13.8.1 EFIS alternate power

This entry is part 52 of 67 in the series 13 - Electrical / Instruments

One of the problems with a 28v electrical systems is that some of the goodies that are available for 14v electrical systems don’t exist for 28v.

One of those “goodies” is a backup battery for the EFIS. During engine start, the battery power will drop. If it goes below around 19v, the EFIS shuts down. Now it takes the EFIS about a minute to power up and it displays engine information. So if it drops offline when I start the engine, I won’t know what’s going on with the engine for about one minute.

Grand Rapids sells a backup battery that will keep the EFIS up if the primary power drops off. But it’s only available for the 14v version.

I thought about getting a small 24v, 5amp battery for this purpose, but then I’ve got a deal with finding a place for it, wiring it into the existing electrical system so it can recharge, etc.

TCW Technologies (who make the trim controller) also have, what they call, an Intelligent Power Stabilizer (IPS). As long as there’s about 12v coming in, it will put out a steady 24v. So I purchased one and tested it out. I was able to drop the input power to about 10v before the output dropped below 24v.

I went it install it on my avionics sub-shelf but I realized that I wouldn’t have anyplace for my GPS.

Here’s version 1 of the sub-shelf.

2013-12-06 IMG_20131206_170639_577 (Large)

So I had to add another level to the shelf.

2014-07-16 IMG_20140716_111956488 (Large)

The IPS unit is on the lower shelf. The GPS will go above the IPS on the top shelf.

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