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Glenns models cap 232

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Rich too15/09/2019 08:11:23
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Posted by Gary Manuel on 14/09/2019 14:05:43:

Good bit of info there Rich, but I have a query.

Imagine a model wired as you have shown in your sketch, and one of the cells in a 4 cell batteries fails short circuit. It then effectively becomes a 3 cell battery in parallel with a 4 cell battery. Surely the 4 cell battery would try to charge the 3 cell battery because there is now enough voltage per cell to generate the required charge current and cause the overall voltage to drop. An in-line diode would prevent this from happening - or does this not happen in practice for some reason I'm missing?

Note that I've never used batteries in parallel myself - I tend to use JR/Spectrum PowerSafe receivers (now obsolete?) when I want battery redundancy.

I believe the point of the article was that the chances of a short are very slim and other equipment failure is more likely. A short is more likely in the event of a crash. And LiFe batteries are very robust, that’s why I use them.

Each to their own yes

Gary Manuel15/09/2019 13:03:40
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My point here Rich was that the whole purpose of having redundancy is that if one leg fails, the other leg should keep the system going. If the overall system fails when one leg fails, then redundancy is ineffective.

Regardless of the low chance of a battery failing short circuit, the fact remains that lack of diodes can potentially prevent the redundancy from working properly. I agree that the addition of diodes increases the chance of a single failure BUT it does allow the redundancy to work properly by isolating each leg. I also agree that the switch is the weak link and far more likely to fail than the battery, wiring or the diode.

As you say, it's each to their own, but each should at least understand all the potential failure modes.

P.S. I'm with you on using LiFe batteries rather than NiMh's.

P.P.S. The previous sketch to yours showed a "Y-Lead" with 2 built in diodes. I think that two separate extension leads with a diode in each and two separate plugs onto the receiver (if spare sockets available) would be better because it removes the single point of failure that exists between the diodes and the receiver.

Rich too15/09/2019 16:10:08
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I would also add that twin batteries become a lot more popular as a way to isolate the ignition systems, but with 2.4 radio it is no longer an issue. We probably do not need to use twin batteries at all......

cymaz15/09/2019 17:04:06
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8648 forum posts
1175 photos

I chose the 2 batteries as it’s useful weight and it needs a fair amount. The KISS principle is great and I do adhere to it when I can

As I need the batteries I was thinking aloud how to best utilise them

cymaz15/09/2019 19:03:26
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8648 forum posts
1175 photos

As promised here is the video about the Jomar Ultimate Battery Backer. Really impressed how it works. Rx didn’t even twitch .

The led indicates there has been a main battery problem, the instructions stress that if the light glows then the problem must be investigated and fixed before flying again.

Edited By cymaz on 15/09/2019 19:05:07

bert baker15/09/2019 19:51:20
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1423 forum posts
303 photos

Have you flown the Cap yet

cymaz15/09/2019 21:34:59
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8648 forum posts
1175 photos

Not yet Bert.......couple more weeks yet.

bert baker16/09/2019 17:45:58
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I have a smoke pump and second c cell size nicad up front,

both don’t work any more just left there for the nose weight,,

there is a weak point on the tail

be careful with the tail

Martin Harris16/09/2019 18:23:57
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8793 forum posts
215 photos

Re. dual batteries, it might be worth bearing in mind that some smart chargers may not sense the correct cut-off point when attempting to charge NiXX batteries simultaneously from the same power supply while connected to a common negative - i.e. using charging sockets in the model. Using separate power supplies allows safe simultaneous charging.

I'm not sure if LiFe cells are similarly affected.

john stones 116/09/2019 18:30:40
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10577 forum posts
1480 photos

Where's a weak point on the tail Bert ? news to me.

cymaz16/09/2019 19:39:02
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8648 forum posts
1175 photos

I have dual switch with dual/ separate charging ports.

Tell me more Bert ! surprise

bert baker16/09/2019 21:12:57
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1423 forum posts
303 photos

Ok,,, it’s not that bad,,,but has happened to mine.

it’s the trailing edge of the tail plane where the cutout is for The servo hatch,

I lifted the tail up with the right tail and heard a crack the tail had broke,,, I couldn’t belive it... it should have coped but didn’t....just need to be careful... you can see where it spit it’s in line with the upper cover line4aad0538-d7af-4da5-87db-a82bfbd56c6b.jpeg

bert baker16/09/2019 21:14:31
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1423 forum posts
303 photos

There was a couple being flown at WWheels last year but think I only saw one this year,,,

Cymaz.. what do you recon for next year WW

cymaz18/09/2019 22:10:01
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8648 forum posts
1175 photos

Did a bit of tinkering after work today. Thought I would take the tank out and have a look .....just in case. I’m glad I did !

c0dac3b2-7588-400d-b42d-2694e359059e.jpeg

john stones 118/09/2019 22:30:05
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10577 forum posts
1480 photos

You ran it with vent tube blocked ?

cymaz18/09/2019 22:55:42
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8648 forum posts
1175 photos

Not me !

john stones 118/09/2019 23:51:03
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10577 forum posts
1480 photos

It a new one then, or a foot pump job ?

cymaz19/09/2019 01:54:16
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8648 forum posts
1175 photos

I’ve got me one of these surprise

cymaz21/09/2019 15:45:30
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8648 forum posts
1175 photos

Tank arrived this morning .....rather nice, plumbing already done. Time to take off the pipe work from the old tank and slip this one in.

 

d3a0a200-8b9d-4153-9d00-44def269863c.jpeg

Edited By cymaz on 21/09/2019 15:48:30

cymaz22/09/2019 14:25:16
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8648 forum posts
1175 photos

Thought I would post this photo if anyone was interested. The lead strips came with the model and put on by the previous owner. To get the plane nose heavy I added the larger Rx batteries and the lead plate above the engine. Hopefully some lead can be removed at a later date.

The tank was 2 hrs putting it inface 3. Just the lack of space and hands like shovels didn’t help.

13a76808-0c17-4e08-9ec0-39da31233147.jpeg

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