battery to charge at. You may have to adjust the voltage again as the battery gets charged.

    Since this model has an ammeter built in, it should be really easy to do.

  4. W5HTW

    W5HTW Ham Member QRZ Page

    Yes, but I would not attempt to use it to charge a badly discharged battery. The initial current draw would likely be excessive. That supply has a fuse, but if pushed to deliver a sudden demand of 30 or 40 amps, there could be damage.

    To charge a slightly discharged battery, not a problem. Do as JEM says. To maintain a charge on a battery, (and I have used that exact supply to do this) simply set the voltage control at 13.8 VDC and it will draw only the current necessary to keep the battery operational.

    If your battery is badly discharged, a standard automotive charger is best used to return it to full charge. That has current limiting and will not cause damage to either the charger or the battery.

  5. K7JEM

    K7JEM Ham Member QRZ Page

    That is the reason to initially set the voltage to match that of the battery, THEN gradually bring up the voltage while watching the ammeter.

    I have done this many times, and it works FB. As long as the output of the PS is not exceeded, there won't be an issue.

  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    There's some risk doing this.

    Car batteries, in fact most all batteries, are best charged by pulsating DC, not pure (filtered/regulated) DC, as you achieve the same charge levels without dissipating as much power in the battery. In an automobile (that's running) or even a high quality automotive battery charger, what's applied to the battery is never pure DC.

    A transformer and rectifier wired in series with known resistance wiring to the battery terminals makes a better charger than a regulated power supply does, and can protect the battery by virtue of calculated current limiting (from known wiring resistance).

  7. WA9CWX

    WA9CWX Ham Member QRZ Page

    I have used marine deep cycle batteries for decades.

    I am currently ( no pun intended) using a pair of 6 volt golf cart battereis. I don't use them for much anymore, but I always keep them for a back up, and have a FEW rigs hooked up to them.

    A proper charger for maintaining them is dirt cheap. Also, a simple timer, set to accomodate the re-charging, based on how often you USE them, is easy and simple.

    IF you are doing a LOT of use/re-charging, take extra caution for the ventilation. Otherwise, at a slow rate, and just a few minuets twice per day, there is little to worry about. Simply a slightly open window will take care of any gasses for minimal charging.
  8. K7JEM

    K7JEM Ham Member QRZ Page

    There are plenty of chargers that are "pure DC". ALL telecom chargers are well filtered DC, and are totally capable of running delicate loads with no battery bank attached.

    I don't know where you are coming up with the "transformer and rectifier" being a better charger, that's simply not true at all. They will work, but they are far from ideal, and a good way to overcharge a battery, if left on for long periods.

  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    ::I tried that after a chili dog but it didn't really work.:p
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    ::ALL telecom chargers are not well filtered DC, Joe. I worked for AT&T for years designing this stuff: The battery chargers are actually called "rectifiers," not power supplies, because for 50 years all they were were rectifiers and had no regulation. I still have several, made by Sorenson, MagneTek and others, right here.

    A regulated power supply without protection circuitry will overcharge a battery faster than a simple rectifier.
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