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HomeTurbineAircraftHelicopterTurbine Helicopters › One battery or two? The need for a second battery?
02-03-2010 10:07 AM  8 years agoPost 41
aussieheliguy

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Australia

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CRAIGD

Except if your using HV servos and Spektrum rx's (good to 9 volts)

I'm running a 4S lipo through a CC 20A Bec set to 8 Volts. This drives the rx, servos and power side of Fadec. I have a Spektrum voltage reg ( 5 volts ) sitting between the rx and gyro and Fadec control input. All running fine so far.

Another option I thought of is using the 7100 rx with voltage reg built in.

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02-03-2010 12:08 PM  8 years agoPost 42
helibeli

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wales.uk

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All this makes a case for having an onboard generator so that if you did have battery failure you'd still be generating power, so you could land and power down.

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02-03-2010 01:08 PM  8 years agoPost 43
MattJen

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UK

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All this makes a case for having an onboard generator

Wouldn't this create more noise ? i know on cars i have had in the past sometimes the radio picks up the whining of the alternator.

I was with some guys who did some extensive testing on both my jetcat and Wren, we found the ECU/Fadec puts out enough interference as it was,
we worked out almost 30% of the range was reduced when the ECu/Fadec was switched on. So wouldn't adding an alternator reduce it further ? and you are adding weight to an already heavy scale machine.

the reason for all my questions or info request is i am about to swap over my zealous into its longranger fuse, and there is not enough room for all the back up batteries i have, hence the reason i am watching and reading this thread with interest.

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02-03-2010 02:02 PM  8 years agoPost 44
PETER ROB

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Devon UK

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onboard generator
If you are thinking of buying a small turbine, Look at the JetCat,PHT2,
this already has an on board generator for buffering the batteries
If it works for JetCat it must be possible on other turbines
As for weight, it is not an issue
Peter R

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02-03-2010 05:06 PM  8 years agoPost 45
seattle_helo

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Seattle, WA USA

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Matt, like Peter mentioned, the PHT2 has a generator fitted. But in terms of redundancy I'd still want some type of aux power source just in case. I guess the best setup would be to charge the flight batts with the generator but if it were to fail the batt would continue to deliver power uninterrupted. Not sure about RF noise. With 2.4GHz it would be irrelevant.

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02-03-2010 05:20 PM  8 years agoPost 46
MattJen

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UK

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Hi Nick

you make a good point, but one thing that would concern me about an on board generator, is their a high risk of overcharging? or the fact i am charging my lypos unattended.

we all know and have read stories of batteries being left unattended and suddenly burst into fire,admittedly they have been charged incorrectly, would we really want to risk our batteries being charged whilst the model is flying ? and also how many times has it been said and reiterated that batteries should never be charged in the machine..

Even Peter as skilled and experienced as he is had an ecu battery burst into fire in his kitchen whilst it was being charged, cos i turned up to his house not long after, and he showed me all the charred wiring.. he commented Lucky escape with that one, that was on my XLV.. and fortunately because of his quick action no damage was caused.
Imagine if it had been on the machine whilst it was flying ? it would have taken me out..

Matt

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02-03-2010 09:40 PM  8 years agoPost 47
seattle_helo

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Seattle, WA USA

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Yes, charging LiPo's would need to be addressed and implemented safely. Not sure how to accomplish that in the air but I haven't looked into it at all. I guess the most practical solution would be to have a transfer switch that simply went to battery power if the generator was interrupted. But that would require charged batteries to begin with.

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02-03-2010 11:15 PM  8 years agoPost 48
ScaleNewbie

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Ryde Isle Of Wight UK

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Hi guys, I have been flying electric for a long while now and am getting into scale. This charging of lipos in the air sounds at best a gimmick and at worst dangerous to me. As some people have said here lipos MUST be monitored at all times when charging. These cells can develop faults and burn very quickly even when charged correctly. Also an on board charging system could in itself get a fault and either cook the lipos or not charge them at all. Disaster!!
In a scale machine by the time you saw the smoke exiting the canaopy it would be way too late.
How many people have had the regulator go on their car and have it overcharge or undercharge the battery, it's happened to me 2-3 times over the years.
You only have to look in the radio section to see that this hobbies reliability record on the electronic side of things ain't that great. On board charging? Sounds like some serious safety implications there I recon.
Very good thread though, think I'll be using 2 reciever battries in future after reading the comments here.

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02-04-2010 12:47 AM  8 years agoPost 49
seattle_helo

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Seattle, WA USA

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We're getting a bit off topic now but, rest assured, charging LiPo's while airborne is just a hypothetical option were discussing here. For now anyway.

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02-04-2010 01:12 AM  8 years agoPost 50
helibeli

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wales.uk

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You don't have to use LI-POS exclusively.

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02-04-2010 07:20 AM  8 years agoPost 51
PETER ROB

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Devon UK

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battery burst into fire
Matt, Was not correct in what he wrote in the earlier post, I have never had a battery catch fire
Since some bad experiences of LiPo's, when in their infancy (gassing up,cell failure) I do not use them, never had one fitted into a scale helicopter ,I now use NiMH cells, exclusivly
One photo(red battery) is of the experience Matt mentioned, plus the other(blue battery)where the wires on both batteries shorted out,
The sorry state of the blue battery, was found when the outer covering was removed
Peter R

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02-04-2010 07:31 AM  8 years agoPost 52
PETER ROB

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Devon UK

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charging LiPo's while airborne is just a hypothetical option
Nick, Are you correct with that statement?
with the JetCat software, it is possible to use both NiMH, or LiPo's
Not haveing a PHT2, I do not know how the generator is monitored, but I am assuming it is regulated by the ECU, therefore charging (or buffering, JetCat wording)should be possible
I only know of one pilot with a PHT2, maybe he could comment?
Peter R

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02-04-2010 02:16 PM  8 years agoPost 53
MattJen

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UK

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Interesting thread,

Peter, Thanks for clarification.

Great info.. on this thread.

Matt

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02-04-2010 06:59 PM  8 years agoPost 54
seattle_helo

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Seattle, WA USA

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Peter R, I may have spoke too soon. I don't know enough about the PHT2 to say anything for sure, so maybe it is possible? I'm not clear on if the generator is strictly for supplemental power, or primary power for the ECU or if it can be used to charge batteries as well. Peter W has one (or two or three). Maybe he can chime in here.

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02-04-2010 08:00 PM  8 years agoPost 55
Peter Wales

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Orlando Fl

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There is no monitoring of the battery via taps so an imbalance is possible, however, I have had to charge the battery up so it never gets enough of a charge in a 10 minute flight to over charge it.

If you are that worried about it, you can start the turbine up and then disconnect the battery and the ECU will run on the generator.

I have had 8+ starts on one charged up 3300MAh LiPo

Peter Wales
http://scalehelicopters.org

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02-04-2010 08:46 PM  8 years agoPost 56
helibeli

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wales.uk

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Did those batteries burn while attached to an intelligent charger? were they top notch batteries?I've only bought Sanyo rechargeables over the years and never had a dud.

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