Power Systems and other stuff for large models
12-08-2003, 11:10 AM
#1
Power Systems and other stuff for large models
OK, In the interest to segregate info that has been generated in the discussion within another post about Power/Switch systems for large models and has wandered off track I am starting this thread to continue the discussion. This will allow the original thread to stay aligned with the original posters needs of Power/Switch systems.
12-08-2003, 02:46 PM
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RE: Power Systems and other stuff for large models
I assume that this was created for answering the data Richi-d posted below; If not, moderator feel free to move it back to the old post.
There were several tests done in the past that suggested this wasn't an issue due to the very limited voltage difference between the two packs in the cross charging process. For example, in trying to charge a 6v pack that lost a cell and is now 4.8v, with a pack that is still 6v is only a 1.2v difference available for the charge process. When the charge first starts, there is a quick but short lived high amperage draw as the two packs tend to seek their own level. The voltage will rise in pack that is receiving the charge, while the voltage in the pack that is charging will drop under load. Thus the 1.2v difference will be reduced even more, thus further limiting the cross charge, because there is not enough voltage different to effectively carry out the charge process.
In the tests that I am aware of, they took two packs. One was a 4.8v pack to simulate a 5cell pack with a bad cell. The other was a 6v pack. The 4.8v pack was nearly depleted. The 6v pack was fully charged. This would never happen in real life, as both packs would be nearly identical in charge status when the cell failed as they would be draw on together in that configuration. Reality would be more like a 6v pack at half charge, and a 4.8v pack at half charge. So the 4.8v depleted pack, and the 6v fully charge pack represent a worse case scenario.
The wired a meter between the two packs, then connected them together. They initially saw about a 2amp spike, but it immediately dropped to well under 1amp as the voltage on the 4.8v pack rose to over 5.xv, and the 6v packs voltages also dropped into 5.xv range. The voltages were fairly close, and both in the 5.x range with the 4.8v pack at the low end, and the 6v pack at the higher end. They were left connected for about 2 hours. After the two hours, both packs were cycled. The 4.8v pack had increased somewhat in capacity, while the 6v pack was slightly reduced in capacity. They summarized that it would take a few more hours to fully charge the 4.8v pack, and bring the 6v pack to depletion. They also felt that even though the 6v pack would be depleted and possibly cause a cell reversal over time, it would take hours of cross charging for that to happen, and all the while the 4.8v pack will have adequate voltage and capacity to continue a flight.
In the end, they felt that since the cross charging would take hours, and the capacity would not vanish but merely be transfered from one battery to a completely usable second battery, there exposure during a 15 minute flight is insignificant if the following are met. 1. Dual 6v packs are used. 2. Both packs have sufficient charge to start with, say at least 30% capacity on each. 3. An ESV test is performed on each battery before every flight. 4. Flights are not longer than say 15 or 20 minutes in length.
I will try to dig up the actual test results and exchanges. It was on the IMAC mailing list last year, as well as a couple other tests that people mentioned here on RUC and on the IMAC and Giant Scale lists. I did the same test once just out of curiosity, but I didn't have a meter hooked up at the time. I just connected a nearly empty 4.8v and a nearly full 6v. Left them for 30 minutes, then cycled them both. There was a decrease in the 6v pack, and an increase in the 4.8v pack, but it wasn't significant and led me to believe the results of their test.
Two batteries to one receiver: you must not connect two batteries in parallel. You have to isolated them against each other, else you have currents between the two batteries. For example: one battery is empty, one is charged - you will have several AMPS of charging current to this point when both are at same level!
The most important thing is: when one battery fails - short circuit (most common) - the other will be discharged at once. In the worst case the second battery will also be damaged
The most important thing is: when one battery fails - short circuit (most common) - the other will be discharged at once. In the worst case the second battery will also be damaged
In the tests that I am aware of, they took two packs. One was a 4.8v pack to simulate a 5cell pack with a bad cell. The other was a 6v pack. The 4.8v pack was nearly depleted. The 6v pack was fully charged. This would never happen in real life, as both packs would be nearly identical in charge status when the cell failed as they would be draw on together in that configuration. Reality would be more like a 6v pack at half charge, and a 4.8v pack at half charge. So the 4.8v depleted pack, and the 6v fully charge pack represent a worse case scenario.
