Monday 3 October 2011

Cigarette Lighter Electricity


I just opened the package and haven't used this thing yet - so I can't comment on functionality - but I wanted to let others know that this unit DOES come with a cigarette lighter plug (as well as a set of alligator clips) that you can attach to the screw posts.



I wasted a couple bucks on a separate cigarette lighter plug when I ordered because the product information says nothing about coming with the cigarette lighter plug.



Oh - There is also a sticker on the cigarette lighter cable warning not to draw more than 150 watts when using it plugged into a lighter socket (use the alligator clips or your own custom wires to connect straight to the battery for full power) Cobra CPI 480 400-Watt 12-Volt DC to 120-Volt AC Power Inverter with 5-Volt USB Output

I has been on ever since I put it in my semi. I have a laptop, a printer, and four chargers for cordless devices hooked to it on a power strip. The fan will come on if I'm watching a movie on the laptop but that is the only time I have ever heard the fan come on. It is exposed to temps from below 0 to 80+ and hasn't complained yet.

The power inverter works great. I used it on a 5000 mile road trip powering a PS3 and iPhone and another cell phone along the way, in addition to other small electronics. To get the most power out of the unit, you need to hard wire it directly to the battery. I mounted it under the passenger seat and ran some 8 gauge wire. Very easy installation. I looked at several inverters before purchasing this one. The usb connection was what sold me on the unit. I now have an easy way to charge my iPhone without having to buy a car charger or taking up one of the regular power outlet slots. Well worth the money. The only thing to note for Amazon is that the product listing advertises that it comes with a carry case. It does not. No problem for me because I don't really care, but it may matter to you. I believe the CPI 475 does include the case.

I just received my Cobra CPI 480 400-Watt unit today.



The lighter cable option allows taking this unit in a different vehicle. My unit came with both lighter plug and jumper cable type power connectors. The lighter plug has a 15A fuse in the tip, limiting output to a continuous 165W (hence the 150W mentioned in the manual). Higher power levels will require direct connection to the battery terminals, or the fuse will blow.



The lighter plug, as noted in other reviews has trouble staying electrically connected in my Cadillac Seville lighter socket, but doesn't fall out. The rear passenger lighter sockets have the same mechanical connection issue.



[The following comments were made from a unit sent back for repair. Addendum comments made against a new unit are at the bottom of this review, and new scope image replaces the old one in customer images.]



With the unit connected to a car battery with the engine running for high power checking, a Hoover 110V hand vacuum runs just fine. I grabbed a 500W halogen contractors light to see what happens on overload. The lamp starts to light and about 200mS later (~1/5 sec) the units starts shrieking and turns off output. [This behavior changed in the new unit (below) which now powers the 500W lamp for a minute] This unit does not recover from this condition automatically. The front panel switch must be turned off, then back on for the unit to recover. This also implies that any motor load with high startup currents has to be substantially started in 200mS or the overload condition will trip on this inverter. 200mS is short, most motor type equipment can take 500mS-1Second to start, which means many motor driven appliances may not work well with this inverter. Think about how long your lights "dim" when your freezer starts. If it's longer than the tiniest of "flickers", then it's probably longer than 200mS.



Since my use is to recharge two electric bike batteries from 120VAC and my cell phone from USB and each bike charger draws 170W peak @ 120VAC during the charge cycle (340W peak for two), this unit should meet my needs.



The battery direct connect cables are about 2.5 feet long and made of 12AWG wire. Something heavier (6 or 4AWG or two parallel sets of 10AWG) should get me from my battery under the hood - past the firewall and into the car with little enough voltage drop to get that 400W capability without burning up 20A lighter fuses or having so much voltage drop due to wiring that the unit shuts off with a low voltage sensing error.



A nice addition is a contractors "pig tail" [8" extension cord and three plugs] to extend the 110V outlets for wall-wart type chargers. Target also has 8-inch "adapter cords" to extend the outlets if you have something physically large to plug-in (Amazon solution:Power Extension Cord, Perfect for Transformers, 1 ft). If I have a lot of wall-wart type chargers (up to 6). GE has a nice widely spaced 6-outlet solution meant to physically cover a wall outlet GE 50759 6-Grounded Outlet In-Wall Adapter, White. This plugs into the pig-tail which plugs into the inverter for running a pile of low power chargers (like cell phones, kids game-boys, camera battery, and a laptop).



I put the CPI480 on the bench to answer a few more basic questions about this unit. See my uploaded "Modified Sinewave" scope photo of CPI 480 output under "customer images".



First, when the power switch is first turned on, the fan runs for 14 seconds, then turns off. This concerned me after reading several reviews saying their fan stays off. [The new unit doesn't do this]



Will the 5V USB output stay on even when the switch is off? In fact the 5VDC output turns off with the front power switch as does the 110VAC. This unit draws no power when the front switch is off, so it doesn't need to be physically disconnected from the battery.



During startup (turn the front power switch on) at 13.5 VDC input with fan running, my unit draws 800mA (0.8A). After the fan turns off, my unit settles down to 650mA (0.65A) for "standby", not running anything. The box says <500mA, so my unit exceeds this by 30%. This high standby power is why I gave this unit 4 stars instead of 5. For comparison, my old Power2Go 160W/400W-surge fan-less brick used to draw about 50mA (0.05A) [can't buy these anymore].



