Battery Power Packs: Are They Too Good to Be True?

Batteries dead? Need to jump start your engine? We test four 17-lb., 17-Ah power packs that can do that job and others. The most expensive is also the best-the Solar ES-5000.


The etymology of the word blivit is questionable. A clean way to describe this term is stuffing 2 pounds of material into a 1-pound bag-a little tough to do. With the advent of small, valve-regulated lead acid (VRLA) hybrid and AGM battery packs, however, its nearly possible.

The battery packs tested here are self-contained units consisting of a valve-regulated, sealed lead-acid battery enclosed in a durable plastic housing with a convenient handle. Included is a separate charger, short built-in jumper cables, and a fused cigarette lighter jack for low current uses.

There are many variations of the basic unit. Some come with built-in lights, inverters, compressors, 12/24-volt convertible units, and even a 24-volt, self-contained MIG welder. Battery power packs are rapidly gaining in popularity, and so is their variety.

We tested several models from low-end $50 units to a $169 pack, which we got at a substantial discount on the Internet for $129. The four units all had about the same amp-hour capacity batteries (17-18 Ah), which seems to be the norm for any power pack under $200. Greater capacity batteries are available, but at a significant jump in weight and price. From what we found, the standard size pack will work fine with any engine using a size group 24 starter battery. Large diesels may require a bigger pack depending on the size of their cranking battery.

The terms manufacturers use to describe the capabilities of these packs are not seen in standard battery references, even though they sound similar. Crank assist amps is not the same as the common cold cranking amps term. Crank assist assumes you have a partially depleted but serviceable battery wired into your system-not enough juice to start the vehicle but not stone dead. In moderate temperatures, the battery pack provides the extra oomph to put the regular battery in the green. They work together in an additive, Gestalt fashion.

Smaller engines may actually be able to start exclusively from these battery packs. They can put out maximum power in amps for about 6-10 seconds, and must be rested 3 to 5 minutes to prevent overheating. The units we tested can do this several times. These packs, however, are not what you need to start a problem engine that needs lots of cranking.

The second term we often see with these units is peak amps. We have not been able to get an official definition of this term, but it is probably what the battery is capable of delivering momentarily into a dead short. This figure is of dubious value, but gives some frame of reference as to how quickly the battery can give up its energy.

What normally dictates how fast a typical wet cell battery can give up its energy is its internal resistance, and is related to how fast acid can migrate through the cells on demand. C/20 is a very efficient rate, and commonly used in the US as a reference. It refers to the capacity of the battery in amp-hours (C), divided by the rate of discharge in hours (20). So, if you discharge a battery at C/20, you are discharging the capacity in a particular battery in 20 hours to a particular cut-off. The cut-off is normally 10.5 volts, at which point the battery is considered fully discharged. If you exceed C/20-discharge faster than 20 hours-then the efficiency of the battery discharge suffers. The effect is great, in that if you discharge a typical wet cell battery at C/5, it will appear to have much less capacity than at the C/20 rate. Why? Because the acid diffusion simply cannot keep up with the four-fold increase in energy demands. The energy is still in the battery; you just cannot efficiently get it all out in a five-hour period. The more efficient a cell, the lower its internal resistance, and the quicker you can get the juice out.

Enter the Dragon
Sealed, lead acid, valve-regulated batteries in general, and the Absorbed Glass Mat (AGM) battery and its hybrid variants in particular, are different animals. Instead of lead compound plates with acid and water mixtures (electrolyte) sloshing around, a thick electrolyte paste is applied to the plates. (This is why you can use these batteries upside down). Some chemical substitutions in these sealed cells dramatically improve resistance to self-discharge, and just enough liquid acid is integrated into the paste to provide for peak efficiency. If you broke open a valve-regulated sealed cell, liquid would not pour out (but the mix would still be caustic). Instead of losing electrolyte during charging, the cells are under slight pressure (controlled by valves that can release under extremes) and charging gases are forced to recombine back to useable chemicals. The close proximity of lead to electrolyte and tight plate spacing make for extremely low internal resistance and much greater efficiency in energy discharge.

Rather than go into more detail than necessary, suffice to say that the AGM is characterized by extremely low self-discharge and extremely high, controlled discharge rates.

AGM manufacturers list cycle life on the order of 500 to 1,000 cycles, which starts to border on the too good to be true. (For more information on AGM batteries, see the test in the August 1, 1999 issue)

But wait, theres more. A brand new technology is now available called thin film, which is supposed to be even better than AGM chemistry. Bolder Technologies in Golden, Colorado, is a maker of thin film batteries and we are attempting to obtain one for testing. Stay tuned.

