Battery isolator solenoid- legal requirement in 19 reg aircraft?

[danny_galaga]

Incidentally, I wired up my accessories wrong when I installed the new master switch. So of course I had to undo the negative side again, where I had just removed my dinky lil battery isolator. So I thought it's going to be a pain in the arse undoing the negative any time I have to work on the electrics. So I put the lil isolator back on the negative. So now, if I want I can isolate the battery completely very easily. 

Edited March 6 by danny_galaga

[skippydiesel]

14 hours ago, danny_galaga said:

Incidentally, I wired up my accessories wrong when I installed the new master switch. So of course I had to undo the negative side again, where I had just removed my dinky lil battery isolator. So I thought it's going to be a pain in the arse undoing the negative any time I have to work on the electrics. So I put the lil isolator back on the negative. So now, if I want I can isolate the battery completely very easily. 

For a quick/ easy job I agree however if you are delving into the electrical entrails of your aircraft, there is no security quite like removing the (-) Neg lead from the battery.

[danny_galaga]

1 hour ago, skippydiesel said:

For a quick/ easy job I agree however if you are delving into the electrical entrails of your aircraft, there is no security quite like removing the (-) Neg lead from the battery.

This lil jigger basically does that. If you unwind it a few turns, it's as if you've taken the lead off. It's basically two lugs held together by a bolt with a handy knob molded on. I would normally always take a negative off if working on the electrics. I can just see me arcing a spanner on the aileron cable. Then I'd have to replace all that for my laziness.

 

I put the jigger back on because the battery is in a tedious position, behind the instrument panel.

[skippydiesel]

Hi Danny,

 

Not sure that  your "lil jigger " is what I imagined a mechanical battery isolation switch to look like . Below is what I imagined but with an extension rod, through firewall to instrument panel

 

[danny_galaga]

Dammit, where's my "Beat Skippy over the head with a big stick" emoticon 😄

 

To sum up this whole thread:

 

1. after doing pretty much all my electrical, I realised I hadn't thought of putting in any kind of isolator in. This happened when there was a discussion about starters getting stuck on.

 

2. Being very pragmatic (read- extremely lazy) I decided I really only need to isolate the starter while on the ground. I sniffed out the easiest thing I could find that would fulfil the task - the jigger. Since im on the ground, I rationalised, it doesn't have to be fancy, or especially accessible. 

 

3. Recent events gave me pause for thought. The big thought was this-

 

Perhaps I have an emergency in the air. Id decided the jigger is really only for ground use. But with a cabin filling up with smoke, there's no way I'm not going to try and isolate the battery. Which means I would be scrabbling around behind the instrument panel.

 

4. JOHN DENVER ANYONE?

 

5. DONT BE LAZY. (Dan beats HIMSELF over the head with a big stick)

 

6. I bought a panel mounted isolation switch.  Go back a page or two and I have posted a pic of the installation.

 

7. It occurred to me I might as well put the jigger back because it's a pain in the ass trying to disconnect the negative on the battery because it's tucked up behind the instrument panel.

 

8. Here we are. 

 

9. Incidentally, if the jigger had been facing the right way, I could in fact have extended it with a rod, sticking out of the instrument panel.

 

10. But it wasn't facing the right way.

[facthunter]

Any Battery terminal Isolator has to handle a lot of current reliably and without any heating or point welding  possible.  A simple check is to  assess if there's any heating when on starting load.  Nev

[danny_galaga]

43 minutes ago, facthunter said:

Any Battery terminal Isolator has to handle a lot of current reliably and without any heating or point welding  possible.  A simple check is to  assess if there's any heating when on starting load.  Nev

All sorted. Case closed 🙂

[skippydiesel]

14 hours ago, danny_galaga said:

Dammit, where's my "Beat Skippy over the head with a big stick" emoticon 😄

 

6. I bought a panel mounted isolation switch.  Go back a page or two and I have posted a pic of the installation.

 

7. It occurred to me I might as well put the jigger back because it's a pain in the ass trying to disconnect the negative on the battery because it's tucked up behind the instrument panel.

 

 

OooooH! we are a tad sensitive Danny - I rechecked-  the only pics I could find, that you posted - Instrument panel with red knob purporting to be a "mechanical  isolator" switch - no detail, no  photo/drawing of the set up. 

 

My crime, for which I offer unreserved craven apologies  😈 - I have provided visual images of a simple mechanical isolator/switch, that could easily be adapted to almost any small aircraft and is particularly adaptable (using extension rod) to batteries located engine side of firewall .

 

PS I still don't like the idea of "lil jigger "  - unnecessary additional electrical joins & weight, all to save a few extra minutes to disconnect the negative terminal - it a free Word! (for some)

Edited March 8 by skippydiesel

[danny_galaga]

On 18/02/2024 at 11:57 AM, danny_galaga said:

A bit of an update. I had put a little motorcycle battery isolator in, but of course that's not easy to reach. Fine if I'm on the ground. But if I happened to need to use it in flight, I'd probably 'John Denver ' myself. 