The wired a meter between the two packs, then connected them together. They initially saw about a 2amp spike, but it immediately dropped to well under 1amp as the voltage on the 4.8v pack rose to over 5.xv, and the 6v packs voltages also dropped into 5.xv range. The voltages were fairly close, and both in the 5.x range with the 4.8v pack at the low end, and the 6v pack at the higher end. They were left connected for about 2 hours. After the two hours, both packs were cycled. The 4.8v pack had increased somewhat in capacity, while the 6v pack was slightly reduced in capacity. They summarized that it would take a few more hours to fully charge the 4.8v pack, and bring the 6v pack to depletion. They also felt that even though the 6v pack would be depleted and possibly cause a cell reversal over time, it would take hours of cross charging for that to happen, and all the while the 4.8v pack will have adequate voltage and capacity to continue a flight.
In the end, they felt that since the cross charging would take hours, and the capacity would not vanish but merely be transfered from one battery to a completely usable second battery, there exposure during a 15 minute flight is insignificant if the following are met. 1. Dual 6v packs are used. 2. Both packs have sufficient charge to start with, say at least 30% capacity on each. 3. An ESV test is performed on each battery before every flight. 4. Flights are not longer than say 15 or 20 minutes in length.
I will try to dig up the actual test results and exchanges. It was on the IMAC mailing list last year, as well as a couple other tests that people mentioned here on RUC and on the IMAC and Giant Scale lists. I did the same test once just out of curiosity, but I didn't have a meter hooked up at the time. I just connected a nearly empty 4.8v and a nearly full 6v. Left them for 30 minutes, then cycled them both. There was a decrease in the 6v pack, and an increase in the 4.8v pack, but it wasn't significant and led me to believe the results of their test.
12-09-2003, 07:57 AM
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RE: Power Systems and other stuff for large models
ORIGINAL: Ben Diss
I was going to use two 4-cell packs into one receiver. Now I'm rethinking this. Would 4 cells make a difference in the context of redundancy?
-Ben
I was going to use two 4-cell packs into one receiver. Now I'm rethinking this. Would 4 cells make a difference in the context of redundancy?
-Ben
There is lots of info regarding this in the following link; http://www.rcuniverse.com/forum/tm.asp?m=424119
12-09-2003, 08:57 AM
#5
RE: Power Systems and other stuff for large models
Mike,
I have to admit I use two pack and two switches into one receiver with no problems on my 33%. I got lost in the other thread but there looks like allot of good stuff there. It would really help if someone had a simple diagram that showed where the Matchboxes, batteries and powerboxes go in relation to the RX and servos. If someone has a link can they please post it? I'm still not sure I fully understand.
RickP
I have to admit I use two pack and two switches into one receiver with no problems on my 33%. I got lost in the other thread but there looks like allot of good stuff there. It would really help if someone had a simple diagram that showed where the Matchboxes, batteries and powerboxes go in relation to the RX and servos. If someone has a link can they please post it? I'm still not sure I fully understand.
RickP
12-09-2003, 09:01 AM
#6
RE: Power Systems and other stuff for large models
ORIGINAL: sfaust
I assume that this was created for answering the data Richi-d posted below; If not, moderator feel free to move it back to the old post.
There were several tests done in the past that suggested this wasn't an issue due to the very limited voltage difference between the two packs in the cross charging process. For example, in trying to charge a 6v pack that lost a cell and is now 4.8v, with a pack that is still 6v is only a 1.2v difference available for the charge process. When the charge first starts, there is a quick but short lived high amperage draw as the two packs tend to seek their own level. The voltage will rise in pack that is receiving the charge, while the voltage in the pack that is charging will drop under load. Thus the 1.2v difference will be reduced even more, thus further limiting the cross charge, because there is not enough voltage different to effectively carry out the charge process.
In the tests that I am aware of, they took two packs. One was a 4.8v pack to simulate a 5cell pack with a bad cell. The other was a 6v pack. The 4.8v pack was nearly depleted. The 6v pack was fully charged. This would never happen in real life, as both packs would be nearly identical in charge status when the cell failed as they would be draw on together in that configuration. Reality would be more like a 6v pack at half charge, and a 4.8v pack at half charge. So the 4.8v depleted pack, and the 6v fully charge pack represent a worse case scenario.
