Bests & Worsts Reviews from Amazon

I just wanted to speak to a few things that people have mentioned in their reviews. Some asked about the amp-hour rating of the battery, others criticized it for not holding a charge for a long period of time, still others apparently were unhappy that it didn't fulfill their expectations after they tried to use it without following the manufacturer's instructions! Okay, what is the amp-hour rating? Don't worry about it - for jump-starting. Amp-hour ratings are essentially meaningless for this purpose. What is more important for jump-starting is the peak ampere output. This unit is rated at 900 amps peak, so it should be adequate for jumping almost everything but those vehicles with large V-8 gas or diesel engines, and, with proper technique, it may even suffice for those! So what is "proper technique"? Well, you have to keep some basic electrical facts in mind. When you turn he ignition key to the "Start" position and the starter first energizes, it draws a LOT of current, typically about 300 to 400 amps for "average" cars, and more for larger ones. (Small cars with smaller engines will draw somewhat less.) The relatively small battery in this unit is designed to deliver surprisingly high power for its size, but there are limits imposed by the internal construction of the battery, and the size of the various connections within the power pack itself. So, you try to start your car, and discover you left the headlights on last night. You grab your handy-dandy little jump-starter and connect it the way the instructions say to: e.g., red clamp to the positive terminal of the battery, and the black clamp to an unpainted metal part of the engine. You get in the car and note, with some satisfaction, that the dome light now comes on. (It didn't before!) You turn the key to the "On" position and watch as the dash comes to life, with all the lights and such. Also, the radio begins to play - good! Now, you turn the key to "Start." The dash goes nearly dead, and you hear a sort of "grunt" from the starter - but no start. Only the dreaded "click-click-click" noise from the starter solenoid that means, "No way, buddy!" @#*#+#^@#!!! So what did you do wrong? Well, let's see. You have a completely depleted large lead-acid battery in your car. When you connected the jump-starter, the dead battery began to draw a considerable amount of power from the (much smaller!) battery in the power pack, probably something on the order of 200 amps or so, if not more. Then, you turned on the key. All the various systems in the car start to draw power from the battery as well, maybe another 20 to perhaps as much as 100 amps, depending on the car. If you sit there gazing at all the pretty lights and listening to the radio, it will draw that much more power, and that energy is lost forever. Finally when you try to start the car, the power pack has depleted too much of its energy, and simply doesn't have enough left to crank your engine. So what's the solution? Easy! Just do this: connect the power pack to the dead battery - then go away for a couple of minutes! Don't get in the car; just wait patiently for a while. Why? Because you are giving the power pack time to transfer as much energy as it can to your car's main battery. The main battery is designed to deliver large amounts of energy in short bursts. Then, when you go back outside and get in your car, don't fiddle around. Close the door, make sure the radio and heater/AC are turned off, and then turn the key in one smooth motion from "Off" all the way to the "Start" position. The engine should crank and start normally (assuming it starts normally all the time: if you have a junker, all bets are off!) Okay, so that problem's solved. Now, back to amp-hours. Where does that become a useful number? Well, it's only good for comparing performance for similar types of batteries being used in fairly low-current usage, such as powering a light (or two, or three...), or maybe even a TV when using an inverter. I'm not going to go into too much detail here; I'll just describe a fairly typical situation. Let's say you are out camping, and you have a nice little lamp your wife thought was "just darling" for camping. It has a 60 watt incandescent bulb in it, and it lights up your camp site quite nicely, thank you very much. Along with that, you have a 20" flat-screen TV plugged in so you won't have to miss a single episode of "Big Bang Theory." Unfortunately, just as Penny is about to give in (again!) to Leonard's wimpy nerd charm, the power pack gives a distorted whine, and the TV and lamp go out! What? It's been on for less than an hour! What's going on here? Well, let's see. Using some basic electricity formulas, we can calculate about how long it should last. The battery in my unit says it's rated at 17 amp-hours. (Hmm. It looks awfully small for that rating, but okay...) Now, the lamp is 65 watts. The TV? Uh - let me see... it pulls... let's see... 85 watts.b So - total draw is about 1.5 amps, or 150 watts. One thing we don't know is the efficiency rating of the built-in inverter on the power pack. We can make a pretty good "educated guess", though. (A quick word about inverters. Their efficiency may vary from something just over 50% when a trickle of power is being used, to something over 90% when the output is approaching the inverters rated output. An inverter will use some power from your batteries even when you are not drawing any AC power from it. This results in low efficiencies at low power levels.) Since the inverter in this unit is rated at 500 watts, and you've been drawing only 150 watts, let's say it's been operating at...oh, let's be generous and say about 70% efficiency. (Close enough for government work...) That means it's been drawing 195 watts from the battery, or 16.25 amps! Yeah, it's gonna be sucked down in somewhat less than an hour... because the inverter will shut down when the voltage drops below about 11 or so. If you want to use it for lights, I would recommend you use CFL lamps, or, better still, LEDs. They draw a lot less current. And - forget that TV: it just draws too much. Use your DVR at home to record Big Bang Theory, and watch it when you get back. Also, don't complain about it not holding a charge when you tried to use it and it was dead after it had been sitting on the shelf for six months! Lead-acid batteries will self-discharge over a fairly short time, and the instructions for these things tell you to recharge them about once a month to keep the battery fully charged. Lead-acid batteries are not happy being discharged to less than 60% of their rated capacity; they will lose their ability to fully recharge if left discharged for very long. Keep it charged up, and it'll last a long time. Anyway, you can leave this unit plugged in to its charger all the time: the manufacturer has designed it so it won't overcharge. That way, it'll be ready whenever you need it. Finally, the initial charge for these batteries takes about 40 hours. When you get a new unit, the battery has an initial charge on it from the manufacturing process. The plates in the battery have to be charged for the full 40-hour period to "condition" them, otherwise, it will never - ever! - be able to gain full capacity, and, in all probability, not last very long. So, when you first open the box, plug in the charger and connect it to the battery, and let it sit there for a couple of days. Don't pay any attention to the green light: it'll probably come on after anywhere from 12 to 24 hours. Just leave it plugged in for at least the full 40 hours, and it'll be good. I bought mine knowing all this stuff beforehand, so I would say, yes, it does what it's supposed to do. I'm happy with mine; I think you'll be happy with it, too, if you are careful to make sure it meets your needs before you shell out your hard-earned money.