Bests & Worsts Reviews from Amazon

This is a review for the Samlex America (PST-300-12) 300 watt 12 VDC inverter. An inverter is a device that converts direct current (DC) to alternating current (AC). This inverter (PST-300-12) converts 12 volts DC to 120 volts AC. I purchased this inverter specifically to create a home-made battery-inverter box using a 33 amp-hour battery (modeled after the Goal Zero 23000 Yeti 400 Solar Generator). A 300 watt inverter is good for powering small loads, like an LED lamp or the chargers of small devices. The biggest mistake people make with a 300 watt inverter is to put too much load on it. If you intend to power your inverter from your vehicle's cigarette lighter, then you should know that this inverter is limited to 150 watts (100 watts, more likely) when using this power source. Therefore, such folks might want to consider a lower-capacity pure-sine-wave inverter instead, such as the 150 watt Samlex PST-15S-12A or the 180 watt AIMS Power (PWRI18012S) 180W Pure Sine Power Inverter with Cables. If you want to wire this inverter for operation above 150 watts, you will need to run wire of the appropriate gauge (8 AWG, 6 AWG, 4 AWG) depending on wire length (3 feet or less, 3 to 6 feet, 6 to 10 feet, respectively). The DC inputs of this inverter use tubular screw-down connections; you may be unable to find crimp terminals (flat-blade terminals) in the appropriate gauge. I assume that flat-blade terminals were deliberately chosen out of considerations for user safety: when the terminals are fully inserted, there is no exposed conductor that might accidentally be shorted. This is probably a smart decision for a potentially mobile device. For 8 AWG wire, check out the non-insulated pin terminals from FerrulesDirect (part PTNB10-12). As alternatives to Samlex, you might look at inverters by Magnum, Xantrex, AIMS, Go Power, Powerbright, and Wagen. If you want to use this inverter with solar panels, you should install a charge controller to ensure that the inverter's maximum voltage limit is not exceeded. Samlex makes another version of this inverter (PST-300-24) that uses 24 volts DC. CONSIDER DC POWER SUPPLIES INSTEAD OF AN INVERTER: You might be better off obtaining DC chargers/power supplies for your devices instead of using an inverter. For USB chargers, just search for: DC USB charger. For computers, go to your computer manufacturer's website and search for: DC charger (or search for: Car). "OWNER'S MANUAL" CAN BE DOWNLOADED: You can find a PDF copy of the "Owner's Manual" online by performing a web search for: Samlex PST-300-12 manual. This is among the best product manuals I have seen; I would highly recommend that you also look at the sections on batteries, wiring, and fusing. If nothing else, look at the Specifications table for the inverter in Section 12. The "Owner's Manual" has great discussions on inverters and batteries. WHAT'S IN THE BOX: ** PST-300-12 inverter; inverter has a standard two outlet (duplex) GFCI (ground fault circuit interrupter) receptacle to connect AC loads ** 14 AWG wire set with cigarette lighter plug to power inverter from car accessory socket ** 12 AWG wire set with battery clamps to power inverter from battery ** Hard copy of "Owner's Guide" ** Two set screws SPECIFICATIONS: ** Input: 12 volts DC ** Output: 120 volts, 60 Hz AC ** Inverter Type: Pure sine wave ** Continuous rating: 300 watts when wired directly to battery with larger cables; 150 watts (or less) when powered by either of the included cable sets ** Surge rating: 500 watts ** Peak efficiency: 88 percent ** DC input connection type: tubular-type screw-down terminals (supplied cables have flat-blade terminals) GENERAL INFO: This is a pure-sine-wave inverter; therefore, it can power many devices that will not work with a modified-sine-wave inverter. The "Owner's Manual" has a good discussion on the differences between these two inverter types. The needs of a lot of folks can be met with a cheaper modified-in-wave inverter; however, some electrical and electronic devices will only run, or will run better, on a pure-sine-wave inverter. Some devices may be damaged when powered from a modified-sine-wave inverter. For detailed discussions, just perform a web search for: pure sine wave vs. modified sine wave inverter. Just one example, CFL lights generally do not work with a modified-sine-wave inverter, but they work perfectly with a pure-sine-wave inverter. Some chargers will only work with a pure-sine-wave inverter. Devices with power factor correction power supply need a pure-sine-wave inverter. According to the manufacturer, when either of the two provided cable sets is used to power the inverter, the load must be maintained less than 150 watts. Personally, I never load an inverter to more than 80 watts if it is powered from a cigarette lighter