Jonathan M Posted January 21, 2019 Share Posted January 21, 2019 Just a couple of questions or so on good practice for looking after larger LiPos, having not used EP for a few years but now with a set of (not exactly inexpensive) Overlander 4S 4250mAh 35/50C batteries for my Wot4. Each LiPo takes about an hour to charge from 35% to full at 1C, a total of four hours' delay if I decide to go flying on a whim. Overlander recommend not charging at over 1C, so what is a safe storage charge (and one which won't harm longevity) to keep the batteries at for a week or longer? 80% or much less? (Long-term I understand that 40% is a usual storage figure, but how long is 'long-term'?) Again, in terms of longevity, is there any point in not charging to the full 100% before going flying? Finally, how low can I habitually go before the Lipo becomes permanently compromised? 35%, 25%, 15%...? I don't expect them to last forever, and I'm not a thrash-merchant and don't expect more than a few full-power bursts per flight, but just looking for some general purpose principles to refresh myself. Jon Quote Link to comment Share on other sites More sharing options...
Keith Berriman Posted January 21, 2019 Share Posted January 21, 2019 Hi Johnathan you have all the basics there and unfortunately it looks like a little more spenditure on charging equipment is needed along with a suitable power supply. Would advise scanning BMFA classified think I have just seen a quad charger on there at reasonable price Quote Link to comment Share on other sites More sharing options...
Dane Crosby Posted January 21, 2019 Share Posted January 21, 2019 Go to the 4Max web site. George has free downloads covering care and use of LiPos. Quote Link to comment Share on other sites More sharing options...
Keith Berriman Posted January 21, 2019 Share Posted January 21, 2019 https://bmfa.org/class1/id/71838 try this link Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 21, 2019 Share Posted January 21, 2019 Jonathan With the right charger you can certainly charge all four LiPo at once so only an hour total. Such a charger will also have a storage charge/discharge capability. Unless you are certain that you are going flying the next day I would advise taking all LiPo to storage level (its about 35% or 3.60 V). Not only for safety but it reduces the electrical 'stress' on the battery and the tendency for it to go a bit 'puffy'. I would also advise that you do not fly much below below 35% capacity. As such a level is also close to the storage level it reduces time for the charger to put all the cells to the same charge level.. As soon as you start a charge it is a good idea to check the individual cell voltages, the charger should be able to do this. If they all start from 3.60 V (storage voltage) then you can be pretty sure all is ok. If one or more cells is more than 0.05 different or rapidly rises towards 4V then the LiPo will neither accept full charge nor deliver the voltage under load. This condition will only get worse as the 'weak' cells are likely to be discharged to a harmful. level well before the good ones. Works for me. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted January 21, 2019 Share Posted January 21, 2019 I started with one charger, then two and so on, but things became complicated with power supply connections. Now I have a quad charger that is my primary, if I think I'll need more packs I use my old single chargers too. I think the most I've got to so far is 10 packs all on at once though it probably took longer setting them all up than it did to charge them! Me, I aim to get no lower than 20% after allowing for the odd go-around or two so I'd ideally be landing with about 30%. Less than 20% really does seem to stress the packs. 30% does seem better for pack life. I suspect that there may be a relationship between current drawn and best final capacity, maybe something to do with the final core temperature of the pack? Just throwing the idea out there Quote Link to comment Share on other sites More sharing options...
Nigel R Posted January 21, 2019 Share Posted January 21, 2019 I have a turnigy Reaktor 300w charger and matching 350e power brick and use a parallel board to charge 4 x 4s 5000mah in one go. Usually takes around 90 mins to do a balance charge on all 4 at once. Storage temperature is important. Maybe more so than storage voltage. 50% charge level is optimal for battery life. The thing to avoid is high storage temperature whilst fully charged. I keep mine charged pretty much all the time as I don't have opportunity to charge just before flying. Not completely ideal. I do avoid keeping them anywhere warm. Lastly. Overlander are certainly reassuringly expensive but I have just as good performance from the zippy and rhino lipos from HK. Ymmv Quote Link to comment Share on other sites More sharing options...