At issue is, if I forget to turn the unit off over night, will I be able to start the car in the morning. Lets say it sits for 15 hours. This unit will consume 9.75Amp-Hours. If temps are a balmy 70F (~20C) then I'd say sure, the car should start the next morning. If I'm in a Minnesota winter at -40, then I'd say the car battery won't have enough power left to start the engine. Even in standby (no power draw from USB or 110V) this unit draws 9W. The case gets a little warmer than skin temp in a room temp environment. This is understandable since this unit is dissipating 9W of power while idling. The fan does run while idling, but it is low speed, quiet, and follows the 3s-on 15s-cycle.



With a 23W CFL table lamp (100W light output) plugged into the output and let sit, the fan turns on at low speed (very quiet) for about 3 seconds then off. It repeats this pattern every 15 seconds, same as "standby".



This unit does "overvoltage" at 15.7VDC, and turns off 120VAC output. It is self correcting (restores 120VAC output) when input voltage returns to the "normal" range. This is important to me as other unit/brands I've owned require cycling the front panel power switch to "reset". This unit does overvoltage "reset" by itself (hands off).



The low power beep indicator turns on at 10.3VDC. It sounds like a cheap alarm clock, strange cell phone ring (or crickets) for an audible alert. It's obnoxious, but not terribly loud.



The 120V output stopped at 9.4VDC, the alarm keeps ringing, and the fault lamp comes on. The unit continues to try to power the output while the fault indicator is lighted. If voltage input is increased back to 9.5VDC, 120VAC operation continues. The beeping and fault lights continue until about 3VDC when the internal electronics can no longer function (probably 5V electronics internally). Again, if you turn off the front power switch, this unit will stop using battery power.



Since writing this review, the standby current is now 750mA @12.6V which exceeds the <500mA@12.6V specification by 50%. I called Cobra support and asked for guidance since this unit does still produce rated power output levels. Tech support first recommended returning the unit to Amazon. Then after explaining that Amazon is a marketing organization and will just grab another unit off the shelf, asked what my chances were for getting a unit which will meet the <500mA @12.6V specification. They then suggested that I return the unit to their Chicago facility where special handling instructions were entered into the Cobra system for my order. So, first thing next week, I'll exchange this unit for one that meets spec by shipping this one to Chicago.



***** New CPI 480 Unit From Cobra repair in Illinois *****



I measure standby current at 115mA at 12.6V. At Undervoltage between 12.0 and 12.3VDC I measure 270mA, well within spec.



I tried overload with a 500W Halogen work lamp and was surprised to see the lamp run for well over a minute before overload cycling @ 3sec intervals in a 41 degree F (5 degree C) environment. The internal fan started almost immediately while the unit was running on 500W overload. This also means the new unit recovers from overload automatically as the specifications in the back of the CPI 480 Operating Instructions say it should. The heavy battery clip cables get warm (not hot) to the touch when the unit is driving 500W, as I'd expect since current draw is likely around 50Amps (figuring 12V and 83% efficiency from spec). I don't have a shunt large enough to make current measurements at this load level.



I don't think I ever heard the beeper though the red overload light did come on. Electrical performance of the new unit (as far as I checked) is excellent! I won't worry about leaving it on overnight as long as temps are moderate (above 40 degrees F/ 5C). 16 Hours at 115mA standby current means just under 2AH capacity is removed from the battery (a typical car battery in reasonably good condition has 15x to 30x+ this energy capacity).



Now I can add my experience with Cobra tech support, (specifically Jorge and Brian) was also excellent. Fast turn around time and the new unit performs as I wanted.



After comparing the scope image of first unit output with the scope image of the replacement unit, I can say the first unit was defective. The new output image shows waveform timing more consistent with a least squares fit of a "modified sine" to a "real sine". From other comments made here, it sounds like there are manufacturing problems making their way to shipped product. Good tech support plus $10 shipping appears to be the cure if you receive a unit that isn't working (like not handling overload right while using provided battery clip cables and a running vehicle charging system, or having too high a standby idle current).



I'm currently running my unit through one 6ft set of 10 AWG stranded cables made from wire and connectors purchased at my local hardware store and a little solder applied to the crimped connectors with a blow torch. With the 500W load attached I get a 1V drop across the 10AWG wire set. This means the wire is dissipating about 50W of power as heat during this overload condition. At 400W (rated power) this 10AWG wire set will dissipate 32W. 32W can be reduced to 8W (12.5W overload) by paralleling with another set of 10AWG wires. So far the under voltage protection isn't triggering. For reference, 32W is about what a coffee cup warmer uses to heat coffee. So reducing this dissipated power level might be advisable for continuous running at high power levels.



If I start getting under-voltage errors, I plan to parallel this set with another set of 10 AWG cables to increase current handling and reduce wire voltage drop losses.



I set my rating of this unit to 4 stars for all the inconvenience of identifying and then having to deal with an out of box failure of the first unit, and a few minor things the new unit doesn't do that it should. That said, when it's working right, this unit is a great little inverter!'


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