Last year I purchased a SB MyT telescope mount to use when I travel to dark sites. The one annoyance to me with SB mounts (MyT, MX+, ME) is the fact that they are designed to work with 48V instead of 12V like almost every other mount along with cameras, focusers, filter wheels, heaters, coolers, etc. This is not a problem when one has AC power available as the mount comes with a very good 110VAC to 48VDC transformer. However, one seldom has access to AC power in the field. While using an DC to AC inverter is an option, inverters are an inefficient way to power a mount especially considering that power out in the field can be a precious commodity.
Software Bisque recommends the 56VDC EGO battery for use with their mounts in the field because their mounts can operate at voltages between 48v and 60V. But again, since almost every other piece of equipment we typically use for astronomy works on 12VDC, I prefer not to add another battery type, to the list of equipment I need to carry with me in the field. And the EGO battery, charger and SB adapter are fairly expensive.
The solution for me and many others is to use a DC-DC voltage boost converter which will take a 12VDC input (actually many take a range of input voltages) and convert this to 48VDC output. This allows me to stick 12VDC power for all of my power needs in the field. There are quite a few different converters available on Amazon for ~$15 to $30. I initially purchased the SMAKN for under $30. The MyT AC transformer supplies a maximum of 1.6A at 48V or 77W so this converter is more than sufficient for the application.
The manufacturer lists the following features for this unit:
1. Embeded Smart Chips provide protection from (1) Over current; (2) Over heating; (3) Short Circuit; (4) High voltage
2. High conversion efficiency and stability with synchronization rectification technology. Up to 95% efficiency.
3. SMT technology
4. Aluminum casing with silicone seal for waterproof, dust proof and anti-shock performance.
The input wires, red + and black -, are 14 AWG while the output wires, yellow + and black -, are 16 AWG as the input current will be 4X the output current in proportion to the voltage boost of 12V to 48V.
I first tested this on the bench with a dummy load to measure the voltage output of the converter and to make sure it was a steady 48V and that the unit did not overheat under extended use. The output of the converter is 48.5V which compares well with the no load output of the SB AC transformer of 47.9V. The converter does not get hot, but does get slightly warm to the touch under extended use. The voltage remained steady within +/-0.3V during extended testing. I was also able to measure the efficiency of this unit to be 95-96% in line with the manufacturer's specs.
Since the converter comes with 2 pairs of pigtail wires I had to decide how to connect the input of the converter to my power supply and the output to my mount. I considered hard wiring the pigtails to the appropriate cables on either side, but then decided to use Anderson Power Pole connectors instead. You will need the 30A version connectors because of the larger gauge of the power input wires. I ordered a 14AWG cable with Anderson Power Pole connectors on one end and a 2.5mm x 2.1mm connector on the other end for the connection between the power supply and the DC-DC converter. For the output, I made my own cable with 16AWG wire and 30A Anderson connectors on one end and a locking 5.5mm x 2.1mm DC connector on the other end. I attach the DC-DC converter to the leg of my tripod and run the wires from there to the power supply and up to the mount.
Since I like to have spares when it comes to any critical component that can fail in the field, I purchased a slightly different converter, the 3A, 144W version from Aweking for ~$25, as the backup. At 144W this is still more than sufficient for use with the MyT. Looking at the two side by side it is apparent that these are built in the same factory, but to slightly different specs, and sold by different distributors on Amazon. The only observable difference is the writing on the backsides identifying the current/power rating and the name of the company distributing
them. The Aweking unit performed identically to the SMAKN unit on the bench.
Next I tested each converter separately to power the mount over several different days. I supplied power to the voltage converters through my Pegasus Power Box Advanced which provides a constant view of the current and voltage drawn as well as a time log of the same and watt-hours. I could find no discernible issues running the mount with the DC/DC converter instead of the AC transformer. I am sold on this approach as a viable field power option.
While I was at it, I was able to log the power draw of the mount under different conditions. I share that here for those trying to figure out what size battery they need to power the MyT. I am using a Celestron C11 Edge with a Stellarview 50mm guide scope mounted with an ADM rail along with an ASI1600MC camera, a SSAG guide camera and Celestron motorized focuser. Total weight should be around 40lbs and is well balanced. Tracking draws 12-16w of power (0.9 to 1.25amps at 13.25V) depending upon the orientation of the OTA. Slews in one axis consume 25-35w (1.9 to 2.6 amps at 13.25V) and high speed slews in both axes take as much as 62w (4.9 amps at 12.7V). Hopefully this is helpful data for others wanting to use their MyT in the field with a 12V battery.
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