Peter Jenkins Posted January 21, 2019 Share Posted January 21, 2019 I agree that parallel charging is the way to go. I fly with 2 x 5S packs in series to give 10S but charge them in parallel and that takes an hour or less. I normally set the charger to stop at 95% capacity to maximise life and do not charge at more than 1C. Remember for parallel charging you should set 2C as the charging current as it halves to fill the packs. If the packs are not at exactly the same voltage the stabilise very quickly once you have connected them. Connect with the main leads first and then the balance leads. I find that the percentage capacity is a bit of a guess as with my LiPo checker it reads 14% with anything between 3.65 and 3.75 v/cell. I try not to go lower than 3.7 v/cell. I would trust v/cell more than percentage remaining by the way. On this regime, my oldest pack is sitting at 80 cycles and is only slightly puffed. There are a bunch at around 50 cycles that are not puffed at all but are a different make. A LiPo is dead if you drop below 3 v/cell and your charger probably won't be interested if it sees that voltage. My charger puts the cells at 3.85 v/cell on storage mode. However, I don't think leaving them at 3.7 v/cell causes a problem. I rarely leave batteries fully charged for more than a day. I charge the night before. I have 2 high capacity chargers and can charge 8 10S packs in 2 hours splitting them into 2 x 5S packs and parallel charging them. Occasionally, I charge each pack separately to make sure that the cell balancing is on a per pack basis as opposed to 2 packs as for parallel charging. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted January 22, 2019 Share Posted January 22, 2019 Peter - re storage at 3.7 there are two types of chemical degredation one occurs towards 3.7 and the other towards 4.2. Sitting in the middle minimise both. Quote Link to comment Share on other sites More sharing options...
Bruce Collinson Posted January 22, 2019 Share Posted January 22, 2019 I’m with Bob, that Quad charger is arguably the most useful single purchase I have made in the three odd years since I returned. Also, I am finding that George’s branded LiPos have far less tendency to puffing up than certain other high profile brands and I strongly suspect that he is cautious with his labelling and other brands are optimistic. Club mates have tended to find the same. Five are due for delivery later! Interestingly I took a straw poll on Sunday whilst flying ( ok, in between flights) and the vast majority fully recharge at about 1C straight after flying. I suspect the majority intend to use them again within a week or two. Parallel boards ... the Quad can charge four different battery chemistries at once, and your i-Thing, from 240 or 12 v. Horses for courses. BTC Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted January 22, 2019 Author Share Posted January 22, 2019 Thanks so much for the helpful feedback, and I'm now totally sold on the GT Quad charger! The ability to bring four biggies up to full from storage in one hour - what's not to like? Just one question: I've read the manual and Mike Freeman's review on the 4-Max site, but can't see if the 'storage' voltage can be adjusted to a level a bit higher (as per Nigel's point above) than the default setting for battery type. The manual indicates that it will charge/discharge each LiPo to 3.75v, but it isn't clear if this can be manually increased to a setting of say 3.85v or about 50%. Anyone know? Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted January 22, 2019 Author Share Posted January 22, 2019 PS: Thanks also for the advice on how far to normally run the packs down in flight. Flying the Wot4 in quite windy (and rather cold) conditions late yesterday afternoon, with a varying mix of half-throttle circuits and a variety of aeros per flight, the packs came down to 60%, the first one on 9 minutes timer, then 55%, 49% and 38% when I changed to 10 minutes and began to up the taps more frequently - which seems a comfortably safe range. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted January 22, 2019 Share Posted January 22, 2019 Don't sweat the storage level, it will make very little difference to be left anywhere in the 35% - 65% sort of region. The worse problem by far is extended periods at high temperatures. In a garage, on a concrete floor, the temperature is relatively constant and either single digits or low 10's, in this country, which is ok for our needs, and easy for most of us to achieve. A few breezeblocks surrounding the lipos help make a fireproof barrier and aid with keeping temperature stable. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted January 22, 2019 Share Posted January 22, 2019 I find the single most useful tool for electric flight is modern radio with telemetry providing consumption and minimum cell voltage. I can set up a warning at 35 or 40% capacity remaining to let me know it's time to prepare for landing, max or instant current and power but even just a low voltage warning is a great comforter as you will be made aware of packs that are on their way out rather than discovering it the hard way. Of course I managed for years without it before it was readily available relying on just a flight timer but telemetry just makes life so much easier. I've taken to using a Unisens-E unit with my FrSky gear to get current, pack voltage, receiver voltage, rpm (when it works!) altitude and rate of climb/descent if I want them all, and the beauty of this unit is that it's as easy to swap between models as just plugging it in line with the battery. Nice to have it but it really isn't essential! The compact battery checkers can be useful but they really don't appear accurate below 50% or so, mine seems to show 14% remaining over a wide voltage range. A rough guide only it seems! Quote Link to comment Share on other sites More sharing options...
