Cobra CPI 875 800 Watt 12 Volt DC to 120 Volt AC Power Inverter with USB port

by Cobra

Product Details

• Product Dimensions: 8.5 x 5 x 2.7 inches ; 4.3 pounds
• Shipping Weight: 4.3 pounds
• Shipping: This item is also available for shipping to select countries outside the U.S.
• ASIN: B00126GF8M
• Item model number: CPI 875
• Average Customer Review: 3.8 out of 5 stars  See all reviews (19 customer reviews)

Product Description

The Cobra CPI 875 is a 12 volt DC to 120 volt AC power inverter with 800 watts continuous power handling and 1600 Watts peak power. This unit contains a 5 volt USB output, modified sine wave, thermal shutdown, reverse polarity protection, low voltage shutdown, low voltage alarm, external fuse, 2 grounded AC receptacles, and includes a carry case, and direct- to battery cables with clips.

Customer Reviews

Most Helpful Customer Reviews

33 of 33 people found the following review helpful:

4.0 out of 5 stars Good Unit BUT you need to know a few things, February 17, 2009

By 

Butch50 "Zen" (Texas) - See all my reviews

Amazon Verified Purchase

This review is from: Cobra CPI 875 800 Watt 12 Volt DC to 120 Volt AC Power Inverter with USB port (Electronics)

This is a very good unit, for what it is designed to do. It is up to Cobra's usual high quality standards. There are a few things you should know before you buy it though.

There are a couple of comments about the unit not putting out full voltage - however, if you go to the Cobra website and read up on this unit you will see that a standard voltage meter will not read the voltage correctly due to the sine wave configuration, instead it will read low voltage. Measurement requires a specialized meter, an RMS if I recall correctly. I have read also that some electronics work fine with the modified sine wave and some pick up some interference. It would probably be worth the time and energy to research which would be the case for your particular electronic application, before buying.

Another quite important thing to know is that this unit, while rated at 1600 watts, will only run at 800 watts continuously. The 1600 watts provides room for start up surge, but not for running more than a few seconds. I bought mine to use in my car. First thing I tried was a 1500 watt heater, and it would run for a few seconds and then stop. Then I tried a 750 watt heater and it ran just fine. So check your application and see if it will be 800 or less watts, if more, get a bigger unit.

Another important thing to watch for on automobile installations is the output of your alternator. Many cars have alternators with as little total output as 60 to 75 amps. You can calculate the amp draw by dividing the AC watts by 12 and then multitplying by 1.1 - so in my case the 750 watt heater draws 69 amps from the battery/alternator. If I had a 60 or 75 amp alternator then there would be a serious problem. Probably the battery would be drained while driving and I would end up with a dead battery, at night, in the middle of nowhere, surrounded by zombies pounding on the windows....

I have a 135 amp alternator, but since I am not sure exactly how much amp draw my car uses while running at night with headlights (most of my driving is after dark) then I am not completely sure how much reserve/overage I have for the inverter. As a result I only run the heater intermittently so the battery won't drain. If your application pulls enough amps to cause the charging system to run at system capacity so that the alternator continuously puts out 100%, the alternator will not last nearly as long as normal. I never run my heater when the engine is idling, at idle the alternator puts out about 40% less.

If you are going to use this in a running car, try and find the total amp draw needed for the car,(I found that my alternator runs at about roughly 60% when idling so I am guessing that my total draw would be about 50% of the total capacity of the alternator at full speed, or 68 amps in my case, but that is a guess) subtract that from the total output of your alternator, and then compare your alternator's power reserve with the draw from the inverter with your application, to make sure you have enough total capacity with some margin. Mine would, based on this theory, run a 2 amp deficit. Or do what I do and run the application only intermittently so the battery gets charged up and the alternator isn't running at 100% capacity all the time, and never while the engine is idling.

If you are going to use this in your car while driving, the supplied cables are not going to work for you, they are too short. The inverter is not weather proof so it can not be mounted under the hood where water can splash up on it, or dust get into it. It needs to be in a weather tight environment with good air circulation, it also doesn't like heat. I took a pair of heavy jumper cables and soldered bolt connectors on each end and ran these to my cars interior. I added an in line 100 amp fuse in case of a short in the cables.

If you are going to use this on a battery only, there are formulas to determine how long the battery will supply the load you need - you can find the info with a goole search easily. It would most likely be worth your time to run the formula before buying, to make sure that you are going to get sufficient run time from the battery you have or plan to get. If frequent recharging is in your future, consider deep cycle batteries.

In summary, this unit works, within it's limitations, and I am happy with it. I would have given it 5 stars, but the Amazon description of the unit's true continuous run capacity should be more detailed than it is.

August 2009 - I see that the description has been changed so that it better represents the 800 watt continuous capacity. Kudos to whoever made that honest change!

12 of 15 people found the following review helpful:

1.0 out of 5 stars Not operating within spec. - defective out of the box, December 20, 2008

By 

Tech Prof "Tech Prof" (N.H.) - See all my reviews

Amazon Verified Purchase

This review is from: Cobra CPI 875 800 Watt 12 Volt DC to 120 Volt AC Power Inverter with USB port (Electronics)

The item arrived nicely packaged. However, when I tested it, it was operating out of spec. The spec for the device is 109 VAC (Minimum) up to 120 VAC. Regardless of the load it always put out 100.1 VAC. It did not matter if I had nothing hooked to it or something running from it. I also checked my battery with another brand of inverter that I've have and everything was working correctly. That inverter (Coleman) put out 114.1 VAC under the exact same load conditions and using the same battery.

THIS IS NOT SAFE because there are many devices that NEED between 110 and 120 VAC. Other devices such as light bulbs, etc would not matter. I have a desire to run delicate electronics with it (laptops, pellet stove, etc) and no way would I take the chance. I am returning the unit for a refund.

I do praise Amazon for shipping very fast and packaging it well. It is very rare to ever have to return anything to them. I hope the refund is equally as quick.

4 of 4 people found the following review helpful:

4.0 out of 5 stars Great product, January 18, 2009

By 

J. Boston - See all my reviews

Amazon Verified Purchase

This review is from: Cobra CPI 875 800 Watt 12 Volt DC to 120 Volt AC Power Inverter with USB port (Electronics)

I bought the cpi 875 to use in case of a power outage, and it seems to power what I need pretty well, although I haven't had to use it for an outage quite yet. I already hooked it up to run a lamp and a propane heater that requires electricity to operate, and it did very well. Has a pretty low profile, so it sits under the hood with it closed, so that should be nice in case the outage is in inclement weather (which they usually are). I figured, instead of buying a generator and dealing with all that comes with those, I would use the Inverter to run some essentials, and just run the car every once in a while to charge the battery back up. The only downside to this unit, I would say, is that it doesn't have a voltage readout, and it doesn't come with a cigarette lighter adapter, in case you wanted to use it for small devices in the car. But, other than that, it seems like it will be very handy in an outage, and should also be nice in case I go on a trip and need to power something. Overall, definitely recommended, and at the Amazon price, it can't be beat.