MattyB

Posted by Robby Mcgee on 30/07/2017 15:45:20: Cuban8 my batteries are 25c so is my math correct it should maintain 16 amps. And can I test with 2 multimeters at same time? If the C-rating they gave the pack were true it could provide 12.5A, but as has been observed above achieving the rated C value is almost never possible nor recommended - most advertised C-ratings are wildly optimistic. On a pack of that capacity I would be surprised if a real world C-rating of more than 10 were achievable. I know I am known here for nannying my batteries and analysing facts and data about them to ensure they perform at their best for the longest period of time, but when it comes to tiny single cell lipos I've come to the conclusion they are simply disposable items. No amount of care seems to help - many seem to die early despite being treated within their C ratings, in-line with the instructions and not over-discharged. I can only assume it is harder to make these small packs to the desired levels of QC because of their small physical size, hence their high levels of failure. Whatever it is though, I wouldn't get too bogged down in analysis at this point - just buy some more batteries and I am certain it will fix your problem. Edited By MattyB on 31/07/2017 10:27:59

Posted by Braddock, VC on 29/07/2017 17:48:58: If it's not a regular flier why not leave it as it is. Personally I wouldn't play with electrics. Super helpful response . The OP does want to convert it, so your personal preference is irrelevant; it's his model after all!

100W/lb will be fine on something like this; 80W/lb would be ok for scale type performance. You may want to consider working around an 8S setup with a lower kv motor so you can use your 4S packs in series and to reduce the current required (meaning a cheaper and lighter ESC can be used). HV setups in larger models like this tend to be more efficient than dragging more current out of a lower cell count pack. Edited By MattyB on 29/07/2017 15:46:08

1/10C? For old school nicads maybe, but not Lipos, LiFes or even modern NiMHs! Us sparkles wouldn't get much flying in if we could only field charge at that rate... Edited By MattyB on 28/07/2017 21:06:10

On the subject of charge rates I have tried a few somewhat quick scientific experiments and found that all my current packs can be charged at 2C without any significant warming occurring. Since heat has a major part to play in battery degradation this is good news. Above 2C there is some variance between packs and sizes - smaller packscseem to warm more than bigger ones, whilst my newest Graphene batteries charge cooler than all my older packs from Gens Ace and HK of similar capacity (not surprising given their very low IR. What does all this mean? Probably not a huge amount - you'd need a much bigger sample size and more accurate temp measurement along with IR and capacity checks throughout the pack life to draw truly valid conclusions. I am comfortable that the current generation of cells can all be charged at 2C every time though with no meaningful impact on cell life, capacity or IR; above that an YMMV dependant on brand, pack construction and plain old luck! Edited By MattyB on 28/07/2017 19:53:26

Posted by og on 28/07/2017 18:02:22: just reading on another forum about a guy who charges his 6s 4000mah in 10 mins at the field using 10-15 amps - surely thats not possible or safe If he can charge a 4000mah in 10 mins at 10-15A forget the safety concerns - he's broken the laws of physics. Is he a time lord by any chance?!!

Intriguingly it appears this thread has driven down the price at Reds, which is now £334 - yesterday I am sure it was £385-390! Anything you want to tell us Thomas?

Posted by Marcol on 24/07/2017 08:02:21: Spitfire arrived on Saturday , all perfect thanks to the packing from Raymond at RC Castle. Looks really good apart from the undersized pilot. I don't understand why all the warbirds have to have a pilot that is obviously too small for the scale of the aircraft . Cost delivered to my door , including shipping and import duty was £367.38 ! Interesting - that is a fair bit cheaper than Reds RC can get them in at by the time P&P is factored in... Posted by tigerman on 26/07/2017 12:47:45: This spitfire looks really a must have model .One question ,can you get spare parts for it and where is the best place to buy one? Reds RC are the only UK distributor I believe, though whether they will carry spares and for how long I don't know.   Edited By MattyB on 26/07/2017 14:52:11