Peter Jenkins Posted January 22, 2019 Share Posted January 22, 2019 Jonathan, a couple of things I forgot to mention in my earlier post, First, always check how much the charger puts back into your pack. That is the only reliable way of determining how much you took out of it. I usually find that while my LiPo checker says 14% remaining, I actually only get around 3,300 mah into a 5000 mah capacity pack. That way, you will be able to "calibrate" what your remaining voltage is telling you and also what your LiPo checker actually means when it says, in my case, 14% remaining. Clearly there is just over 30% remaining. Second, check the internal resistance of new packs. Keep checking them every time you charge. With a parallel charge for 2 packs, I see readings from around 7 milli ohms up to 30 milli ohms. I find that it is not worth using the pack for serious flying if the IR goes above around 30 milli ohms. If you are charging a single pack, then double those figures since the resistance of two 10 m ohm resistors in parallel is 5 m ohm. With 3 or more then the solution is in the equation 1/R = !/R1 + 1/R2 + 1/R3 etc. Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted January 22, 2019 Author Share Posted January 22, 2019 Good advice Nigel. I store my LiPos in a safe-bag inside an old metal tool-box on the concrete floor of the shed. I do charge them in the house, but inside the safe-bag on stone flooring in the fireplace and stay around to keep an eye on them! Bob, telemetry is a very useful idea (just a case of swapping my ordinary Spektrum 6-chan RX for a Lemon one plus telemetry module) but should in the first instance become familiar with setting a relatively safe limit on the TX timer - and be prepared to land a minute early if I know I've been torturing the battery too much! Thanks for the additional info Peter. Your checker sounds right dicky! Mine seems okay, and I normally eyeball the display which gives the volts of each cell rather than just the percentage screen. On my little battery checker (which I use for checking my small 1s DLG Lipo's ranging from 300 to 900mAh) I've taped a table on the back showing volts and percentage charge: 1s % 4.20 100 4.09 90 4.00 80 3.94 70 3.88 60 3.84 50 3.81 40 3.79 30 Don't know quite how accurate my figures are (can't remember where I originally got them), also I check them at no-load rather than applying the 0.3A load button which would of course give a lower figure. I assume the normal LiPo checkers don't apply any load? I do tend to note the milliamps put back in on the charger screen, and do a quick mental check to work out percentage used.... more to keep my brain oiled than by way of proper record-keeping! I've now ordered the Quad charger, so will also get into the habit of checking resistance. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted January 22, 2019 Share Posted January 22, 2019 FWIW I time my flights to give me (by experience, trial-and-error) just over 20% remaining after I land. I then store them like that until I'm ready to go flying again. I charge at 1C, even though most of my packs say they can be charged faster, and discharge to 50% if I've charged a pack and had to bring it home unused. My oldest LiPo is 9 years old this week, and still hauls my Align 500 heli around. If it's doubtful whether or not I'll fly on a particular day I've got a few models which fly on A123 packs, which can be stored fully charged seemingly without any detrimental effect. Mine are almost 12 years old now and are still performing, though with reduced flight times compared to when new. I charge in LiPo Sacks, and store my packs in compartments in a box built out of plasterboard. Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted January 22, 2019 Author Share Posted January 22, 2019 Maybe old LiPos are like the early light-bulbs - which originally lasted much longer until the sales department insisted on impurities being included in the gas! On another note, having just ordered the Quod charger, I note that 4-Max recommend using the following connectors: EC3 and XT60 connectors are good for up to 35Amps 4mm connectors are good for up to 70 Amps XT90 and EC5 connectors are good for up to 90Amps 6mm connectors are good for up to 120 Amps 8mm connectors are good for up to 200 Amps The Deans style connectors are good for up to 40 Amps Previously ignorant of this aspect of things, I'd previously just gone ahead and soldered Deans onto the four Lipos, the 70A ESC (max draw with my prop is 54A) and the Watt Meter - so also ordered a job-lot of XT90 connectors to replace them all! What is the down-side of not replacing the Deans? Final question: what is the screeching noise I normally hear when I advance throttle from about 80% to full? Could it be something amiss mechanically in the motor/drive, or is it something acoustic to do with the prop? Quote Link to comment Share on other sites More sharing options...