or via alligator clamps. If the fuse supplying your vehicle's cigarette lighter blows, or if the wires are getting really hot, you are over-loading the circuit. As discussed later, to use this inverter with higher loads the inverter must be wired directly to a battery with cables of the appropriate wire gauge (8 AWG, 6 AWG, or 4 AWG, depending on cable length) and with fuse protection on the positive cable. If you want to power small loads (like an LED light) during a power outage, you could plug this inverter into a jump-starting battery pack using the included cigarette-lighter-plug cable. A lot of folks do not understand the limitations of batteries. Even a 100 amp-hour battery can only power a 60-watt incandescent light bulb for about 17 hours; therefore, I recommend that you use LED lights that require one-fourth of the power as an incandescent light. This inverter draws about 0.5 amps at no-load (when it is turned on with nothing plugged in). Because of this no-load (idle) current, the inverter can drain a battery dead even if no loads are plugged into the AC sockets. Therefore, switch the inverter off if the inverter is not loaded (you could also install a battery switch on the positive cable). The inverter is 9.69 by 5.76 by 2.58 inches and weighs 3.46 pounds. LOAD LIMIT IS 150 WATTS WHEN USING INCLUDED CABLES: Most folks who are considering this inverter probably want it to use in their car, truck, or van. The unit comes with two connecting cables: (1) a 14 AWG wire set with cigarette lighter plug; and (2) a 12 AWG wire set with battery clamps. According to the manufacturer, if you use either of these wire sets, the inverter load must be limited to less than 150 watts (or less, depending on the fuse size in your vehicle). As I said, I never load an inverter to more than 80 watts when it is powered from a cigarette lighter or via alligator clips. You should check the fuse size for your vehicle's cigarette lighter circuit: you should limit the load on the inverter so that the continuous load is always below 80 percent of the fuse rating. For example, if the fuse is 10 amps, then inverter load should be limited to 80 percent of 120 watts (10 amps times 12 volts), or 96 watts DC load, or about 80 watts AC load (accounting for inverter efficiency). Remember, some loads have a starting surge; if a fuse blows when a load is initialized, then the load is too big. NEVER replace a fuse with a larger fuse! Wire insulation could melt and a fire could start in the dashboard. WIRING INVERTER FOR OPERATION UP TO 300 WATTS: If you want to run this inverter at the full load capacity of 300 watts, then you need to connect the inverter to the battery with cables larger (in diameter) than those supplied. The biggest challenge in wiring this inverter may be finding wire terminals that will work adequately with this inverter's DC inputs (which are tubular screw-down connections for flat blade crimp terminals, not screw posts for ring terminals). You might try the non-insulated pin terminals from FerrulesDirect (part PTNB10-12). The manufacturer recommends the following gauges for the two wires (positive and negative) that connect the battery to the inverter: ** 3 feet or less - - - 8 AWG wires (0.1285 inch diameter) ** 3 feet to 6 feet - - - 6 AWG wires (0.1620 inch diameter) ** 6 feet to 10 feet - - - 4 AWG wires (0.2043 inch diameter) ** Greater than 10 feet - - - not addressed (therefore, not recommended) Note: A lower AWG number means a thicker (larger diameter) cable. A thicker cable means less electrical resistance. You can, of course, use a lower gauge (larger diameter) wire than the minimum specified. For example, you can use 6 AWG if 8 AWG is specified. It is very important to have the least resistance possible between the battery and inverter. Every component in the path can add to resistance (the wires, the connectors, the fuse holder, the fuse, the connection points, etc.). Therefore, cables should be as short as possible, lugs should be well-crimped (perhaps soldered), and connections should be tight and have maximum contact surface area. Ring terminals that are tightly screwed down (with a washer) provide a much, much better connection than alligator clips. I make my own cables. This is not a risk-fee do-it-yourself project: if you make a mistake, a resulting failure could cause fire, injury, or even death. You need to know how to do it correctly and how to inspect finished cables. Acquiring the knowledge and skill to properly strip cable and crimp connectors is best done with a professional, who can also inspect your finished work. You should also know when soldering is beneficial and how to solder properly. Most folks will be much better off purchasing ready-made cables. Most ready-made cable comes with ring terminals at both ends. Unfortunately, this inverter