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Author Topic: Power Supply w/ Battery Backup  (Read 1741 times)
KJ4RQX
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Posts: 7




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« on: November 10, 2013, 05:56:03 PM »

I'm setting up a truck mounted mobile station.  This station has a set of golf cart batteries, and a generator.  I plan on using the generator instead of the truck's alternator to charge the batteries during extended operation (feild day, emergency, hilltopping) and i'm looking at power supplies.  I like the Powerwerx 30amp SS-30DV power supply because of it's physical size and the powerpoles.  I plan on pairing this with 100w HF transciever, using it to charge the batteries, and powering small 12v accesories around the station.

Here is my question.  Knowing that the power supply could be simultaneously charging the batteries and powering the equipment, the power requirements could exceed the 30amp surge capacity of the supply.  Does anyone know whats going on when this happens? will it shut off, or supply what it can and let the batteries make up the difference?
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K1CJS
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« Reply #1 on: November 11, 2013, 04:55:55 AM »

The best way to determine that is to see what the spec sheet on that power supply says.  I would think that the supply would just keep trying to do its thing until it blew, most would. 

If it were my setup, I would feel better with some sort of automatic disconnect, with a visible indicator, to disconnect the battery bank if its supply voltage went too low.  Of course, you could do that with a good, big voltmeter, but that isn't automatic and wouldn't 'protect' anything.
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K0JEG
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« Reply #2 on: November 17, 2013, 10:59:27 AM »

I use a Samlex SEC 1223 and a West Mtn Radio PWRgate between a telecom grade gel cell. I had to adjust the voltage up on the PS a little to get the PWRgate to correctly charge the battery (amazing the loss on DC power just from the cables). Works very well, and in fact I've operated for hours on battery only and not realized it. The nice thing about the setup is that it is a charge controller, so that the batteries are actually charged to optimize their life instead of a standard bulk charge that can sometimes cause problems, especially if you deep-discharge the battery regularly.

Might be overkill for typical lead acid, but should keep everything protected. I'd be more concerned about the batteries' lives shortened by improper charging more than the power supply.
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AA4PB
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« Reply #3 on: November 17, 2013, 01:16:54 PM »

The power supply has over-current protection. In most cases that means that exceeding 30A momentarily will cause the supply to shut down until the load is removed (in some designs you have to cycle the power switch to reset the supply). If you really want to recharge a low (say 50% or more depleted) battery at the same time you are transmitting then you really need a larger supply. If you are okay with not transmitting until the battery is nearly fully charged then the 30A supply should work okay. Once the battery is fully charged it doesn't take much current to keep it topped off.

Note also that continually connecting a nearly depleted battery to a 30A supply without some sort of current limiting on the battery may shorten the service life of the battery. For example, if the battery is down to 10V and you connect it directly across a 14V power supply the battery may draw more current than the mfgs specified maximum charge rate for a period of time.
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W8JX
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« Reply #4 on: November 19, 2013, 06:05:28 AM »

The power supply has over-current protection. In most cases that means that exceeding 30A momentarily will cause the supply to shut down until the load is removed (in some designs you have to cycle the power switch to reset the supply). If you really want to recharge a low (say 50% or more depleted) battery at the same time you are transmitting then you really need a larger supply. If you are okay with not transmitting until the battery is nearly fully charged then the 30A supply should work okay. Once the battery is fully charged it doesn't take much current to keep it topped off.

Note also that continually connecting a nearly depleted battery to a 30A supply without some sort of current limiting on the battery may shorten the service life of the battery. For example, if the battery is down to 10V and you connect it directly across a 14V power supply the battery may draw more current than the mfgs specified maximum charge rate for a period of time.


Very simple solution here even though I doubt that power supply will ever be over drawn.  Simply get a 1 farad carcaudio electrolytic capacitor and place it in parallel with load. It will easily feed rig during SSB peaks and reduce peak demands on power supply during charge. It will also stabilize voltage when just on batteries. Audio buffs discovered this trick years ago because it WORKS!  For some reason some are against usingna proven setup.
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