So I picked up a panel mounted isolator from Whitworth marine. Much the same as the ones with the red plastic key, but these look tidier. Might as well have form AND function if it's available. Installed it where my USB outlet was, which I moved over. Looks tidy there and it's just about the shortest amount of extra cable at the location 🙂

 

[skippydiesel]

Yes - I read that Danny. I commiserate with you, in that I too had an aircraft where the battery was mounted cabine side of firewall. I accept/understand, that in certain aircraft this is the logical (only?) location and you have to live with it.

 

Your isolator (not sure what it looks like behind the aesthetic red nob) seems to be one where the battery leads extend for some distance to the isolating mechanism. While this is better than no isolator, it seems to me to be a compromise, in that the optimum position for an isolator is as close to the battery as possible.

 

I am not suggesting in any way, that what you have, is not the best that can be engineered - merely expanding on what I see as being the most desirable configuration for a safety device of this kind.

[danny_galaga]

1 hour ago, skippydiesel said:

Yes - I read that Danny. I commiserate with you, in that I too had an aircraft where the battery was mounted cabine side of firewall. I accept/understand, that in certain aircraft this is the logical (only?) location and you have to live with it.

 

Your isolator (not sure what it looks like behind the aesthetic red nob) seems to be one where the battery leads extend for some distance to the isolating mechanism. While this is better than no isolator, it seems to me to be a compromise, in that the optimum position for an isolator is as close to the battery as possible.

 

I am not suggesting in any way, that what you have, is not the best that can be engineered - merely expanding on what I see as being the most desirable configuration for a safety device of this kind.

I thought I had posted a pic of the isolator on its own, but maybe it's another thread. My isolator is the same mechanically as the one you posted. In fact if you posted a Narva, it's exactly the same. Instead of a switch shaped like a key, it's a switch shaped like a knob. In fact, the knob comes out just like the key. If I lost the knob, and couldn't easily find that style in a shop, then I'm pretty sure the Narva key would fit straight in.

 

In any cae, an isolator is a switch. It really doesn't matter how it works, so long as it does. I think one of the guys here has some sort of home made knife switch with a rod attached. It's all good. So long as the contacts can handle the cranking amps for however many seconds. It's not like you are normally opening it under cranking conditions with big Frankenstein arcs spraying out of it! In fact, almost anytime you use it (extra safety feature when plane is parked) there is zero current going through it. Or zero in my plane anyway. 

 

The isolator on my instrument panel is about 200mm from the battery by the way. 

 

Edit, maybe not exactly the same, now I look at the picture but you catch my drift. It is an isolator. For my battery.

Edited March 8 by danny_galaga

[Kyle Communications]

I have been reading through this thread and to be honest there are a lot of misconceptions here. RFGuy is correct on everything.

Always have a isolator switch direct from the battery terminal somewhere as first port of call for isolation. Put that in the negative lead to isolate the return path from anywhere on the frame of the aircraft. This switch needs to be able to pass the 100 to 200 amps that the starter motor requires....

 

A regulator is a regulator but yes there are older style linear regs and later switching regs but all really need a large capacitor to ensure the electrical buss has filtered flat DC to all the electronics or electrical equipment that requires DC. The capacitor is just a big filter thats all.

 

Diodes are usually 600V PIV in most regulators so highly unlikely of any breakdown if the alternator goes open.

Most regulators and especially the genuine Rotax one usually fail internally by heated spade terminals or pcb failures due to being under designed to take the amount of current through those terminals for a long time. This higher current causes heat because ALL connections have some resistance which will create heat and over time this resistance gets higher and then the heat becomes more and so on until there is a failure.

 

Its a good idea to have a master relay..this is usually a solenoid style but those contacts can still weld together..there are some new solid state DC relay ones good for 100 amps that look really good and I am actually going to use these in my next 2 aircraft instead of the older solenoid style type.

 

DC buss needs to be clean..the only way to clean the lumps off the "rectified AC" this stops the noise and buzzing etc in your radio and also much better for any EFIS style equipment

 

 

 

 

[danny_galaga]

I think 100 amps would be a bit marginal,even for the motorcycle starter the 912 is using. My isolator is rated at, I think 1000amp for 20 seconds and 100 amp continuous. That's overkill, but it's actually the smallest I could find 😄

 

Fully agree on having it on negative, but once I decided to upgrade my isolator, it was much easier to mount on the right hand side, which is the positive side if my battery. The lead pretty much goes from the battery to the isolator without touching anything, so no danger of a short there (which is generally why we like the isolator on the negative) . 

[danny_galaga]

I should point out that if I put an isolator on the firewall, with a mechanical extension into the cabin, that would take about the same amount of cable as installing it in the instrument panel like I did. The battery is inside the plane..in the panel in this is just as good, and one less thing to go wrong (the extension). 

