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Discussion
Ask REVOLECTRIX battery guy
Hello All
I have been asked to start a discussion room about LiPO batteries topics to focus will be. 1. Production Processes 2. Cell Design & Raw materials 3. Cell Design parameters effecting performances 4. Safety by Design or Process 5. Root causes of failures or performance variances 6. Performance improvement techniques Feel free to ask and we'll try get back to the forum asap, maybe even with a video |
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Sounds interesting.
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Sub...
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Hello John,
Can I add another topic to your list? From a manufacturer's point of view, what are the recommended practices for handling, storing and maintenance of LiPo batteries, and when is a battery considered past the point of safe use? If a battery has mechanical or structural damage, when is that considered unsafe to keep using it? It's understandable that due to cost, modellers don't want to just chuck out batteries that, despite their appearance, may still be perfectly safe and serviceable. After reading various discussions, there seems to be no definitive information on the above issues from any other manufacturers. If you have anything John, with photos, it would be much appreciated. Thanks mate. |
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Last edited by vimy g eaou; Jul 05, 2017 at 12:59 PM.
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Good idea for a thread, here's a few questions to get things started:
- What is the process that allows for higher/lower C ratings? Is there a hard upper limit. I appreciate the definition of "X"c differs manufacturer to manufacturer but presumably you are all working under similar chemical/physical constraints that mean beyond a certain point it becomes impossible. - We know we shouldn't go below 3-3.3 voltage at rest. Does this value change for high current applications when the voltage sags? - Is there a sweet spot where C rating/capacity/weight/voltage are optimal for power delivery? Like with an amps per gram type measurement? |
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Last edited by REVOJohn; Jul 05, 2017 at 08:24 PM.
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OK Power Delivery with trades off on C rating:Capacity:Weight:Voltage Actually i thing your trade off wold be purely on design not considering ability to process the design all tjings equal Power Out: Trade off on; Cost of Cell (Raw ingredients) vs Weight vs Safety Level vs Cycle Life Give you an example. We recently design a high capacity cell for a US military application. expected cycle count 1. C rate as large as we could get it (we had the 5200mAhr cell down at 0.6mohm per cell) and light as we could (`120g) but the trade off was cycle life |
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Last edited by REVOJohn; Jul 05, 2017 at 08:23 PM.
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Thanks John, for answering my questions. If I can come up with anything else, I'll post it.
Just thought of one... I know there is always going to be a weight penalty with batteries used for anything to do with aircraft, that's a given. Has anyone tried some sort of chemical contained in a membrane wrapped around the entire battery, that can be released to put out a fire? |
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Last edited by vimy g eaou; Jul 06, 2017 at 09:03 AM.
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Thanks for taking the time to talk with us. |
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I have heard from time to time of a break in process, is there actually one recommended for lipo and what performance - current and capacity- changes can be expected with the first few cycles and or break in. Thanks !
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I believe some factories wanted to ask customers to break in packs as the factory production process of formation was shortened to save time and $. Formation is the process of waking up the cell to get its capacity and SEI layer activated. This takes time = $ personally we never asked anyone to do such breaking in but in a recent Singapore military project the customer had laid the packs for 24 months at a low SOC and when they tired to use them they failed quite quickly. When i tool some of the same remaining packs and broke them in first they were fine. On the other hand some packs were left at 100% SOC for 24 months and there was nothing i could do, they failed very very early due to kathode degredation, normal to see this with very thin electrode formats for RC and at high SOC and long time the electroltye reacts with kathode and eats it away. As a practice for high rate cell I think its a good idea anyway, especially after long periods of storage to reactivate the SEI later to either form it again or remove it if too big. We're thinking of putting this auto function into the Grand Touring series of chargers Depending on how much the factory process was shortened you could see up to 10% but i would think 5% of so max capacity uplift. More important is the IR improvement you would get thus increasing cycle life |
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