Duncan Disorderly

I thought the BMS had its own way of managing the supply charge? You're correct, you can't run one through your normal charger, it's a self contained system and I can't even get my head around how using both could even happpen! I need to read up more about them. In the meantime, headroom is your friend.

No, I didn't use a BMS. This is my prototype and I wanted to keep it simple. To mitigate against the risk of overcharging a cell, I'm charging to 0.05v per cell below the maximum allowed voltage. There are 8 cells in the parallel chains, so if one decides to go rogue and stops charging to 4.15v then there's headroom in the system to allow the 7 other cells in that parallel chain to take up the slack on the duffer's behalf. With the seven at 4.2v, the duffer can be as low as 3.80v and the charger will still see 4.15v coming back at it and terminate the charge. Because I charge it so slowly, I should pick up on those cells beginning to take longer to charge way before anything begins to start getting warm. (However, as an aside, this may be a fine reason against making the parallel chains too short, as the shorter the chain the more each cell will have to contribute to make up any shortfall - so longer chains are better? Discuss!) I also used high quality, new cells. Not the best, but HQ. They were all at an identical voltage when soldered into parallel, so I haven't soldered in any imbalances. The whole system is pretty much at tickover, so nothing is being stressed. None of which flawlessly picks out a dying cell, I agree - I'm mitigating not eliminating - but I don't know of many BMS that will isolate a single dying cell either - think of the wiring harness! - so I'd probably just fuse each cell first anyway. None of the above is to disagree with the fundamental of your comment, which is: Use a BMS, folks! To which I'd add: "...and if you don't then build in a sensible amount of headroom instead - and understand what can still go wrong". It's why this thread is a "Here's what I'm doing..." rather than a "Step by step guide to..."

That looks fantastic! I wish I could get around to things as swiftly as that. The fuse is overkill. I did it because I just copied Russ's and even he said it wasn't necessary, just dotting the Is and crossing the Ts. Let us know how you get on with it. That inlay is weird! Maybe laser cut in before the sheey of ply was laminated up?

...presumably preferring to advance the hobby by means of hearsay and Chinese whispers, and it's all Spektrum's fault anyway. How dare you attempt to make anything better through use of data ! The funny thing is, I didn't once notice the log-keepers saying how daft not keeping a log was, yet plenty came back the other way (in a good-humoured way on this forum - but flak nonetheless!) Great thread leccy - it's been a really interesting read.

Nothing can ever move forwards without comparative data. We don't all have to do it but it definitely helps if some do. The weirdos will step up to the plate unbidden and we're perfectly happy to help the rest of you out.

This is the pair of Turnigy Heavy Duty 6S 3300 60C batteries that drew the short straw and are currently being subjected to my brutal charging regime. I was expecting them to at least puff a bit. The one side that looks a bit out of shape has got fluffy velcro on it. Reminder - they'd each had somewhere around 200 charges at 1C before having 12 amps stuffed into them 125 times. I was trialling one of them at 15 amps but couldn't bear it any longer (me, not the battery). IR constant at 1.2/1.3 per cell whenever I get to measure it at the same temp and SoC, so I'm not noticing any degradation despite my sadism. They're used in several planes so the previous flight data is a bit trickier to extract with my simpleton logging system, but the 12A x 125 is accurately logged cos it's part of The Great Experiment.

If your hobby was travelling to your flying site, I reckon that'd be a good idea.

What, me? 😇 I did attend the first couple of charges, mainly because I did the soldering... But I normally charge inside a metal filing cabinet in a tiled room in a semi-derelict house (because I spend all my money on damned LiPos!) and that's about as good as it's going to get. I've seen the hideous pics but I've also poked a fully charged LiPo with a sharp stick until it blew up, then assessed what my risk was, several times over the years. It takes a surprising amount of poking and produces a hell of a lot of smoke but I'm not having much success in making them flare up like torches, even when I pierce several cells at once. Many, but by no means all, LiPo fires are down to parallel charging and/or not balancing, so I avoid both of those. Knocking the max voltage back a notch must help a little bit too. I also set timers to cut the charge off after a certain period regardless of charge state, and rubber band together each charge + balance lead from the 4 port chargers so I can't inadvertently cross-wire balance and charge leads across the ports. I have an old outside loo that I dream of converting into my battery emporium! The thing is, if this works as it appears to work, I'm going to have an awful lot of batteries for sale and no need for the emporium.

