jump starter
great unit, powerful and long lasting charge Read more

JSCUSTOMKING












Product video 1
Rated 4.8/5 across 21 reviews — highly regarded by customers.
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great unit, powerful and long lasting charge Read more
Great car booster, works perfectly Read more
I’m impressed with this one. It’s very simple to use, it comes fully charged, it has a flashlight that you can switch into a flashing light for an emergency. The storage case is perfect, it’s small, has usb ports for charging phone etc, and it charges quickly. Thumbs up. Read more
I’ve used this a couple of times so far and it started both vehicles without hesitation. One was an 8-cylinder pickup and the other a mid-sized car. In both cases it had more than enough power and the engine fired right up. The display is large and easy to read. I like being able to see actual percentage of battery and wattage while charging instead of guessing from a few tiny LEDs. Charging over USB-C was straightforward and uneventful. My only concern is the clamp lead design. The cables need to be two to three times longer. On my truck, I have to connect to a positive lug near the alternator and ground to the engine block. That puts the clamps close to belts and pulleys while cranking, with very little room to reposition the unit safely out of the way. I’ve replaced this style of jumper clamp before on other boosters. The plastic that makes up the clamp body itself tends to degrade after living in a vehicle through heat and cold cycles. That has been the failure point for me in the past. Replacements aren't expensive, but they all appear to be made in the same place and of the same quality. Aside from the clamp length and long-term durability question on the clamps, the unit itself performs well and delivers the power it claims. It’s a good item to keep in your roadside emergency kit. Read more




The media could not be loaded. Solid jump starter that’s simple to operate and convenient to carry. The display is easy to read, and the unit holds a charge well when not in use. It powered up my vehicle quickly and doubles as a handy backup charger. Definitely a useful item for emergencies. Read more
I tested the JSCUSTOMKING battery booster and overall it performs well, with a few minor frustrations and one misleading spec worth calling out. In my testing, the capacity came out to about 10,230 mAh when discharged from full at 5V and 1.75 amps. Charging from empty took roughly 8 hours at 30 watts and put back about 11,605 mAh. Those numbers seem reasonable for a unit in this class. The construction quality is good. The plastic case feels durable and the large LED screen is easy to read and clearly shows charging status. The built in flashlight is bright enough to be useful for roadside work. The battery pack uses an automotive grade prismatic cell, which was a suprise. The jumper cables are well thought out. The wire gauge is appropriate, the clamps are strong, and everything is properly insulated. I like that the negative wire is intentionally shorter than the positive wire to reduce the chance of accidentally shorting the clamps together. Jump starting my lawn mower worked without any issues. The included storage case is also a plus and fits all the components comfortably without forcing anything. There are a couple of downsides. The rubber port protector on the end broke off immediately, even before real use. It is a small thing, but still disappointing. The bigger issue is the product description. It lists the battery capacity as 8250 amp hours, which is simply not realistic. A battery with that capacity at 12.8 volts would power a house for days. If it were capable of delivering 8250 amps, that would be over 100,000 watts and would instantly melt the wires and probably your hand. In reality, engine starting typically draws around 5,000 to 10,000 watts for a few seconds. This unit is much more likely in the 800 to 2000 amp range, and only briefly. The product works, but the specs are misleading and should be corrected. Despite that, for the price and the overall build quality, I can overlook the broken rubber cover. It is easy to setup and use. The instructions are printed on the back. The jump starter does what it is supposed to do, and I would still recommend it, just with the expectation that the advertised numbers are exaggerated. Read more




This item is a jump starter to assist in starting a vehicle with a weak or dead battery. It arrived with a 96% state of charge. I used the provided charger and usb cable to bring it to 100%. I note that the wall charger has a rating of 20 watts and the device did indicate it was receiving up to 20 watts. The device can charge at up to 65 watts if one uses a more powerful charger. In addition to boosting a weak battery, it also has two usb A charging ports. I tested them, and they were capable of charging my Galaxy S21+ cell phone in superfast mode. That is great! It also has a light, but it is not very bright. So I went into a fully dark room and could see well using that light. It will be useful to see one's battery while attaching the provided cables from the booster to the weak battery. I also note that a voltmeter shows there is 16.2 volts always present at the output ports whether the booster is turned on or off. So be cautious. I have not had the need to use this on a weak battery yet, but with its high amp output capability it will be useful when that situation arises. The instructions state to start the vehicle within 3 seconds of connecting to the battery. Not sure that is possible if one is doing this alone. Read more




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