Chicago Electric 12-Volt Jump-Start and Power Supply - 38391-4VGA
3 consumer reviews
Average Product Rating:
A Jump Start In A Box
Jul 29, 2009 (Updated Mar 15, 2013)
Review by glen22
Rated a Very Helpful Review
Pros:Inexpensive and compact
Effective in starting autos with weak batteries
Cons:Charge state requires periodic monitoring for long life
The Bottom Line: Highly recommended, particularly in areas with limited emergency repair/tow service
Recommend this product?
For years, I have enjoyed exploring some of America’s more remote areas, particularly its deserts. Camping, backpacking, hiking, exploring, - it’s all good. Some of these places aren’t hard to access with an ordinary vehicle, then traveling by foot, while others may require a four-wheel-drive truck or other high-clearance vehicle just to get to the trailhead. On one morning day years ago, after marking my camp's location (between 60 and 600 miles of desert on all sides), I packed up and got ready to leave, only to find the vehicle was taking a long time to crank over. It finally dawned that a simple breakdown due to a dead battery could be rather hazardous to one’s health. So I began taking along a few essential emergency tools, extra water, and other supplies. I also took along an extra charged auto battery, but this didn't work as well. It was very heavy, required a battery case for safe storage, and was always in the way. Once back home, I found that it also did not take to being stored in a high heat storage area outside the house, and died rather quickly, even though I always kept it on a battery charger.
I replaced the spare battery with another ‘emergency tool’ - the Chicago Electric 12-Volt Jump Start and Power Supply - Model 38391 (38391-4VGA). It’s a 12-volt, portable backup or ‘jump-start’ battery for use when other vehicles and jumper cables aren’t an option. It is made in China and sold by Harbor Freight, although I have seen many such products of identical or near-identical specification and features sold under a variety of English-language brand names. This has to be one of Harbor Freight’s more long-lived product numbers, as the Model 38391 has been available on the U.S. market since at least 2002, and probably longer. My instinctive aversion to purchasing a foreign-made product was overcome when I could not find a similar U.S.-made example.
The Model 38391 uses a 12-volt sealed lead-acid battery in a tough, durable plastic housing, weighing a total of 19 pounds. This housing has a rear screw-mounted panel, enabling removal and replacement of the sealed battery if needed (I’ve never replaced mine). This is a laudable feature, although whether or not you could save money by changing out the battery compared to simply purchasing a new replacement may be questionable. My own example cost all of $39.95 back in 2003, but I regularly see many of these jump-start products on sale from time to time.
The Model 38391’s internal battery is a 17 amp/hour size, with a capacity of 400 cranking amps (starting power) and 900 peak amps. Many manufacturers advertise peak amps, which is usually much higher, but this standard is difficult to quantify and has little bearing on performance in starting a cold, dead engine. Instead, look for battery size (amp/hour) and cranking amps (CA) rating (or, as an alternative, cold cranking amps [CCA] rating). CA and CCA are probably the most important specification when considering performance of a jump start battery (Cranking amps is a rating used to describe the discharge load in amperes which a new, fully charged battery at 32 degrees F (0C), can continuously deliver for 30 seconds and maintain a terminal voltage equal or greater than 1.2 volts per cell.)
This model is basically a jump start unit, and does not have the small built-in tire compressor featured on similar types of products. The latter could be useful for car-size flats or low tires, but they add complexity, and their integral construction may inhibit adequate cooling when used in high temperatures for extended periods (unless fitted with an internal fan). I prefer to use an oversized can of tire inflator/sealant for emergency (car) tire flats in city driving, and a separate and more powerful air compressor/tank and tire plug kit for the truck when out in the 'blue'.
I am not a fan of those low-priced "battery booster" products that only allow you to use the vehicle's cigarette lighter or power port to charge the vehicle. Since the cigarette lighter socket or port was designed to light cigars and cigarettes, not function as power connections, using them for the latter can lead to many problems. In addition to issues with incompatible sizes, the connecting plugs can be poorly made and make inadequate electrical surface contact with the socket owing to poor retention. Large-gauge booster cables with alligator clamps that attach directly to the battery terminal(s) are much more efficient and certain. In two minutes, you can pop the hood, attach the cables, jump the battery, start the engine, and be done. Of course, this experience is from my own car and truck, which were designed with relatively easy-to-access battery terminals.
Also, most of the very small cigarette-lighter-connected, misleadingly named "battery booster" emergency power units on the market these days are not really jump or emergency start batteries at all, but merely a very small 12v battery that uses a low-powered trickle charger to partially recharge the weak onboard battery - after 10-20 minutes of waiting. And if that limited amount of recharge turns out to be insufficient, you're out of luck. These battery-to-battery trickle-chargers are a truly bad idea, and I've never met anyone who was happy with them.
