Startup Voltage Sag & TCW Power Stabilizer

[Noah]

Anybody flying with one of these care to provide a review of the TCW Intelligent Power Stabilizer? http://tcwtech.com/IPS-12v.htm

Uses step-up DC/DC converter to provide sufficient voltage to EFIS / EM / GPS during engine startup when bus voltage can sag due to significant starter load.

From what I understand, modern avionics will not be damaged from low voltage if powered up during engine start, but this low voltage can cause a reboot so that you lose that flightplan you just entered prior to engine start. Its also a good idea to monitor oil pressure during engine start, which in my case will be on the engine monitor only.

The TCW solution seems like a lighter and simpler solution than a fully redundant bus or an aux battery, which incidentally, it looks like TCW recently added to their product line:
http://tcwtech.com/IBBS.htm

Since I have a lightweight permanent magnet starter, voltage sag will be significant, like <8V from what I have read - and that's with a healthy battery! AFS requires 10V minimum per their manual, and a GNS430W requires 10V (11V for com radio).

For people without an aux battery or redundant busses, do you just boot up all your avionics and enter flightplan info after engine start? Or is there some other reasonable workaround I haven't considered?

[wobo9a]

Noah -

I installed the TCW device to stop my GRT EFIS's from rebooting during start-up and it has done the job. I did it for the single purpose of monitoring engine parameters during start, but have come to see other advantages.

I now find myself doing all my knob twisting /awos/ altimeter setting / clearance delivery kind of work before starting and it is a calmer, less-hurried environment in the cockpit without the engine running. Getting these chores done before start also allows me to give more sustained attention to how the engine is warming up and what is going on in the outside world once I start the prop spinning. (We had a dog walk into a spinning prop on my airport once - left quite an impression.)

Dave Woboril
9A

[Noah]

Thanks for the response Dave.

Another question I wonder about is in battery-only (failed alternator contingency), many avionics shut down at about 10V. This unit will continue to put out 11.25V until bus voltage falls to 4V - ostensibly giving you considerably more "useful time" from the battery.

Anybody ever tested this device in this manner- that is to say run the battery down with everything powered and see whether things work as advertised - without melting down / burning up?

[RNewman]

The IPS units do actually provide a bit more run time out of the battery for the reason you identified, however, we do not specify this or make any promises in this regard. In a typical lead-acid battery used in aircraft applications nearly all of the stored energy is available with the battery voltage between 10 volts and 12.6 volts, below 10 volts the remaining energy in the battery is quite minimal. Our tests have confirmed what we have read from battery manufactures, about 95% of the energy storage is provided down to the 10 volt level. However, by utilizing the IPS you do have access to that last 5% or so, and in the "dark stormy night" scenario that last 5% might translate into the extra couple of minutes you need.

Regarding operation at very low voltages, i.e. 4-5 volts of input voltage, we have done extensive testing in this area and the IPS product is designed to operate at these levels while still having thermal safety margin on the components. Additionally, the IPS product has activer thermal monitoring to ensure that it is not overstressed during prolonged operation if operated in conditions beyond worst case. (Vin minimum, I load maximum, Ambient temp at max).

Best regards,
Bob Newman
TCW Technologies, LLC.
www.tcwtech.com