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Old Jan 16, 2004, 02:42 PM
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United States, NY, Marion
Joined Sep 2001
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Question
If you are/were building smaller Irate 3s packs what do you suggest

I'm about to spend some of my rather limited resources on either the 850 or 1100 mAh Irate cells to use with our high school club planes. We're about to move up to a brushless AXI-2212/34 to be used with an Ultimate Bipe and then hopefully an indestructable EPP 3-D ship.

I'd like to make the packs as durable and test/balanceable as possible and am looking for suggestions in that vein.

Here are some specific questions but feel free to add you own thoughts on the matter.

1. Do you recommend using PCBs?

2. Are people happy with aluminum solder offered by CBP?

3. Would you recommend each cell being individully connected to a Dean's micro and then two different harnesses created one to wire them 3S and the other for parallel charging?

4. What size and brand of shrink wrap has worked really well for you?

Oh and yes, I have considered purchacing premade packs but am too hard headed/cheap/poor to not at least make a first attempt myself.

Thanks for your intelligent well reasonded responses,

Hugh Mason
Newark Electric Flyers- Learning By Doing
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Old Jan 16, 2004, 04:06 PM
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Midland, Tx / W. Lafayette, Ind.
Joined Dec 2002
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ive had good results using the aluminum solder and flux from CBP. i assembled my first lithium packs of CBP 500 cells last night and didnt have a problem at all. the shrink wrap from CBP works really well and shrinks a huge amount, so dont do like me and order shrink thats barely bigger than the cells, order some than is a good 1cm or so bigger than the pack you plan to make.

i had god luck cutting thetabs on my cellsa bit shorter and then at an angle, the wraping the tab around the wire 1 turn and soldering it. made for a very secure solder joint.
jonathan
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Old Jan 17, 2004, 07:08 AM
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United States, NY, Marion
Joined Sep 2001
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Jonathon,

Thanks for the reply.

I'm still looking from those that have used pcbs and parallel chargeable configurations.

Lets hear some more for those who have been flying their packs a few months.

Hugh
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Old Jan 17, 2004, 09:02 AM
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coventry uk
Joined Nov 2002
824 Posts
Hi
I have fitted balancer circuits to some of my 3s packs but the rest I will tap with male bec plugs so I can access each cell and if needed rebalance them, makes things simple as there can be no mistake as my main connection is a micro deans, and the bec plugs will only be used for testing [very small]. All my packs are series soldered; my prebuilt packs have pcbs. My home built ones dont.

t.n
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Old Jan 17, 2004, 09:29 AM
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Hugh,

For what it's worth:

For teaching high schoolers, it might be of interest to construct your packs as shown in:

http://www.rcgroups.com/forums/showt...n&pagenumber=6

It's a long thread; the first few and the last post would be of most interest initially.

Demonstrate parallel and series connections and, incidentally, replace crash-damaged cells with ease.

I would suggest Etech 1200 cells, for economy and adequate performance.

- RD
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Old Jan 17, 2004, 09:31 AM
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United States, NY, Marion
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t.n.,

I like this idea as there would be less continuous plugging and unplugging of various harnesses to the main connector. One would however have to make the conscious effort to check and maintain ballance rather than allowing the parallel charging to do it automatically.

Which solder are you using and are you satisfied with its performance?


Thanks for your input,

Hugh
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Old Jan 17, 2004, 09:53 AM
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United States, NY, Marion
Joined Sep 2001
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RD,

If I'm reading things correctly, you're advocating using good separable connectors to each cell so that:

1. Cells will always be charged in parallel and thereby balanced

2. Replacement of a single damaged/weak cell would be rather trivial.


Do you have any problem with use of the small bullet style connectors? I'm not familiar with the Sermos connectors that you mention.

Thanks for more great info.

Hugh
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Old Jan 17, 2004, 10:33 AM
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Hugh,

There's discussion of the bullet-type connectors in the thread mentioned above and in several threads about connectors per se.
The best of them will certainly work well for you.

Actually, I use large enough cells that I don't need to parallel them whenever I can, and so charge them individually. With the 1200 size, you would need to teach how to connect and charge groups of two or three cells in parallel, then how to connect the groups in series for flying.

I have used the Sermos connectors exclusively for some time, for the very reason some folks would avoid them, I think: they are non-polarized, universal type connectors, offering maximum circuit flexibility.

From the teaching perspective again, students would have to understand their connections - the Sermos won't (in effect) make any decisions for them. The Sermos do have adequate housings for insulating their contacts, so accidental shorts will not be an extraneous problem for the students

- RD
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Old Jan 17, 2004, 10:39 AM
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Safety First

I should add that I would provide and teach a safe environment before and during hands-on charging, and I would check each connection as the student made it.

- RD
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Old Jan 17, 2004, 10:50 AM
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United States, NY, Marion
Joined Sep 2001
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RD,

We're talking about high school freshmen through seniors here. If it can be plugged in backwards it will be even with their best intentions and knowlege/training. Its way too funny when they reverse polarity on IPS motors, the plane taxis backwards and even though this has happened before wonder whats up.

I'm worried about unplanned costly, pyrotechnic displays in the gym so will go for a polarized system.

The Irate 1100 mAh cells at $10.50/cell look like the best current deal going for this capacity. Even the 850s will supposedly delivery similar capacity as the Etec 1200s when both are pressed near their limits.

Thanks so much for the additional info. We wouldn't be nearly as successful as we are without the Ezone as our main informational resource.

Hugh
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Old Jan 17, 2004, 11:15 AM
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coventry uk
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Well you would only have to check the balance every say 5 cycles, extending to say 8-10 if you find the cells are not going out of balance, also I only have a 5amp max lipoly charger and use etec 1200 3s packs paralleled together [ high amp draw helis] which allows me to charge them paralleled, but if I charged all my cells 0series all parallel [4x 3s etec 1200s] I would need a 12amp charger. I have found a 0.01v difference between cells in a 3s pack since checking but I had 2 older packs die on me with nearly 1v difference, they had been well used and I think once the cells start on that slippery slope they deteriate rapidly if left unchecked.

i use Ersin 399 Multicore lead free 5-Core solder, works great, i always clean my tabs with wet and dry then quickly tin them prior to building in to packs.

t.n
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Old Jan 17, 2004, 12:00 PM
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coventry uk
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http://www.rcgroups.com/forums/showt...5&pagenumber=3
this discribes the balancers i use and intend to put female bec conecters on so i can balance my cells when they need it.

t.n
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