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Can I have two Life batteries powering my Futaba receiver?

Receiver battery redundancy protection

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Tim Flyer07/06/2018 12:51:57
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I am currently in the process of getting set to assemble a Seagull 30cc Hurricane Warbird. I was wondering about adding receiver battery redundancy protection. To make my assembly simple I’m thinking of using the Futaba 14ch receiver which will leave me 5 spare slots. I use LIFE batteries and was wondering whether it might be sensible to use two 1500mah batteries rather than the single 2000 mah battery I was planning to use. I will be using 8 servos in the plane . The retracts will be electric and powered by a separate battery not in the receiver circuit. If I slot two batteries into the receiver plugs might they “fight each other “as they run down? As mentioned the third battery will be separated from recent power by removing the middle wire of the lead on the connection . 

Edited By Timothy Harris 1 on 07/06/2018 12:53:31

Edited By Timothy Harris 1 on 07/06/2018 12:55:37

Roo Hawkins07/06/2018 13:10:25
80 forum posts
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Have you thought about using two rxs one battery to each one one rx will control the ail and flaps one side and the other rx the other side. Plus two servos for the elevator and split the elevator one controled by one rx and the other by the other. The you will have two batteries and two rx with split control and if one battery or rx go wrong you still have some control.

Edited By Roo Hawkins on 07/06/2018 13:12:05

Rich too07/06/2018 13:20:40
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Tim,

Yes, that is a system I use the most. The batteries will not fight each other. One receiver, two LiFe batteries and switches, plugged into separate channels. I recommend that you invest in decent switches, as this is a common failure point.

Tim Flyer07/06/2018 13:21:50
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Thanks Roo that sounds a good idea. I hadn’t thought of that . This model uses two elevator servos so that sounds a good idea

Tim Flyer07/06/2018 13:26:03
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Cheers Rich too I will weigh up costing etc . So far I haven’t had receiver failure but have suffered switch failure so well noted the 2 battery 1 receiver might be the way I go on this . This forum is a great knowledge pool ! Cheers 😊 Tim

Rich too07/06/2018 13:29:57
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Yep, receiver failure is rare, and I would only consider two receivers on much larger models.

robert chamberlain22/09/2018 03:43:52
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Hello all,--I am new to LiFe battery technology and am uncertain as to the charge rate. AS luck would have it, my cell phone battery has one, rated at 5 volt and 1000MA and my wall charger says the same thing on the label. All new wall chargers for flip phones say 5 volts 2000 ma. Does this mean to imply that these batts can take a 2C charge rate? Of course, I do not plan on using this cell phone batt in an aircraft, but I was wondering if this was indicative of all LiFe batts?-------thanks in advance, Bob in Kansas

robert chamberlain22/09/2018 04:02:06
88 forum posts

Concerning Tim's comment above: My question is, if using 2 batts plugged into the receiver, what would happen if one batt should fail? Wouldn't' the other batt try to feed into it? As I only have 6 ports on the rec, why couldn't I just use a "Y" extension, plugging the two batts into one end and then only having to use one rec port?

If we are talking about a 2 cell LiFe batt, isn't that a little too high voltage? Every thing on my radio is 6 volts. Thanks for any input. Maybe I'll just go to NiMh--------Bob

Biggles' Elder Brother - Moderator22/09/2018 04:07:34
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Hi Bob,

How's things in Kansas?

Regarding charging your LiFe batterries: yes you can charge at 2C - generally I wouldn't do so though. I doubt that it makes a lot of difference but I believe in charging only at 1C.

Note though, you will of course need to use a LIpo sytle charger with a LiFe setting.

BEB

Rich too22/09/2018 06:53:24
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Hi Bob,

Pretty much all of my models use two LiFe batteries. There is nothing wrong with using a Y lead, and I tend to share with a servo. Most systems can take the slightly higher voltage, certa8nly Futaba that I use,

I agree with BEB and charge at 1C....

Percy Verance22/09/2018 07:34:39
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7071 forum posts
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Surely a Futaba 14ch receiver has more than one battery input? surprise

Luckily, most of my (9 ch plus) receivers have three battery inputs. Two standard (marked BD), and one high current......big green M6 socket.

pro rxs.jpg

Given that it might all end up in a fairly large model, I think I'd be inclined to use a safety switch. Here's an Mpx one. Several types are available. This one has voltage regulation for each battery, plus safety circuitry to prevent a duff battery from discharging the second pack...... These are specifically intended to be used with Life/Lipo battery packs. Not cheap of course (£100), but how much might the model be worth?

