Battery Minder/Tender Install question

[CGFlyer]

*I did search the hangar forum first*

Basic stuff here, but with winter upon us, I'm trying to get ahead of the cold starts on the battery. It's my third airplane I've owned, and the first one that didn't already have a hard-wired plug in for a battery tender. So, I want to do some research and ask for recommendations before I go buy a harness for my mechanic to install.

Any advice or help is greatly appreciated!

Cheers,
Dan DeMarchis
N2303D
KEZF
Fredericksburg, Virginia

[Bruce Fenstermacher]

Here is a "kit" of some but not all of the acceptable parts that a licensed aircraft mechanic might use to fashion a suitable plug for you. https://www.aircraftspruce.com/catalog/ ... athaik.php

It's a minor alteration.

Of course you could look at this "kit" and decide what parts you might need and only buy those parts. This can be fairly simple. There are a mirad of plugs that could be used for example you might us this plug, one for your tender and one for in the aircraft and you want to fuse the positive wire coming of the positive terminal of the battery so the hot side of the wire is as short as possible. BTW your tender may already have this type of plug on it.

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Secure the wire and plug with tie wraps so that you can open you engine cowl and easily plug it it.

Talk to your mechanic was too parts what he needs to be comfortable doing this.

[GAHorn]

Here is a "kit" of some but not all of the acceptable parts that a licensed aircraft mechanic might use to fashion a suitable plug for you. https://www.aircraftspruce.com/catalog/ ... athaik.php

It's a minor alteration.

Of course you could look at this "kit" and decide what parts you might need and only buy those parts. This can be fairly simple. There are a mirad of plugs that could be used for example you might us this plug, one for your tender and one for in the aircraft and you want to fuse the positive wire coming of the positive terminal of the battery so the hot side of the wire is as short as possible. BTW your tender may already have this type of plug on it.
shopping.jpg
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Secure the wire and plug with tie wraps so that you can open you engine cowl and easily plug it it.

Talk to your mechanic was too parts what he needs to be comfortable doing this.

Just a heads-up on a couple things… Ive used those very SAME inline fuse holders on autos…. and BURNED UP THREE of them without the fuses blowing!
I believe it was due to disimilar metals used at the crimped female fuse terminals inside the fuse holder itself creating a “resistance hot spot”. Just FYI.
Also, be aware that the exposed positive “plug” post of the mating plugs offer an opportunity for an accidental “short” should it be “hot” and come into contact with the airframe.

[Bruce Fenstermacher]

George, you have to stop thinking of a nail as a fuse.

The point I was trying to make is there are lots of electrical components ie plugs, that could be used and used safely. Almost anything can be used unsafely. I've seen lots of stuff in the last 5 years.

Here is the problem with this type of plug.

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Note one of these pictures shows a set with both red (normally hot) wires going to the shielded side of the plug and white (normally neutral or ground) to the exposed pin. But notice the other set is showing a plug with the red wire to the shielded side and a red wire to the unshielded side of the other plug.

In an aircraft you would want the plug with the red shielded side going to your battery with a fuse of some type as close to the battery as possible to reduce the length of unprotected wire to the absolute minimum. So long as nothing gets stuck in the socket of the positive side of the while its bouncing around your engine compartment there will be no short. Better yet to get and USE a cap for this plug when not in use. Now that we are done in the engine compartment you will need the opposite plug on your tender. And no matter what color the wire the hot positive side of that plug will be exposed. You could be careful and have the tender unplugged when it is not connected to the aircraft but the chances of that happening all the time are as great as a cap being placed on the plug connected to the battery.

So what might you use. I like Anderson Power Poll connectors.https://www.google.com/aclk?sa=l&ai=DCh ... EBc&adurl=

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You would need 4, the come in crimp and solder type. The contacts are more protected than they look in this picture. You can configure then so you can not plug them together incorrectly. They can be mounted with a 4-40 screw so they don't have to be floating about and still be plugged into while mounted. They come in lots of colors beside the traditional red and black. They come it lots of sizes to handle loads to 100 amps. I've used these plugs in hundreds of places in the last 30 years in my RC airplane hobbies and well and many many other places. I've never had something short into a open plug. At one time these were not cheap. Now like everything you can get clones from China that work every well.

Before we go on since I brought it up, most everything is made today in China even though it may be sold by a reputable supplier. You have to look at the quality of ALL stuff today and decide if it is the quality you want and trust. I now there is cheap China grade stuff and there is more expensive not as cheap China grade likely because the brand they are being sold under demands a bit more quality.

I'll post about fuse holders later.

[Bruce Fenstermacher]

Inline fuse holders.

inline fuse holder.jpeg

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The two round glass tube BUSS fuse holders are very common to find in aircraft. Here is the key to using them safely IMO. Looking at them when they are open, there is a long side that holds the fuse and the cap. The cap being short easily slips back uncovering the bare contact. This side should NEVER connect to the hot power side. Same thing could happen to the other long side but the lead would have to slip through much further. And if you take a small tie wrap and put it around the lead as it enters the longer holder and then tighten it, the wire can not slide out exposing the bare contact. the hot side wire should be as short as possible were it connects to the battery.

The bottom fuse holder is for blade style fuses more common today. You can wire these either way. Insure the fuse blades go into the female connectors in the holder, snuggly. If they become loose a slight squeeze of the female connector with a plyers with fix it. You do not want a loose connection here or the heat from resistance will burn them up.

Now for a story

Recently I was tasked with checking the timing on a SureFly SIM (mag). These are all retrofit installations and SureFly supplies a glass tube BUSS style inline fuse holder similar to the top picture. The well respected installer ran the unprotected wire from the battery on the fire wall, through the baffle and across to the SIM on the left. About 18" of unprotected wire. They wired the cap end of the fuse holder to the battery lead. It had been installed 4 years. In order to time a SIM you must remove aircraft power which is supplied by this wire. The simplest thing to do is twist the cap and remove the fuse which is what I did leaving the cap end hanging in space never really thinking about the fact that the cap end now exposed to the world, is HOT. All went fine timing the SIM and I moved to the right mag as we normally would when timing two mags. As I was loosening the mag hold down, my custom wrench (a necessary evil for most mags) slipped and caught the mag timing box ground wire. The ground wire alligator clip slipped off, propelling the wire into the HOT exposed SIM lead and that SIM lead grounded. Before my brain could register the noise of my tingling mag wrench as it feel to the floor I was looking at 18" of 16 ga wire glowing red and melting every thing it touched, Instantly I realized, that dam SIM lead is hot. I was lucky I had another wreck suitable to very quickly remove the SIM lead from the positive battery terminal. We got very lucky. We only damaged and needed to repair several wires. Luckily we didn't have a fire or I didn't react by grabbing the red hot wire with my hand to unground it.

When I related this story to a fellow A&P he said that is why they don't install the supplied round BUSS inline fuse holder, but substitute the blade fuse style cause it's harder to accidentally ground the hot side. And now you know why I'm sensitive to how long the unprotected wire is when using these inline holders.

[johneeb]

Thanks for the Story Bruce, I learn something here.
Johneb

[Avee8or]

The kit sold at Spruce works well--if a bit pricey. I have on the 170 & 195. Uses Anderson 50 connector, and has a cover that keeps the connector on the plane clean and safe. Interestingly the Anderson connector is on a pigtail that uses the SAE type connectors to connect to the Batteryminder tender. As long as you follow instructions using this kit, there is no issue with reversing polarity on the SAE connector.