What We Tested
We obtained four representative battery packs from what we initially thought were four makers. As it turns out, Century Manufacturing-the folks who bring you all sorts of electric welders and battery chargers-seems to be in this battery pack business in a big way. They have models available for every conceivable need and size, including big trucks. They also manufacture under the brand name Solar, which was one of the models we purchased.

Our first unit from Century, the model 850, was recently on sale at Costco for $39. How good can this be? This is a bottom-of-the-line, power pack that many discounters carry.

The second came from West Marine under the name Roadmaster Jump n Start JNS 1800, which sells for $100.

The third pack, the Solar ES-5000, is made by Century, and was the most expensive. It has a highly regarded Genesis battery. We found it on the Internet for $129, somewhat below the suggested retail price. This was mitigated somewhat by the $14 shipping charge via UPS ground.

The fourth and last pack, the Superex, came with a $10 rebate coupon that drops the price to $40. It has a different case style and built-in light.

They all come with typical separate small, cheap, basic chargers that everyone in this electronic society has by the dozens. All packs have convenient built-in handles and DC plugs with rubber or sliding covers to reduce corrosion. The West Marine pack has two DC plugs, as well as a switch to turn the DC plugs (but not the jumper cables) on and off. A separate DC cable with plugs at both ends also comes with the West Marine, Solar and Superex packs. These can be used as an alternative way to charge the battery from a vehicles cigarette lighter.

Instructions for the Solar and Century packs say not to use an inverter of more than 300 watts to keep the battery from overheating under prolonged discharge at these relatively high currents. The others did not address inverter issues.

The two Century units have press-to-test buttons showing level of charge. You also have to press the button to see if the unit is charged, which is a nice feature. Only the West Marine and Superex units have it. The West pack also has a nifty storage box for both the charger and DC-DC cable. On the Superex unit, the cables clamp into the back for storage, like two hip pockets. The others all clamp to inverted side posts. All of the units weighed about 17.5 lbs. and were easy to lug about by the handles.

The Tests
We devised a test protocol to check the units at a low current supply, medium current supply, and engine starting current. For the low and medium current tests we used a BatTest 12-20, a microprocessor-based battery tester that puts a constant current load on the battery, and is adjustable from less than 1 amp to 20 amps.

The cutoff voltage is also adjustable to meet differing standards of discharge level. We chose a 10.5-volt cutoff for the low current tests that would place the units at 11.7 volts open circuit after a four-hour rest. This is typical of the industry definition of a 100% discharged battery.

Each test result was transferred to a laptop computer for graphing with the included BatTest software. We chose 2.5-, 5-, 10- and 20-amp discharge levels for the BatTest.

For the simulated engine starting, we wanted a more empirical approach than simply jump starting a car, because this can vary from 150 to 400 or more amps. We chose, instead, a car battery discharge tester that can place sustained resistive loads as great as 150 amps on a battery.

For a more common comparison, we also placed the tester on a group 27 deep-cycle battery. Amazingly, the Solar ES-5000 AGM unit was able to nearly match the static discharge level of the group 27 at 101 amps for 6-second bursts at about the same voltage level. Of course, the larger battery could sustain these levels for much longer periods, but nevertheless, this is an impressive showing from such a small battery (see the Test Table). These amp levels are different from cranking amp tests that use dynamic loads. Eighty or more amps indicated in this test is enough capacity to easily boost a healthy gasoline engine in warm weather.

All of the units except the West Marine pack worked perfectly out of the box. When we got the West Marine Roadmaster, we found that the battery did not register a charge on the built-in meter. This is not a good sign, as even sealed batteries cannot sit much more than a month before they begin to loose recharge capacity through such mechanisms as the formation of calcium oxide on the plates. We did a controlled equalization charge, followed by five charge-discharge cycles with a different, multi-stage charger. Equalization is not normally recommended for a sealed battery due to electrolyte loss problems. The battery recovered nearly completely. When we notified West Marine headquarters of our experience, they were very concerned, and tested four units in inventory to determine if this was a fluke. All checked out. At 5 amps, discharge times ranged from 155 to 172 minutes.

Another issue we raised to West Marine was the short 30-day warranty and instructions inside the box not to return it to the store, but rather to call the 800 telephone number of the battery maker. (In fact, each of the batteries had the same type of instructions…to not return it to the store if there is a problem.) West Marine reiterated its unconditional satisfaction guarantee that applies to all products-even if the battery is a year old. You might save yourself some bother by testing the charge level with the built-in tester. Pass on it if the battery is not nearly fully charged. All of the other units were in the green before we charged them. Once charged, these units will last several months before needing recharging.

