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Backup/Redundant batteries

Old 02-01-2012, 10:39 PM
  #26  
OhD
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Default RE: Backup/Redundant batteries


ORIGINAL: jgg215

Jim,
We all know that good ideas are often developed independently but Keith Hoard and I both developed a balance plug redundant system on our own and used it at the Nats. But who knows, it was probably done earlier by others....
See the thread on the NSRCA website for a discussion and description of potential problems:

http://nsrca.us/forum/index.php?topic=167.0

John Gayer
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Thanks John. Until we hear of someone doing it earlier you are the guy. As Brian said, it is a brilliant idea. I hope Chris gets rich from it but in the mean time he is doing everyone a great service by providing the adapters. I told him he should charge $10.

Jim
Old 02-02-2012, 01:41 AM
  #27  
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Default RE: Backup/Redundant batteries

ORIGINAL: OhD


ORIGINAL: serious power

Hi J-P,
Sometimes we see what we want and do not see the rest.
That 'Hint' says a 'bec' !!
The guys are talking about a 2nd battery , all be it a BIG one or in fact 2 cells from a BIG battery.
I will leave you to work it out.

Edit; I believe that the Emcotec Dual batt unit is the ideal way to use Chris's and Jim's idea - which is just brilliant for anyone that may be tight on the weight limit - like me.

Brian
This is the post I had started when I was interrupted by a phone call:

We need someone to jump in and tell us who came up with the idea originally to tap into the balance connector.

Regarding the Emcotec Dual Battery unit. It sounds as though the batteries are isolated from each other somehow but it is not clear how the one that is at a higher voltage will charge the one at the lower voltage. It sounds like it does and that could be a problem. If the motor battery gets too low the small receiver pack will try to recharge it. If this is so, it seems almost certain that the receiver pack would end up at 7.5 volts or so at the end of flight. Maybe that is okay as it is close to the storage voltage but if it goes much lower it won't provide much margin. What do you think?

Jim O
Hi Jim,
It is not moving charge from one to the other.
It is monitoring voltage on both separately. If one is higher it takes from that one only , until they equalize. Under normal circumstances (with 2 equal batts,, ) it will keep them at the same voltage, by discharging (using) the higher one first at all times - I believe.
I am already using one ,and have already done a variety of tests. - not with 'your' idea yet but I will for sure.
We are wondering (kicking ourselves) how we missed this one - well done & thanks for sharing.

Brian
Old 02-03-2012, 07:27 PM
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Default RE: Backup/Redundant batteries


ORIGINAL: nonstoprc

On tap into the power pack as the backup source, just wonder if somebody has experience doing so with CC ice hv. Any chance of interference from the ESC?

Talked to Castle Creations customer rep about providing the backup voltage from 2s in a 10s powering HV ICE 80, and was told CC does not recommend it. The reason is that the ESC could be damaged.

Just like to share the info.
Old 02-03-2012, 10:28 PM
  #29  
OhD
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Default RE: Backup/Redundant batteries


ORIGINAL: nonstoprc


ORIGINAL: nonstoprc

On tap into the power pack as the backup source, just wonder if somebody has experience doing so with CC ice hv. Any chance of interference from the ESC?

Talked to Castle Creations customer rep about providing the backup voltage from 2s in a 10s powering HV ICE 80, and was told CC does not recommend it. The reason is that the ESC could be damaged.

Just like to share the info.
Sounds like a marketing guy. I'd like to hear a technical explanation how it could damage the ESC. Maybe it can't stand a common ground. That would be important to know.

Jim O
Old 02-04-2012, 04:13 AM
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Default RE: Backup/Redundant batteries

Yes. figuring out the common ground is one of the reasons sited. The other is that switching regulators are poor in dealing with two battery sources.
Old 02-04-2012, 12:19 PM
  #31  
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Default RE: Backup/Redundant batteries


The CC ICE2 HV 80 has no physical connection between its battery power connections and the power and ground leads of the throttle connector. For THIS specific ESC, you can pick any two adjacent cells on the balance connectors of the motor battery to power a regulator. I have several hundred flights on this ESC using Tech-Aero regulators without any problems. I make no distinction about which balance connector to use. However you do NOT want to use two inputs from the motor battery on different sets of cells. That will cause a direct short through the regulators and the receiver ground bus bar. Always use a separate backup battery and regulator.

It's been said several times on various threads that you should not parallel swtching regulators or BECs with any other power source. If the regulator says it will accept an input voltage that is substantially greater that 8.4 volts and will regulate to 5-6 volts, it is not appropriate.