does not use ring terminals at the DC inputs; instead it uses tubular screw-down connections. If you cannot find flat blade crimp terminals of the appropriate size, you will have to come up with some means of modifying your ready-made cable to be securely fastened to the inverter's DC inputs with maximum surface area contact. When buying cables, make sure you meet the requirements specified by the inverter's manufacturer (wire gauge based on length of cable). Keep the DC power cables as short as possible. You can buy ready-made cable from Amazon and from stores (including online stores) for RVs and boats. I recommend inspecting ready-made cable as thoroughly as home-made cable. If you want custom cables (cut exactly to length you want), then try car-audio shops, boat shops, RV repair shops, and auto-supply stores, etc. You can also find professional electricians at the shops who might install your inverter for you. I typically purchase wire by the foot at either a large hardware store or marine-supply store. I typically use marine-grade ring terminals. Having a real crimper helps tremendously! I typically use red wire for positive and black wire for negative. I always use heat-shrink tubing at the connectors: heat shrink will increase the life-expectancy of the connection by minimizing corrosion. If I do not use red cable for positive and black cable for negative, I use red heat shrink at the positive connectors and black heat shrink at the negative connectors. If you do not use heat shrink, electrical tape is better than nothing at all. FUSE IS REQUIRED ON THE POSITIVE CABLE: If you wire this inverter for 300-watt operation, you must have a fuse (or circuit breaker) on the positive wire. The fuse should be installed as close to the battery as possible (within 7 inches per the "Owner's Manual" . . . closer is even better). The manufacturer specifies using a UL Class T fuse, or equivalent, with ampere interrupting capacity (AIC) of at least 10,000 amps. A table in the "Owner's Manual" lists a fuse size of 40 amps (which is the maximum input current of this inverter). If you want to be professional about it, you could use the NEC (National Electrical Code) methods for determining fuse size. When wiring loads to batteries, I prefer to use marine-grade fuse blocks that connect directly to the positive battery terminal (i.e., there is no wire between the battery and the fuse block). FAN OPERATION: The inverter is cooled by the air surrounding it. Your inverter may run too hot if you keep it in an enclosed space with insufficient air flow (like a trunk). At higher loads, a fan will start that will establish forced air flow through the inverter; therefore, you need to keep the air space around the inverter clear. The cooling fan starts and stops based on measured temperature: the fan starts if temperature at a "hot spot" inside the inverter reaches 48°C (118.4°F) and shuts down when temperature lowers below 42°C (107.6°F). The inverter has a high-temperature shut down if it gets too hot. LOW-VOLTAGE ALARM AND LOW-VOLTAGE SHUT DOWN: The inverter produces an alarm when input voltage drops to 10.5 VDC; the inverter will automatically shut down at an input voltage of 10.0 VDC. The inverter will automatically reset from a low-voltage shutdown when input voltage is restored greater than 11.5 VDC. Be warned, based on the capacity of the battery and the discharge rate, it is possible that the battery could be over-discharged by the time that the alarm is received. Over-discharge may shorten the life-expectancy (the number of discharge-charge cycles) of the battery. HIGH-VOLTAGE SHUT DOWN The inverter will automatically shut down if input voltage rises to 16.5 VDC. Therefore, do not connect unregulated solar panels to this inverter; instead, use a charge controller to ensure that input voltage is less than 16.5 VDC. OVERLOAD/SHORT CIRCUIT SHUT DOWNS The inverter has a continuous load rating of 300 watts and surge power rating up to 500 watts for less than 1 second. If there is an overload, the inverter will automatically shut down, an orange LED status light will turn on and an audible alarm will sound. The inverter must be manually reset to recover from an overload shutdown: (1) the cause of the overload must be removed or otherwise corrected; (2) the inverter's power switch must be switched OFF for at least 3 minutes; (3) after the inverter has been switched OFF for at least 3 minutes, the overload should be reset and the it may be switched ON. INVERTERS AND MOTORS: If your inverter is going to run inductive loads (such as motors) then you need to consider the volt-amp requirements of your load instead of the watts, based on power factor and starting current. Starting current can be five to seven times higher than running current and can last for several seconds as the motor starts.