Chris Bott - Moderator

Tom, must be my age, I can't remember. I think you may well notice a slight improvement in performance as they warm at the start of the flight. But you may also notice less warming than is evident in your LiPo's

Thanks Tom, that will be very interesting. I assume that is the FMA Cellpro 10S ?

I have to agree for smaller models. My smaller 3S models have been disappointing on A123's. The extra weight and bulk has just been too much. My fellow club members Multiplex Mentor has been extremely successful on 4S A123 from Puffin. That is likely to be the lower size/power where they start to come into their own.

Good luck Tom, let us know how it goes. If it works well, and I'm sure it will, your long term view of their lifetime cost will be interesting. That will take a long time mind you!

Hi Timbo, you didn't expect to say forget the LiFePO4 stuff and not get a reply from me did you? I believe there is definitely an argument for using A123 at the budget end. Particularly with the Calamato Sport sized models. Depends how you want to go, you pays your money and makes your choice as they say. A 6S A123 pack at around £60 will fly it extremely well. More importantly it will last a long time, pretty much no matter what you do to it. If you want a few packs and not to charge at the field, then LiPo's are going to be quite a bit cheaper. But however I look after them, they need replacing over and over compared to the err.. life of a LiFe

Kris there are many other chargers available at many prices from UK outlets like Giantcod, Foamyjets, BRC, RCMDirect etc. There's also a good range available from Hobbycity in China. The thing to look for is a LiFe option, and then the power rating, which will tell you how fast it can charge your required cellcount.

Jack have a look at A123systems.com and about A123 batteries Cheers Chris

John, Futaba, JR, Multiplex, Sanwa and Spektrum radio all come with made up nicad/nimh packs, but as you say its not worth getting into a spin about   In the summer I recommended an A123 electric setup for a lifelong IC flyer and he has been chuffed to bits with it ever since. He had already bought a Multiplex Mentor model which is designed for 3S 3200 LiPo. For it I recommended the following:- From www.hobbycity.com  TR 35-48-B 900kv Brushless Outrunner TURNIGY Plush 60amp Speed Controller TURNIGY BESC Programming Card (Not essential but makes ESC programming much easier) Turnigy Accucel-6 Balance Charger & Discharger (only charges at up to 5A so not the fastest A123 charger available) HXT UBEC 5/6v output, 5.5~23v Input (UBEC to supply receiver voltage from the flight battery) Female Polyquest - Male JST 4S (adapter balance cable for balance charging) and From http://www.puffinmodels.com/ 4S A123 pack. x 2 (which fitted this models battery tray perfectly). NOTE: John Emms at Puffin is always very helpful to recommend setups for any particular model.

Yes John they do look like them, but the technology is very different. You are quite right not to trust battery holders, especially in airborne packs. This is in line with BMFA advice too. I'm sure most radio makes come with welded or soldered up packs though..

John A123's are just another type of battery. That I prefer 'cos they are easier to look after. See here http://www.puffinmodels.com/category.php?dept=265

Tim After a couple of years of using them, I find myself using LiPos for smaller models and A123's for 40 size and above. This is because they do weigh more, and are a bit bulkier. But there are so many advantages, its certainly worth having a go. Remember that for the quick charge times you need a charger with an A123 setting that has a high power rating. Best of luck, let us know how you get on. Chris

Hi John My "Wombaling" tends to take three different forms: 1. I turn up at the field with a plane, 4 LiPos and a Transmitter. Have a natter, 4 flights a natter and go home. 2. I turn up with a 6S A123 equipped 40 sized model, a leisure battery, charger and transmitter. Fly for 10 mins, and then charge for 10 mins while I have a natter and keep this up for the whole afternoon. 3. I turn up with a 6S A123 equipped 40 sized model & 1 spare battery, a leisure battery, charger and transmitter. Fly for 10 mins, swap batteries and fly while I charge for 10 mins and keep this up for the whole afternoon. Of course there can be any combination of the above with more than one plane too.. Well thats the theory, I often contrive to break something or "land" at an odd attitude, but I guess we all do that from time to time.

Tom Have you done any more tests with these batteries? I've actually had some go end of life now, but that's after over 2 years of very hard abuse. see http://www.modelflying.co.uk/forum/forummessages/mps/dt/4/UTN/4983/last/1/V/6/SP/332397698539340417482 The ones that have died are the two that I had to solder directly to after the tabs were ripped off in a crash. I think the soldering is probably significant in their demise.

Hi Kris Any more thoughts on getting some A123's yet?

John I don't know your plane sorry, but I fly lots of 40 sized models on 6S A123 batteries. These differ from LiPo's in that they are almost indestructible, entirely safe, are very long lasting and can be charged in 10 minutes. Full power lasts right to the end of the flight, they even run out almost instantly - just like I/C. They are a little heavier than similar LiPos, but you can use every last drop, unlike Lipo's Have a look on the forum for other threads on A123

A nice chap called Allan Bowker made us a great video of the event too. I'll try to put it here, but if that doesn't work I'll leave a link.