The wired a meter between the two packs, then connected them together. They initially saw about a 2amp spike, but it immediately dropped to well under 1amp as the voltage on the 4.8v pack rose to over 5.xv, and the 6v packs voltages also dropped into 5.xv range. The voltages were fairly close, and both in the 5.x range with the 4.8v pack at the low end, and the 6v pack at the higher end. They were left connected for about 2 hours. After the two hours, both packs were cycled. The 4.8v pack had increased somewhat in capacity, while the 6v pack was slightly reduced in capacity. They summarized that it would take a few more hours to fully charge the 4.8v pack, and bring the 6v pack to depletion. They also felt that even though the 6v pack would be depleted and possibly cause a cell reversal over time, it would take hours of cross charging for that to happen, and all the while the 4.8v pack will have adequate voltage and capacity to continue a flight.
In the end, they felt that since the cross charging would take hours, and the capacity would not vanish but merely be transfered from one battery to a completely usable second battery, there exposure during a 15 minute flight is insignificant if the following are met. 1. Dual 6v packs are used. 2. Both packs have sufficient charge to start with, say at least 30% capacity on each. 3. An ESV test is performed on each battery before every flight. 4. Flights are not longer than say 15 or 20 minutes in length.
I will try to dig up the actual test results and exchanges. It was on the IMAC mailing list last year, as well as a couple other tests that people mentioned here on RUC and on the IMAC and Giant Scale lists. I did the same test once just out of curiosity, but I didn't have a meter hooked up at the time. I just connected a nearly empty 4.8v and a nearly full 6v. Left them for 30 minutes, then cycled them both. There was a decrease in the 6v pack, and an increase in the 4.8v pack, but it wasn't significant and led me to believe the results of their test.
I assume that this was created for answering the data Richi-d posted below; If not, moderator feel free to move it back to the old post.
Two batteries to one receiver: you must not connect two batteries in parallel. You have to isolated them against each other, else you have currents between the two batteries. For example: one battery is empty, one is charged - you will have several AMPS of charging current to this point when both are at same level!
The most important thing is: when one battery fails - short circuit (most common) - the other will be discharged at once. In the worst case the second battery will also be damaged
The most important thing is: when one battery fails - short circuit (most common) - the other will be discharged at once. In the worst case the second battery will also be damaged
In the tests that I am aware of, they took two packs. One was a 4.8v pack to simulate a 5cell pack with a bad cell. The other was a 6v pack. The 4.8v pack was nearly depleted. The 6v pack was fully charged. This would never happen in real life, as both packs would be nearly identical in charge status when the cell failed as they would be draw on together in that configuration. Reality would be more like a 6v pack at half charge, and a 4.8v pack at half charge. So the 4.8v depleted pack, and the 6v fully charge pack represent a worse case scenario.
The wired a meter between the two packs, then connected them together. They initially saw about a 2amp spike, but it immediately dropped to well under 1amp as the voltage on the 4.8v pack rose to over 5.xv, and the 6v packs voltages also dropped into 5.xv range. The voltages were fairly close, and both in the 5.x range with the 4.8v pack at the low end, and the 6v pack at the higher end. They were left connected for about 2 hours. After the two hours, both packs were cycled. The 4.8v pack had increased somewhat in capacity, while the 6v pack was slightly reduced in capacity. They summarized that it would take a few more hours to fully charge the 4.8v pack, and bring the 6v pack to depletion. They also felt that even though the 6v pack would be depleted and possibly cause a cell reversal over time, it would take hours of cross charging for that to happen, and all the while the 4.8v pack will have adequate voltage and capacity to continue a flight.
In the end, they felt that since the cross charging would take hours, and the capacity would not vanish but merely be transfered from one battery to a completely usable second battery, there exposure during a 15 minute flight is insignificant if the following are met. 1. Dual 6v packs are used. 2. Both packs have sufficient charge to start with, say at least 30% capacity on each. 3. An ESV test is performed on each battery before every flight. 4. Flights are not longer than say 15 or 20 minutes in length.
I will try to dig up the actual test results and exchanges. It was on the IMAC mailing list last year, as well as a couple other tests that people mentioned here on RUC and on the IMAC and Giant Scale lists. I did the same test once just out of curiosity, but I didn't have a meter hooked up at the time. I just connected a nearly empty 4.8v and a nearly full 6v. Left them for 30 minutes, then cycled them both. There was a decrease in the 6v pack, and an increase in the 4.8v pack, but it wasn't significant and led me to believe the results of their test.
