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Lipo maintenance questions

Discussion in 'Electronics' started by Dave King, Apr 4, 2013.

  1. Dave King

    Dave King Well-Known Member

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    I wanted to ask a few questions about lipo batteries. I"ll number them so that if you want to any any of them you can reference which question. Thanks in advance.

    1. Up till now I have been only using the storage mode and the charging modes on the Hyperion Super Duo 3 charger. Is anyone using the discharge mode? If so how much are you discharging them? I have heard conflicting stories as to whether or not you need to full charge a brand new battery and then discharge it.

    2. I have a lipo that went bad, it actually created a rather large arch and sizzle when I connected it which put burn marks on the pin of the JST connector. Has anyone else exerperienced this or know what causes this?

    3. I noticed that my Duo 3 charger stores the batteries two different ways which is making me wonder whats going on. After I fly and my batteries are down to the low 14 volt range, when I go to put them in storage mode the Duo 3 charges them up to roughly 15.8 volts. However if I have a fully charged battery that I know I'm not going to use for a little bit I will put it in storage mode and the duo 3 will store them down to about 15.1-15.2 volts. This charging pattern is very consistent as I was wondering why this is? If I take one of the batteries that was stored up to 15.8 volts and then hit store again the charger will take them down to 15.1-15.2 volts. Anyone else experiencing this?

    4. How are you guys recycling bad lipo batteries?

    Thanks as always for your help and input.

    Dave
     
  2. Gary Haynes

    Gary Haynes Administrator
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    1. I only use the discharge mode on new batteries. Full charge, discharge to 3.3v, full charge, discharge, Full or storage charge. I want to make sure the new battery is ok. Looking for cell gap and battery ohms to be good.

    2. Where did it arc? Do you have pictures? If it arced in the battery itself then that battery should be disposed.

    3. If you fly and then go to storage mode then the charger will take the battery to the storage level as set in the menu for that battery. What storage value do you have set?

    4. Not sure what you are asking about 'recycle'? If you are asking how do you get rid of it when it is no longer usable I have seen two methods. One can be found HERE and is the better method. And the other is more violent.
     
  3. Michael McVay

    Michael McVay Active Member

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    Dave,

    1. I have used the discharge mode with I first bought a pair of the MaxAmps 11,000 batteries and was having trouble with low voltage warnings early in my flights. I did a couple cycles just to make sure the batteries held the full 11,000 capacity (which they did). I then found out those batteries can not keep up with the power draw of a CS8 which caused the voltage to drop too low. Other than that, I do not use the discharge mode - just charge and store modes.

    3. Do you have one or two of the Hyperion chargers? I ask because I have two and they were storing batteries differently. It turns out there is a firmware upgrade for the chargers. The one I got from QC last fall was on a different firmware than the second one I had gotten more recently. After upgrading they now act the same way. However, as to your questions, I have gone into the menus for each battery profile I have stored and changed the discharge voltage from 3.8 (default) to 3.7 and adjusted the storage percentage to 50%. By doing this I now get a consistent storage voltage of about 3.85 per cell which, from my searching, hits the middle of the recommended storage voltage from most sites. Most places I found said to store lipos between 3.8 and 3.9. Before the firmware upgrade there was not an adjustable storage % for each battery profile.

    Hope that helps a little.

    Michael
     
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  4. Dave King

    Dave King Well-Known Member

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    Thanks Gary. I will check my settings when I get home. As far as the arc it arched inside both EC5 connectors. The Ec5 connector of the flight control board, and also of the battery. The arch was more than your typical arch you will see when you connect the EC5's together. It put a tremendous amount of black carbon on the pins of the negative connection on both connectors. The battery was not damaged itself physically. The battery EC5 connector has a lot of carbon on it, so much I don't feel like cleaning it up or connecting the battery would be a good idea. The FC EC5 had just enough carbon on it that it cleaned up nicely. It just arched for a couple of seconds and then the connectors started to sizzle and I then pulled it out. It did not damage to the CS8 from what I can tell because I flew last week without any abnoralities besides having one BL temp going a little higher than I would have liked to seen (98 degrees peak, AVG current was fine) 2nd highest temp was 82. I have since put a new motor on it, put compressed air on the BL, and triple checked the motor alignment. I don't think the two were related because I have run 4 sets of batteries and they all were fine with the same flight time of 12 minutes.
     
