You may own a Corvette which is parked for long periods. If so, have you ever had a dead battery? Even the best battery when not connected to anything slowly discharges because of the chemical processes at work inside it. Once hooked to your car’s electrical system, besides that tiny, self-discharge rate any electrical accessories which operate all the time make for a current draw and, after 1982 once Corvettes were equipped with devices, such as engine computers, sound systems with memories and digital clocks, current draw when the car’s electrical system was turned off became an issue for owners who drive their cars infrequently.
Today, even if the car is locked and the key fob is in your nightstand, Corvettes have a number of electrical devices which draw current, such as: keyless entry receiver, engine computer and a number of other onboard devices, On-Star “wake-ups” during the first 48-hours after shutdown, security system, evaporative emissions system self tests lasting up to an hour after shutdown and devices left plugged into live auxiliary power ports.
The battery rundown time depends on “reserve capacity” which is how many minutes a fully charged battery can sustain a designated constant load of 25-amps before it is discharged. For a 12-volt battery, “discharged” means voltage will have fallen to 10.5 volts or lower. If reserve capacity is high, battery run down time will be longer. If the reserve capacity is lower, then run down time is shorter. For example, according to GM Service Information (GMSi), if your Corvette has a battery with a reserve capacity of 110-minutes, you have a 50-milliamp “active draw” and you start with an 80% charge; it will take about two weeks for the battery to discharge to 50%.
Suffice to say, if a period of non-operation is more than a couple of weeks, the battery may discharge to the point of a no-start condition. Then, you either charge the battery or jump-start the car and let its alternator recharge it. These significant-discharge-then-recharge or “deep” cycles reduce battery life. The durability of typical automotive batteries is degraded if they’re subjected to deep cycles on a regular basis.
The solution to this problem of batteries getting discharged when a car is not operated for a while is a “smart” battery charger designed to keep vehicle batteries charged during periods of non-operation. Typically, they have two charge rates: a maximum rate of between 1.5 and 5-amps and a maintenance rate of between 220-milliamps and 1.0-amp. Upon connection, if the battery is partially discharged, a smart charger–such as the AutoMeter “Battery Extenders” tested for this article–brings a battery up to full charge using it maximum current output. At that point, a microprocessor senses battery voltage at a nominal level and backs-off the charge rate to between 0 and 250 milliamps, depending on load. It “floats” the charge current at that level which is just enough to keep the battery at its optimal charge voltage, which depending on battery type, is 12.6-12.8-volts or 6.3-6.4-volts for ’53 and ’54 Vettes. This feedback-controlled, reduced-charge rate eliminates overcharging and extends battery life. There is no need to monitor an AutoMeter Battery Extender. Just plug it in, connect it to the car and forget it.
When the Corvette Action Center debuted it’s Product Evaluation Pages in the late-’90s, one of the first products we tested was the first-generation AutoMeter Battery Extender. It was one of the early entries into smart charger business, which, today, is huge with a plethora of products from various manufacturers. The original Battery Extender (PN 9201) proved to be quite a successful product selling about 50,000 units in 20 years on the market. We should add that two decades is an amazing life span for an electronic device.
In 2015, AutoMeter redesigned the Battery Extender product line incorporating more modern technology, a widened feature list and more competitive pricing. This second design AutoMeter charger line was released in three versions, 1.5-Amp (PN BEX-1500), 3.0-Amp (PN BEX-3000) and 5.0-Amp (PN BEX-5000).
One advantage of these new chargers over the original Battery Extender is their three modes of operation: “charging”, “maintenance” and “desulfation”. The first two modes are standard for any smart charger and were available from the old 9201s. What’s new is the “desulfation” mode. Lead-acid storage batteries can develop lead-sulfate crystals on their plates. When a battery becomes “sulfated,” its ability to hold a charge is degraded. Mild cases of sulfation can be mitigated by “pulsing” the charge voltage and current which can cause the crystals to separate from the plates. If an AutoMeter BEX-series smart charger senses sulfation is developing, it goes into the “desulfation” mode where voltage and current are varied in a way that causes the crystals to separate.
