Mouldy Posted October 26, 2007 Share Posted October 26, 2007 Ok, two Ripmax Impulse 3S1p 16C packs. Both have always been balanced charged and have never been fast charged. Both have had around 7 cycles. Niether is showing any outward sign of damage. However one seems to be dead. It wont charge or balance on either of the chargers I have, (gone mad and bought an estation BC8!). Ive put a volt meter across each cell and the reading is 1.4V on all three Dosent look good really but the main question is why should this be?? Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted October 26, 2007 Share Posted October 26, 2007 1.4V per cell is BAD NEWS!! My guess is that it has been inadvertantly left connected. Even though the radio / powertrain is not actually switched on, the impedance of an ESC alone will pull down the battery over a relatively short period of time. First and last time I did it, it took just 4 days to knacker the pack. It also started to puff up slightly - so straight into the saltwater then garbage bin it went. Quote Link to comment Share on other sites More sharing options...
Mouldy Posted October 27, 2007 Author Share Posted October 27, 2007 Interesting about the ESC as I didnt know that. And yes they have been charged and put back into the planes and connected. However not for four days! Went flying on Friday afternoon, the batteries were removed and put on charge the following day although they were left in the van over night. This is when the problem first showed and to be honest I dont know if it was the battery left in the plane or the one in the flight box. Another lesson learnt the hard way then! Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted October 28, 2007 Share Posted October 28, 2007 The reason it took 4 days to discharge mine to critically low level was because they were pretty freshly charged and used only for around 10 mins or so before stopping for the day. Likewise, the capacity of the pack will also determine the time taken to discharge of course. If yours were already run down a bit, then the drain via the ESC would happen much quicker, EG "in the van overnight" It is vital that any LiPo pack be fully disconnected from the circuit when not used. Quote Link to comment Share on other sites More sharing options...
Helidel Posted October 28, 2007 Share Posted October 28, 2007 I agree, all ESCs will drain, and the larger (more powerful) the motor /ESC the more drain you'll get.My Banchee-Axi-Jeti drains almost 1 amp when connected but switched off!TimboI placed a message on the A123 thread in error, about my Power and TX Lipos.It could be my age Del Quote Link to comment Share on other sites More sharing options...
Mouldy Posted October 28, 2007 Author Share Posted October 28, 2007 OK guys, all taken on board. Thanks again! Quote Link to comment Share on other sites More sharing options...
Malcolm Keen Posted October 30, 2007 Share Posted October 30, 2007 At the moment my Lipos are in a casserole dish in the shed in a fully charged state, and as far as I am aware they are snug, happy and tucked up like a hibernating tortoise.But?? ---- Keep them in the shed, move them indoors, keep them outdoors . do they mind the cold, the frost etc etc Wot do you fink Quote Link to comment Share on other sites More sharing options...
Mouldy Posted November 1, 2007 Author Share Posted November 1, 2007 To my knowledge, cold dosent harm them but they discharge quicker. IM sure Tim will correct me if Im wrong! Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted November 1, 2007 Share Posted November 1, 2007 Well as with most things leccy, there is a myriad of opinions out there, and some conflicting stuff too! Speaking purely from personal experience, I have not yet suffered any noticeable problems with my LiPos ( I have around 40 various packs currently ) despite not following the warnings about cold temperature issues The following is all “recommended” treatment, from various sources. As we mostly know, the normal maximum permissible voltage with Li-pos is 4.2 per cell. Below 10 degrees C that falls to 4.15V - so if you charge up to 4.2 in the warm and then let the battery get cold out on the field or when stored in a cold workshop - you effectively have an overcharged battery. EG: If they lose say .75 volt when they are cooled, then they likely will gain .75 if they are warmed. Some say that a pack charged to 100% should not be subsequently cooled below room temperature. Therefore if planning to take a pack out into the very cold weather, a charge to perhaps just 90% or so of capacity is advisable. Cells at 90% or less capacity can be safely cooled below 32F (0C). Cell temperature during use is proportional to current draw. The pack starts the flight at a particular temperature and this rises throughout the flight. If you have to store them for more than a month or so, it is also advisable to discharge them to 3.7 - 3.9 volts per cell and then put them in the fridge or freezer, - protecting from moisture. Lipo capacity drops about 10% a year at room temp but only 2% a year when discharged and cold. If you do store cold, then do NOT store fully charged. Remember the maximum safe voltage for a lipo decreases with lower temp, so a pack fully charged at room temp, stuck into cold storage will be "overcharged" when it has cooled down. Storage alone at low temperature does not reduce cell life, however charging at normal rates when the cell is cold can harm the cells. The FMA CellPro charger actually senses ambient temperature and adjusts the charge to protect the cells. Bet you wish you hadn’t asked now don’t ya ! Quote Link to comment Share on other sites More sharing options...
Mouldy Posted November 1, 2007 Author Share Posted November 1, 2007 The BC8 has a storage program for LiPo's.. Quote Link to comment Share on other sites More sharing options...
Malcolm Keen Posted November 1, 2007 Share Posted November 1, 2007 Thank you gentlemen for all your help, I am now going to lay down in a darkened room and try to soak up the info.When you have been100% IC and your knowledge of electric stopped with your bike lights the you better brace yourselves cos "I will be back." Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted November 1, 2007 Share Posted November 1, 2007 welcome to the steep learning curve of electrickery flight Quote Link to comment Share on other sites More sharing options...
Former Member Posted November 4, 2007 Share Posted November 4, 2007 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
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