Flight Battery or Ubec ?

Have been involved in electric flight for 10 yrs now, but have upped my game into the larger heaver model running on 8, 10, and 12 s lipos. In the past the ESC has a built in bec, but the ones that I now use are Opto, which of course need a separate bec.
Here the question arises. In the past, I have used a 2s lipo , and as I use deans connectors, have to attach a deans to the bec to complete the connection, then the bec is plugged into the switch harness and the other end of the switch goes to the RX. So what , I hear you say. That system means the bec cannot be turned off with the switch, only the RX.
After some thought, I was worried about the 2s lipo not lasting for a full flying session, that I purchased some 6v flight packs , and installed them . Now I can switch off the supply, whereas with the lipo I couldnt
My question to the members is, did I do right, or had I missed a trick wiring in the lipo?
I must say the installation using the 6v battery looks neater and has less connections.
What do YOU think ?

Garry

I always used a 6V pack when I was using the heavy currents from 6s upwards
When I now use the 2s lipos I fit a Power Box sensor switch, but that then makes it expensive
So for my pennyworth I think your ok with the 6V packs

Garry - for a minor swap-round of connections - battery - switch - ubec - rx instead of battery - ubec - switch - rx, you have solved your problem!
I use a ubec in my Bullet, simply because there is no room for another battery, I can barely squeeze in the flight battery!
I've put an external plug n socket into the + feed to the speedo, so that when I plug in the battery, the rx and servos become live, but the motor remains dead (and safe) until I complete the external connection, on the field.
All my smaller models use the ubec built into the speedo.

Eric, I think you may have missed the point of my post. I had lipo, BEC, switch , rx. I now have battery, switch, rx. I was worried if the 6v battery would be able to support what was asked of it, on the other hand, I was also worried that I was unable to switch off the bec and wondered if this would drain the lipo. I have gone now with the battery system for 2 reasons. 1 One less connection, 2 I can switch everything off. Still not sure if I have gone the right way, hence the thread

Garry

Garry
Is there a reason why you can't put your switch between the 2s LiPo and the BEC?

I appreciate the desire to be able to switch off the Rx but doing a sort of HAZOP study how do you prevent the possibility of the rx being 'off' with the ESC still connected to the main battery?

You can tell that Garry used to be a plumber - he's still trying to put the tap on the outlet, not the inlet! :evil:
.
Regarding Simon's query - you can't, except by training yourself to connect the Flight batt to esc last, and disconnect first. (Much the same way as we work the tx/rx switchery - and how I've wired up my Bullet)).

The way things are installed, this would mean taking the wing off after each flight Simom, and if as I have just seen, lipo, to switch with an adaptor to switch, to BEC to rx would mean even another connection.

Garry

Hmmm!
I think I will stick to my 3s LiPos and ESC BEC. There is no switch and only one connection!
The only possible human set up error is forgetting to switch on the Tx first.

Why don't you cut the deans off the uBec, then put a standard RC connector (a la 6V nimh) on the ubec. Cut the battery side connector off the standard RC switch and put a deans on it. Now you can plug the outgoing side of the switch into the uBec and the deans into the Lipo. Now you have the best of both worlds, you can easily remove the Lipo, or, if the switch has a charge socket you can charge the Lipo in the plane. Using the appropriate charger, of course.

charge the Lipo in the plane - - - NOT a good idea! :evil:

How strange that it should take someone who doesnt live in this country to solve what I have been trying to solve for ages !!!! Thanks Klippy :woohoo: :woohoo: MY prob was I was looking at the prob from the wrong side. I couldnt see how to utilize the lipo, cos the wire was too thick to put a standard RC connector on , BUT THE SWITCH CAN HAVE A DEANS ON !!!!!!! Klippy, you are a gem mate.

Now this has brought up another subject.

Klippy said charge the lipo in the model . I read that and before I had read Eric s post , I thought NO
After reading Eric s post, I still thought NO, then reconsidered. I have never done it , but why not ???
We are all told how dangerous lipos are , or are they ?? Look at the mish mosh I have been using before the rewire, and Lets work out a rough average. I fly, weather permitting twice a week, average 10 flights per session, so if one lipo per flight, would equal 20 recharges. Lets say I fly 46 weeks out of 52 average, so that works out at 920 recharges per year. I have been doing this for 10 yrs + so I have averaged 9200 recharges without any incident whatsoever
Have I been lucky ??/ who knows ?? or is it because I know of the danger that I am careful of how I charge, and check and double check before charging. Now had I done all 9200 charges with the lipo in the model, in theory , nothing would have happened.
Maybe we are TOO wary of the H and S peeps.
However, I will still charge the lipos on the bench rather than in the model, cos I have done so in the past, but it does make you wonder if we are brainwashed these days .

Garry

Garry
It all comes down to the degree of fire risk.
NIMH batteries almost never catch fire.
LiPo certainly can which if it does will almost certainly set light to the plane and thus create an even bigger fire.
It is just a matter of what is a justifiable risk to you bearing in mind the by removing the LiPo that risk to the plane is completely avoided.

I would have to say that the risk of the plane being destroyed by simply hitting the ground is almost certainly a good deal greater!

Thanks Garry, I was only proposing you charge the flight Lipo in the plane, not the power Lipo for the ESC. Having dissected a Lipo the plates are microscopically thin, there are literally 100's connected in parallel in one cell. Should there be a mechanical failure between the plates the Lipo is going to go up in smoke. Said mechanical failure will be caused by flight loads or transport and handling. Leaving the flight Lipo in the plane reduces the chance of failure to flight loads only.
In my humble opinion most used Lipo fires are caused by mechanical failure on the wiring side, most normally due to handling when unplugging, especially if you do your own soldering.
A better solution if you do your own soldering would be to use bullet connectors, properly insulated of course, then you have the benefit of distance between the connectors as well, not to mention being able to get hold of the damn things!
If you consistently use deans then buy a small pair of outside circlip pliers, then carefully drill the right sized hole in each connector. This would need to be slightly off centre so you don't short circuit the terminals if you drill too far, then you use the pliers to prise them apart.

Are Deans really that hard to separate?
Maybe I just have strong fingers!
Then there are some cheats that make them easier to separate but I am sure an electrician would not approve!

I have always charged my 2S lipo's in the planes :ohmy:
I found I could not open Deans with my Arther Ritus hands so went with the yellow cannot remember what the are called
found them nearly as bad
I now use only the red 5mm and the 6mm blue ones, something to get a grip on