Switch Mode Power Supply

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I picked up a Parallax 55 Amp power supply really inexpensively on Amazon.ca for $93 (I think they made an error on the price, the price almost tripled the day after I made my purchase). and want to use this as a battery charger for commercial trucks. Trouble is, the output voltage is set to 13.8v and I want to bump it up to 14.4v. Here are two pictures of the circuit board In the close up, I marked one item as "pot" in blue. This pot takes a #2 Phillips for adjustment. Would this pot adjust the voltage?
 
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Uh why would you buy a $100 power supply when you can buy 10 chargers specifically made for vehicle battery charging for that price?
 
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More than likely it will adjust the output voltage. Mark where it is at and give it a try. Can't say I've ever heard of anybody doing this before, not saying it can't be done, but you could buy a low end roll around charger for that money.
 
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George7941

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To reply to both posters, switch mode power supplies are very compact unlike roll around chargers. In a shop environment the bulk of a roll around charger isn't a big issue but I am not operating in a shop environment. Do you want to carry multiple chargers out to a truck to total 55 amp output? I was planning on an Iota DLS55/IQ4 which functions as a three stage battery charger but the internet buzz on RV forums is that Iota has taken a nose dive in quality recently and are very troublesome. If no one knows for sure then I will adjust the pot and see what happens.
 
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I do believe that pot is for the voltage, bust out your DMM and plug in the unit and give it a twist. I use a MeanWell RSP-500-15 as a battery charger, and it can do what no automatic charger can do, which is hold voltage high enough for long enough to finish the task within 12 hours or less. All automatic chargers revert to float/maintenance voltages too quickly, as it is safer to undercharge a battery. The MW Power supply is very compact. Its voltage trim pot was on the circuit board. 1K ohms. I removed it and added a 10 turn 1K ohm potentiometer and can now easily dial in any voltage from 13.12v to 19.23v. I also added some more fans as I often max out the unit at 41 amps when quenching a depleted battery. I also added an Amp hour counter inline. Volts are less than half the story, regarding charging. Powermax sells some adjustable voltage RV converters, upto 100 amps, and 60 amps and above are PFC, so they still work off of a 15 amp standard household outlet. 100 amps and adjustable voltage switching power supply puts any wheeled battery charger to shame, and for a fraction of the size. The low and slow tricklers out there can just set it so 13.2v and get a fraction of that 100 amps, or crank it to 14.7 to properly feed that Depleted Odyssey group 31 AGM.
 
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Check that the output of your switcher power supply is floating from the AC input power. Some switcher power supplies do not have electric isolation. If your switchers output is not floating someone touching the vehicles metal body while the battery is being charged and one or both of the vehicles battery connections are still connected, could be electrocuted.
 

George7941

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Success! The pot is a 430 ohm pot and adjusting it to 370 ohms gives me 14.6v output, I will leave it at 14.6v. A voltmeter connected between one of the output terminals and a good ground (copper water pipe) showed 58 V AC - uh oh! But an ammeter at the same place, thus shorting the output terminal to ground, shows 0.3ma AC/ 0.1ma DC. The same ammeter shorting incoming neutral to ground shows 45 ma. So I am not sure where the 0.3 ma is coming from. The output does not seem to be totally floating. The 0.3 ma seems safe enough and the outlet where this charger will be plugged in is GFI protected. The charger will certainly be exposed to very cold temperatures, if the electrolytic capacitors freeze then I will have to replace them. Very impressed by the wattmeter! Its display looks awfully similar to the ScanGauge display. The simultaneous display of four parameters is certainly very useful. The amp-hrs going into the battery can be aproximated from the watt-hours, but I was curious as to whether the meter integrates the amperes and displays it as amp-hrs?
 
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Originally Posted By: wrcsixeight
I do believe that pot is for the voltage, bust out your DMM and plug in the unit and give it a twist. I use a MeanWell RSP-500-15 as a battery charger, and it can do what no automatic charger can do, which is hold voltage high enough for long enough to finish the task within 12 hours or less. All automatic chargers revert to float/maintenance voltages too quickly, as it is safer to undercharge a battery. The MW Power supply is very compact. Its voltage trim pot was on the circuit board. 1K ohms. I removed it and added a 10 turn 1K ohm potentiometer and can now easily dial in any voltage from 13.12v to 19.23v. I also added some more fans as I often max out the unit at 41 amps when quenching a depleted battery. I also added an Amp hour counter inline. Volts are less than half the story, regarding charging.
Thank you sir. Due to your posting, I have bought MeanWell and the inline watt meter. Intention is to use as battery charger, mostly at equalizing charge, as I have other automatic chargers as well, which didn't seemed to quite fully-charged a battery.
 
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Originally Posted By: kb27
te]Thank you sir. Due to your posting, I have bought MeanWell and the inline watt meter. Intention is to use as battery charger, mostly at equalizing charge, as I have other automatic chargers as well, which didn't seemed to quite fully-charged a battery.
Your welcome. However, there are a few important details I left out. Meanwell makes many power supplies. The RSP-500-15 is one which does not shut down on overload, but holds constant current on overload. Not all of Meanwells offerings have this feature. Some will Shut off entirely on overload making them not suitable for the task of charging a depleted battery which can max out the power supply. Most people underestimate the ability of a battery to suck current when depleted. Also, the inline watt meter I use, comes with 14 awg aluminum leads. I replaced these with 8 AWG copper leads. The 14 awg aluminum got very warm passing 41 amps. Not so with the 8 awg. The voltage drop with the stock 14 awg aluminum compromised the charge times and can't be recommended for continuous duty. While it claims to be a 130 amp watt meter, I would not trust it to pass more than 40 amps for 30 minutes before overheating with the 14 awg leads. The directions claim 50 amps continuous and I feel this is too generous. Since EQ'ing a flooded battery does not require high amperages only about 5 amps on a 100 amp hour battery, you should be OK, but with 14 awg aluminum leads there will be a large difference between the voltage on output terminals and battery terminals and you will have to account for this voltage drop during the procedure.
 
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If the leads get shorted I hope that switcher has a good foldback circuit. If it's TOO good, the unit treat a very low battery as a short and not supply current. Cold temps make electrolytics change their parameters in ways switcher output regulators don't like.
 
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George7941

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I will install a 60 amp fuse on the output, hopefully that will protect the circuitry in case the leads are ever shorted. There will be other guys, drivers and warehouse personnel who might have to use it and they are not going to be as careful with it as I am.
 
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Originally Posted By: George7941
Success! The pot is a 430 ohm pot and adjusting it to 370 ohms gives me 14.6v output, I will leave it at 14.6v. A voltmeter connected between one of the output terminals and a good ground (copper water pipe) showed 58 V AC - uh oh! But an ammeter at the same place, thus shorting the output terminal to ground, shows 0.3ma AC/ 0.1ma DC. The same ammeter shorting incoming neutral to ground shows 45 ma. So I am not sure where the 0.3 ma is coming from. The output does not seem to be totally floating. The 0.3 ma seems safe enough and the outlet where this charger will be plugged in is GFI protected. The charger will certainly be exposed to very cold temperatures, if the electrolytic capacitors freeze then I will have to replace them. Very impressed by the wattmeter! Its display looks awfully similar to the ScanGauge display. The simultaneous display of four parameters is certainly very useful. The amp-hrs going into the battery can be aproximated from the watt-hours, but I was curious as to whether the meter integrates the amperes and displays it as amp-hrs?
+1 on the use of a GFI circuit breaker for this application, sounds like a great way to insure no one gets zapped.
 
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