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Old Jul 02, 2002, 01:02 AM
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Kokam 140 Terminals fragile

Just a warning, the solder terminals are very fragile on these LiPoly cells. They are about three times the thickness of cooking foil. I already tore one terminal. I suggest the following solution: After soldering leads, shrink-wrap so all exposed contact is covered (unlike in the picture). Then glue a scrap of 1/32" balsa to the back of the battery and to the shrink-wrapped terminals. This will prevent them from flexing and stressing the terminals.
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Old Jul 02, 2002, 02:56 AM
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Inari, Graham suggested a better way. Solder leads on, then fold the terminals down and wrap with Sellotape. Better description on his site about these. Look in the post about him selling them.
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Old Jul 02, 2002, 04:14 AM
Sticky Shepherd
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http://www.indoor.flyer.co.uk/terminals.htm

Look at my signature line, that is an example of swings and roundabouts like this one.
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Old Jul 02, 2002, 05:19 AM
in persuit of low wing loading
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If you look in the original LiPoly thread from mid-May, I used the celo/heat shrink technique because of concern about tearing the terminals. I think the key is to bend the terminals just once -- when the wires are hooked up, and then have them pass back over the pack to exit the shrink at the bottom of the cell. This uses more wire, but helps insure that no lateral forces are placed on the terminals. The celo tape serves two purposes (1) to keep objects from touching the ends of the terminals where they bend over and are exposed, and (2) to help keep them in place so they don't touch each other and keep forces from tearing them. Here's a picture showing my assembly steps -- including a template for attaching 1/16x1/32" magnets. Also note the wires soldered on opposite sides of the cell's terminals. BTW, I used the lightweight clear shrink tubing from http://www.Airdyn.com which adds only marginally to the weight. Most of the increase in weight comes from the wires and JST plug. A single-cell pack including wires/plug, shrink wrap, and 4 magnets weighs 4.1g. Hope this helps.
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Last edited by Gordon Johnson; Jul 02, 2002 at 06:55 AM.
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Old Jul 02, 2002, 12:21 PM
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Well, that is simpler, isn't it?

Thanks guys.




If snakes had wheels, I'd put a Mabuchi 550 in one.
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Last edited by Inari; Jul 02, 2002 at 12:24 PM.
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Old Jul 03, 2002, 08:57 AM
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LiPoly Cell Protection

To protect the 140mAh LiPoly cell on my new build Micro Taxi (aka Lightning), I mounted it in the plastic charging center and stuffed a piece of GWS R4-P receiver foam in place to hold it securely.

Click here for a larger image.
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Old Jul 03, 2002, 08:59 AM
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The result is a compact charging center with On/Off switch and charge jack that gets inserted back into the model.

Click here for a larger image.
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Old Jul 03, 2002, 09:02 AM
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The mating connector that comes with the model is then soldered to my Bob Selman BSLipC1 LiPoly charger.

Click here for a larger image.
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Old Jul 03, 2002, 02:30 PM
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Excellent solution for that bird. Plug and Play (or Flug and Play for our German-speaking friends).
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Old Jul 03, 2002, 05:03 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
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Greg,
Nice solution. Mine is to go to go flying with six or seven charged LiP cells with JST plugs installed and tiny wonder magnets glued to the Airdyn clear shrink tubing so I can just keep swapping cells and always have one on the charger. Last month I was not able to run out of charged batteries in a 3-hour session -- and I flew a lot. This is the same strategy I've used for NiMH and NiCd packs. Problem is, my NiCd and NiMH packs and three Bob Selman chargers are being put out of business by these LiP cells.
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Old Jul 03, 2002, 09:23 PM
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CAUTION: The tabs on the Kokam cells are not intended to be soldered and damage to the plastic seal may result. The cells that FMA Direct imports and distributes to your favorite suppliers will have a tiny p.c. board across the end with the tabs sonically welded to the board. You can then solder to the board terminals. This is the "bare" cell. The cells will also be offered with a protection circuit on the same board that protects against undervoltage. A regulated BEC output will be included on the PCM board that provides current to the receiver & servos after motor cut-off. FMA will also distribute a product that acts like a CA but is conductive for attachment directly to the tabs. I tested this a time back by putting together 12 series joints in our Microlite wire to connect from a pack to a KP01 motor and it created no measureable voltage drop. You just twist the wires together then apply a drop of the adhesive and touch with an accelerator.
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Old Jul 03, 2002, 10:34 PM
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The conductive CA sounds interesting.
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Old Jul 03, 2002, 11:21 PM
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I recieved today a new Kokam cell from Dan Hurd. I cannot solder to the plus lead. The minus lead soldered perfect, but the plus lead has a different finish on it and will not accept solder. I tried silver solder and the flux that comes with it, but that did not work either. Other than the conductive CA mentioned above, does anyone have a suggestion. Is there any conductive epoxies easily available. Do you think any of the liquid metal products will work.
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Old Jul 03, 2002, 11:29 PM
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Marks, solder to the other side of the terminal. Two different metals on the terminal. Then flip both terminals down and tape 'em that way. Prevents them from tearing off and from shorting on things.
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Last edited by Inari; Jul 03, 2002 at 11:34 PM.
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Old Jul 04, 2002, 02:28 AM
Sticky Shepherd
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When you flip them down be sure there is some tape underneath, T think the cell is mylar covered but its best to be on the safe side.

Or to put it another way: http://www.indoor.flyer.co.uk/terminals.htm

Graham
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