I concur across the board with your assertions above.
I was one of the guys that did some testing. I found that the reality of the cross charge was NON-existent with flight loads in place. I actually monitored the voltage and mAh through-put coming and going from each battery and addtionally at the load. Dispelled many myths for me.
12-09-2003, 09:09 AM
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RE: Power Systems and other stuff for large models
ORIGINAL: mglavin
Steve
I concur across the board with your assertions above.
I was one of the guys that did some testing. I found that the reality of the cross charge was NON-existent with flight loads in place. I actually monitored the voltage and mAh through-put coming and going from each battery and addtionally at the load. Dispelled many myths for me.
Steve
I concur across the board with your assertions above.
I was one of the guys that did some testing. I found that the reality of the cross charge was NON-existent with flight loads in place. I actually monitored the voltage and mAh through-put coming and going from each battery and addtionally at the load. Dispelled many myths for me.
12-09-2003, 09:28 AM
#8
RE: Power Systems and other stuff for large models
ORIGINAL: RickP
Mike,
I have to admit I use two pack and two switches into one receiver with no problems on my 33%. I got lost in the other thread but there looks like allot of good stuff there. It would really help if someone had a simple diagram that showed where the Matchboxes, batteries and powerboxes go in relation to the RX and servos. If someone has a link can they please post it? I'm still not sure I fully understand.
RickP
Mike,
I have to admit I use two pack and two switches into one receiver with no problems on my 33%. I got lost in the other thread but there looks like allot of good stuff there. It would really help if someone had a simple diagram that showed where the Matchboxes, batteries and powerboxes go in relation to the RX and servos. If someone has a link can they please post it? I'm still not sure I fully understand.
RickP
Rick
I gotta suggest that utilizing the Matchbox with the Powerbox seems over the top to me. However technically there would be some benefit, BUT you are introducing several new failure modes and increasing the system complexity if not the cost. As you may well know the Powerbox offers four ports per channel, this allows direct connection to four rudder servos for instance. Running a Matchbox through a single channel port is limiting the available power and increasing the impedance of the specific link to all four servos. Obviously taking advantage of the individual channel ports requires using matched servos if there linked together, in this case the Hitec Digitals really shine, IMO...
I think if I had to use the Matchboxes I would power them up directly.
What are your model specific requirements? Maybe we can offer some alternatives that make sense.
12-09-2003, 10:05 AM
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RE: Power Systems and other stuff for large models
ORIGINAL: RickP
Mike,
I have to admit I use two pack and two switches into one receiver with no problems on my 33%. I got lost in the other thread but there looks like allot of good stuff there. It would really help if someone had a simple diagram that showed where the Matchboxes, batteries and powerboxes go in relation to the RX and servos. If someone has a link can they please post it? I'm still not sure I fully understand.
RickP
Mike,
I have to admit I use two pack and two switches into one receiver with no problems on my 33%. I got lost in the other thread but there looks like allot of good stuff there. It would really help if someone had a simple diagram that showed where the Matchboxes, batteries and powerboxes go in relation to the RX and servos. If someone has a link can they please post it? I'm still not sure I fully understand.
RickP
The batteries plug into the green ports on the side.
Jason
12-09-2003, 03:31 PM
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RE: Power Systems and other stuff for large models
Hey Stephen
What is your typical set up as far as battery voltages? four or five cell and if five (six volt) are you using a regulator? what brand radio/reciver?
Right now I am using two four cell packs, two switchs and one reciver. JR radio/reciver. this is on 33% size plane.
I guess I want to know if I could be doing better?
Thanks
What is your typical set up as far as battery voltages? four or five cell and if five (six volt) are you using a regulator? what brand radio/reciver?
Right now I am using two four cell packs, two switchs and one reciver. JR radio/reciver. this is on 33% size plane.
I guess I want to know if I could be doing better?
Thanks
12-09-2003, 04:45 PM
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RE: Power Systems and other stuff for large models
There is a great article here http://www.rcbatteryclinic.com/parallel.html
regarding redundant battery systems> Simple, 2 packs, two switches, plug each into receiver. Done!
regarding redundant battery systems> Simple, 2 packs, two switches, plug each into receiver. Done!
