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Battery backer

Discussion about Tx, Rx, Servo's, Batteries, Chargers, and all the other things we like to talk about..
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spike spencer
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Joined: 17 Mar 2015, 22:23
Location: Salisbury UK

Re: Battery backer

Post by spike spencer »

I agree with all he suggests but Robbie's two .pdf files are in conflict:
"switch.pdf" shows both the Pos and Neg lines being switched. In reliability terms this doubles the probability of a failure in that supply line - power loss occurs if either one of the switch contacts fail.
In "battery backer.pdf" file, the double pole switch contacts are shown in parallel in the Pos line (GOOD). This hugely reduces the probability of failure as both sets of contacts have to fail simultaneously (ProbFail therefore classified as "extremely remote") to cause a loss of power in that line.
Spike S.

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Barry_Cole
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Joined: 10 Mar 2015, 09:30
Location: Hampshire UK

Re: Battery backer

Post by Barry_Cole »

Roger,
Two reasons for using the RX8R, it is fitted with the latest series of RF chips and is stated as giving up to 40% more range than the X8R (Although this seems to have more than enough range). Also if you are going to use the RB-20, the RX8R supports S-Port switching which means that whichever Rx is being used, all the telemetry will be sent back. If you use the X8R you have to bind one of them with telemetry off.

Also if you are using a single Rx you can plug a second receiver like the RX4R into the S-Bus IN port as a backup.

Almost all of the receivers have all 16 channels, available. If you need a few more, you can plug a 4 channel decoder into the S-Bus out port.

Hope that helps. I sent you an e-mail with my phone number if you want a chat.

BC

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RobbieB
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Re: Battery backer

Post by RobbieB »

[quote="spike spencer" post_id=23199 time=1559717232 user_id=74]
I agree with all he suggests but Robbie's two .pdf files are in conflict:..........'
[/quote]

Yes I suppose so but that configuration was for a flying buddy that never removed his batteries but suffered persistent black wire blues so isolating the negative feed at the switch helped limit the damage - a little. I personally do it as shown in the first diagram.

You could always re-introduce that higher level of redundancy if you wanted to switch both poles by using a 4 pole double throw switch.

It's also worth mentioning that switches well within the required current rating are chosen and they are the very best quality too - silver flashed/make and wipe contacts preferably.

Jolly Roger
Posts: 414
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Battery backer

Post by Jolly Roger »

More great ideas - thanks again.

As for diodes, this looks like it would be well within itself?...

https://uk.farnell.com/multicomp/p600d/ ... KU-9564985#

And switches...a confession: I stopped using them 10 years ago. I just carefully plug the battery directly into the rx when I'm ready to fly. Yes it's not as convenient as a switch, but it cuts out 2 connectors and one component so reduces risk. However, if I'm fitting diodes I'll need the extra connectors anyway between battery and rx so may go back to switches.

Can anyone suggest some decent quality switches at a reasonable price?

Barry - thanks for email - yes RX8R look good on balance.

Rog

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Barry_Cole
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Re: Battery backer

Post by Barry_Cole »

Roger,
If you prefer not to have switches you could do this:-
Attachments
Power Circuit.pdf
(17.03 KiB) Downloaded 54 times

Jolly Roger
Posts: 414
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Battery backer

Post by Jolly Roger »

That would do it nicely Barry. Although I've got to admit I was expecting (a) someone to persuade me switches are a good thing, and (b) where to buy reliable switches cheaply. :D

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Peter Balcombe
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Location: Clevedon, North Somerset, U.K.

Re: Battery backer

Post by Peter Balcombe »

Roger,
Unfortunately, switches are effectively just a moveable connector, where the connection is operated by a lever or slider - so suffer from similar reliability issues to connectors.

As has already been mentioned, it’s best to:
a) use contacts rated conservatively for the expected maximum current,
b) parallel up multiple sets of contacts (to reduce impact of one making a poor contact),
c) use wiping contacts if possible (to self clean as contact is made),
d) use good quality contacts (gold plated are best to reduce tarnishing impact).

Jolly Roger
Posts: 414
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Battery backer

Post by Jolly Roger »

[quote="Peter Balcombe" post_id=23214 time=1559771448 user_id=165]
Roger,
Unfortunately, switches are effectively just a moveable connector, where the connection is operated by a lever or slider - so suffer from similar reliability issues to connectors.

As has already been mentioned, it’s best to:
a) use contacts rated conservatively for the expected maximum current,
b) parallel up multiple sets of contacts (to reduce impact of one making a poor contact),
c) use wiping contacts if possible (to self clean as contact is made),
d) use good quality contacts (gold plated are best to reduce tarnishing impact).
[/quote]

Thanks Peter. Could you possibly give a link to a suggested type?

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Antonia
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Joined: 17 Mar 2015, 22:30
Location: Oxfordshire

Re: Battery backer

Post by Antonia »

Hi Rog,
Have you ever thought about magnetic switches? Just to throw another idea out there....
Mel and I have used Jeti - https://www.esoaringgadgets.co.uk/index ... ath=46_108
and
T9's Hall switches - https://www.t9hobbysport.com/search?s=Switch
to good effect, on our larger models, and they have no moving contacts to wear and fail, and with the Jeti main switches you can control both high voltage motor and receiver/servo circuits at the same time with a ESC with a energising switch function, expensive yes, but they work well for me, but just call me "a Jeti fan girl!..." sorry for crashing the party :oops: ...
Antonia
Last edited by Antonia on 07 Jun 2019, 21:19, edited 1 time in total.

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Peter Balcombe
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Location: Clevedon, North Somerset, U.K.

Re: Battery backer

Post by Peter Balcombe »

Thanks Antonia - a good alternative, albeit at a price as you say.

Roger, unfortunately I don’t have any specific component in mind as I have not used anything heavier than the heavy duty charge point slide switches in models I have built so far.

It depends how many servos you are expecting to cope with, but you are probably looking at reliably switching up to 8-10A to be safe with a large model with lots of high power servos.
There are some heavy duty double pole slide switches out there, but I think most tend to be rated at <5A, so you need to check the specifications for each carefully.
Miniature toggle switches are also usually limited to 6A @ 28V, so you are probably looking at standard size toggle switches to get 8A or more. Toggle switches also tend to have silver or gold plated contacts which is better than plain brass.

There are so many different switches out there, so you have to be able to look at the specifications to see what each are capable of. Unfortunately, many modelling suppliers just sell “switches” or “heavy duty switches” without identifying actual current ratings. You often tend to have to go to an electronic component supplier to get specifications. Note that you need to look at the low volts DC rating, not the 240v AC rating.

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