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Old Jul 03, 2004, 10:13 AM
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Parallel Lipo Packs-Final Connection?

For final connection, is it better to conect cells in series then connect in parallel or the other way around?

ex. lets say making a 3s4p pack.
Is it better to connect the cells as 3 - 1s4p packs or as 4 - 3s1p packs?
And why?

Thanks
Rob
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Old Jul 03, 2004, 11:08 AM
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I would think 3 1s4p packs would be better since it would make checking for balance easier, but I might be wrong
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Old Jul 03, 2004, 03:39 PM
luc
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yep, I would do the same. best is to be able to charge the 3 packs in //.
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Old Jul 03, 2004, 03:42 PM
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Thanks Guys, I was thinking the same but previously doing the opposite.
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Old Jul 03, 2004, 06:25 PM
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I read somewhere you always connect in series first...Then parallel.

Which brings me to another question. I've got two brand new 3s packs that want to hook up parallel for 3s2p.
1) Do I hook them up to charge both packs individually or will it be safe to wire them together and charge as one?

2) In either case. If the voltages of both packs are the same is that good enough, or do I need to discharge them or something first?

Thanks,
Mike
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Old Jul 03, 2004, 08:21 PM
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Perth Westen Australia
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Quote:
Originally Posted by CryHavoc
I read somewhere you always connect in series first...Then parallel.

Which brings me to another question. I've got two brand new 3s packs that want to hook up parallel for 3s2p.
1) Do I hook them up to charge both packs individually or will it be safe to wire them together and charge as one?

2) In either case. If the voltages of both packs are the same is that good enough, or do I need to discharge them or something first?

Thanks,
Mike
1 check to see that voltages of both packs are the same
2 link them together and keep that way for charge and discharge
3 if you unlink them and charge and discharge them seperatly at any time
repeat step 1 before you link them up again.
(Im assuming the packs you have are same cell make, capacity and age.)
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Old Jul 03, 2004, 09:05 PM
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Quote:
Originally Posted by gtstubbs
(Im assuming the packs you have are same cell make, capacity and age.)
That's not necessary:

http://www.rcgroups.com/forums/showthread.php?t=170524

- RD
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Old Jul 03, 2004, 10:40 PM
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Quote:
Originally Posted by RD Blakeslee
Ya I know, but it makes me feel a bit safer particularly if he is going to permanently solder etc the packs together.
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Old Jul 03, 2004, 11:28 PM
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Hey fellas, Thanks abunch for the info. I'll finish up the plane tonight.

Yes, the packs are the same. Both never used, Kokam 2000 3s packs. I'll be using a Triton.

As mentioned above... are there any steadfast rules about making your own larger packs, i.e. Series first then parallel????

Thanks again,
Mike
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Old Jul 04, 2004, 02:59 AM
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In general when building multi "S" and "P" packs, its suggested to parallel before series.

You could also build parallel "modules" to join in series externally. As RD and Luc can further explain, this is likely the safest and most flexible way to build packs on your own for a variety of configurations.
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Old Jul 04, 2004, 03:04 AM
luc
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Yep here are some 2P packs hooked either in serie or // thru different multiplugs
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Old Jul 04, 2004, 08:02 AM
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Quote:
Originally Posted by CryHavoc
... are there any steadfast rules about making your own larger packs, i.e. Series first then parallel????

Thanks again,
Mike
Mike,

It's been done both ways, so there are no "steadfast rules".

Experience has shown that it is generally better to go parallel first, then parallel sets in series, for the reasons given in posts 2 and 3.

Also, see post #s1-3:
http://www.rcgroups.com/forums/showt...ks#post2347381

But, IMO, The best way to wire packs in the light of all experience to date, for reasons of safety and reliability with simple, straightforward hardware, is the way luc does it, using Multiplex plugs.

Luc, I wish you would publish a set of photos of your connections to each cell and each plug, referenced to a a wiring diagram, for folks who are starting out in eflight and need step-by-step instructions.

Hereís the way I wire my plugs:

http://www.rcgroups.com/forums/showthread.php?t=236246

And hereís what my 3-cell packs look like (safe and functional, but lucís are much neater):

http://www.rcgroups.com/forums/showp...3&postcount=28

- RD
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Old Jul 04, 2004, 10:56 AM
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Thanks for the info and photos. My applications typically involve squeezing 10 lbs. sausage in a 2 lb. sack - so I will require soldering the connections, with no room for the plugs and extra wireing.

As I mentioned, I have been combining individual 3s and 2s packs with the cells soldered to pcb's (kokam or from aircraftworld) in parallel.

Does anyone make a commercial pcb which joins cells in parallel? My experience indicates that the pcb's protect the cell tabs better and packs can be built more compact with out wires running along the side of the pack.
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Old Jul 04, 2004, 11:12 AM
luc
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RD
I don't have the capabilities you have on drawings...
But the connection is ez: each mpx plug has 6 connection; in order to be able to draw a max of 45A, you need to join 3 connectors on each side. Then you clhoose between a // connection (only for charging, you don't need big wires as 3 wires will go on the main plug) and serie (for discharge). In that case, use thicker wire (13 ga is ok).
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Old Jul 04, 2004, 04:46 PM
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Heres how I do it similar to LUC

Pictorial development
http://www.rcgroups.com/forums/showt...adid=153655for

|| setup
http://www.rcgroups.com/forums/showp...2&postcount=13
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