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Old 25-04-2017, 17:31   #1
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Using a charger for a battery source

I have a diaphragm bilge pump fail. I took it off the winter stored boat and brought it home. Any reason why I can't use a battery charger for a power source to test it? I have both a low amp Battery Tender, and a higher amperage conventional charger. I am just not sure if a charger has to sense voltage to start sending current. I would prefer not to use jumper cables, wire, and a vehicle battery.
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Old 25-04-2017, 17:43   #2
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Re: Using a charger for a battery source

I have a smart (yeah right) charger that won't put out any voltage unless it senses some battery voltage. When I need to test some thing like a small motor driven devise I use my old dumb charger set to a high enough amp setting to run the component momentarily.
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Old 25-04-2017, 17:46   #3
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Re: Using a charger for a battery source

kod, nobody knows specifically what chargers you actually have, so how can we help?

Why not try what you have and see?

You have the parts, we don't.

Good luck.
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Old 25-04-2017, 18:32   #4
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Re: Using a charger for a battery source

If you play around with 12v, a far more useful tool is a DC lab power supply. Can be bought for reasonable monies on eBay or Amazon around $60. I have a 5A unit and it gets tons of use. Very handy for boat related activities, testing pumps, bulbs, LED current tests etc. mine has even done some electrolysis for rust removal on parts in the garage. Very handy to bring to the circuit you are trying to test vs a battery. Displays voltage and amps as well. I have found they are OK as far as accuracy but my high end Fluke meter has the last word. Surely good enough for boat work though.
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Old 25-04-2017, 19:18   #5
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Re: Using a charger for a battery source

Many modern "smart chargers" have a low voltage cut-out to protect chargers and prevent other problems by a damaged battery. This feature means they don't work as a 12v supply for bench testing.

I always use my Booster Pack - massive thing that I've had for 7 years and it still kicks ass (buy a good one).

These are not only great for bench testing, I rum my electric infiltrator off it, our 12v trolling motor in small harbors, and used it once to start the boat when I left he battery switch on "All" by mistake one night.

I'd advise that every boat have one of these. Tough to call AAA for a boost offshore...
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Old 25-04-2017, 19:27   #6
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Re: Using a charger for a battery source

+1 on the bench supply. Mine is always used during repair or new module development.

+1 on giving it a try w/ the charger. Connect a voltmeter across the output so the DUT behavior will correlate to the charger voltage.
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Old 25-04-2017, 19:49   #7
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Re: Using a charger for a battery source

Stu, dude, lighten up! Battery Tender is a brand. I guess I could have said a Sears 90734 for my second charge, but I didn't. It is just That I will be home with something that needs testing, and as most cruisers used to do, I am trying to work with what I got. I know I could use jumper cables, clamped to a lighter gauge wire, with alligator clips, but I was just wondering if there was an alternative.
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Old 26-04-2017, 06:40   #8
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Re: Using a charger for a battery source

You need to know the pump's amp pull at startup, ensure your source can provide it, many have no overload protection and will get very hot before (hopefully) shutting down.

A battery gives a buffer in between, and will help with the higher-amps startup
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Old 26-04-2017, 07:00   #9
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Re: Using a charger for a battery source

Just open the hood of the car if you have one and use that battery.
Some automotive battery chargers are actually quite high voltage, and I believe put out AC power, although they may be pulsating DC if they have a diode bank?
But I have done what your asking and had it work
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Old 26-04-2017, 09:00   #10
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Re: Using a charger for a battery source

Some chargers don't put out a very clean DC. I would stick a battery in there just to do your test with cleaner DC. Steal one from your car.
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Old 26-04-2017, 12:38   #11
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Re: Using a charger for a battery source

I actually tried using a cheap battery charger as a power supply. First thing I found was that the voltage was all over the place at high frequency. I put a large capacitor on it, which helped a bit. But, I quickly destroyed the equipment I was powering. Lesson learned.

As others have said, put a battery in there, or use a regulated power supply. I bought a 5A power supply intended for lab use for $10 at a yard sale. Works great. I run a 12 volt VHF radio from it, as well as a bilge pump (used to flush my tankless water tank at home).
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Old 26-04-2017, 12:58   #12
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Re: Using a charger for a battery source

Quote:
Originally Posted by hamburking View Post
I actually tried using a cheap battery charger as a power supply. First thing I found was that the voltage was all over the place at high frequency. I put a large capacitor on it, which helped a bit. But, I quickly destroyed the equipment I was powering. Lesson learned.

As others have said, put a battery in there, or use a regulated power supply. I bought a 5A power supply intended for lab use for $10 at a yard sale. Works great. I run a 12 volt VHF radio from it, as well as a bilge pump (used to flush my tankless water tank at home).
A battery acts as a capacitor to flatten out the suppose DC. Most of which is only modified half wave out of a cheap charger.
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Old 26-04-2017, 13:15   #13
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Re: Using a charger for a battery source

The answer is yes you can use a cheap charger to temporally power the pump. I've done it hundreds of times in my life. I also have a private dock with some small boats I pump the rain water from. Power is close by each boat so instead of carrying a battery I use a charger. The pump is a communist (Rule copy) 12 volt bilge pump. It's been doing the job for years.
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Old 26-04-2017, 16:30   #14
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Re: Using a charger for a battery source

One of the best and cheapest power sources is an old redundant computer power supply. Find an old trashed computer on the road side or wherever and remove the power supply and wire it up. Very clean 12 volt and other voltages such as 5v, 3v etc. See Turn a Computer Power Supply into Bench Power | Make:

I use these all the time and for free.


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Old 26-04-2017, 18:43   #15
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Re: Using a charger for a battery source

Do the latter. You need ballast i.e. a battery. Or else....
Sorry Ann, I'm still in a bad mood
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