Yes, I didn't realise I was getting so many cycles, though I'd noticed that I hadn't bought any LiPos for ages. Good job I keep a log! Without it I'd just have to guess, which would be useless as evidence. I'd say it'd make sense for anything 4S or above if you need more than 4 of them. The £285 includes a £55 charger so knock that off if you already have something you can use at the field. For anything using packs in series it's a no brainer. Last summer I was flying 12S and 10S planes on the same day, 6 flights on each, 24 batteries to fettle. It was getting ridiculous!

I have no idea! As Ian Dury once sang... "Don't ask me, I'm an idiot I'm afraid". But it certainly looks like you have the makings of a decent amount of energy storage there. No disadvantage to have fewer in series and more in parallel but a 5S10P configuration would use them all up and maybe even mean you could leave them in those nice holders. Mine's powering a pair of chargers so I thought 24v would hold up a bit better under load. The Li-ion charger just sees it as a massive 6S LiPo for charging (yes, a LiPo not a Li-ion - set with a 4.16v cutoff). Rather amusingly, given how I've been banging on about charging at high C rates, my home charger dribbles out a rather feeble 4A, so I'm recharging the Li-ions at a vertigo-inducing 0.1C Glad it's inspired you. I've been inspired in turn by what everyone else is doing. All these brilliant methods that people have come up with. Seems like the lead acids and the generators can be pensioned off, other than for permanent sites.

That's a cunning plan. It didn't occur to me to go big on mAh and leave them at storage voltage, which would still give many charges due to the mAh "overkill". And a quick charge of a morning if it's going to be a heavy day. Brilliant. Totally gets around the storage charge problem, which my brain was too small to conquer. I love how this thread has brought all these different strategies to light!

I've just had a quick check of my logs (shout out to leccyflyer's current topic!) and the 4 Zippy batts in my 1st post have each had 333 cycles in just one plane (Pilot NG, 1332 flights) in the last 30 months, plus whatever else they've flown on top of that. They've never seen 4.18v. They haven't had much of the 4C charge treatment yet though - all of that has been on the 3300s @ 125 cycles each over the late autumn & winter. When I started in 2015 I used to think I'd be happy if a LiPo lasted 100 cycles. Clearly that requires updating! At the very least, those £40 Zippy packs have done 400 flights each so I'm very happy at 10p per flight (+2p per recharge) - and that's assuming that they've all died today, which they haven't. They appear to be in better condition now than they've ever been. I can't explain it but I'm beginning to think some of the golden rules need updating, or relaxing a little. I think the 4.17v max charge is a lot of it, and the best thing about that is it makes absolutely no difference at all to your flight time, because if you're flying your batts down to the last 0.03v then that's why your batteries are knackered. Does anyone else have an opinion on them only being fully charged for 10 minutes, or is that a red herring? Chemistry was never my strong point but if you took the mantra of "don't leave them charged up" to its logical conclusion, you'd only charge them immediately before use. I didn't really set out with doing that in mind, it's just a by-product of the new routine. But I like it. Two other things occur to me: I like to have at least 6 flights, which meant 6 packs. Then when I started flying 12S it meant 12 packs, which could cost almost as much as the plane. It was a bit like running a care home for batteries too. Now 4 packs get me a whole day at the field flying 12S. If the new routine happens to be a better way of managing them then that's a win-win. We'll see if the high C charge rate kills them but I've done 125 charges on each 3300 pack now, and they had a couple of hundred cycles on them at 1C to begin with... how many cycles do you want for £50? If you do fewer flights of a day then just knock the charge rate back to suit your style of flying. Often there's only Russ & me at the patch so we like to bang out the flights alternately (so we could actually get away with just one/one set of batts, rather than two). If your circumstances only allow one flight an hour then you can do this and still stay at 1C. The extra available speed is there if you need it. I can't explain enough how useless I am at making things, so if anyone is sitting there thinking "It's all well and good for him being able to do that" then think again. I was insanely proud of myself that day. I'm not even very good at assembling ARTFs. I'm quite a good pilot though!

Hopefully showing the fuses... Setup with both chargers. They're so tiny. Pete made up some XT60 to banana sockets so we could use all our existing charging leads (though I notice I've set it up the wrong way round) as none of us had XT60s on anything. Probably a bit heavy to carry comfortably with two packs in one box, though possible. I just bought two boxes and duplicated the system for heavy use days - and having one to lend out has already converted a couple of people.

Russ tried frying one before and it was good for 30 sec. Took about 5 sec per cell but we borrowed an enormous industrial iron that sped things up. I guesss for flight packs they're going to be pushed a lot harder than these ever will be so every weld matters. No planes fall out of the sky if I get mine wrong!

