aeajr

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I have been using 6-7 cell NIMH packs in my aerobird. I am building a new plane that needs 8 or 9 cell packs and have decided to build my own packs out of 2/3 A 1100mAh cells. Here are my questions for all you experts:

1) Is there any particular reason why I would need to use tabs to connect the cells as opposed to wire? I presume the tabs are easier for the manufacturers to do in mass production, but I plan to solder large capacity wire. Any obvious concerns here? If so, where can I get the tabs?

2) Shrink wrap seems to be the common way of bonding cells together. Where can I get it? Is there any reason why I couldn't just epoxy them together and insulate them with tape?

3) Are there any particular benefits of one connector vs another? Sermos, Deans, Tamaya? There seem to be so many varieties.

If you have a good resource for building packs, please point me to it. I am always looking for good reading material.

Give me your wisdom so that I don't end up hurting myself and my plane due to my ignorance.

ballgunner

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The tabs on individual cells make it easier to assemble a pak. The main thing to worry about is overheatng the individual cells. Nicads will vent under excessive heat and you will lose capacity. The idea is to tin all joints before assembly. Use a high capacity iron and touch the connections very briefly. Just enough to make the joint.
With tabs you can set up the batteries side by side for soldering which lets you see immediately if the joint is made. The tabs will bend to let the batteries be placed side by side. Shrink wrap keeps the cells in position and helps to prevent joint breakage. It is available from Batteries America, Tower Hobbies, Hobby People and lots of other web sites.

ballgunner

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P.S. Sorry I forgot the part of your question concerning connectors. It seems that most of the old pros use Sermos. I have some that are Tamiya and some that are JST as used in most park flyers and paks from GWS. The JST connectors are available from Hobby Lobby. I know the perfectionists will opt for heavy wire to the connectors. Just don't get to carried away with that idea. You must have a fairly good degree of flexibility because you will not always have a straight line run from Pak to ESC or motor.

aeajr

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I will have to check out the JST connectors. I am not familiar with them.

Thanks!

00hex

JST connectors are pretty flimsy. If you're using 1100 mAh cells (HeCells?) you're probably drawing too much current for them.

aeajr

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I don't know what they are rated for, but most speed 400 motors draw around 9-12 amps as I understand it. I have never measured it. The kit calls for 600-800 mAh batteries, but I wanted a little more duration so I went for the 1100. Not too much more weight. If it seem sluggish, I will just go to 9 cells.

00hex

Yeah, that's probably a bit much for JSTs.

The 600-800 mAh batteries they suggest are probably NiCds. 1100 mAh NiMHs are close to the same weight as 600 mAh NiCds. Your plane should do just fine.

aeajr

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00hex

Thanks for the comments on the battery weight. I didn't even think of the idea that they were recommending NiCAd packs. Yes the 11 mAh NIMH should be close in weight. Now I feel more confident that I have ther right stuff for my plane.

Loran

I made a jig from scrap pieces of wood in my shop to hold the batteries together as I solder them. If you need details on the fixture let me know. I make my own tabs from .005 thick brass. It works great. Also I CA my batteries together after I solder the tabs. After the CA has dried I use SHO GLUE to fill in all the filets between the batteries. I don't use any shrink wrap other than what the batteries come with from the manufacturer. Keeps the heat down. These are all the old tricks that I learned from racing 1/10 pan cars. As for connectors, Sermos or Deans Ultra work the best. DO NOT use Tamaya! They have too much resistance and get hot. When this happens it takes the power draw from your batteries. Which results in shorter run times.

Highflyer

I knoiw this thread is somewhat old but i thought i'd show you guys this: http://www.rcuniverse.com/reviews.ph...w&reviewid=109 go to this page it is a great resource for anyone interested in building their own battery packs.

aeajr

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This thread is still active.

I loved that link you provided. Great.

I haven't built the packs yet, so this will be helpful.