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HomeAircraftHelicopterMain Discussion › Lipo cell replacement?
10-17-2015 10:21 PM  34 months agoPost 1
meowguy

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Saco, ME

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Just curious if anyone has successfully replaced a cell in a 6S 5000ma pack. If so, where did you get the replacement (Pulse cell) and was it difficult or especially tricky other than not shorting it out and blowing yourself up?

"Sweet dreams and flying machines in pieces on the ground." J. Taylor

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10-17-2015 11:14 PM  34 months agoPost 2
Heli Fanatix

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Fountain Valley, CA

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It can be done, I do it all the time for my personal use. I've even made 7S and 8S packs

- I usually use many packs of the same cell count, capacity and c rating
- when any of these packs go bad, they become donor packs
- warm with a heat gun and carefully separate cells w/o wrinkling it
- I would separate the bad from good cells and have it ready to go
- this is where you have to have a good 60w soldering iron & skills
- tape it together iniatially and than heatshrink
- nothing to it ... Just take your time and protect the leads to keep from shorting. A lot can go wrong just soldering connectors on a pack. Have a plan and procede carefully.

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10-18-2015 01:38 AM  34 months agoPost 3
Rob43

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Midland, MI USA

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Not doubting you, but I am surprised that they last long after soldering the tabs. I've had some bad experiences after replacing damaged cell balance taps before.

Rob

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10-18-2015 02:12 AM  34 months agoPost 4
Heli Fanatix

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Fountain Valley, CA

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If you do the soldering correctly, it helps to have a good hot soldering iron, right ingredients, jig and soldering skills ....it will be fine. It's the always the cell that goes bad for me. All tabs stay intact for me, just have to be careful when handling them. It can happen to a new, pack for 10 flights or 200 flights. I used to match nicad matched packs back in the 90's and use that method.

I have a load test rig capable of simulated amperage demands of heli's. I would cycle each cell individually for 6 cycles. I also picked up an ESR meter and rate each cell. I use the best of the bunch .. Since that is all that I can do. It's tough to say ... Some packs have been in service for years and others as short as 2 months. I just rebuild the packs again ... No stress.

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10-18-2015 02:42 AM  34 months agoPost 5
Rob43

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Midland, MI USA

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Well, clearly, you have more specialized skill and experience in this area. Interesting stuff. Have a guy at our club who similarly can seem to do anything like this. He's an instrument specialist in our company. Not the greatest pilot, but he has all the right tools and skills to use them...

Rob

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10-18-2015 03:00 AM  34 months agoPost 6
Dan Minick

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Columbus, WI

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I have made packs up before out of old cells. The right solder and flux really help with the aluminum tabs. But I have never used any in high current situations

Team Synergy, Team FBL Rotors-------if its not broke...it will be!

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10-18-2015 05:40 AM  34 months agoPost 7
Heli Fanatix

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Fountain Valley, CA

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I must emphasize on comfort level and skill level. Some are engineers and others are pilots, I'm fortunate to be both. I don't assume I know everything but I can share with you guys I do research extensively to understand the concept, make an flow chart and develope a solid plan. Im an automotive technician and have been taking apart entire vehicles, re-wire, paint & bodywork, build 1000hp force enduction engines, install 26 channel alarms (I took two 7ch DEI alarm & two 6ch DEI modules and combine it to a single 4 button remote) and cut & clip my own street legal import right hand drive vehicle. So I guess all that has prepared me for the RC Heli Hobby.

Since I can build and test fly my own machines, nothing is lost in translation. I have develope a method when learning a new trait. But it does help to understand everything. I usually read the manual three times, contact manufacturers for questions, make notes and have a log of everything.

For example, for the sake of this conversion, it's about replacing / rebuild a pack:
- first, it's about soldering
- learn and research how to solder correctly
- the key is to avoid a cold solder, make sure to have
- at least a 60w iron
- right material
- make sure nothing is moved when cooling
- take apart cell w/o wrinkling the foil
- orient the cells in correct position
- reassemble same as you have taken apart

I have rebuild 6S ~ 14S and it's not a problem if you observe all the correct soldering techniques. But I do :

- know how to autorotate
- backup RX power supply
- piloting skill to pull maneuvers to test the soldering work
- all my bases are covered

So if you have steady hands, proper tools, patience, know correct techniques, follow instructions and observe all precautions..than just think positive and empower yourself .....You can do it!

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10-18-2015 08:00 PM  34 months agoPost 8
meowguy

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Saco, ME

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Thanks everyone. This is good advice and I should be able to give it a try.

"Sweet dreams and flying machines in pieces on the ground." J. Taylor

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10-20-2015 02:22 AM  34 months agoPost 9
cudaboy_71

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sacramento, ca, u.s.

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I've done 6s 5000 pack cell replacement several times before. A few things repeating what's said above; correct flux and solder for one.

But, the main problem I've had is when you buy a pack the cells are closely balanced in IR from the factory. When you replace a cell you're usully putting in a new cell with much lower resistence than the existing cells.

This does not play well with the other cells, and in the 4-5 >5000mah packs I've done, the lifespan is much shorter than I'd expect. What does that mean? It means the next highest IR cell now has a much higher load on it and goes out much quicker.

This is largely anecdotal, as I have not performed any formal tests. But, here's what my last 3 packs have consistently done:

all cells normally operating from new with IRs in the 2-3mu range; afer 50-100 cycles or so in the 3-4mu range; after 100-150 cycles in the 4-5mu range. Now, one cell goes rogue....usually discovered after a flight where HS drops before the usual time has elapsed. Immeiately after the flight I'll take the IRs and one cell will be >10mu. That cell is toast. So, I'll replace that cell with a new one in the 2-3mu range. I won't get another 5 flights out of that pack before another cell drops. Now, since I've usually purchased a 2s pack of the same manuf/model/C rating and MAH, I have one more spare. I'll put it in and what do you know? Another 5 cycles later another cell drops.

Like I said, this is largely anecdotal. Maybe that pack is just tired and all of the cells were about to die anyway. But, here's some evidence to the contrary: I had a set of 2 6s 5000s I ran in my 700 that dropped a cell. Not wanting to repeat the above process I simply removed a cell from each pack and ran them as a 10s pack for my logo. That set lasted another 50 cycles before dropping another cell.

Do with that info what you like. In short: It can be done. But it may not be worth the time/money. YMMV.

if it ain't broke, break it.

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10-20-2015 02:42 AM  34 months agoPost 10
JEEPWORLD2002/2

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Blue Bell, Pa

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To be quite honest cells age and the newer will be carring the others n vesi versa. Now I would cut off bad one n make it into a 5 s n pair that with another 5s to make ten or make a 3 s n a 2s Rx ? I did make a few 6 s from a 14s stick pack I got a great deal on but hand no 700 to fly it in but the packs didn't take it well n only lasted 50 or so flight on a tp I made had 4s brand new n add 2s more n eventually the 2s puffed while the 4 s lost capacity m alway had balance issues. Again just my opinion spit it down to sum thing useable n ditch the bad one or two

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