Dad_flyer Posted January 22, 2019 Share Posted January 22, 2019 How low a temperature is OK for lipo storage? I have just started and wonder if the garage will be ok if we have a long cold spell like we had last winter. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted January 22, 2019 Share Posted January 22, 2019 Posted by Jonathan M on 22/01/2019 20:49:11: Maybe old LiPos are like the early light-bulbs - which originally lasted much longer until the sales department insisted on impurities being included in the gas! On another note, having just ordered the Quod charger, I note that 4-Max recommend using the following connectors: EC3 and XT60 connectors are good for up to 35Amps 4mm connectors are good for up to 70 Amps XT90 and EC5 connectors are good for up to 90Amps 6mm connectors are good for up to 120 Amps 8mm connectors are good for up to 200 Amps The Deans style connectors are good for up to 40 Amps Previously ignorant of this aspect of things, I'd previously just gone ahead and soldered Deans onto the four Lipos, the 70A ESC (max draw with my prop is 54A) and the Watt Meter - so also ordered a job-lot of XT90 connectors to replace them all! What is the down-side of not replacing the Deans? Final question: what is the screeching noise I normally hear when I advance throttle from about 80% to full? Could it be something amiss mechanically in the motor/drive, or is it something acoustic to do with the prop? I'd always thought the ratings were higher than that, more like: JST connector - up to 5A 2mm bullet connectors - up to 20 Amps 3.5mm bullet connectors - up to 40 Amps XT60 connectors - up to 60 Amps Deans / T-Plug - up to 60 Amps EC3 connector - up to 60 Amps 4mm bullet connectors - up to 70 Amps EC5 connectors - up to 120 Amps 6mm bullet connectors - up to 120 Amps 8mm bullet connectors - up to 200 Amps I use XT60s for up to 50ish Amps without any issues, before the XT60s I used Deans for the same sort of uses, though Deans can be subject to wear/heat issues. Edited By Bob Cotsford on 22/01/2019 22:22:39 Quote Link to comment Share on other sites More sharing options...
Nigel R Posted January 22, 2019 Share Posted January 22, 2019 No minimum temp for storage that I'm aware of. They lose performance if you operate under about 10 deg.About 30 deg is optimal performance temperature. Not for storage though. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted January 22, 2019 Share Posted January 22, 2019 Deans are fine on 50a. Leave wwll alone! Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted January 23, 2019 Author Share Posted January 23, 2019 Posted by Nigel R on 22/01/2019 23:26:49: Deans are fine on 50a. Leave well alone! This is the advice I like! Quote Link to comment Share on other sites More sharing options...
Dad_flyer Posted January 23, 2019 Share Posted January 23, 2019 Thanks. Nigel R Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted January 23, 2019 Share Posted January 23, 2019 Posted by Simon Chaddock on 21/01/2019 21:15:25: Unless you are certain that you are going flying the next day I would advise taking all LiPo to storage level (its about 35% or 3.60 V). Not only for safety but it reduces the electrical 'stress' on the battery and the tendency for it to go a bit 'puffy'. Works for me. Are you sure about these figures as they seem at odds with most others? My batteries are incapable of producing any meaningful power at 3.6V - and I've always considered 3.7V as the lowest off load voltage that I would want to see at the end of a flight. The consensus of opinion for the accepted figure for storage appears to be around 3.8 to 3.85 volts. But what do I know? My storage regime is whatever the pack is at when I finish a flying session - usually either full or 90% discharged! I'm coming to the opinion that the worst thing is inactivity - the two Rhino packs I have used regularly for well over 5 years (could be considerably longer) week in, week out, still deliver their full capacity and I haven't noticed any drop off in performance. I have habitually taken 3600 mAh from these 4000 mAh packs (measured by telemetry) which by my calculations is 90%, with a terminal voltage of just over 3.7V. They are still as tight as the day they hit my doormat - not even a suggestion of puffiness. Other packs which I have not used regularly have been left at storage charge for extended periods - guess which ones have puffed and/or lost capacity? Edited By Martin Harris on 23/01/2019 11:02:08 Quote Link to comment Share on other sites More sharing options...
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