There is another important issue on getting maximum battery life. The small chargers that come with these units are not trickle chargers that can be left plugged in. With the exception of the Superex charger that only puts out 16.5 open-circuit volts, all the others put out over 20 volts. We left them plugged in for 24 hours, and all but the Superex had battery voltages approaching 16 volts-enough to kill these batteries if left in this state very long. Unless you can remember to unplug the charger, we recommend using a cheap mechanical 110-volt timer to automatically shut off after 18 hours. Its cheap insurance.

Contrary to our original expectations, these units can indeed jump-start engines; there is enough juice for several 6-second bursts. They also have significant value for auxiliary low-current uses-or even to run moderate size inverters for relatively short periods. You cannot get more than 17 Ah from a 17-Ah battery, but these units certainly reach new heights in getting it out more quickly than we have come to expect from our other battery tests. Predicted life of 500 to 1,000 cycles remains to be seen. Odds of achieving this number are greatly enhanced by not overcharging.

At the low-end, we like the Century 850. We thought it would be a toy but were surprised it worked so effectively. In all tests it performed nearly as well as the most expensive packs, coming up just a little short in the maximum boost mode. It even has a circuit breaker in the DC auxiliary mode, like its more expensive brother the ES-5000, so you don’t have to chase around for fuses, as one would have to with the Superex and West Marine packs.

It does not come with a DC-DC cable to charge from other DC sources, like the other three packs, but a cable can be obtained from Radio Shack for a few dollars. The short 19″ jumper leads are a bit of a pain as you may have to work from an awkward position to reach some batteries to boost them. (The reason for short leads is that they minimize power loss at maximum current output). Solving this problem isn’t so simple because when you add cable length, and engage jumper jaw-to-jaw contact, you significantly reduce the maximum available current from the booster battery. If you must add cable length, use the shortest and heaviest supplemental cables you can find.

It is difficult to predict the cycle life of the Centurys generic battery.

We recommend a small, waterproof nylon draw bag secured to the carrying handle for keeping the separate charger from wandering off.

The other low cost unit, the Superex, is also a serviceable choice, and includes a built-in light. As mentioned, we like internal self-setting circuit breakers better than the Superexs fuse, which is external and subject to corrosion. We do like the hip pocket storage of the jumper cables, which also makes the unit more stable than the thin profile of the Century packs. The only downside is the increased possibility of moisture being retained on the jumper jaws or crimped connections that could promote corrosion. The slightly longer jumper leads are handy, but the 6-gauge cables are small.

The West Marine Roadmaster Jump n Start was a mixed bag. Nearly dead at first, we were able to get it up to snuff by carefully equalizing it, and then charging and discharging it several times with a multi-stage charger. The packs case, while larger than the other units, has a good storage area for the charger and DC-DC cable, neatly solving the lost-component problem. The case dimensions make it more stable and less likely to be knocked over. The jumper leads are short like the Century 850, however, and the external fuse for the auxiliary DC output is vulnerable to damage.

We were put off by the 30-day warranty, but West Marine has assured us that their ironclad No Hassle Guarantee applies to this product, regardless of any paperwork inside. West Marine customers should be aware of this, so they arent confused by the manufacturers instructions.

The Solar ES-5000 is the unit with the most bang for the most buck. First, it has a brand name AGM battery with an extensive test history behind it, rather than one of the generic batteries found in the other units. It claims more than 500 cycles; none of the others address the issue. It also retains a charge better than the others, claiming up to 50% capacity even after two years storage. (One other pack claims 80% capacity after three months.) We cannot validate these claims, but this whole class of battery is characterized by significant long-term storage capability, on the order of seven times better than wet cell batteries.

The Solar pack has 40″ booster leads. The quality of the booster jaws is noticeably better, which means they will transfer energy more effectively in the boost mode.

Lastly, in the tests the Solar had the best performance-marginally at the low-current applications, but increasingly better as current demands increased. This was particularly noticeable in booster testing as the voltage held up significantly better than any other unit under the starter current loads. This would also make it a better choice for intermittent 300-watt inverter use.

The Solar ES-5000 is our clear overall favorite, and a Best Buy if you want maximum performance, use it extensively or plan on storing it for long periods without charging.

Contacts-Solar ES-5000, Internet source: Radio Accessory Hq., 6700 Freeport, Blvd., Suite 105, Sacramento, CA 95822; 888/438-7247; Century Manufacturing Co., 9231 Penn Ave So., Minneapolis, MN 55431; 800/328-2921. Superex Canada, 601 Gordon Baker Rd., Willowdale, Ontario M2H 3B8 Canada; 800/268-3319. West Marine, 500 Westridge Dr., Watsonville CA 95076; 800/262-8464.