Another improvement of the new Battery Extender design is that the unit’s housing is made of a lightweight plastic and is sealed making the device water-resistant to the IP65 standard which means that, not only can it stay dry during a three-minute spray with a water jet, but it’s, also, impervious to dust. In our testing, we found the new, sealed housing not as valuable as an anti-moisture-and-dust measure as it is an “insect repellant” measure. We have two of the old Battery Extenders, which were vented for cooling and one of them is used outdoors under a carport. We’ve found that insects, especially little spiders, like the interior of the first design Battery Extenders–so much so that two or three times a year, we have to unplug it, then use shop air to blow though the housing’s exterior vents to get rid of partially eaten insects, spider poop and spiders. In short, we definitely like the hard plastic housing used by AutoMeter in the current Battery Extender design.
Three other features of the BEX-series chargers are: automatic overcharge protection, reverse polarity protection and spark-free connection. With the first two systems, there’s very little chance of screwing-up a battery by not paying attention to how long it’s connected nor connecting red to black and black to red. With the third, you don’t have to worry about a little spark when you connect the second cable and remember: connect red first and black second.
We like that all Battery Extenders always come in a kit which includes two sets of leads. One set has traditional spring-clips on one end and another set with ring terminals on one end. Both sets of leads connect to the charger with a quick-disconnect mechanism. The ring terminal set is good in a case where the Battery Extender is always connected to the same vehicle.
Some smart chargers have designed-in protection which prevents the user from mistakenly connecting a 12V charger to a 6V battery. The charger senses the battery’s voltage and if its below 5 volts or so, the charger will not function. AutoMeter decided to let the user take responsibility for knowing the voltage of their battery, so, according to Mike Gathman, AutoMeter’s Vice President of Engineering, all the BEX chargers will, “…charge batteries down to an open circuit voltage of 3 volts. It is up the user to select the proper charger or (with the BEX-5000) charge voltage that matches the battery they are charging. The BEX chargers have a timer that will terminate the charge and flash all the LED’s when the charger senses the charge is not making proper progress due to a defective battery, a large parasitic draw, or wrong battery voltage.”
We have tested the BEX-5000 against some other chargers and, indeed, it will charge a very low battery when some other products will not.
The final advantage of the new BEX line is that they are priced lower, and with the BEX-1500 and BEX-3000, a lot lower than the first generation Battery Extenders. Thank modern circuit design, lower component costs and lower-cost manufacturing for that.
Our favorite AutoMeter BEX charger is the 3000. We have two in service and one of them has been working almost continuously for three years. The BEX-3000 is compatible with all types of lead-acid batteries: wet cell or “flooded”, absorbent glass mat (AGM) and gel cell. It has a selector button used to set the kind of battery to which the charger is connected. It’s street priced at about 60 bucks and it’s price point coupled its optimization for flooded, AGM and Gel Cell batteries
We don’t recommend the BEX-1500 because some batteries in C5/C6/C7/C8 are AGM. While the BEX-1500 functions with AGM and gel cells, it’s optimized for flooded batteries, only. Additionally, it’s very low output makes it impractical for Corvette use if the goal is to charge a partially discharged battery prior to its acting as a maintenance charger. For that reason, we think the 1500, is better suited to ATV, UTV and motorcycle applications. Finally, in our view, its price is too high. For about ten bucks more you can have the 3000 with twice the max. charge rate and compatibility with AGM batteries.
The BEX-5000, AutoMeter’s flagship smart charger, offers the highest charge rate and selectable output voltages of 6-,8-, 12- or 16-volts whereas the 1500 and 3000 are 12V only. When operating the 5000 at the first three voltages, the maximum charge current is 5-amps, however, in the 16-volt mode, its max. is 3-amps.
The Battery Extenders’ safe ambient temperature range is -4°F to 122°F. Sustained operation outside that range, may cause a malfunction. Their input voltage range is 108 to 132-volts AC.
For more information on AutoMeter’s Battery Extender line of smart battery chargers, see the charger page on AutoMeter’s web site.