12-09-2003, 05:52 PM
#12
RE: Power Systems and other stuff for large models
Several years ago I used 5 cell packs with diode isolation. These worked fine but extra complication was introduced. One day I read the article above by Red Scholefield and have used this simplified system ever since. No problem what-so-ever.
Ken
Ken
12-09-2003, 08:26 PM
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RE: Power Systems and other stuff for large models
I use dual 6v NiMh 2700mah packs on my 40% airplanes. On my 33% Edge 540T, I used dual 6v NiMh 2150mah packs. I don't use a regulator on either setup with JR receivers and a mixture of JR, Airtronics and Futaba servos in the same airplane. I've used 6v packs for years now on both JR and Futaba receivers.
The only thing I do is that when I first take the packs off the charger, I let the plane sit for about 10-20 minutes to avoid any servo jitter from the high voltage immediately off charge. A JR rep told me that the jitter won't really hurt anything, but you want to avoid doing it all the time. Since I can get in a full day of flying on twin 2700mah packs, I only do overnight charging. By the time I take the airplane off change in the morning, and get it to the flight line, do the pre-flight inspection, fill it with gas, and get myself ready for flying, its been much longer than 10-20 minutes and the servos never jitter. If you were going to fast charge it at the field alot, and want to immediately take it off charge and go fly it, a set of regulators might not be a bad idea.
The only thing I do is that when I first take the packs off the charger, I let the plane sit for about 10-20 minutes to avoid any servo jitter from the high voltage immediately off charge. A JR rep told me that the jitter won't really hurt anything, but you want to avoid doing it all the time. Since I can get in a full day of flying on twin 2700mah packs, I only do overnight charging. By the time I take the airplane off change in the morning, and get it to the flight line, do the pre-flight inspection, fill it with gas, and get myself ready for flying, its been much longer than 10-20 minutes and the servos never jitter. If you were going to fast charge it at the field alot, and want to immediately take it off charge and go fly it, a set of regulators might not be a bad idea.
12-10-2003, 08:34 AM
#14
RE: Power Systems and other stuff for large models
ORIGINAL: mglavin
What are your model specific requirements? Maybe we can offer some alternatives that make sense.
What are your model specific requirements? Maybe we can offer some alternatives that make sense.
I think my set up is fine now, 33% with eight 8411's all around on four (Ail-R, Ail-L, Elev, Rud) matchboxes. Two NiMH 2150's plugged into two seperate ports on the single RX. I didn't power any servos seperatly with the matchboxes.
My next project is a 30%er and I think I'm going to do the same, but with smaller batteries Two 1800's perhaps? The only thing I am not doing is testing the flight packs, can you tell me what's involved with this? Just a voltage check under load? If you have any suggestions for a more robust system please let me know.
I see your point about using the Hitecs and the powerbox. If you insist on using 8411's and matchboxes for simplicity then you probably don't want to get involved with the powerbox, just power the matchbox individually. Thanks for all the info guys.
RickP
12-10-2003, 08:57 AM
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RE: Power Systems and other stuff for large models
I'm running 7.2v lipos reduced to 6v on ign and rec-works great and lasts all day long. The regulators seem to hold voltage right around 6 volts exactly-so I dont get the jitters you guys are talking about. Do most of you guys run nicads, nimh on your big birds? Just curious.
Weight was not an issue on this plane(H9 SU31,3W106), but it does have long, heavy gauge leads to the tail and wing servos.
Weight was not an issue on this plane(H9 SU31,3W106), but it does have long, heavy gauge leads to the tail and wing servos.
12-10-2003, 09:47 AM
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RE: Power Systems and other stuff for large models
ORIGINAL: RickP
The only thing I am not doing is testing the flight packs, can you tell me what's involved with this? Just a voltage check under load? If you have any suggestions for a more robust system please let me know.
The only thing I am not doing is testing the flight packs, can you tell me what's involved with this? Just a voltage check under load? If you have any suggestions for a more robust system please let me know.