Posted by brokenenglish on 26/07/2017 13:41:33:. My main interest has always been ic flying, and I just don't want to get involved in wiring up circuits, etc., unless it's for a spark ignition engine! If you want a plug and play solution one of these units will do the job for packs up to 6S and save wear and tear on your charger (discharging a lot of packs on your charger is not a great idea, as the charger itself has to dissipate that energy as heat, causing additional wear to the fan). When you're not using it for making dead batteries ready for disposal it can be used to return any undischarged packs back to storage voltage, helping to lengthen their life and retain capacity and reduce the rate IR (internal resistance) increases. Edited By MattyB on 26/07/2017 14:46:26

Posted by trebor on 22/07/2017 19:52:26: Thanks, I hoped there was a magic way to do it on the tx. Wishfull thinking, I plumped for freeing up a spare channel so I could adjust it in the field. Now all I have to do is figure out how to program the Frsky tx I've done this on Spektrum before but I feel a headache coming on. Diff in OpenTX is easy to set as a variable in the mixer line, but there is a subtlety to be understood around the order it is applied in relation to the trim offset. Luckily Mike Shellim has authored an excellent guide to help you out... Edited By MattyB on 22/07/2017 22:08:23

OP, forget rpm for now; what is your target pitch speed (the max speed of the airflow coming off the prop)? To calculate tell us the max speed you are looking to attain under power, then add 20-25%. Once we have that we can work out the rest more easily.

Posted by simon burch on 04/07/2017 23:39:40: Li-po are Lithium polymer, not Lithium Ion... Simon Not according to Wikipedia or Battery University... "A lithium polymer battery, or more correctly lithium-ion polymer battery (abbreviated variously as LiPo, LIP, Li-poly and others), is a rechargeable battery of lithium-ion technology using a polymer electrolyte instead of the more common liquid electrolyte. High conductivity semisolid (gel) polymers form the electrolyte for LiPo cells that are being used in tablet computers and many cellular telephone handsets." "To make the modern Li-polymer battery conductive at room temperature, gelled electrolyte has been added. Most Li-ion polymer cells today incorporate a micro porous separator with some moisture. Li-polymer can be built on many systems, the likes of Li-cobalt, NMC, Li-phosphate and Li-manganese, and is not considered a unique battery chemistry. The majority of Li-polymer packs are cobalt based; other active material may also be added. With gelled electrolyte added, what is the difference between a normal Li ion and Li ion polymer? As far as the user is concerned, lithium polymer is essentially the same as lithium-ion. Both systems use identical cathode and anode material and contain a similar amount of electrolyte." Edited By MattyB on 06/07/2017 15:51:55

Lipos are Lithium-ion packs. Do you mean LiFe (Lithium Iron)? Confusingly they are Lithium-ion too! I admit I have not used LiFes as power packs so don't know a huge amount about them, but from what I understand they are much more resilient to storage at elevated SOC. Having said that one of my cheapo HK LiFe soft RX packs swelled and died within 6 months of purchase, though I suspect that is much more likely to be a QC issue (my others have been fine). Edited By MattyB on 04/07/2017 17:06:51

The yanks seem to manage it just fine!

