Fats Flyer Posted February 17, 2010 Share Posted February 17, 2010 Hi, I have been told different stories about joining 2 x 3 cell lipo's together to make a 6 cell pack. I am upgrading to a 500 size heli which uses 6 cell packs .I have plenty of 3 cell packs which i used for my 450 size heli's,they are the same make and size, which i do know they have to match. Now.......people tell me that joining 2 packs in series is no good, the only way for the best power is to use a ready made 6 cell pack. This baffles me, surely it's still a 6 cell pack regardless of how it's put together. How can this affect power? Will they last connecting this way? Can i ask you good people for all your input,with about as much info possible ,i like to know the ins and out's . Cheers Vince Quote Link to comment Share on other sites More sharing options...
simon burch Posted February 17, 2010 Share Posted February 17, 2010 If these are going in a Trex500, I wouldn't plan on your packs lasting long. I know a lot of people who used their trex 450 packs doubled up, and they didn't last long, possibly because of the older packs having low C ratings. I can't see any reason why you can't do it. Lots of people run 4 and 6 cell packs in series in high power 8s and 12s set ups. Like you say, the packs need to be matched and have a good C rating to survive the demands of a 500 class heli. If it gets you going in the first instance, I wouldn't worry about longevity. I run my 500 on Hobbycity 2650Mah 30C packs, and I can't tell the difference to the Hyperion packs which are just about double the price. Cheers, Simon. Ps. If you are not looking for ultimate performance, a 3000 pack will fit in to give a bit more duration. Quote Link to comment Share on other sites More sharing options...
Fats Flyer Posted February 17, 2010 Author Share Posted February 17, 2010 Hi Simon, The packs i want to use are a 2450mah 30C rating so should hold ok (i think). Maybe, the point you have raised(low ''c'' rating) is the reason why people suggest not to use them. I'm not doing hard 3D flying (i cant do it) It's just for general flying as thats what i like at my age. Quote Link to comment Share on other sites More sharing options...
James M Posted February 17, 2010 Share Posted February 17, 2010 BRC Hobbies do a pre wired lead Quote Link to comment Share on other sites More sharing options...
Dusty Posted February 17, 2010 Share Posted February 17, 2010 I dont own a 6s pack, largest being 5s pack and all the packs I use in series are exactly the same brand etc etc.. I monitor each cells voltage regulary of the lipo and balance them too, hence never had a problem so I am sure you will be fine! Its easy enough to make your own series connector too. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 17, 2010 Share Posted February 17, 2010 Perfectly acceptable procedure. The packs should all be as closely matched as possible in capacity and C rate but otherwise, connect away. Quote Link to comment Share on other sites More sharing options...
simon burch Posted February 17, 2010 Share Posted February 17, 2010 I use bullet connectors, so I don't need to use another lead. I'm not a fan of Deans connectors, but each to their own. At 30C you should be fine. Might be a bit of a squeeze under the canopy, but you can tweak the battery tray to give more room. That's what I had to do with my Turnigy packs. Cheers, Simon Quote Link to comment Share on other sites More sharing options...
Fats Flyer Posted February 18, 2010 Author Share Posted February 18, 2010 Thanks for all your reply guy's, much appreciated. Simon, i too use bullet connectors, much easier than deans i find. Timbo, why is it people say it's no good to connect 2 packs together, is there any difference ...i.e slight loss of power or power packs dont last as long? I did think what you have confirmed as i couldnt see why it would differ.. thanks Vince Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 18, 2010 Share Posted February 18, 2010 Well to be extremely picky, there could /will be a very slight loss whenever extra joints or connections are made in any power supply, and of course the potential for incorrect connections etc. As long as the packs are the same ( as above ) then no other problem at all...after all, a so called 6s battery is merely 6 single cell "batteries" connected together in series!One other consideration is balance charging - if you keep them together for all time then you will need to decide how to configure the balance plugs - adaptors are easily made or bought which effectively turn two 3s balance plugs into one 6s plug. Alternatively, separate them out, and charge as two x 3s packs. Contrary to being a problem I find the flexibility of positioning and so on to be an advantage in some models, apart of course from the ability to use the separate packs in other models. Go for it.Edited By Timbo - Administrator on 18/02/2010 15:40:18 Quote Link to comment Share on other sites More sharing options...
Fats Flyer Posted February 18, 2010 Author Share Posted February 18, 2010 Thanks timbo, I certainly will go for it. I will still keep them as seperate packs and charge seperatley as well ,this way i can use them for both the 450 and 500 size heli's. Edited By vinnie on 18/02/2010 15:47:53 Quote Link to comment Share on other sites More sharing options...
Chris Card Posted February 18, 2010 Share Posted February 18, 2010 Vince, I know this is probably stating the obvious so forgive me, but please make sure the packs you're joining in series are in an identical state of charge (eg. both fully charged). Otherwise when you discharge them one pack could become over-discharged before you spot the overall voltage dropping too low. Apart from that though, I'll second what everyone else says. I use 2 4S packs and a 2S pack in series to give me 10S in a 72" Extra and that puts out 2.5kW at the propeller. No signs of loss of power from wiring three packs in series! Edited By peevie on 18/02/2010 17:53:53 Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted February 18, 2010 Share Posted February 18, 2010 Suppose the packs are at differing stages of their 'lives'? One pack has had 10 cycles, the other has 60, for example. Just wonderin'.... tim Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 18, 2010 Share Posted February 18, 2010 Not ideal TBH as they are likely to have widely differing IR which will likely cause one to discharge quite a bit differently to the other. Bit of an unknown really, as even supposedly identical packs from the same supplier can show quite different IR after just a few cycles, so probably safest advice is to use closely matched packs. If you have no means of reading the IR, then at least go by the packs general performance stats on discharge and recharge figures. Quote Link to comment Share on other sites More sharing options...
Fats Flyer Posted February 18, 2010 Author Share Posted February 18, 2010 No Worries with the age of the packs. I got 6 packs all at the same time with the same c rating and same size 2450mah packs. Timbo,Whats the best way to try and match packs up please?, all ive got is a tester that plugs in to the balance lead to give each cell voltages. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 18, 2010 Share Posted February 18, 2010 Well assuming your charger does not measure IR ( Internal Resistance ) then probabaly the only other way is to set up a discharge -chage cycle and try to nmatch up the packs which have the closest results of capacity taken and put back in IYSWIM.You could connect the cell monitor at the same time to watch for any weakening cells if your charger does not have this facility. Quote Link to comment Share on other sites More sharing options...
Fats Flyer Posted February 21, 2010 Author Share Posted February 21, 2010 Okee Dokee, cheers Timbo, i only have the B5 charger Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.