If you log and chart your packs with regular capacity checking you will find you have a reasonable reserve as low as 1.15v to 1.12v per cell and still have about a 30% reserve capacity. To log and chart your pack, in a nut shell you would fly as you do now, but log the time of each flight, and the loaded ESV meter before and after each flight. Don't fly beyond the 1.2v cutoff point. When you are done for the day, you would cycle your pack and see how much capacity was left in each pack. From that you can figure how much capacity you had left, how much current your airplane uses on a typical flight, how much capacity total was used, and determine the number of flights the left in the remaining capacity minus a 2 flight reserve. Once you have your capacity logged with ESV readings, you have a good idea where you stand before each flight by comparing the current ESV reading with the logged data. Also, if something is amiss, you will see it in a discrepancy between the two.
12-10-2003, 10:40 AM
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RE: Power Systems and other stuff for large models
I have been running two NiMH 2700 mAH 5-cell packs in parallel without regulators on a 33% bird for several years without a problem. I peak charge the packs between flights with the Ace Smart Charger. I don't get the jittery servo problem because I don't use JR servos on the plane. I'm using a Futaba PCM receiver and Hitech 5945 and 5735 servos.
I have another 33% bird that I'm using two NiMH 2700 4-cell packs in parallel with regulators. The reason for the lower voltage setup is that it has a couple of JR 4721 servos. They do not like the higher voltage. Again in combination with a Futaba PCM receiver.
Peak charging between flights allows me to fly all day with peace of mind.
I have another 33% bird that I'm using two NiMH 2700 4-cell packs in parallel with regulators. The reason for the lower voltage setup is that it has a couple of JR 4721 servos. They do not like the higher voltage. Again in combination with a Futaba PCM receiver.
Peak charging between flights allows me to fly all day with peace of mind.
12-10-2003, 10:41 AM
#18
RE: Power Systems and other stuff for large models
ORIGINAL: RickP
Mike,
I think my set up is fine now, 33% with eight 8411's all around on four (Ail-R, Ail-L, Elev, Rud) matchboxes. Two NiMH 2150's plugged into two seperate ports on the single RX. I didn't power any servos seperatly with the matchboxes.
Mike,
I think my set up is fine now, 33% with eight 8411's all around on four (Ail-R, Ail-L, Elev, Rud) matchboxes. Two NiMH 2150's plugged into two seperate ports on the single RX. I didn't power any servos seperatly with the matchboxes.
My next project is a 30%er and I think I'm going to do the same, but with smaller batteries Two 1800's perhaps? The only thing I am not doing is testing the flight packs, can you tell me what's involved with this? Just a voltage check under load? If you have any suggestions for a more robust system please let me know.
Stephen suggested the correct methodology for logging and cycling the batteries to determine where your at with your power supply. You'll need a charger that can cycle and display the mAh capacity left in the battery and or a device such a Sirrius Super Tester, which is a stand alone load and data logger.
I see your point about using the Hitecs and the powerbox. If you insist on using 8411's and matchboxes for simplicity then you probably don't want to get involved with the powerbox, just power the matchbox individually. Thanks for all the info guys.
RickP
RickP
Happy Holidays
12-11-2003, 03:03 AM
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RE: Power Systems and other stuff for large models
O.k. guys,
this is not a redundant system to plug in two batteries in parallel! You have to isolate them against each by a Diode!! What some people tell in this board is dangerous! You will get real problems if one battery fails. It is not the same: one 4cell pack and one 5cell pack in parallel - maybe you are right with your tests. But if one cell has a short circuit you have currents about 10 - 20A!!!! Had seen that a few years ago - it was a single 5 cell battery - one get a short - the other four bursted!! In this case - this is the most common- you will crash down if you didn´t decouple both batteries!
Your test assumes that one cell is getting high impedance - this case is not very often!!
Trust me - I know what I´m saying!
To POWERBOX and MATCHBOXES:
This is the best solution: You plug in the receicer to POWERBOX, the matchbox to the POWERBOX and the servos to the MATCHBOX. To power the Matchbox you can take a lead from any output channel of the Powerbox to the PowerIN of the matchbox! Every output of the Powerbox is good enough to burn down a shorted cable - so don´t be afraid - this is more than enough POWER to run 8 Powerservos. Take a strong short lead to get enough Power to the MATCHBOX!
I remember- one the website www.dual-power-control.com are pictures of Sebastiano´s installation...
this is not a redundant system to plug in two batteries in parallel! You have to isolate them against each by a Diode!! What some people tell in this board is dangerous! You will get real problems if one battery fails. It is not the same: one 4cell pack and one 5cell pack in parallel - maybe you are right with your tests. But if one cell has a short circuit you have currents about 10 - 20A!!!! Had seen that a few years ago - it was a single 5 cell battery - one get a short - the other four bursted!! In this case - this is the most common- you will crash down if you didn´t decouple both batteries!
