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12VDC Power Supply


Dennis H

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For want of a better place to put this, I've placed it here for general discussion.

Every now and then something quits on our coaches. i.e. awning doesn't retract fast enough, water pump doesn't work etc. etc. We do the easy stuff first, like checking for a blown fuse or chafed wiring. Usually, after checking for those, I run a test lead from a known source, usually directly from the battery to the offending device to ensure it's getting power. If it still doesn't work I then pull it for bench testing. So, the purpose of this post is to ask all you learned people if there is an easier way to do the initial test? I was thinking instead of carrying a roll of 10ga wire in my toolbox, unrolling it, hooking it up to the batteries and running it to wherever I need it to go for test purposes, what if we had a 12VDC power supply that would do the same thing. Plug it into 120VAC, let it convert it into the needed 12VDC and off we go? Would that work? Is something like that available in a small enough package to carry in our toolboxes? What do you guys think? Below is one thing I found on Amazon but I don't know if it would work. Anyone?....Dennis

https://www.amazon.com/Waterproof-Transformer-Adapter-100V-265V-Computer/dp/B07MZP9247/ref=sr_1_21?dchild=1&keywords=12vdc+power+supply&qid=1615138106&sr=8-21

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Like John suggest...if a 12v device doesn't work, use the multimeter to ensure the device is getting 12 volts when it's supposed to.  If not, then figure out where the break in the circuit is and fix it.  If it does provide 12volts, then look at the device.  So no reason to worry about supplemental 12volt sources.

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I find my Power Probe IV to be a good diagnostic tool. Not only functions for continuity, voltage, current, etc., but also can supply power or ground connection directly to an item. That said I do have a digital switching power supply but that is more of a bench testing piece that stays at home. 81RS9BXO24L._AC_SL1500_.thumb.jpg.cee6e9222876adc19881381a944513e3.jpg81hEXwW22CL._AC_SL1500_.thumb.jpg.bc7f71434a79d480ee7a3b3c2987de87.jpg

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Dennis,

I got the Power Probe 3SO3AS and love it. It has a switch to power 12V and a breaker when I short it out. Check it out. They have much nicer units but for what I need this is great. I also bought a 5amp power converter so I didn’t need to buy the extension cable.

Paul

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Dennis, I purchased a 120 VAC to 12 VDC adapter over 10 years ago to power my 12 VDC Fish Fillet Knife.

This is what I purchased back then from Amazon which is a 5 amp device. https://tinyurl.com/4edsvxff

However, there are many to select from now plus they have 10 amp ones also.

I simply use a 12 VDC plug that has a 6 foot pigtail where I soldered on alligator clips to the ends. I can use this to supply 12 VDC to any device I need to test.

Works like a charm.

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If you really need something fairly small and portable rather than the testing tools already mentioned, one of those rechargeable 12v batteries for a cordless tool will work.  Something like a DeWalt drill, etc...  you just have to fashion some type of connection leads for it.  It seems like a lot of those tools are going to much higher voltages now, but should be some 12 volts types still around.

Jim

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Interesting replies. Perhaps I wasn't too clear on my thought process. I'm old and it's Sunday. A couple folks on here have been having trouble with their awning and their water pump. Perhaps they are experiencing the same issue with undersized wiring. Not everyone has or knows how to use a meter. Many who have them, don't spend the $$$$ for a really good one and rely on the HF freebie. I bet 95% never read the instructions that came with the meter.

My thought was to have a simple tool to use to ensure 12VDC was getting TO the device. I have a couple Flukes that I use as well as the 12VDC probe. My thinking was in reading a few of the recent posts the device is receiving power from the batteries, just not enough of it. For instance, Monaco used 14ga wire to power the macerator on my coach. Then they ran the wire over, under and through about 100' of crap just to get it to the wet bay. By the time the 12VDC traveled that 100' it left less than the necessary 12VDC to adequately power the pump so the pump struggled and finally just quit. After replacing a couple pumps I checked the final voltage and discovered the problem. I rewired the pump using 10ga wire and the pump now runs as designed.

IF you have a good meter and know how to use it, then you really wouldn't need a 12VDC device. However, let's assume you don't have a meter and/or don't wish to take the time to learn how to use it, then what could we use to provide a quick and simple jumper to the 12VDC device to ensure it's getting the proper voltage to the motor? Thanks, I hope that's more clear........Dennis

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Ordinary personal computers have a power supply that converts 120AC to 12DC, but they are limited to the amount of current that is designed into a PC, and not the current consumed by electric motors or other higher-amp devices.  If you go with your #10AWG idea, be sure and put a fuse or circuit breaker near the battery positive end.  It would be easy, and dangerous, to accidentally drop a hot lead onto something combustible.  I like the other tips suggested.

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I read a tip on here (I think), buy a male an a female plug and wire alligator clips to them. If you need to apply 12v to something far from your battery plug your  newly wired plugs onto each end of your 50' extension cord. You now have a 50' test lead. I thought it was a great idea an plan on doing that soon.

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Tom, that tip was from one of our members here on this forum. I have actually done that and it works great as long as you don't need a significant amount of amps. Of course a shorter extension cord could handle the amp load.

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Well, I have done all of the above that is discussed in this thread and I hit on something simple that works great for trouble shooting 12vdc electrical issues in the coach.

I purchased a 12vdc - 12amp battery. the size is 6"x 4" X 4". I made up a wiring harness that is12 gauge wire, 3 feet long with Spade Connectors to attach to the battery and Alligator clips on the other end to trouble shoot with. I can take it right to the source of the problem to trouble shoot a component.

To keep the battery fully charged when I am not using the coach and parked in the Barn I keep it hooked up to a Battery Tender. If I have a need to charge it while I am Traveling I connect the battery up to the chassis battery's with the provided Alligator clips to charge it.

The Battery is the same style they use in Computer Back Ups for back up power.

Works great!!! It's Simple and no fussing with wires or cables.

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