Posted by Jon Harper - Laser Engines on 04/07/2017 15:22:35: Morris is also not a competitor and is a nice bloke to deal with. I have spoken with him on the phone, serviced his 200v (running on glow) and shot the breeze about all things engine. He is even eager to try one of our petrol engines once i have a production spec version ready. There are no issues there, i never even mentioned his customer service, but his current products do not work on our engines, are not recommended and i am yet to see a conversion from anyone that really works well which is why i have nothing nice to say. Its nothing against him personally, just the whole idea that slapping a cdi unit and walbro carb on any engine you can find makes it into the perfect petrol. Its simply not the case and if you check the FAQ section of the Laser website you will see that i say the same things there as i do here. Some engines respond better than others, and ours do not work at all when converted in this way. ...except that we and many others have converted them, and they work just fine, as good if not better than the competition from Saito. I am quite sure you have forgotten more about engines than I will ever know, but it seems somewhat strange you are prepared to comment on the reliability and performance of a converted engine you have not seen since it left the factory. Posted by Jon Harper - Laser Engines on 04/07/2017 15:22:35: I have never rubbished a competitors product but make no secret of the fact that i think i can do better with my own engine. And you can complain about it not being finished yet but perhaps i should sell every idea that comes into my head and let the customers do the R&D at the expense of their models? Not a good alternative really is it and not something i am prepared to do. If i wasn't the only person here that might speed things up too. I also wasn't aware my development work was 'much plugged'. I have posted updates on the development progress, but why would i plug something i cant sell? People were interested/excited by the prospect and wanted updates. I post them as and when i have something to tell them. Oh and dont tell me where i need to put my energies. You simply have no idea what you are talking about in this regard and i am well aware of what needs to be done and the time pressures involved. We are years behind where we should be and i am trying all i can to catch up. It is nothing personal, ultimately the market will decide. Your potential customers have been telling you in multiple threads the 180 is already a killer product, but it remains unobtainable so they are instead converting engines or buying from your competitors. Meanwhile the huge majority of modellers under 40 who fly IC are using petrol engines, whether you like them or not. I am sure Laser can do well in the short term churning out glows, but that market must be limited in the medium to long term as the baby boomers leave modelling over the next decade. Posted by Jon Harper - Laser Engines on 04/07/2017 15:22:35: Anyway my original post was purely intended to assist another modeller and make sure he has all the information he needs before deciding where to spend his money. As an engine designer and manufacturer there is a chance i know more about it than the chap asking the question so thought i would caution him so he didnt waste his money and make sure he does sufficient research before proceeding. Your first post in this thread was helpful to the OP, but I fail to see how the second ("You wont hear nice things from me!" ) gave him any great insights into the subject of petrol conversions. Edited By MattyB on 04/07/2017 15:48:12 Edited By MattyB on 04/07/2017 15:51:04

Posted by The Wright Stuff on 04/07/2017 15:05:56: But when we're talking about small number statistics, personal experience is not sufficient to get insight. It's like saying: "Last week I bought a lottery ticket but didn't win the lottery, and the week before, I didn't buy a lottery ticket and didn't win the lottery. Therefore buying a ticket makes no difference to my chances of winning the lottery" Yep, completely agree. Personal experiences area extremely unreliable measure when it comes to battery performance simply because the way they are used and stored is hugely impactful on their life and performance. Anyone who says "these packs are great, but those are rubbish" Posted by The Wright Stuff on 04/07/2017 15:05:56: If there is any way I can store LiPos in a manner that means an already vanishingly small probability of spontaneous combustion is turned into an even smaller risk, then I'll take it. I only have 3S up to 3300 mAh. I don't really care about the battery life. To be honest, I don't really even care about my models all that much. I do care about my house, my life, my wife and baby daughter... Yes, that is the key point here - if you want the safest option you MUST store at lower voltages to reduce the available energy in the event of a fire. At 3.7V/cell there is next to no energy left in the pack and you could quite put a nail through it with only a mild fizzing the result; try that with a fully charged pack and you will get a very different result.

There is lots of info online if you do a quick Google... Quick extract from the first thread I found: "The motor is one that I believe my LHS got from BP, used with a TBird9 ESC. I believe this is the motor: http://www.bphobbies.com/view.asp?id...7&pid=B2552589 I used them in my Guillows DC3 with good performance on 3s, with tiny Thimble Drome 5x3 props on 3s. Seem to be reasonably powerful for the weight/size/price." You may also want to look at a higher Kv motor and/or bigger prop on 2S. I have my old HK Spad flying very nicely on the stock 2S bell motor once I'd put it on a diet to get it to just over 400g - that thread is here... Edited By MattyB on 04/07/2017 15:00:06

Posted by Jon Harper - Laser Engines on 04/07/2017 11:23:16: Posted by stu knowles on 04/07/2017 11:12:37: Morris mini motors https://www.morrisminimotors.com/conversion-kits/super-tiger-conversion-kits.html​ I haven't used or indeed seen one but I hear nice things. You wont hear nice things from me! Attacking someone whom you presumably see as a competitor on a public forum is pretty low. Perhaps investing your energies in getting the much plugged but still unobtainium Laser petrol engines to market might be a better idea? That is after all the main reason people convert your engines with aftermarket kits... You may not think much of Morris' or JE's conversions, but in our experience they throttle and run at least as good if not better than the "proper" petrol four strokes from the likes of Saito or NGH (not hugely surprising given many of those were not designed from the ground up as gassers). Constantly rubbishing conversions as "not as good as a Laser" is academic given petrol Lasers are not available to buy at this time. In addition whenever we have dealt with both Morris and JE they have exhibited exemplary customer service - Morris travelled >200 miles for free to troubleshoot a crash damaged Saito gasser for a friend of my Dad's that had been recalcitrant following repair. All sorted with a smile, he is a genuine enthusiast who shares his knowledge readily with others, and every time we have interacted with JE it has been a similarly positive experience. And as an added bonus they do not post on here rubbishing their competitors either... Edited By MattyB on 04/07/2017 14:30:37