Your test assumes that one cell is getting high impedance - this case is not very often!!
Trust me - I know what I´m saying!
To POWERBOX and MATCHBOXES:
This is the best solution: You plug in the receicer to POWERBOX, the matchbox to the POWERBOX and the servos to the MATCHBOX. To power the Matchbox you can take a lead from any output channel of the Powerbox to the PowerIN of the matchbox! Every output of the Powerbox is good enough to burn down a shorted cable - so don´t be afraid - this is more than enough POWER to run 8 Powerservos. Take a strong short lead to get enough Power to the MATCHBOX!
I remember- one the website www.dual-power-control.com are pictures of Sebastiano´s installation...
12-11-2003, 08:03 AM
#20
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RE: Power Systems and other stuff for large models
ORIGINAL: Richi-d
O.k. guys,
this is not a redundant system to plug in two batteries in parallel! You have to isolate them against each by a Diode!! What some people tell in this board is dangerous! You will get real problems if one battery fails. It is not the same: one 4cell pack and one 5cell pack in parallel - maybe you are right with your tests. But if one cell has a short circuit you have currents about 10 - 20A!!!! Had seen that a few years ago - it was a single 5 cell battery - one get a short - the other four bursted!! In this case - this is the most common- you will crash down if you didn´t decouple both batteries!
Your test assumes that one cell is getting high impedance - this case is not very often!!
Trust me - I know what I´m saying!
O.k. guys,
this is not a redundant system to plug in two batteries in parallel! You have to isolate them against each by a Diode!! What some people tell in this board is dangerous! You will get real problems if one battery fails. It is not the same: one 4cell pack and one 5cell pack in parallel - maybe you are right with your tests. But if one cell has a short circuit you have currents about 10 - 20A!!!! Had seen that a few years ago - it was a single 5 cell battery - one get a short - the other four bursted!! In this case - this is the most common- you will crash down if you didn´t decouple both batteries!
Your test assumes that one cell is getting high impedance - this case is not very often!!
Trust me - I know what I´m saying!
I'm not arguing against the Powerbox, since the Powerbox adds a whole other set of functions a single dual battery setup doesn't offer. And my next airplane will most likely get one even if its just to allow me to test the product for my own use. But the Powerbox isn't the ideal solution of all configurations. For those not willing to shell out a few hundred for a Powerbox because they don't feel the need for the on board voltage meters, short protection, regulation, etc, the dual battery setup is very common, works perfectly well, much much cheaper, and does indeed cover a whole host of failures that a cause a single pack setup to completely fail. The Powerbox just brings the redundancy to another level, but also at a significant cost increase. The pilot has choices, all of which are good and offer increasing redundancy and functions, from a single pack, battery backup devices, dual packs, to Powerboxes. There isn't a single perfect option for all configurations, much to our dismay.
12-11-2003, 11:34 AM
#21
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RE: Power Systems and other stuff for large models
Hi- SFAUST
Why do you want to built in two batteries if you don´t do it for redundance? If you don´t want redundance, you can fly with a single pack! The second - parallel - battery is only more weight if you don´t decouple them!!!
The advantages of a POWERBOX are not only that there are 100% redundance - further more you get the full Power to every servo! I see you with a very big plane on this picture- how do you ensure that the servos get the power they need? And with such long leads you may have a lot of trouble... and so on... with a Powerbox all those problems (and more) are eleminated!
And there are smaller/cheaper solutions from MODELLBAU-DEUTSCH. There are different types of Powerboxes in offer. You can ask Gerhard - he will give you best advice.
For example this one: http://www.modellbau-deutsch.com/e/h...wer_box_12.htm
Why do you want to built in two batteries if you don´t do it for redundance? If you don´t want redundance, you can fly with a single pack! The second - parallel - battery is only more weight if you don´t decouple them!!!
The advantages of a POWERBOX are not only that there are 100% redundance - further more you get the full Power to every servo! I see you with a very big plane on this picture- how do you ensure that the servos get the power they need? And with such long leads you may have a lot of trouble... and so on... with a Powerbox all those problems (and more) are eleminated!
