David Ashby - Moderator Posted June 30, 2008 Share Posted June 30, 2008 Hi John, good choice there! Ok, you can discharge at .8 that should be fine. The min voltage will be no less than 2.5v or perhaps a bit more. Having said all that - I don't cycle Li-Po's. Tim may correct me but I can't see the point. Just charge and go, then re-charge. Cycle your NiMH's if you like .......The set-up should look like this (sorry - just reproducing the set-up on my floor!) The balancer lead goes to the JST-XH converter and the Li-PO plugs into this while the charge lease go into the batteries JST orange plug. Hope that helps? Quote Link to comment Share on other sites More sharing options...
JohnnyB Posted June 30, 2008 Share Posted June 30, 2008 Hi David,Thanks so much for such a quick reply, especially as you also went to the trouble of showing me the complete set-up to boot. Brilliant.But, even after several tries at charging and discharging, whenever I press the start button, all I get is - "battery check, wait please....." followed by - " ERROR, contact break." This is really annoying as all the conections seem OK as they will actually only connect in a particular way.Starting to sound as if I've got a duffer piece of kit........Thanks again David.John. Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted June 30, 2008 Share Posted June 30, 2008 John, you have got the main batt lead plugged in as well as the balancer plug right?Can you post a piccy of your set-up? Quote Link to comment Share on other sites More sharing options...
JohnnyB Posted June 30, 2008 Share Posted June 30, 2008 David, I've got the balancer connected up to the charger and the white charge battery connector to the balancer socket. The red power plug on the battery is free, ie. not connected to anything. Does this sound right to you.Cheers,John. Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted June 30, 2008 Share Posted June 30, 2008 Ahhh.....You're doing it different to me as you're using a separate balancer right? rather than use the chargers in-built balancer? So it sounds like you're not pressing a button on your balancer to get things going? What balancer are you using ? Quote Link to comment Share on other sites More sharing options...
JohnnyB Posted June 30, 2008 Share Posted June 30, 2008 David, No, I am using the chargers own balancer, but is that JUST A BALANCER and NOT actually a charge circuit as well?Looking even closer at your set up, it actually appears that you have an additional cable, not supplied with the charger, connected to the banana outputs and the red power plug of the battery. The one that actually powers the Medevac.If this is the case, then it means that I've got to buy an additional cable with banana connectors at one end, and a male battery connector (JST) at the other??This is my very first attempt at using a balancer/charger and I just assumed that the output from the charger connected to the adapter board was a charge/balancer COMBINED. I thought that the banana output sockets were for direct charging only and for use without a balancer. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 30, 2008 Author Share Posted June 30, 2008 Right first off C rates and stuff.The C rate of a LIpo generally refers to its discharge capability, and is simply the capacity X the C number - so if your battery is 800m/ah and the battery pack states on it somewhere that it is for instance 10C then you can dischage ( IE "use" ) it at 10 X 800 = 8000m/ahr ....which is 8amps. Charging should only ever be done ( with or without balancer ) at 1 x C ...again , in your case, 1x 800 ma so chage it at .8A IF YOUR CHRGER LETS YOU.If not, then try .5A as its OK to charge at lower than 1C but never higher. Most ( in fact nearly all ) chargers require you to connect the main battery pack leads to the charger output even if you have a balancer connected as well.Exactly what charger / charge-balancer are you using John? Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted June 30, 2008 Share Posted June 30, 2008 John, you need one of these The balancer connector only does that on the Graupner's (and many others) so you always need to hook up the main pos/neg leads too. These leads only cost a few quid from model shops. Get some of these or make up your own and you'll be ok. Quote Link to comment Share on other sites More sharing options...
JohnnyB Posted June 30, 2008 Share Posted June 30, 2008 Hi Timbo,Thankyou for your reply.This electrickery is really fascinating to me and I really want to master it all. Today has proved to be a GIANT step forward as now, with the help of David, I have just discharged the Medevac Lipo, and then programmed it to re - charge at .8mAh. I'm completely flushed with a sense of success..!! Yahoooo.David says he does'nt cycle lipo's - just charges and goes. I probably won't bother discharging the Medevac lipo's in future as they get pretty much discharged while flying, BUT, surely they need to be balanced regularly for optimum performance??The charger that I bought is the Graupner Ultramat 16, and actually only bought it yesterday while at Wings and Wheels. Reading the instruction book this morning, actually phased me completely at first, as you can see from the writings above.It seems to me though, that quite alot of different charging cables are required with banana's at one end and various plugs at the other - to suit the various battery connections...!! These do not seem to be on general sale, so presumably I've got to develope yet another skill - that of soldering. Connectors are generally easily available, I've noticed. Some would say, that for a complete beginner, getting the Ultramat 16 is abit ambitious, but in a way I'm future proofing - hopefully. But then I thought I was doing that when I bought my Futabe F9 - the following year 2.4 came out.... (doh!!!)I really do appreciate you Guy's helping out on this brilliant forum as for people like me can learn so much - especially me making a comeback to this wonderful hobby after so many years away. Such a steep learning curve learning ALL the skills in aeromodelling - building, engines, R/C, covering,electric motors/batteries/charging - AND flying.What a Great Hobby.Cheers,John. Quote Link to comment Share on other sites More sharing options...