  5. Dave King

    Dave King Well-Known Member

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    Hi Michael

    Right now I only have one Super Duo but I just bought a 2nd one and the E fuel power supply that I have not received yet. Thanks for the heads up about the firmware, I will double check to make sure they are the same.
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I notice a little initial arc when first connecting the 4S Lipo to the MK PDB inside the EC5 housing -- usually on the negative side of the plug. However, as has been covered before, this is just the caps charging up. It's more of an initial flash that sustained arcing -- if you see it for more than a fraction of a second, then I suspect that the EC5 connectors might need to be replaced.

    I also find that if I fly until the LiPo hits 14.4v, when I remove the LiPo, the battery voltage bounces back up to anywhere from 14.8 to 15.0v -- essentially at storage voltage. The only time I need to use the Store mode of the Hyperion is if I didn't use a battery on a particular day or the flying got shot down because of bad weather.

    You can see this on the graph in the initial test report I did at http://rathergoodguides.com/RGG_documents/RGG to Comparing Certain LiPo Batteries 1-03 2013-02-21.pdf (see the red line on the graph at the top of page 4).

    Andy
     
  7. MIke Magee

    MIke Magee Active Member

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    On this topic, 10 days or so ago, I followed Andy's Rather Good Guide to applying a conformant spray(highly recommended to read and do) . In the process of tearing everything down, I noticed that the PDB EC5 was extremely distressed from these arcs. In fact the plastic was melted, thin and cracked on one side. One would not normally notice this - I did because I had the PDB on the bench inches from my eyes for inspection. I replaced the EC5 and would suggest that folks get down there and look at it periodically. Just sayin ...
     
  8. Dave King

    Dave King Well-Known Member

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    Good idea
     
  9. Joshua Barker

    Joshua Barker New Member

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    Dave,

    Dave,

    1. In regards to the different settings on your charger, there are different uses depending on how many packs you are using and what you are trying to accomplish. Each setting has its time and place. You know your first two but in regards to the discharging or cycling features there are a couple of factors that dictate which method to use. The main reason you would discharge a pack on your charger is to cycle it for storage or analysis. If you are looking to cycle a pack I would recommend just using the cycle feature. This only works with one battery however and cannot be done in a sync mode. If you would like to cycle two packs at once you can sync discharge, then sync charge to get the comparable same effect. I would recommend discharging your pack down to 3.0V per cell. This way all of the lithium in the pack is then used. The charger has safety features built in that will not allow an individual cell to drop below voltage unless of course it is already damaged. In regards to analysis the same principles apply but just make sure you either record the results before going to the next step in the process or have your PC in line recording the data.

    2. This would definitely be tied to a short of some kind. Whether internal or external the pack shorted on itself causing extreme heat and the results you saw.

    3. In regards to storage there is definitely a gap in where the voltage range is sustained for storage. The good news is however that both voltages you describe are in the correct location for storage and will not damage the pack prematurely. I am unsure as to why the voltage fluctuates in this particular way however.

    4. Your local radio shack and batteries plus should recycle lithium packs as well.
     
  10. Dave King

    Dave King Well-Known Member

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    thanks Josh.
    Question to all forum members, why do some people only discharge to 3.3 v/cell when some people discharge to 3.0 v/cell?
     
  11. Joshua Barker

    Joshua Barker New Member

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    I believe it is a common misconception. When Lipos were first introduced into the RC market the thought was that 3.0V was the danger point. As long as you set your system up to cutoff at this point in use you were safe. The truth however is that the cells inside a pack discharge at different rates. Albeit a small difference overtime you have cells that separate enough to have a single cell drop below voltage. This will destroy the capacity in a cell and the pack will be useless.

    People recognized this and adjusted accordingly by raising the point of Cut off on their ESCs. Anywhere between 3.2 to about 3.6 volts depending on the application. This since has become the standard and is why many discharge to a higher voltage than 3.0V. The good thing about many smart chargers and in this case specifically the Hyperion units is that they have a built in balancer that monitors each cell and keeps it from over discharging or charging.