Yes, I knew it'd be the above 1C charging that would split the jury and it's what took me so long to do it, I think. I've got tons of LiPos so I just took an old pair of 6S 4500 and an old pair of 6S 3300 (which are the ones I use most) and spanked the living daylights out of them when charging them up - and continue to do so. Even so, I still find myself staring at the charger thinking, "Am I really going to put 12 amps through this?" because old habits die hard. I still charge at 1C at home, don't ask me why because I don't know any more. I thought I knew but it turned out that I didn't. I mean, I cannot deny what is staring me in the face, no matter how much I read up on it. I don't want it to work either, because it's challenged my knowledge and I like the comfort of what I know not having to change! Can you set one LiPo aside to try it out? IMHO it's charging them over 4.16 or 4.17 that kills them (Phil Lewis posted a table somewhere that blew my mind - can you post it here please Phil?). Or draining every last volt out of them. Stay between 4.16 and 3.80 and it appears that they last forever. Maybe it's also something to do with the the fact that they're only having to hold a full charge for 10 minutes before they're back down to 3.80 again, rather than overnight? I don't know, but whatever test I throw at those batts they just smile back at me. I do have good throttle management but I also fly big aerobatics, so they're always being 'gently pushed'. And don't forget that the spec on these batteries is a 5C charge and, unlike the discharge C rate nonsense, I actually believe it may well be somewhere around there. Rest assured that the moment I find out otherwise I'll let you know!

Looks like you got there over a decade before me! That's a work of art. It's very good to know others are out there doing this stuff too. Will check out LiFePo4 as they're not on my radar usually

It was the LG M50LT 21700 that I ended up using. 144 of them inc VAT and delivery cost £508.10 (Aug 2023), which made up the three packs. Stupidly, I didn't order any spares but every single cell was at 3.55v on arrival, not even 0.01v variation, let alone any dead ones. Cell Supply do much better prices wholesale, so buy over 50 cells if you can. The fuses are lorry fuses at 40A just wired inline between battery and the XT90 sockets on the side of the case to prevent anything going bang. Probably OTT but why not? Pics to follow.

PeterF - yes I nearly jumped in with those huge Multistar LiPos and that's a really good price for all those mAhs! However, it was still a LiPo fuelling a LiPo, so I was still caught in the discharge cycle and having to second guess if tomorrow would be a good flying day. Substituting Li-ions for LiPos was the final piece of the jigsaw, as it means they can stay permanently charged (they settle down to about 4.16), seemingly without issue**, so are always ready to go. That was the bit that changed the way I went flying because it's much more like having an IC plane (or "one of the very few advantages of having an IC plane", but let's not go there...) You must have some absolutely MASSIVE planes! **mine are new. I'm going on Russ's version using the 18650 cells (all 120 of 'em) which is now 4 years old, so roughly 3000-3500 LiPos charged with that box.

Phil - yes they're car fuses. Can't remember their rating. I'll take some more pics soon.

That's fantastic to get 12 years out of your batteries! I have a feeling this was a good idea.

Hi Phil That's exactly how I tend to use it - pre-load a couple of LiPos at home and charge the rest at the field. I was at the point of needing to buy a new load of LiPos and figured that it was a good time to jump in and try it. Russ just quietly gets on with it but I think it should be shouted from the rooftops, especially to the heavy users out there. Wish I'd had it when I was flying F3A. However, using LiPo packs as the source isn't a good idea. All that discharging to storage milarkey partially defeats the objective. The whole point of this setup is to have it charged and ready to go at all times, which needs a more considerate cell supplying it! Wake up, look out of window, go flying.

I made two boxes for myself because I live in a field and have to walk 300m to my car for about 5 months of the year, so being able to carry my plane + batteries + everything else I need in one trip was important. So one box in the winter when I'm walking, two boxes in the summer when I can get my car to the house. I haven't weighed it but it's nowhere near the weight of a lead acid. Each cell is approx 68g and the packs I made have 48 cells in them, so 3.3kg plus the case, chargers & LiPos. Maybe 5kg all up? I charge all sorts of LiPos with it. Fellow fliers at the patch are beginning to realise that they don't need to go home when they're out of batteries, as I seldom use all the electrons up. The chargers will charge anything you have the leads for! As I said, I never used to charge at above 1C. Never. It was one of my golden rules and I've only ever flown electric. Then Russ asked me why not, and because I'd never gone there, all I could say was "...because I read that you shouldn't." But the empirical evidence was right in front of me and increasingly hard to ignore. Hundreds and hundreds and hundreds of cycles on the same batteries, all being charged at 3C or above. Nothing going pop or boom or even puff. The Zippys in the pics have over 400 cycles on them and you can still put a ruler down the side. I simply ran out of reasons why I shouldn't do it because there weren't really any there to begin with, other than "I'm scared" (which I was). Caveat: use batteries that can be charged at above 1C. They cost a little more but not much really if you put any value on your time or their longevity - and 40C Zippys and 60C Turnigys aren't exactly posh, daft-money batteries. For me, a good portion of the reason for doing it falls apart if you're going to wait an hour per recharge, though if that works for you then that's all that matters. Well worth recycling the bike batteries to have a go cost-free and see if it suits you too. It's a different routine and takes a while to bed in, but I wouldn't go back now.