The Model 38391 is also fitted with a switchable, non-removable 3.6-watt spotlight, two short booster or power feed 6-gauge cables with spring-loaded copper alligator clamps, a 120/12-volt transformer and power supply for recharging the battery, and a cigarette lighter receptacle or power port for use when powering small 12-volt devices. In addition to the fixed spotlight housing, there is a rotary on/off power switch, light on/off button, charge test button, a 12v recharging port and charging light indicator, and an analog DC voltmeter with needle-indicated charge state mounted on the front panel.
The six-gauge (6-ga.) welding (small multistrand wires) copper cable used on the product tested here is really the minimum gauge for a product such as this, and is acceptable only because of the very short length of cable employed. I would certainly look for larger 4-ga. or 2 ga. copper cable on similar products that feature longer cable lengths, to ensure that excessive current resistance does not become a factor.
The Model 38391 also came with a 12v wall-wart transformer/charger to plug into household current, and a separate cord with cigarette lighter plug fitting that attaches on its other end to the recharging port. This last accessory is apparently intended to charge the jump-start battery from a vehicle’s 12-volt system, which of course is the exact reverse of the product’s primary purpose. As a result, I’ve never used it.
While the instruction manual indicates that the Model 38391 has an additional side-mounted port for supplying a built-in power supply for recharging via a 120v recharging cord, my version did not have this feature, and I have always used the supplied 120/12v wall receptacle transformer (wall wart) with a negative polarity plug connected to the front panel’s charging port to keep the battery at full charge.
In use, the red booster cable clamp is attached to the positive battery terminal, followed by attaching the negative (black) clamp to a non-moving metal part on the vehicle engine/frame. The power switch on the front panel is turned on, and after a one-minute wait, the vehicle being jumped is then started. The first cranking attempt is limited to five or six seconds. A second cranking attempt may be made after waiting three minutes. Once the vehicle is started, the power switch is turned to 'off', then the black booster clamp is removed, followed by the red clamp. After such a large current drain, the Model 38391's battery should be recharged as soon as possible.
A charging indicator light turns red to indicate that the battery is charging. The Model 38391 is fitted with a safety switch and overload protection to keep it from being overcharged. Additionally, the voltmeter has a red zone commencing at 14.8 volts to indicate overcharge condition, and the manual requires you to disconnect charging power if this condition is indicated. The voltmeter test button requires a very firm, solid push until it completely bottoms out, or you will not obtain an accurate voltmeter reading.
When the charging indicator light goes out, an automatic cutoff is engaged, disconnecting the charging power supply. Then the wall-mount transformer can then be disconnected if desired.
The operating manual indicates that the Model 38391 can be left attached to its plugged-in charger to keep it in a steady charged state. I’ve never done this, for two reasons. The first is that I don’t like to leave wall-wart transformers plugged in at all times. The second has to do with the charging system. I have never been able to get my example to commence charging again after being charged once and left on its charge transformer for long periods of time. Instead, the transformer’s plug must be removed, then reinserted in the unit's charging port. This may happen because the recharge function only starts if the battery gets down to a fairly low state of charge, say 50% (indicated). But I’ve never been willing to let it get that low. Starting batteries, particularly small emergency ‘jump-start’ versions, do not take well to multiple cycles of discharging to 50% capacity or less.
At first, the Model 38391 received no real use at all. Instead it was stored indoors, and was recharged from time to time when its charge level dropped to 75% (according to the green scale on the product’s analog voltmeter). From time to time I would take it with me on vehicle trips to remote areas, where it got banged up and knocked around - but as it wasn't needed for a jump-start, it was never used.
Later, I began to carry it in my daily commuting vehicle. This saved the day one very hot afternoon when, after finishing up a business visit, I returned to a large, mostly empty parking lot. The car refused to start. It was one of those days when no one else was around, and I have since wondered if I would have found anyone with the inclination to provide a ‘jump’, or would have had to wait for my insurance company’s emergency repair service. As it turned out, I needed no help. Instead, I attached the Model 38391's clamps, turned the power button to ‘on’, and cranked the vehicle, whereupon it immediately turned over. The start problem was later traced to a weak battery and bad battery cable. Since then, the Model 38391 has been used three more times to start a vehicle with a dead or weak battery.
Amazingly, the Model 38391's battery lasted well nearly 10 years before becoming noticeably weak. I attribute some of its long life to the fact that I have not left it outside exposed to high heat, nor have I used it for convenience purposes, i.e. to power radios or other non-essential accessories. Here in Arizona, even so-called ‘sealed’ batteries can suffer low electrolyte levels and early death when exposed to high heat for long periods. Also, I was careful to keep the battery charged, and never let it get below a 75% indicated charge state on the voltmeter. After 10 years, it's all washed up, but that's great performance for a $39.95 product in my view.
I recommend the Model 38391 and others with similar features for their utility in starting stranded the average car with a low or weak battery. I do not recommend this unit for larger trucks, particulary those with diesel engines, which can require a substantial amount of cranking power to turn over.
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