If you obey these rules you should not have trouble nor cause any damage to your ESC. An appropriate ESC is one that is labelled optically isolated. Check that it is fully isolated by confirming open circuit between the throttle connector power and the battery high side of the ESC and separately an open circuit of the ground wire and the battery low side of the ESC. If your ESC instructions directs you to cut the power connection in the throttle connector, it is not an appropriate ESC.

You can use non-optically coupled or common ground ESCs but it requires a lot more thought and strict adherence to process when you swap batteries in the model.

John
Old 02-04-2012, 02:00 PM
  #32  
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Default RE: Backup/Redundant batteries

Here is a diagram that should answer a bunch of questions. I used a Jaccio and a Tech Aero regulator just to show both brands will work properly with this redundant set up. You do not need to use 2 different brands. Also, I show a 6V and a 5.7V input but as long as the primary source is higher than the back up source, again you will be fine. The pic shows an 800mah back up pack (all I had available for the pic) but that is way overkill as with this setup the battery will sit idle unless needed and a 300mah should be more than enough since we only use 50-60mah on a typical flight
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Old 02-04-2012, 02:44 PM
  #33  
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Default RE: Backup/Redundant batteries

One more thing to consider is that on the JST-XH (Hobbyking) type connectors, there are no clips on the plugs themselves so only the friction of the pins in the connector holds the balance connector to the redundant adapter so you might consider leaving all of the pins in the connector and just covering them with shrink tube. The Polyquest have a good clip and only the 2 required pins need to be in the connector. The TP plug also has a clip. We left all the pin in on the JST-XH and also the TP ones as the pins are rather short and the clip is not as robust as the Polyquest type.

(Sorry just noticed the Polyquest pic has the connector upside down so you can't see where the clip attaches)
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Old 03-24-2012, 04:32 PM
  #34  
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Default RE: Backup/Redundant batteries

If you have been running this system for awhile like I have you will be tempted to do away with the backup battery and fly with just the tap off the motor battery. After all, the backup never does anything. Well don't do it. On my first flight of the day yesterday I was off to a great start and then I did the outside snap on the 45 degree downline and I heard a big cracking noise and could see parts flying. I had no idea what had happened but I knew it wasn't good. I throttled back and landed as if nothing were wrong except I noticed the motor had stopped at the end of my rollout. When I tried to taxi back, I noticed the motor wouldn't run. I could see the canopy was gone and when I got over to the plane I could see the battery pack was also gone.

I don't know if I had been distracted when I installed the batteries and failed to secure the velcro straps or if it is possible the straps are worn out. In any case they let go and canopy wasn't strong enough to contain the 2.5 pound pack at who knows how many g's. I found the canopy after a long search and it had a number of tears but I should be able to fix it. I never did find the battery pack but we can feel good that it didn't start a fire after a 400 foot drop.

Moral of the story, always carry a pack independent of the motor power system.

Jim O
Old 03-24-2012, 06:03 PM
  #35  
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Default RE: Backup/Redundant batteries

Glad you still have a plane, Jim.
I agree, a redundant battery system is cheap insurance especially if you tap the motor battery.
John
Old 03-27-2012, 08:15 AM
  #36  
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Default RE: Backup/Redundant batteries

The Dual battery back is in place to bring the plane back if one battery system fails during flight.
Note: We need to also worry about the connectors we are using. The balance plug connectors on the main power batteries are not the best connector. Single point tin plated.
I would replace the jumper wire every 200 flights.

Some folks are not using a switch to turn on radio system. Plugging the battery into a jumper in to the rvcr. You need to check the contact area the pin. Some low cost jumpers are a folded contact this makes a very poor connection. It is ok if the unit is plug in once a day. But using a half dozen times a day is not good.
Replace those with good contacts. And replace those every year. Take the old parts and put then a fun plane.
So the question what is a good contact. The Old 3 pin deans is good. Two contact points on a solid pin.
There are others don’t save 8 dollar’s spend the money here also.

Get the right connector’s and replace them yearly.

See you on the flight line.
Mark


Old 08-01-2012, 04:35 PM
  #37  
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Default RE: Backup/Redundant batteries



[/quote]

I used the male half of Futaba extension and spliced it to a balance connector adapter. The Black wire attaches to the pin with the black wire on the balance connector which we'll call pin one, and the red wire then attaches to pin three. Perform a test before you connect it to anything. The output should look exactly like a 2s LiPo.

Jim
[/quote]


Just tested this set up last night and it worked well. My only concern is how long do these hold up? I don't have a lot of confidence in those little balance connectors. I have a back up but don't want to test it.

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