 

If the jigger faced the right way, it would be ideal because there's not one centimetre of extra cable used (it bolts directly on the battery terminal) . Facing the right way, I could have run a tube straight from that to the instrument panel 

[Kyle Communications]

1 hour ago, danny_galaga said:

I think 100 amps would be a bit marginal,even for the motorcycle starter the 912 is using. My isolator is rated at, I think 1000amp for 20 seconds and 100 amp continuous. That's overkill, but it's actually the smallest I could find 😄

 

 

I always use continuous rated switches....none of this 20 sec stuff as they never cut the mustard. 100 to 200 amps continuous..same as this solid state relay its apparently 100 amps continuous Max Surge 260 amps for a short time..heaps of overkill for a master but solid state DC switches are a bit hard to get

 

This mob below also sell Tefzel wire...it all mainly supplied for race cars on this site. But its local here in brisbane

 

 

12-24V 100A Solid State Relay

WWW.NRTAUTOMOTIVE.COM.AU

---

Solid state relays (SSR) have no moving parts, eliminating failures normally associated with conventional mechanical switching relays. Rated up to 100A, this SSR provides faster switching time, improved...

 

 

[facthunter]

I thought we agreed the manual setup was superior to the Relay.  The required size relay is not light in weight either.  Nev

[skippydiesel]

2 hours ago, Kyle Communications said:

I always use continuous rated switches....none of this 20 sec stuff as they never cut the mustard. 100 to 200 amps continuous..same as this solid state relay its apparently 100 amps continuous Max Surge 260 amps for a short time..heaps of overkill for a master but solid state DC switches are a bit hard to get

 

This mob below also sell Tefzel wire...it all mainly supplied for race cars on this site. But its local here in brisbane

 

 

12-24V 100A Solid State Relay

WWW.NRTAUTOMOTIVE.COM.AU

---

Solid state relays (SSR) have no moving parts, eliminating failures normally associated with conventional mechanical switching relays. Rated up to 100A, this SSR provides faster switching time, improved...

 

 

I recommend that this supplier go on Danny's Started   A Spare parts List

[sfGnome]

A big advantage of SSRs is that the control current is so low. The relay is on all the time, so the current draw of a solenoid is significant if you lose your alternator and want the battery to get you home. Of course, with a 0.6V drop at 100A, that’s 60W you’re dissipating (presumably during starting), so you’d want it to to be bolted to a nice big lump of metal as a heat sink. 

[danny_galaga]

9 hours ago, sfGnome said:

A big advantage of SSRs is that the control current is so low. The relay is on all the time, so the current draw of a solenoid is significant if you lose your alternator and want the battery to get you home. Of course, with a 0.6V drop at 100A, that’s 60W you’re dissipating (presumably during starting), so you’d want it to to be bolted to a nice big lump of metal as a heat sink. 

Just when I was thinking I'd consider it 😄

 

I'm a big fan of every single watt of energy going to the starter when you are starting. That big lump of a battery is basically there just for that. It's also why I wasn't keen on a regular isolator relay/solenoid although that will draw less than the SSR it looks like (maybe 2a X 12v = 24w).

 

In both cases, they are losing power all the time your key is on. 60w reliably (I guess 60w at start, and less otherwise but start is when you want the least loses), or 24w continuous with chance of contacts burning or fusing. Also that particular SSR has rather small terminals. Big cables tend to pull/twist so I wouldn't want them just hanging off those terminals. Maybe there's a bigger one, but then it might be dropping even more watts. 

 

Nope, I'm very happy you guys convinced me to put SOMETHING there. And I'm extremely happy with the isolator I went with, even though if I spent more time on it I concede I could have made the cable run a bit shorter. The cable run is still probably less than half what the kit suggested, and maybe a 1/4 or less of what I've seen in planes that have to have the battery rearwards!

 

All in all, pretty pleased with myself 😊

Edited March 8 by danny_galaga

[danny_galaga]

My alternator is 204W by the way. Even the regular relay is using more than 10% of the alternators output just being there. Let alone 60W 😲

[facthunter]

It's the starting current that's critical.  Nev

[facthunter]

A good check of the starting circuit is crank the engine continuously for a bit more than 10 seconds and feel the entire circuit for warm spots. Run the engine dry of fuel the day before and leave it turned off. I'd duplicate the earth wire from engine to frame to be sure the linkage or cables don't end up taking current.  Nev

[danny_galaga]

I have the negative battery lead going to the back of the starter. Because the starter was designed for the BMW 650, it has a couple of superfluous lugs on the back. They bolted to the BMW crankcase but just hang out in the air on the Rotax. Perfect for bolting the cable on. Gets the current right where you need it most, at the brush box of the starter for the shortest run. Then a lead goes from there to the negative bus bar on the instrument panel. 

[danny_galaga]

Actually misremembered that. Cable does go to back of starter. Negative bus bar is fed by a wire straight from the negative battery terminal 

[RFguy]

dunno if I would use an SSR in that service

The SSR must be rated at the stall current, which is probably  2 x the battery CCA !