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OutBack's stand-alone inverters with integrated battery chargers

MSTE Meyer Solar Technologie introduced its MPT500 charge controller last September. An additional version known as the MPT1000 followed in December. The MPT500 is available for batteries of 12, 24, 36, and 48 V. The 48 V version is suitable for a system power of up to 700 W; the smaller version is intended for use at up to 500 W.

	© MSTE Meyer Solar Technologie
The new MPT500 charge controller from MSTE adapts its charging procedures to the current. In addition, it contains a deep discharge protection.

What is unusual about this charge controller is its ability to select the charging procedure with the highest efficiency from among four different options. For low currents, as at sunrise and sunset, the control functions via a small series charge controller. For greater insolation, the MPT500 switches directly and automatically, and loads the batteries at maximum capacity.

The controller functions according to the MPPT principle (Maximum Power Point Tracking). With this process, a voltage-current characteristic for the solar modules is measured every few minutes, and the optimal range of performance determined. In this way, the battery is charged until the end-of-charge voltage is reached. At this point, the MPPT controller operates in every case. Using constant voltage, it continues to charge the battery, which is still not completely charged – although it has reached the end-of-charge voltage. The true charging status is then determined with a microprocessor. Benno Meyer, founder of MSTE, did not want to reveal more details on the process.

If the battery is nearly full, a lower voltage is used to prevent degassing and overloading. As soon as the battery has been completely charged, the controller is run down to a lower, so-called 'float' voltage, which holds the charge constant. MSTE specifies a maximum efficiency for the device of 98.5 percent.

Three LED's are affixed to the front of the aluminum casing. A red one detects errors; a green one shows charging status; and a yellow one displays the selected charge voltage at the end-of-charge range. In contrast to previous devices from MSTE, the MPT500 has a deep discharge protection. The charge controller costs €397 ($427) before taxes in any of its versions. For an extra €30 ($32.3), an LCD display to show the charging current is available.

The expanded MPT1000 is no longer only available in 36 and 48 V versions, but also at 24 V. It is suitable for systems of up to 1,500 W. Unlike the MPT500, the MPT1000 does not have a deep discharge protection and simply uses a red diagnostic LED. This net retail price is €948 ($1,020).

MSTE Meyer Solar Technologie
Salemer Strasse 36
88697 Bermatingen, Germany
phone +49/7544/74-3055, fax -3075
mste-meyer-solar@t-online.de
www.mste-solar.de