https://www.cellsupply.co.uk/21700-batteries

My friend Russ put one of these together in 2019 and it's still going strong today. The moment I saw it I knew it was the solution. It only took me four years to get around to making mine. I fly aerobatic electric models up to 6000W/50cc size, so I've bought more than my fair share of LiPos over the years. There had to be a better way - and there is. It's a 40,000mAh (just scale it to suit your needs) Li-Ion pack at 24v connected to one or two ISDT 20A chargers, to allow a pair of 6S 5000mAh LiPo packs to be charged simultaneously at 4C, all housed in a Screw-fix metal carry case. For a single charger system it cost £285 including various delivery charges but not including my time. Each pack took about 2 hours to solder up, with about the same again to sort out the cases & wiring. I should note here that I'm a known incompetent relating to all building matters, so Russ supervised me and very kindly finished off the wiring and cases when I fell over exhausted at the end of the day due to inhalation of too many solder fumes. I made three packs in all - two for me and one for my mate Pete. Final pic is the 12S flying day version but usually it's just one charger and a pair of LiPos for 6S flying. I'll try and get some better pics of how it's wired in the box. There be fuses. I've got the component list knocking around somewhere if anybody wants to make one. It doesn't take much to spend £285 on LiPos, and the advantages are huge: you can leave it charged up all the time and it doesn't complain. This totally changes how you go about flying. Charge the box as soon as you get home, leave the LiPos at storage charge at the field (I generally land at 3.75). The Li-Ions will last forever because they're barely breaking a sweat - Russ built a 2nd box a year ago and can't tell which one he's using. So you can go flying at the drop of a hat, and leave all the decisions about which plane you're going to fly until the minute before you leave the house. No more "Oh if I knew the weather was going to be like this I'd have charged those other batteries." It's like having a can of petrol, only less smelly. And the bit I was nervous about - the high C rate charging - has proved to be worry free. At the moment I'm flying 6S 3300mAh Heavy Duty Turnigy packs and charging them at 12A, which takes about 10 minutes. I cap my flights at 7mins30 so you can pretty much fly non-stop if you don't mind being a patch-hog. Previously I've always, always, always charged at 1C or below, like I was a member of some death-cult, but I'm 250 charges in and I see no performance issues or increasing internal resistance - the Zippy 4500s hover around 0.9 and the Turnigys around 1.3 per cell. Happy batteries - and they had a couple of hundred cycles on them pre-chargebox. Only charging to 4.17 makes an amazing difference to battery life. That Phil Lewis knows his onions. I've been using this for 4 months now and waited to see how things turned out before posting. I can honestly say that, for me, there is no other way of going about electric flight. Just my two 4 port chargers would have paid for this box, let alone the dozens of LiPos. This is the first topic I've started so please excuse the mess. Long time lurker. Thought I'd contribute for once. Oh... and definitely use the balsa sticks to assemble the initial cells all nice and tidy. The masking tape was like herding cats.

A pilot log and a plane log - both just ultra simple Notepad affairs - date/time/club/weather, then plane/flight #/duration/anything interesting. Usually about 2 mins of cut and paste with another minute of updating. I taught myself to fly so would write down what I wanted to achieve pre-flight and then fill in the day's successes and failures when I got home. It grew from there but has been stripped back to basics since, though I do note when I'm learning new manoeuvres (which is lots) or any maintenence. Wishing that I'd put it all in a spreadsheet but it's probably too late now. Some of the stats are interesting - who knew that December is consistently a better flying month than June; or that spring, summer and autumn average out to be minutes apart from each other, with winter not nearly as far behind as you might think? I was going to do a log for batteries too but didn't bother in the end. I'm now recharging at the field with my Li-ion briefcase masterpiece, so only need two Lipos anyway. Really interesting to see what everyone else is doing.