And there are smaller/cheaper solutions from MODELLBAU-DEUTSCH. There are different types of Powerboxes in offer. You can ask Gerhard - he will give you best advice.
For example this one: http://www.modellbau-deutsch.com/e/h...wer_box_12.htm
12-11-2003, 12:59 PM
#22
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RE: Power Systems and other stuff for large models
ORIGINAL: Richi-d
Hi- SFAUST
Why do you want to built in two batteries if you don´t do it for redundance? If you don´t want redundance, you can fly with a single pack! The second - parallel - battery is only more weight if you don´t decouple them!!!
Hi- SFAUST
Why do you want to built in two batteries if you don´t do it for redundance? If you don´t want redundance, you can fly with a single pack! The second - parallel - battery is only more weight if you don´t decouple them!!!
But, I don't think most people feel the need for that full level of protection based on the excellent results we are having in the states with the current approach. And adding all that stuff that they may feel is unnecessary also adds weight. So I think they tend to piecemeal their redundancy approach buying just what the need in order to keep the costs appropriate, and the weight to a minimum. I see so many airplanes with some of the solutions, but rarely one with everything.
Its kind of like sex. If one condom works 98% of the time, very few will see the need to wear two or three condoms even thought it would without a doubt offer additional protection. The one condom seems to be working fine, and offering the level of protection most people desire, so they don't see the need.
The advantages of a POWERBOX are not only that there are 100% redundance - further more you get the full Power to every servo! I see you with a very big plane on this picture- how do you ensure that the servos get the power they need? And with such long leads you may have a lot of trouble... and so on... with a Powerbox all those problems (and more) are eleminated!
The servos on my airplanes are getting adequate power from using dual 6v packs, heavy duty wiring, minimal use of connectors, short servo leads, gold pins, heavy duty switches, etc. I've measured the voltage at the servos in the tail (longest lead), and with that setup the servos are seeing more than adequate voltage and current measured at the higher end of the designed servo voltage range. In my opinion, and with my experiences, it isn't an issue in a properly setup aerobatic airplane up to and including 40%. This however doesn't include a 40% B25!!
And there are smaller/cheaper solutions from MODELLBAU-DEUTSCH. There are different types of Powerboxes in offer. You can ask Gerhard - he will give you best advice.
For example this one: http://www.modellbau-deutsch.com/e/h...wer_box_12.htm
For example this one: http://www.modellbau-deutsch.com/e/h...wer_box_12.htm
12-11-2003, 02:17 PM
#23
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RE: Power Systems and other stuff for large models
Its kind of like sex. If one condom works 98% of the time, very few will see the need to wear two or three condoms even thought it would without a doubt offer additional protection. The one condom seems to be working fine, and offering the level of protection most people desire, so they don't see the need.
-Ben
[Sorry, I couldn't resist.]
12-11-2003, 07:03 PM
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RE: Power Systems and other stuff for large models
ORIGINAL: Ben Diss
Will my plane still feel the same if I use two batteries?
[Sorry, I couldn't resist.]
Will my plane still feel the same if I use two batteries?
[Sorry, I couldn't resist.]
12-12-2003, 03:04 AM
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RE: Power Systems and other stuff for large models
Good morning-
the Powerbox 12 offers a 100% redundance cause in the switch are 4 double contacts so you have 4 points of connection for each battery - not only two as in a common heavy duty switch!! You have with a single battery on this switch more security than with a common switch!! Ground is bypassed - so no point of failure.
The switching is very strong, so it is not possible that it switches itself.
If you want real good heavy duty switches- you can get them also from Gerhard - it´s the same switch as above but you have 4 double contacts for ONE!! battery... and the cables are about AWG12 (I don´t know exactly the U.S. sizes) - so who needs more!
the Powerbox 12 offers a 100% redundance cause in the switch are 4 double contacts so you have 4 points of connection for each battery - not only two as in a common heavy duty switch!! You have with a single battery on this switch more security than with a common switch!! Ground is bypassed - so no point of failure.
The switching is very strong, so it is not possible that it switches itself.
If you want real good heavy duty switches- you can get them also from Gerhard - it´s the same switch as above but you have 4 double contacts for ONE!! battery... and the cables are about AWG12 (I don´t know exactly the U.S. sizes) - so who needs more!