Neddy Posted February 20 Share Posted February 20 My aging lithium battery now is 10yrs old it is bloated still holding charge but I have been told it could now be dangerous. I have been looking around and finally settled for 2200mah 11.1v lithium battery which is rated at 70 C . Reading about C ratings the higher the C rating means it can be discharged at a higher rate and recharged at a quicker rate and not be damaged. Also has more storage capacity. Looking at prices it seems this is something to consider. I have seen some batteries rated at 10 C at prices well above higher C batteries. It seems another form of robbery these low C batteries won't last and will soon run out of charge. So it's something to look at when choosing your new battery. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 20 Share Posted February 20 C ratings are something to be taken with a pinch of salt and seem to be used as a marketing tool by some suppliers but should indicate their suitability for different uses. It's entirely possible that better quality cells could be made as lower C rate than cheaper high C ones but could last better. They relate to the maximum discharge current that the cells are supposed to be able to supply. In theory, my 3000mAH 110C packs should be able to supply 330 Amps although they would only last for just over half a minute. Handy for an emergency car start though! 1C signifies the discharge of a battery's capacity in 1 hour - so for an EDF using its charge in 4 minutes, this would be discharging at 15C (60 minutes/15). However, a pack sold as 15C would be unlikely to supply this level of discharge without a significant voltage drop, hence the use of much higher C rates for demanding applications. That (normally cheaper) pack would be fine for pottering around with a scale or vintage model. I wouldn't recommend charging faster than 1C though even if the pack says you can. They are likely to have a reduced life if this capability is used regularly. Quote Link to comment Share on other sites More sharing options...
Geoff S Posted February 21 Share Posted February 21 The 'C' code is indicative of the internal resistance of the battery but most manufacturers exaggerate. I have a meter to measure internal resistance accurately and hence the 'C' rating - none live up to the spec claimed. Theoretically, a 30C rating means you can draw 30 x capacity safely - so 66 amps from a 30C 2.2 AH LiPo. I rarely push my packs hard so I'm happy with lower C ratings, but anyone flying ducted fans (say) needs a battery capable of sourcing high currents and must opt for high C. Quote Link to comment Share on other sites More sharing options...
Neddy Posted February 21 Author Share Posted February 21 Price is no indicator of quality and C rating. The battery I bought 70c was $29 au. Including the delivery. I have seen exactly the same battery for sale at another shop at $80 au plus $20 delivery. Then there is AliExpress selling brands at $7.00 . I have seen the same battery at $50 elsewhere. Quote Link to comment Share on other sites More sharing options...
Duncan Disorderly Posted February 21 Share Posted February 21 4 hours ago, Martin Harris - Moderator said: I wouldn't recommend charging faster than 1C though even if the pack says you can. They are likely to have a reduced life if this capability is used regularly. I would. But only if you need to - e.g. recharging at the field. I'm running a test on this at the moment on another thread. So far, the "reduced life" is running at 143 charging cycles at 12A on a 6S 3300 battery (which had about 200 cycles at 1C on it before I started the test). So that's getting on for a 4C charge rate. The battery is rated at 5C for charging. I'm still getting consistently low IR numbers and good performance - I haven't noticed any drop off and I fly big aerobatics (with good throttle management). This is a cheap pair of Turnigy packs on test, not exotica. So, the question is: if this charging regime is reducing the battery life, how many cycles is reasonable for a cheap pack? Because I'm very happy with the number of cycles I'm getting out there in real life! To answer your question - I've found that high C rated packs tend not to have to work as hard as low C rated packs because there's more "go juice" in them, which is why they're heavier. As Martin & Geoff say, ignore the actual numbers because they'll be exaggerated, but you can use them as a guide for workload. Charge them no higher than 4.15 and you'll double their lifespan. Don't discharge them past 3.7. Try to average around half throttle or below over the duration of a flight. That seems to be what kills batteries to me (from 10,000+ electric flights experience). I'm always very happy to pay the extra few quid, and carry the extra few grammes, for a higher rated pack. I see no harm in you having a 70C battery whether you need one or not! 1 Quote Link to comment Share on other sites More sharing options...
Neddy Posted February 21 Author Share Posted February 21 My 70c battery is slightly deaper in dimensions also it weighs over 200g most other batteries weigh are around 160g. Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted February 21 Share Posted February 21 As said, take the C ratings with a pinch of salt, generally the more 'c's' the bigger and heavier the battery. Quote Link to comment Share on other sites More sharing options...
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