JohnnyB Posted June 30, 2008 Share Posted June 30, 2008 Cheers David,I've actually adapted a 2 pin plug with banana's at the other end and everything is now working fine.Now I can see the full potential of this charger, it seems a really good piece of kit. Thanks again for your invaluble help. I really appreciate all you have done.Cheers,John. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 30, 2008 Author Share Posted June 30, 2008 Yes Ron, soldering will be a necessary skill if you intend experimenting with electric flight in any sort of serious way. A small selection of the various adaptors I have made up. Notice the lead with the banana plugs at one end, and assorted plugs spliced and hard wired into a "multiway" harness type of thingy. I actually have two of these, one in the workshop, and one in the car. Quote Link to comment Share on other sites More sharing options...
JohnnyB Posted June 30, 2008 Share Posted June 30, 2008 Cheers Timbo,Yes, I really do intend to get into electric flight in a big way in the very near future. You never cease to amaze me with your idea's and innovations and I will certainly be having a go at some of them - especially that multi purpose multi harness type thingy. Oh, and I also hope to construct an electric motor thrust rig as you showed on another thread. But how do you get the proportions of the arms correct to get the accurate thrust measurements? Or do you make just them of equal length?.The road ahead is certainly a long one - but I'm on my way.Cheers,John. Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted June 30, 2008 Share Posted June 30, 2008 Hey!!! Well done John, good stuff, glad we can help. If you're serious then the Graupner 16 will be fine, it'll grow with you and still be relevant and useful when you've moved on to bigger stuff. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 30, 2008 Author Share Posted June 30, 2008 Yes John...equal lengths for both horizontal and vertical beams, measured from centreline of motor to hinge point, and hinge point to pressure point on scale. Quote Link to comment Share on other sites More sharing options...
David Lawrence Posted July 17, 2008 Share Posted July 17, 2008 I know I am joining this very late, but I have a simple question, as someone about to abandon his 10+ ic engines and take to the electric path......I usually fly up to about 6 times per session.....do I need to charge 6 or so Li-po's for a day's flying? That sounds very expensive to me!Also, I live out in the sticks, and have never had a problem with 35mhz Futaba kit, but now that 2.4 has come along, it seems sensible to switch....any advice? (As a Futaba man from way back, I am thinking about their cheapo 2.4 kit.....6 EX or something similar? Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted July 17, 2008 Author Share Posted July 17, 2008 Well yes and no really...depends how long you wait between sessions ! Lipos will generally require 1 hour to fully charge so for X flights you will either need X packs, or simply put the first empty pack on charge at the field as soon as you land. Fit pack number 2 and go fly.....meanwhile.... pack 1 is charging.... and so on. Obviously extra chargers means doubling up the availability of packs etc. Allowing for the odd natter ( very odd sometimes in my experience ) and cofee and buns.... your first pack will be ready and re-charged before you have cycled through your various packs in successive flights.For electric flight 2.4Ghz is a godsend - I am a Spekky man m'self, but I beleive the 6EX is OK - if a little limited on memory and mixing etc. Do not give away your IC engines just yet ! Quote Link to comment Share on other sites More sharing options...
David Lawrence Posted July 17, 2008 Share Posted July 17, 2008 Thanks, Timbo, that is really helpful.Now two more questions.......I assume from what you say that I can use my car battery to re-charge at the field? Do you have any recommendation of a decent li-po charger that does not cost the earth, which is both 12v and 240v enabled? Also, do I need to buy a Balancer as well?Second: I used to be quite a passable flier with several low-wingers and even a FW 60" with a 4-stroke under my belt a few years ago. I have had plenty of the statutory re-kitting experiences, and I am also a bit older now, so for my first lecky I would like to play a bit safe....perhaps a high-wing scale ARTF?A Cub, Decathlon, Beaver etc....any ideas?Many thanks in advance Quote Link to comment Share on other sites More sharing options...
