clearyconnoly Posted October 16, 2017 Share Posted October 16, 2017 Small electrical problem which is wrecking my head:- Have put together a battery powered LED display using a LiPo battery (Venom 30C 3S 2200mAh 11.1V LiPo Battery) powering 12V LEDs. Worked fine until battery ran down, and now I can't recharge it. - Instructions say never to let the battery run down completely… but surely it can't be that fragile?- Also wondering if I need to unplug battery from circuit before recharging? My circuit has a switch, so thought it was enough to turn it off.- There is also the wiring: I used the two outside (red and black) wires from the output plug (there are four, three black, one red). I snipped and stripped wires and connected to switch using wire nuts…What am iI doing wrong?Advice would be much appreciated Link to comment Share on other sites More sharing options...
bigclive Posted October 16, 2017 Share Posted October 16, 2017 The lithium protection circuit may either prevent recharging of an over-discharged cell or try and recover it by trickle charging until the affected cell/s reach around 3V before kicking into full charge mode. The main hazard with lithium cells is if they get reverse charged by more than about 12% as the voltage across them rises to the point that it causes copper electrode ions to travel across to the aluminium electrode and that can form conductive pathgs through the electrode separator. If you are trying to charge the pack on an intelligent charger it may just reject the pack if one cell is below 2.5-3V. If the cell voltages are above zero then gently trickle charging the affected cell until it reaches about 3V will often recover it. Beyond that if the cell shows signs of not charging fully or self discharge then it may have suffered copper bridging inside and should not be used. Strangely enough, I made a video about over-discharge of lithium cells. Link to comment Share on other sites More sharing options...
empyfree Posted October 16, 2017 Share Posted October 16, 2017 - Instructions say never to let the battery run down completely… but surely it can't be that fragile? Yeah, you’ve over discharged it! You will need to build a low voltage cut off into your circuit to avoid killing any more cells. Lots and lots of info on this sort of battery (including storage, charging and discharging) on various RC (remote control) websites. Big powerful LIPo cells like that can be quite dangerous. Read up and be sure what you’re doing before wiring another one in, you could get burned or worse. I used the two outside (red and black) wires from the output plug (there are four, three black, one red). I snipped and stripped wires and connected to switch using wire nuts…What am iI doing wrong? You say the “output plug”. This sounds more like the balance plug. Is there also a larger set of red/black cable coming out of the battery? Most often the smaller multi core plug is used for charging, you’re 11.1v battery is made up of three cells, so you’re possibly only powering your circuit off one of them... Link to comment Share on other sites More sharing options...
Jivemaster Posted October 16, 2017 Share Posted October 16, 2017 Lithium batteries are intolerant of bad charge and discharge regimes. They have several wires to enable monitoring of the charge and discharge of each cell. which is usually done on the circuit board rather than the battery. Lots of designs use a single cell and a boost converter simply to avoid the hassle of balancing the charge to each cell in a series battery. Some Lithium batteries will recharge slowly if left on charge from flat, for a long while. Some will not recover if one cell has been forced into reverse polarity during discharge. Some cells are available with internal protection for charge and discharge, but these may be current limited to less than you need. Link to comment Share on other sites More sharing options...
abbotsmike Posted October 16, 2017 Share Posted October 16, 2017 Li-Po cells are very sensitive to over discharge. Because of their intended use in RC cars/planes, they often have no protection, as they are rated for such high discharge rates that a protection circuit would be impractical. That 2.2Ah 30C Battery is rated for discharge at 60A in short bursts. Link to comment Share on other sites More sharing options...
sleah Posted October 17, 2017 Share Posted October 17, 2017 I'll also echo that you have to be careful with LiPo batteries. They need to be treated with utmost respect, not just for correct operation but for your own safety. LiPo's are supposed to be stored in a discharged state - not fully discharged as already mentioned - so some have circuitry that slowly discharges them when not in use. So even though your circuit is switched off, it sounds like the LiPo's are self-discharging. Link to comment Share on other sites More sharing options...
Jivemaster Posted October 17, 2017 Share Posted October 17, 2017 From www.venompower.com Max Volts per Cell: 4.2VMax Volts per Pack: 12.6VMin Volts per Pack: 9VCharge Rate: 1C (2.2A) You NEED to control the charge and discharge profiles. You must stop discharge just before 9v pack voltage occurs, then you must charge at 2.2A max to the point where the charger says full. Maybe locating each cell in the multi pin connector will help you determine whether all the cells are kaput or just one, maybe applying 4v across each cell will return the battery to usable, but likely not. Consider using a LiPo battery in a retail available car jump starter pack that has a 12v output connection. https://www.machinemart.co.uk/p/clarke-clippjs-multifunction-jumpstartportable/?da=1&TC=GS-010317075&gclid=Cj0KCQjw1JbPBRCrARIsAOKj2Pn8GFzUSXQicXcFJQb_F09znsooJ9w0qWecnzjHSWVmOJITW0tj2TcaAtYtEALw_wcB Is one of many on the web. Supposedly it has a 9.6AH battery and all the correct charge and discharge control circuitry, so in your application would last longer that the venom pack per charge cycle AND last for more charge/discharge cycles because it's protected electronicly. Many other brands and models of 12v Lithium battery packs exist and are available from shops, there could be a transport issue with web based purchases. Link to comment Share on other sites More sharing options...
musht Posted October 17, 2017 Share Posted October 17, 2017 The very popular, so popular that there are fakes, Imax B6 charger https://hobbyking.com/en_us/imax-b6-50w-5a-charger-discharger-1-6-cells-genuine.html The 3S in the battery code, is 3 cells in Series. LiPo 3.7V flat 4.2V full. The small molex plug on the battery pack is the balance plug that plugs into a charger like the B6 so that no cell overcharges. Echo concerns about using Lithium Poly , its optimised for low weight and high discharge applications, with no physical or electrical protection. Water dosen`t put out a lithium fire. 5V may need a bit of reconfiguring LEDs but plenty of large USB power banks around. 3 in series 18650 NCR batteries with correct charger if you need 12V. Link to comment Share on other sites More sharing options...
adam2 Posted October 17, 2017 Share Posted October 17, 2017 I would re-think the whole idea of using this sort of battery. Too delicate, and very dangerous if anything goes wrong. I would prefer old fashioned battery technology for anything home built or improvised, sealed lead acid or nickle cadmium if possible. If lithium must be used then buy a matched battery and charger from a reputable supplier and follow the instructions to the letter. Link to comment Share on other sites More sharing options...
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