85063big.jpg

 

 

 

Edited By Percy Verance on 22/09/2018 08:06:11

Frank Skilbeck22/09/2018 18:07:20
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4159 forum posts
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Posted by robert chamberlain on 22/09/2018 03:43:52:

Hello all,--I am new to LiFe battery technology and am uncertain as to the charge rate. AS luck would have it, my cell phone battery has one, rated at 5 volt and 1000MA and my wall charger says the same thing on the label. All new wall chargers for flip phones say 5 volts 2000 ma. Does this mean to imply that these batts can take a 2C charge rate? Of course, I do not plan on using this cell phone batt in an aircraft, but I was wondering if this was indicative of all LiFe batts?-------thanks in advance, Bob in Kansas

Bob, be aware that the phone wall charger is just a power supply, the phone actually controls the charge process. My Tx uses a single 3500 mah LiFe cell for power, I charge it using a 2000mA phone charger but the Tx limits the charge rate to 1500 mA .

Note a fully charge LiFe cell is 3.6v per cell and a 2s LiFe pack is a good replacement for a 5 cell Nimh pack.

Allan Bennett22/09/2018 21:10:21
1399 forum posts
37 photos

A simple way to prevent two separate power sources interfering with each other is to simply install a Schottky diode (with a suitable amps rating) into each +ve battery lead before they go into the Y-plug or into two separate receiver inputs. Then if one fails in some way, the other will not be able to feed power into the duff one, but will continue to power the receiver. I've got such a system in several of my aircraft -- fixed wing and helis -- using BECs rather than batteries as the power sources. I've also added an LED to each 'channel' to give an indication if one of the power sources has failed.

Martin Harris22/09/2018 21:37:11
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If you have any concerns over the slightly higher voltage of 2S LiFe over 5S NiXX then using silicon diodes will drop 0.6v while performing the same function.

Rich too23/09/2018 08:17:45
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If it’s good enough for DA....

**LINK**

Paul Marsh23/09/2018 10:15:23
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I seem to use twin rx packs on models larger than 20cc nowerdays or if a new build which might have powerful servos

I use these as well, the Powerbox ones are ok, but at £80 each very expensive and at that price it makes you think about not using dual batteries. So Rapid have them for £25 and have a few.

yak3battery.jpg.

Percy Verance23/09/2018 10:21:09
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A Powerbox switch at £80 actually isn't that expensive if it means you avoid an expensive crash Paul.

Smashed model, damaged engine, broken servos, possible internal damage to receiver. What might all that cost to put right?

Paul Marsh23/09/2018 11:06:35
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Posted by Percy Verance on 23/09/2018 10:21:09:

A Powerbox switch at £80 actually isn't that expensive if it means you avoid an expensive crash Paul.

Smashed model, damaged engine, broken servos, possible internal damage to receiver. What might all that cost to put right?

True, but as I sell things to people at shows, it's surprising what people will do to save a quid! A chap came in saying his model crashed due to a faulty switch , which he had with him, and was looking at a new one. I showed him our best switches, but they were £8 each, the heavy duty Futaba/JR ones. He said it's too expensive and have I got anything cheaper.
We also had some normal switches, good quality, but £5 each. he said it's too expensive and will try to repair the switch he had with him to save some money... I give up...crook

The model is only worth as much as it's weakest link... the switch is a weak link and if it's worth £2.5 then the model is worth that.

Engine Doctor23/09/2018 11:31:09
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Posted by Allan Bennett on 22/09/2018 21:10:21:

A simple way to prevent two separate power sources interfering with each other is to simply install a Schottky diode (with a suitable amps rating) into each +ve battery lead before they go into the Y-plug or into two separate receiver inputs. Then if one fails in some way, the other will not be able to feed power into the duff one, but will continue to power the receiver. I've got such a system in several of my aircraft -- fixed wing and helis -- using BECs rather than batteries as the power sources. I've also added an LED to each 'channel' to give an indication if one of the power sources has failed.

yesThats my preferred method too. I also use a separate switch for each battery fitting the diodes into a "y" lead between the switch and Rx .

Piers Bowlan23/09/2018 11:47:30
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1470 forum posts
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Posted by Engine Doctor on 23/09/2018 11:31:09:
Posted by Allan Bennett on 22/09/2018 21:10:21:

A simple way to prevent two separate power sources interfering with each other is to simply install a Schottky diode (with a suitable amps rating) into each +ve battery lead before they go into the Y-plug or into two separate receiver inputs. Then if one fails in some way, the other will not be able to feed power into the duff one, but will continue to power the receiver. I've got such a system in several of my aircraft -- fixed wing and helis -- using BECs rather than batteries as the power sources. I've also added an LED to each 'channel' to give an indication if one of the power sources has failed.

yesThats my preferred method too. I also use a separate switch for each battery fitting the diodes into a "y" lead between the switch and Rx .

OK, so to ask a silly question, what is a 'suitable amp rating"?

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