Posted by Bill_B on 04/07/2017 11:45:43: Just out of curiosity I wonder what brand and capacity the batteries were that failed in the OP? Probably more important what was the age and usage pattern. Had these cells been consistently stored at full charge for long periods?

Posted by The Wright Stuff on 04/07/2017 08:00:38: Posted by MattyB on 03/07/2017 18:12:05: The only possible provocation must be temperature change, surely? No, not necessarily. Whilst extremely rare lipos can internally short due to dendrite growth - if the dendrites get long enough the anode and cathode meet. This normally requires long term storage of the pack at elevated (>4V/cell) voltages throughout the life of the pack, though. Another good reason for storing them at storage (~3.7-3.8V/cell) voltage! Thanks Matty - we can rely on you to provide a detailed and balanced explanation! Out of interest, how does the risk profile look when storing cells below storage charge (e.g. 20%-30%)? I realise this is bad for the cells for other reasons, but does the risk of dendrite growth continue to go down, or does it start to climb again? It is only bad if the cells self discharge down to a voltage where they would be damaged (generally considered to be 3-3.2V/cell). Self discharge is normally very slow with lipos though, so providing you are using your batteries reasonably regularly (say once a month) it should not be an issue to store them at ~3.6V/cell. However, whislt there is plenty of evidence that storing at an elevated SOC increases the rate at which capacity reduces and IR increases, I've not seen anything that scientifically describes the benefits of storing below 3.7V/cell. I think there are probably other factors that would dominate over a tiny reduction in storage voltage (i.e. variable QC in the manufacturing process and usage patterns for two), so my recommendation would be to store at 3.7-3.8V/cell unless flying again within 48 hrs and feel safe in the knowledge your packs have the best chance of a long and happy life!

Posted by ChrisB on 03/07/2017 09:01:52: Posted by John Bisset on 02/07/2017 22:33:05: Ouch. What does your friend think started it? I use a stainless steel box about 30cm eachs ide (old surplus item), with the Lipo bag inside. I wondered if that was OTT - I think I've decided it is not. John No, he doesn't know. None of them were puffed and he'd left them as they were, without any checking of capacity/charge. I think a lipo bag inside a box is a good idea! Ideally each lipo should be individual such that is can't spread to its neighbour but that's not realistic when you have more than ten or a dozen. Posted by The Wright Stuff on 03/07/2017 09:13:21: That's the aspect that concerns me most. If we believe it to be literally true, then why did the fire occur then (and not earlier or later)? What changed? The only possible provocation must be temperature change, surely? No, not necessarily. Whilst extremely rare lipos can internally short due to dendrite growth - if the dendrites get long enough the anode and cathode meet. This normally requires long term storage of the pack at elevated (>4V/cell) voltages throughout the life of the pack, though. Another good reason for storing them at storage (~3.7-3.8V/cell) voltage! Edited By MattyB on 03/07/2017 18:26:42

You could also try a power off dive test to check CG...

Agreed, this forum template is rather antiquated; with ever increasing numbers using phones and tablets as their primary browsing device I think it's overdue a refresh.

Just found this review. Some interesting caveats in post 1... "Notes for impatient people! - Do NOT run the stock ESC with 3s. It WILL burn! - This is NOT a beginner plane! it is extremely stable in calm air, but does not take crashes particularly well in its stock form! - If you want the plane, buy it as a kit. The stock ESC is rubbish, the prop, and servos are rubbish."

There's a thread on RCGroups... looks like it might be rather bendy, but the reviews seem good as long as you go either separate aileron servos. Super cheap too!