|
|
|
| General RC Aircraft Discussion Discuss anything RC related |
Topic Review (Newest First)
|
| 12-19-2015 05:59 PM | ||
| kip51035 |
Re: Battery Problem or Not??? Yeah Thanks a lot!! I have set for storage three two cell packs and one three cell pack. The volt meter I use is designed for LIPO's and scans each cell one after the other. After I set them for storage the cells in each pack were really close in voltage. One heli the power cord is buried inside, so I ran it tied down with the meter on it until at rest it was within the storage voltage. Thanks again! |
|
| 12-19-2015 12:19 PM | ||
| stegl |
Re: Battery Problem or Not??? As Max says , must use a per cell voltage storage reading. With a questionable battery you could have 3.6 + 4.1= 7.7 V total and the cells are not balanced correctly nor ready for storage . I used those two numbers just to show a comparison between two cells and a total voltage reading. The voltage difference doesn't seem large at .5V but it is for lipos. Cell imbalance should be no greater than .05v from the highest to the lowest cell readings in the pack but better to be even less than that. At least that is the way I do it as others may believe otherwise and do things their way. |
|
| 12-18-2015 06:48 PM | ||
| Max |
Re: Battery Problem or Not??? Quote:
Depending on the charger, they set storage from anywhere from 3.8 to 3.85. So 7.7 will work. I would even go to to 7.6 |
|
| 12-18-2015 05:57 PM | ||
| kip51035 |
Re: Battery Problem or Not??? I picked up an IMAX B6 charger discharge unit. I put the 4-Channel heli on it. The battery is one of the original questionable units. I set it for storage with a 1 amp discharge, it has been on for over 100 minutes now and the voltage has gone from 7.93 down to 7.75. I believe the storage voltage is suppose to be 7.7. Is this normal? |
|
| 12-17-2015 09:11 PM | ||
| stegl |
Re: Battery Problem or Not??? You will get many many suggestions on chargers from real cheap to higher cost better quality. My preference is Thunder Power as their after service backing is very good to excellent. The model 610 is the version I am thinking of. Can be bought as 12v power or for a bit more comes as an ac or 12 dc plug in. Do a total discharge of you defective lipos and drop at any place that recycles batteries. When buying lipos there is a wide range of qualities and sizes available through Hobby Wholesale in Edmonton or mail order thru Great Hobbies out east. |
|
| 12-17-2015 06:59 PM | ||
| kip51035 |
Re: Battery Problem or Not??? These are 1500 mha LIPO batteries and all I have is the chargers that came with the heli. The one I am using puts out 500ma. It charges by the three pin plug. Yes I did leave them fully charged. I fired up the choppers weighted down in the shop. The F-Series and it ran a minute or so then started to slow and at about two minutes it stopped and the light went out. Now it reads no voltage at all and will not take a charge. The one marked 4-Channel worked for a couple of minutes then slowed. The cell that was the highest voltage showed a lot lower voltage than the other when under load. Now both cells read 3.8-something. Where can I get some new LIPO batteries and a proper charge discharge battery manager? |
|
| 12-17-2015 12:38 PM | ||
| michaely |
Re: Battery Problem or Not??? This is from batteryuniversity.com: "Overcharging Lithium-ion Lithium-ion operates safely within the designated operating voltages; however, the battery becomes unstable if inadvertently charged to a higher than specified voltage. Prolonged charging above 4.30V on a Li-ion designed for 4.20V/cell will plate metallic lithium on the anode. The cathode material becomes an oxidizing agent, loses stability and produces carbon dioxide (CO2). The cell pressure rises and if the charge is allowed to continue, the current interrupt device (CID) responsible for cell safety disconnects at 1000–1,380kPa (145–200psi). Should the pressure rise further, a safety membrane on some Li-ion bursts open at about 3,450kPa (500psi) and the cell might eventually vent with flame. Venting with flame is connected with elevated temperature. A fully charged battery has a lower thermal runaway temperature, or vents sooner, than one that is empty. For Li-cobalt the threshold is between 130–150ºC (266–302ºF), nickel-manganese-cobalt (NMC) 170–180ºC (338–356ºF) and manganese 250ºC (482ºF). Li-phosphate enjoys similar and better temperature stabilities than manganese. Lithium-ion is not the only battery that poses a safety hazard if overcharged. Lead- and nickel-based batteries are also known to melt down and cause fire if improperly handled. Properly designed charging equipment is paramount for all battery systems and temperature sensing is a reliable watchman." I would discharge the battery so that you eliminate the "overcharged" cell now showing 4.3 volt. I've had some success with lipo packs where voltage on one of the cells is significantly different from the other cells (but not at a high 4.30v) by bringing down the average cell voltage to "storage levels" (nominally 3.85v), doing several charge/discharge cycles, using a charger with a balancing circuit. This has significantly narrowed cell voltage differences and the stabilized the narrower differences. Others will say toss the pack if one cell has already gone significantly beyond 4.20 volts. good luck, |
|
| 12-17-2015 11:05 AM | ||
| Max |
Re: Battery Problem or Not??? If your batteries are LiPo's, you have to apply LiPo discipline for storage and charging. Lipos aren't your Nicad's and Nimh's. Sounds like you ruined the pack. Usually this is done by leaving a Lipo sit for long periods fully charged. This is a no-no. Once a cell gets damaged from sitting around, its pretty much toast. Having any cell below 3V is a really bad sign of toasted-ness  Also- Are you using a smart(intelligent) charger? If yes to the above, are you using the balance charge mode? The wal-wart chargers that come with the inexpensive toy helis for lipo charging are the worst. They don't balance charge and only go off the maximum pack charge. Meaning one cell could be too low and the other dangerously over maximum |
|
| 12-17-2015 10:25 AM | ||
| stegl |
Re: Battery Problem or Not??? I have found that on one occasion my charger balance board did not make a great connection on one of the charging pins and the voltage reading was way way out of line on that one cell. It did a shutdown after a while and I think this was because of the imbalance. Smart charger. I pulled the balance lead out and back in to make a better connection and all was well. Question on the voltage readings ; were these voltages read off the charger , voltage level meter or a regular voltmeter by checking each cell individually ? Some charger reading are not all that accurate off the balance connector . The voltage level meters that plug into the balance leads can be off from cell to cell. The best is using any regular voltmeter checking each cell individually . Even though it could be off slightly , you are using or getting a comparison from cell to cell with a constant voltage meter. I have made up a charge cable that charges one cell at a time , set charger for one cell and charge that weak cell for a while , say 10 or 15 minutes at a little less than C1 and see if the voltage changes. If it doesn't then I would say the battery is toast . Do you leave your batteries fully charged all the time ? Or close to storage voltages ? AND as Cloudniner says never ever leave the charger connected ; unattended . |
|
| 12-17-2015 09:38 AM | ||
| cloudniner |
Re: Battery Problem or Not??? Kip You don't indicate if you are using a balance connector. In a case like this I would think a balancing charger would be a smart move. In the case of a charger set for 2s and not using a balance connection the charger is going to keep pumping in current until it gets to 8.4V or the charger times out. It is my understanding that one should not go above 4.2V per cell. The balancing charger would drag down the high cell preventing (hopefully) the over voltage. This is one of the dangers with LiPo batteries. If one battery is very low or damaged the current will continue to pump into the good one which can and has caused fires. Never leave them unattended. P.S. This time of year one should be putting on a storage charge which is 3.85V per cell. |
|
| This thread has more than 10 replies. Click here to review the whole thread. | ||
Your Privacy Choices