Any portable air compressors to run off battery lead?

[EdMat]

I've made my point; polarity of the connectors and gauge of wire are two issues to be aware of when using an SAE-to-battery wire designed for a (low-amperage) battery tender as a source of power for any load, including an air compressor.

Do what you want.

Actually if its a simple DC compressor with no digital readouts, led's, electronic switches etc. it will work even if hooked up with reverse polarity. The amount of reduced output it would have would be dependent on the amount of timing advance built into the commutator and brush placement. The compressor part itself does not care which way it turns.

 

[UtahPete]

Actually if its a simple DC compressor with no digital readouts, led's, electronic switches etc. it will work even if hooked up with reverse polarity. The amount of reduced output it would have would be dependent on the amount of timing advance built into the commutator and brush placement. The compressor part itself does not care which way it turns.

Thank you. I believe that is why some folks are able to claim success running off a sae lead designed for a battery maintainer.

Just because you can doesn't mean you should. I was trying to answer the OP's perfectly reasonable question, not start a debate.

 

[IdahoMtnSpyder]

Not quite so. It does have an SAE connector as one of the cord options, BUT that connects directly to the battery, not to an existing battery tender cord. It cannot plug directly into your battery maintainer connection because the polarity will be reversed.

Hey Pete, you've got things confused! As you said in your prior post the recessed terminal of the SAE pigtail from the battery is the positive terminal. But the Battery Tender is reversed. The exposed terminal of the BT is positive. It has to be that way because a charger pushes current back into the battery through the positive terminal so the charger has to have its + terminal plug into the the + terminal of the pigtail. The charger voltage is greater than the + voltage of the battery or it does not push current into the battery.

The SAE connector on a load device, such as a compressor, has to have the + input connect to the + output of the pigtail. Therefore, the + input of the compressor is exposed and plugs into the recessed terminal of the battery pigtail. So yes, the compressor above will work plugged into the battery tender pigtail.

 

[IdahoMtnSpyder]

OK, I think I just got things cleared up in my mind. The OP asked if a compressor can be plugged into a battery tender lead. The answer is yes, if he is asking about plugging into the battery tender pigtail connected to a battery which most of us understand him to be asking. But if he is asking if the compressor can be plugged into the SAE pigtail lead from a battery tender, which seems to be what Pete is thinking, then the answer is no unless you use an adapter. In this case Pete is correct.

But the big question is, "Why would anyone want to plug a compressor into a battery tender?" Most battery tenders won't have the capacity to run a compressor, and the really smart ones won't operate if the load connected to it is anything other than a battery.

 

[UtahPete]

This is my experience and understanding of the difference.

I'm not saying I'm right. So, if there's something wrong with my observation or conclusion, I am open to having that pointed out to me.

 

[SLICE]

Thank you. I believe that is why some folks are able to claim success running off a sae lead designed for a battery maintainer.

Just because you can doesn't mean you should. I was trying to answer the OP's perfectly reasonable question, not start a debate.

internet forum utahpete.... i'm glad i did not ask what's better 9mm or .45 because we all know 10mm rules.

 

[FrogmanDave]

internet forum utahpete.... i'm glad i did not ask what's better 9mm or .45 because we all know 10mm rules.

Just as long as you don't mind being kicked by a mule every time you fire the thing :roflblack:

 

[IdahoMtnSpyder]

View attachment 199603

This is my experience and understanding of the difference.

I'm not saying I'm right. So, if there's something wrong with my observation or conclusion, I am open to having that pointed out to me.

OK, I'll take a stab at it. The problem, as I see it, with your illustration is you show the battery as a load when connected to a charger. The battery is never a load in the usual sense of the word. An electrical load is a device or circuit that freely allows current to flow through it from the positive side to the negative side of the source, irrespective of the source voltage. (An exception is when there is a current blocking component that only allows current to flow when the voltage is greater than the blocking threshold.) When a battery is connected to a charging source, be it a charger or another battery, current is forced to travel through the battery only if the source + voltage is higher than the battery + voltage. Therefore the battery is not a load in the usual sense. It is also very unlikely the charger's pigtail + terminal will ever accidentally contact the negative terminal. Charger cables with alligator clips are a whole 'nuther safe handling issue!

When it comes to pigtails with SAE connectors being attached to the battery for any reason, be they permanently connected or temporarily connected by alligator clips, safety precautions are paramount. You don't want an exposed terminal connected to the + terminal of the battery as you illustrate. If it were to contact any part of the vehicle that is grounded you would have instant sparking and fireworks, and maybe even a fire! That is why all charger/maintainer pigtails connected to the battery have the + terminal as the recessed terminal. Every charger/maintainer that has an SAE connector has the exposed terminal be the positive terminal since in order for it to work the charger + terminal must be connected to the battery + terminal.

Any cable for a load connected to vehicle power using an SAE connector, such as a trailer pigtail, always has the positive terminals exposed and the negative terminal recessed. It has to be that way because all the + terminals on the vehicle side need to be recessed to protect them from accidental grounding. The ground terminal on the vehicle side is exposed since it poses no risk if it contacts a grounded vehicle part.

 

[Bensonoid]

A picture is worth a thousand words. Battery tender SAE connectors are clearly marked + or -.

 

[UtahPete]

Mac, your reasoning makes perfect sense and Bensonoids' photo confirms it. Thanks fellas.

 

[IdahoMtnSpyder]

A picture is worth a thousand words. Battery tender SAE connectors are clearly marked + or -.

There's always a fly in the ointment! My Battery Tender brand has the + & -markings as you show. My Diehard charger/maintainer has no markings but the lead going to the exposed terminal has a white stripe indicating it's the positive lead. Also, my NAPA charger/maintainer has a white stripe lead going to the exposed terminal and no + & - markings.

I think it's safe to say the exposed terminal on an SAE connector on the factory installed pigtail on a charger is always the + terminal. I think it's also safe to say every pigtail that connects to vehicle power with alligator clips or a cigarette lighter style plug, or is correctly and permanently connected to the battery or other vehicle harness connection, will have the recessed terminal be the + terminal. We can also be assured that every accessory intended to be connected to vehicle power via an SAE connector will have the exposed terminal be the + terminal. When using alligator clip connections always connect the red clip to the positive terminal of the battery. The + connection on any accessory always connects to a +12 volt source on the vehicle.

Now, I think we (I) have :bdh: enough. Hopefully it has been helpful to at least one or two members!

 

[AdmiralS]

I carry a Ryobi 18v Compressor on the bike with a 6ah battery. Has worked flawlessly for 2 years