Thanks Timbo Where has everyone been? Is it me or has this forum been quiet? I guess, like me, everyone actually has other stuff to do from time to time

Phil Have a word with Mike Woodhouse at freeflight supplies He does a mylar film they use for covering lightweight freeflight models. Various thicknesses, and it comes clear or aluminised. The aluminised looks just like chrome, very very shiny. You need something on the balsa like balsaloc and then it irons on and shrinks tight. And its much lighter than Solarfilm. Mike should help you with which weight to use and techniques. I once used the lightest under tissue, it strenghened everything for punch resistance and it was possible to use complex colour patterns in the tissue.  I beleive the aluminised is actually the material used by the RAF as "window" in a cloud of shreds to draw a radar guided missile away.. Note: it may block RF so your aerial will have to be outside. But this will go for any metallic finnish.

Kris that is a lot of current! Whilst I have pulled 120A from A123's it was only a bench test and I didn't leave it running long. You may manage that with 2P, but at these currents A123 voltage sags considerably (which controls current). 120A is 40C and even if they would hold up at that throughout, its only 1.5 mins of power. You don't happen to be near South Staffs/West Midlands do you? You could possibly have a go with a 6S of mine..

I think we are going to settle for longer charge times, we each take a large 12V battery to the field, but 400W is a lot to ask from that. I do have 2 chargers that will do 6S. But if we fly in turns and have a natter in between, the models are soon ready. And I sometimes fly a smaller model in between too. If you are confident in your figures and are happy to experiment and measure volts and amps, there is another charger option FOR 6S ONLY. Maplin sometimes have these on offer at £15. http://www.maplin.co.uk/Module.aspx?ModuleNo=44736 or try ebay etc. Take the case off to allow better cooling and they do a pretty good fast charge at the 22V setting. Current actually settles at around 9A and drops off as the battery approaches final voltage. You may wish to monitor the charge manually until you have confidence. Usual disclaimers apply, this is not what the item is designed for.

You are absolutely right on all counts I have a rough rule of thumb of 100W/cell, that seems to give a good duration in many types of model. Danny and I have 90 Sized Sea Furys (see other threads) We have 8S in these giving 1100-1200W and flights are a little disappointing at 7mins or less. (proving the rule) So we are trying to find a way to increase duration without going 8S2P (which will be heavy and take longer to charge) The only way is with more cells, so we want to try 12. That means 12S and a new low Kv motor. Or we are hoping 6S2P will do the job, just by using a bigger prop. Luckily Danny has a slightly higher KV motor too, so we'll be experimenting soon.

Kris Sounds like you've hit the nail on the head. I can get more capacity for the same weight by using LiPo's but got fed up of having to treat LiPo's with kid gloves, power dropping off through the flight, capacity reductions and short life etc etc. I still use them for smaller models. Are you sure the Bandit and Katana will carry the weight? 6S A123 is a lot heavier than 4S LiPo's. I'm afraid I don't know the models, but would be very interested to know. Cheers Chris

Hi Kris I'd try with 6S1P to start with and see how you get on. To charge at 400W at the field takes a huge leisure car battery. Lighter means less power used etc etc... Chargers with an A123 program are quite prevalent these days. Try Hobbycity, Giantcod, Foamyjets, BRC, Puffin and many others. As you've already spotted, the main features to look for are an A123 setting and the power of the charging circuit. I believe that there is a chip available for the 109 to make it an A123 charger. Or there's a mod here (untried by us as we don't have an Astro). http://www.rcgroups.com/forums/showthread.php?t=602445 I would think the Sebart Angel would go well on 6S. Depending on yr flying style, you could eek out the duration. Don't forget that you get full power with A123's right to the last drop. Then they drop off very very quickly. So you can always use 2300mAh. Just don't be prop hanging by the ground right at the end of the flight. Use the power in bursts, (you can prop for lots of power) and cruise sometimes conserving the battery. Conserve energy between manouvres and you'll be surprised at the duration.

Hi Stephen  I'm afraid the answer is no. Lipo's need charging to a terminal voltage of 4.2V/cell LiIon's should be charged to slightly less, I believe 4.1V/cell, but don't quote me I haven't looked that up. A123's need charging to a terminal voltage of 3.6V/cell  and this is a setting appearing on more and more chargers. They need a balance every now and again, but again, this needs a balancer set to 3.6v/cell rather than the LiPo or LiIon equivalents. To answer your last question, yoyur maths is correct, it would take an hour at that rate, or probably more. As with all these types, charge rate drops off towards the end of charge, elongating the charge time.  We charge at 10A wich means it takes 10-20 minutes.  Note: For bigger cell counts, this requires a hefty supply battery for the charger!

Stephen Great choice, you'll enjoy this one. The motor is just right on 8S A123's It's extra weight meant it could be mounted right on the bulkhead without spacers and the cowl could be shortened to a scale like length. We always use APC Electric props, they are just big ones! Danny is yr scotchbriet and paint man, I'm sure he didn't prime, but he did scuff every nook and cranny with the scotchbrite. PS if you want to write a post first and paste it here, use notepad, it copies and pastes better. Good luck with the model