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Use of power product with power source

In order to appreciate this 'story,' I have to explain a few things. First, we live in a Recreational Vehicle (we are one of the many remnants of the many hurricanes that hit the state of Florida a few years ago, and due to economics alone, we have been unable to find a more suitable domain).

Along with this vehicle, we just purchased what is called a "macerator," which is somewhat of a pump to take care of the human waste in the collecting tank; from there, it is delivered directly to a sewer system that is also connected to a "bungalo" (spelling?); we live on a farm, which is owned by my wife's parents. But living in the "apartment" is out of the question because it has huge problems when it rains and, in fact, one or more of the hurricanes made the situation worse, which is why we are not living there.

To get back to the "macerator," it is a product that calls for 12 V DC, at 15 Amps. We were told by an electrician (and also a friend) that we needed a 12 Volt DC power source that would handle "at least" 25 Amps.

Now, here is the question: it states in the material that comes with the power source that it can handle anything that requires "no more than 25 Amps." Does this mean that, for example, if one were to hook up a device that requires only 15 or 20 Amps, would the "device" pull only what it needs -- or would 25 Amps be delivered to the device regardless?

Another way of address this question would be to ask -- will the power source be appropriate for "anything" that runs on 12 Volt, DC, as long as the "device" does not require more than 25 Amps?

I would "really" appreciate it if those who know about this topic would e-mail me directly at snipped-for-privacy@aol.com; otherwise, I will await an answer on this group.

I do appreciate any help!

Mark

Reply to
mea305
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Yes, it should work for you. Another way is a spare car battery and a chargerif the unit doesn't run all the time. That way you can use it for a while if the electric is out.

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Member of DAV #85.

Michael A. Terrell
Central Florida
Reply to
Michael A. Terrell

Anything connected will only pull the ammount it needs. Look at it as your car battery can supply 200 amps or so for a short period of time. The starter needs that to crank the car. The light bulbs need only a few amps or less for the smaller bulbs, they draw wht they need. Same with the radio. Now if you drop a screwdriver across the battery, it will draw just about all the battery can put out and look like a welding rod. Devices in your house work the same way on the 120 volt AC. A toster oven will take lots of current while the digital clock will take almost nothing, but they are both connected to a 15 or 20 amp circuit.

Reply to
Ralph Mowery

I'm not quite sure. Since the source is a voltage source you are supplying a specific voltage for it to use and it should draw only the amount of current that it can handle(excep it if has some problem). The problem ofcourse is that if the voltage source cannot supply enough power(which means current here) because then it won't have enough power to do its job.

Thi is why you can't use ~10 AA batteries to supply it because they will not be able to supply the current(or atleast will die very quickly). But AFAIK you can always supply more because the device *should* only draw what it needs.

For example, you could use a car battery since it is 12V and can supply that amount of amps(although it probably isn't a good idea depending on the device).

So, say, you have a power source as 12VDC that can supply 1M amps and your device only draws 25 amps... then it *should* be ok. If your power source could only supply 10 amps then your device will probably not work. An analogy might be that you can always have more than enough food to survive but never not enough.

The caveat here is that if the device shorts and it could draw much more power than it needed and if you end supply that much then it could cause some problems. A fuse should take care of this though. There also the problem of transient current draw. The device might draw only a few amps on avg but draw a ton of amps in short spikes... the power source may or may not be able to handle this.

Most likely you should have no problem though if you get a power source that can supply atleast the maximum rated current that the device will draw.

Idealy you would want to get a power source that is specifically design to work with the devices that are going to be using it. If you cannot do this then try to get a general power supply that can handle all the power that you plan on drawing from this so that you don't end up blowing fuses. I'm sure someone else here will probably give a more specific answer though. Just realize that not all power supplies are equal and it might save you a headache later on.

Jon

Reply to
Abstract Dissonance

A power source's ratings are "up to" the rated amps; they can provide anything from zero (er, except some switchers which have a minimum current draw to stay in spec) to the rated amps.

So, drawing 15 amps on a 12v 0-25 amp supply is fine.

Now, the thing about motors is their rated for their *running* amps, not their *starting* amps. Motors usually require a brief surge of amps when they first turn on, which is why you usually provide a larger amp capacity than stricly needed. Otherwise, you may see a reduced voltage (due to overcurrent) right when it's most detrimental to the motor.

For example, the motor in my central A/C unit is rated at 30 amps at

240 volts. However, for the first few seconds it draws 123 amps instead, until the motor gets running. We ended up planning for the 123 amps, not the 30, to keep it happy.
Reply to
DJ Delorie

I'm curious why you don't just use the RV's battery that can provide the

20A if it's any good...

Yup. the macerator may need more than it's stated Amps to start so you mauy want to check how the supply handles short-duration overloads.

or if that thing doesn't rutn at full power 24/7, consider using a battery that's connected to a charger...

Bye. Jasen

Reply to
jasen

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