    Basically on the charger you can safely discharge to a lower voltage. In an application that detects cutoff based on full pack voltage you need to create a buffer zone for the inconsistency in voltage of these cells.
     
  12. Dave King

    Dave King Well-Known Member

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    thanks Josh, so in your opinon the Hyperion Super Duo 3 has built in circuitry to where you can safely discharge lipos down to 3.0 volts per cell and not reduce its long term effect on charging?
     
  13. Joshua Barker

    Joshua Barker New Member

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    The Hyperion unit does detect off of voltage and will stop a charge if an individual cell tries to drop below the stated cell voltage cut off. This is not a complete look at the system or battery however and is a good reason why analysis of the data you can collect from this is important. If you do discharge and it stops go to the balance option and see all of the cells. Confirm they discharged evenly or near so anyway. You shouldn't expect a perfect balance during discharge but if the cells are further than a couple tenths of a volt apart you likely have a cell or cells that are not holding voltage correctly. The charger can be a great tool in assessing a pack for any reason.
     
  14. Dave King

    Dave King Well-Known Member

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    Understood!! That makes sense. Thanks again for the input.
     
  15. MIke Magee

    MIke Magee Active Member

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    This is a follow up and this could be important for all EC5 users. The plastic melted way again, and I can now see what the issue is.

    The "male" side of the EC5 is slotted to provide the ability to expand into the female barrel. The batteries are of course all female. In my case, somehow, the Males got compressed stightly. It could have been insertions that were less than parallel, who knows.

    It appears that when these slots are compressed, the connection points between the male connector and female barrels are reduced, meaning that all of the amps are traveling through less area - heat happens.

    By inserting a perfectly sized phillips screwdriver into the male side, I "re-spread" the male connector so that it once again makes contact with the entire area of the female. EC5 heat is spread uniformly and I have had no further plastic distress.

    Just an experience to share, sorry for the R rated terminology.
    -m

     
  16. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    That's a great description of the problem, Mike (even though I blushed at certain anatomical details) ;) .

    I think the precursor to the problem that you might notice is that the connectors are too easy to insert or break apart -- if that happens the odds are (in my experience) that the male pin has become compressed and it's probably time for the screwdriver procedure.

    Andy.
     
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  17. MIke Magee

    MIke Magee Active Member

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    Ya. I blushed typing it, but I tried to be as clinical as I could.
    -m
     
  18. Joe Azzarelli

    Joe Azzarelli Active Member

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    So lets say that when flying a cell gets down to 3v or even 2.9v -- of course when you shut down the cells all measure above 3v. Does that momentary dip below the threshold of hell ruin the lipo? ( Haven't done it, just want to know...)
     
  19. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I don't think it damages the LiPo, Joe.....the transient excursion isn't what will do it, based on received prejudice from the Internet -- it seems to the be the prolonged excursion below 3v/cell that causes the problem.

    But, as I say, this is purely based on what I've seen on the Internet.

    "You cannot believe quotations that you see on the Internet," Abraham Lincoln.​

    Andy.
     
  20. Joshua Barker

    Joshua Barker New Member

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    LOL. Andy, I like the quote. Didn't know that about old Abe.

    Joe,

    From our experience there is a loss of capacity if you drop below the rated voltage for a given cell. An almost negligible amount on a single over discharge but it is becomes worse if this is a repeat problem. We have been able to track trends for different systems and a common issue we found was with cutoffs that are set at 3.0V precisely. The results I am mentioning come from the RC Car market but the same principles apply. The 3.0V cutoff has a flaw. It detects this based on full pack voltage, therefore an individual cell can drop below 3.0V. Repeated over-discharge of a cell will slowly deteriorate it's capacity and discharge capability. This cell then becomes the downfall of the pack as it will fluctuate to full charge and discharge faster than the other cells and will eventually puff.

    Going to 3.0V however is not damaging. It is the dips below this that are an issue. If you can monitor the individual cells and maintain them at or above 3.0V you should be fine.

    Josh
     

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