wire up cig lighter for battery charging

Help me understand guys..
I plan to use one cig lighter for always hot so I can charge cell or ipad and to use to trickle maintain the battery. I originnaly planned to run that wire direct to the battery post with inline fuse near battery. Now I wonder because I now have several things that need constant power.
New plan: One wire from battery side of master relay to inline fuse. Then on to the bulkhead behind panel somwhere to fuse block. Then cig wire to fuse block and other things ofcourse.
Will that work for trickle charging??? Or do I need to go direct to the battery post instead with the cig plug and another line from master relay to fuse block??
Hope this is not tooo silly of a question but this wiring gets me confused easily at times.
Thanks all

What do you need to power besides the lighter socket? Do you need the ability to kill them in an emergency? If so, they shouldn't be on your hot bus. I'd have to brain refresh,but I think Part 23 says 5 amp max on a hot bus. Older Cessna's typically had fuseholders near the battery for Hobbs and clock. Later for radio keep-alives.

One cig plug wired to avionics and one wired to always hot so I can use it on ground w/o turning on master switch. That's the idea anyway. I've heard others use the cig plug for a low amp trickle charger of 1.5 to 3 amp so I planed on fuse of no bigger than 5 amp. I have an EMS that has clock that needs constant power and I might need something else that I may not be aware of yet. But if I use a single wire fused near battery and run it to the fuse block will putting a trickle charger in the plug cause any problem with other things attached to the fuse block? Does the power connection make a difference if its at the battery post or at the battery side of master relay.?
Thoughts on this are appreciated. Thanks

Bill,

What you're suggesting should work just fine.

Makes no difference if your feed wire is physically connected at the battery post or the battery side of the master relay. Electrically they are the same node. The tiny bit of resistance between them in reality (the resistance of the short section of heavy gauge battery cable) is negligible at the low current you're talking about.

Just make sure that the in-line fuse is as close as possible to that connection point, to minimize the length of unprotected "hot" wire.

Connecting a trickle charger shouldn't adversely affect your other loads. A fast charger, depending on its design, might put out high voltage pulses that could potentially damage your avionics. But a simple trickle charger should only put out a steady 13.6-13.8 VDC, which is perfectly fine.

-Roee

Thanks Roee!

I used 14 AWG wire and a 7.5 A breaker on mine.

Like you, the intention was to charge the battery from the cigarette lighter but that didn't work out so well, the one time I needed it.

It was 5*F above zero, on a windy ramp in mid-Michigan (KIKW to be exact), and my battery was DEAD! To use the cigarette lighter to charge the battery meant I had to leave the canopy cracked, which I didn't want to do, due to blowing snow. I eventually got the thin started but it took some time.

As soon as I returned home I put the battery connector in place and put the pigtail right by the oil door. (See the picture below of the batter tender I use.)

This may not work with your -8, due to the battery location, but it is worth considering.

For my HR-II, I installed an accessory plug that can be switched between the master (switched) bus and the hot (battery bus). Hot bus was protected with a 15 A fuse near the battery and a 7.5A breaker near the plug.

The switch I used is a keylock, so that I can leave it in the switched bus position for normal operations and switch it to the hot bus for charging on the ground. This prevents the inadvertent discharge of your battery caused by an accessory load left on.

It's a keylock so that pax cannot accidentally (or otherwise) switch it in flight.

might want to think about a battery tender going bad on the same circuit as your avionics. i have had several go bad and have to be tossed. the schumacher tenders just stopped charging but i have seen cheap ones be set up to overcharge and i tosse them new [harbor freight].


bob noffs