JohnnyB Posted July 17, 2008 Share Posted July 17, 2008 Hello David,Well, just my twopence worth regarding chargers. I'm just building up to making a start in Electrickery, and after some considerable thought, I went for the Graupner Ultramat 16. This charger costs about £98, but will charge just about anything you will ever want to charge, so although is quite expensive in initial outlay, it is very 'future proof'. This model has a built in balancer and comes with adapters for all popular Li-po cell connetions. Also, it has mains and 12v operation. A real all round piece of kit - Oh, and the instructions are very clear, making it easy to programme - very important in my case......All the Best,John. Quote Link to comment Share on other sites More sharing options...
David Lawrence Posted July 17, 2008 Share Posted July 17, 2008 Yes, I read the review of it in RCME, but felt that £100 for a charger was a bit strong, even with balancer included....it's not as if I am going to need to charge Nicads, Nimh's what have you again! Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted July 17, 2008 Author Share Posted July 17, 2008 I agree - but then again Graupner is a well established and reputable company who make / brand good quality equipment. I am afraid I am a charger junkie, having got through about 6 in as many months - my current model is the junsi 1010B on which I have a review on the forum here - I have had a problem with oit though and it has been replaced and I have just finished modifying it to enable firmware upgrades via the Internet. If £90 is a bit beyond your budget, then the IMAX / bantam Lipro 6 and its many clones is still a good charger IMO - for half that money.It does not however come with a mains PSU although these are widely available for not much money - or make one from an old PC PSU - easy to do - I did a link / feature on this some time ago. If you use your car battery to recharge at the field beware that it can soon run down to the point where it wont start your car! Your better off buying a decent capacity "leisure battery" and keeping it in the boot.Any of the models you suggest will be fine as an intro to leccy flight - move on up to EDF jets and the like after you have a bit more experience Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted July 17, 2008 Share Posted July 17, 2008 Hmmm Quote Link to comment Share on other sites More sharing options...
David Lawrence Posted July 24, 2008 Share Posted July 24, 2008 What is that about, Myron?I have actually gone for a Seagull Space Walker, since I did feel that I wanted something a bit more interesting, and I cannot have completely lost the ability to fly low-wing.My only problem now, which no0-one ver seems to mention is that I am going to have to learn soldering skills.....that is really crazy in this era of trying to get new folk into flying! Quote Link to comment Share on other sites More sharing options...
HughG Posted October 15, 2008 Share Posted October 15, 2008 I have 3 flight packs, each of 8 x 3500 mAh NiMH cells in an assembly which clamps the cells together, so allowing replacement of individual cells without soldering operations. The packs are used in a Reichard Svist (electric powered glider).Two of the packs seems to have deteriorated such that maximum revs in my set-up are about 1000 rpm below results from the 3rd pack. The deterioration is confirmed by various measurements with an Astro Whatt Meter.All three packs seems to charge up to about the same voltage.The individual cells all have about the same voltage after charge. Is there a simple way to check which of the cells in the packs might have deteriorated? Quote Link to comment Share on other sites More sharing options...
nasa_steve Posted October 16, 2008 Share Posted October 16, 2008 you are correct they will show the same voltage the only way you could possibly test them is by testing each of the cells under load...... the ultramat range of chargers are excellent my philosophy is you really do get what you pay for i've been down the cheapo route and to be honest it does not save you anything in fact it will end up costing you more in the long run. i've had cheapo chargers that have even killed cells due to over charging or early cut-off points. to add to Timbo's point about flattening your car battery the Ultramat won't let you do it it will warn you of low battery input voltage they have some really good built in safety feature's that if you are new to electric flight you really could do with. as for soldering there are so many different battery connection methods you really need to learn to solder......one of the RCM&E specials did cover the subject in some depth so it may pay to look out a copynasa Quote Link to comment Share on other sites More sharing options...
HughG Posted October 16, 2008 Share Posted October 16, 2008 Nasa,Thanks for your comments. What I eventually did was to make up a circuit using some resistance wire as a load and then checked each cell individually. At about 2 amps, there was a clear differentiation between two of the cells from the rest in one pack, and three cells from the rest in the other. The difference showed mainly in the voltage drop under load, and also in the current drawn.In the next couple of days, I'll make up a pack with the good cells and see how it performs.I use a Ripmax Prodigy II charger, which provides similar reports eg low battery input voltage, and setting limits on discharge rates, low voltage etc etc.(I can solder quite well - I have a big iron for heavy duty and a temp. controlled iron with a fine point for fine work. I bought the 'clamp' packs with individual cells 'cos the supplier didn't have a welded pack meeting my requirements at the time. Has proved to be very useful and versatile). Hugh Quote Link to comment Share on other sites More sharing options...
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