Features January 2008 Issue

Xantrex Battery Accessories

XBM, C40 allow you to track battery performance and regulate its charging.

During our wind generator comparison (June and July 2007),

Practical Sailorhad a chance to evaluate the performance of two Xantrex products that were integral to our testing setup (photo above left), the XBM Battery Monitor and the C40 Charge Controller.


XBM Battery Monitor

We found that in order to evaluate the wind generators’ performance effectively, we had to be able to monitor and log the cumulative amp hours each produced during the entire test period. The XBM Battery Monitor enabled us to do this.

The XBM monitor uses microprocessor technology to provide complete battery status information and features a lighted, easy-to-read digital LCD readout showing volts, amps, amp hours consumed, and operating time remaining.

Xantrex XBM Battery Monitor
For the wind generators’ test, the test apparatus (far left) included a Xantrex XBM battery monitor and a C40 charge controller. Housed in a plastic bin, an apparatus was hooked to each wind gen at the test site (below).

Another handy feature is a bar graph that displays the battery’s current state of charge in a simple graphical format. Historical information such as charge efficiency, deepest discharge, and average discharge are available at the touch of a button—buttons that are splash proof, allowing the meter to be flush-mounted in a semi-exposed location.

A neat option for the XBM monitor is a communications kit containing hardware and software to enable battery monitoring from a Windows-based laptop. The included Windows 98/ME/2000/XP software allows boaters to analyze the performance of their battery system and remotely control the battery monitor. The software can simultaneously display real-time data on all parameters displayed on the battery monitor’s LCD screen, and also can log, save, and graphically display historical battery performance information, such as the number of charge/recharge cycles.

The XBM Battery Monitor works with any battery type and is compatible with both 12- and 24-volt DC systems. It comes with a one-year manufacturer’s warranty.

C40 Charge Controller

Another key piece of gear used in our test set-up was the Xantrex C40 charge controller. Charge controllers regulate the voltage generated by onboard, renewable energy systems (wind generators and solar panels, for example) by monitoring battery-charge condition and shifting excess power to a resistive or "diversion" load to prevent battery damage due to overcharging. This helps maintain and extend battery life, while protecting batteries from failures related to over or under charging.

Wind Generator Test

The Xantrex C Series C40 can be used as a battery charger, diversion, or load controller. It can be configured for 12-, 24-, or 48-volt DC operation and works equally well with NiCad, flooded lead acid, gel, or AGM batteries. The C40 has a charging/load current of 40 amps DC, with a max peak current of 85 amps.

As a battery charger, the C40 provides three-stage battery charging (bulk, absorption, and float) and comes with a multi-color charge status LED. It can also be fitted with an optional battery temperature sensor for increased battery charge control accuracy.

As a DC load controller, it features a low-voltage disconnect warning indicator and field-adjustable set points for automatic low- and high-voltage disconnect. It also has a manual reset switch for emergency low-voltage operation.

Finally, in the Diversion Controller mode (which was used during our test) the C40 automatically directs extra power to a dedicated load (such as bank of large resistors or an electric water heater) to prevent battery overcharging.

Xantrex XBM

For our test setup, we mounted both the XBM battery monitor and C40 controller (along with a dump load and a 550 MCA starting battery) in large plastic container. Both the XBM and C40 units worked flawlessly during our five-day test, where both units were exposed to sunny days, rainy days, and temperatures ranging from the 70s to the low 30s.


Both the XBM monitor and the C40 controller are well-constructed, and installation for each was pretty straightforward—although as with any electronics installation, users with little or no prior experience may want to have an electronics technician help out or at least check that the installation was done correctly once completed.

Unlike the XBM monitor, the C40 enclosure is not weatherproof and the unit must be mounted "indoors," in a well-protected area away from spray or moisture. The only word of caution our tester noted with regards to the XBM monitor was the tiny, jeweler’s sized screws used to mount the small wires of the interface cable to the back of the unit. They worked well during the test and while they probably won’t see much use once the monitor is installed, their small size calls for care when tightening them—it also means you’ll want to provide support for the cable to prevent stress on the wires due to excess movement.

Another feature that deserves noting is the unit’s soft-touch buttons.

Practical Sailor has received reports that the buttons on similar electronics have worn through due to repeated use. We’ll let you know how those on our unit hold up during long-term testing. Stay tuned.

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