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Old Oct 15, 2009, 07:15 AM
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8387mike's Avatar
Perth Western Australia
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Help!
How to make a LiFePo4 Pack

Hi All,
Can any body help me with How to make a LiFePo4 pack, I need to make a 800mah-1400mah 6v+ RX pack for an IOM racing yacht.

Before any body says "just get LiPo" the area in the hull where the battery sit's can get a very tiny amount of dampness, which i have sealed again and again, so i don't want $1000s of boat boat burning to the water line (would be great to watch and then i could buy a new boat, but the war department won't let me(wife)).

So the questions are do i need to run balance leads and charging leads? or do you just build then like NiMh packs?

Any help or even better pictures of what others have would be great.

Look forward to you response's

Mike
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Old Oct 15, 2009, 07:28 AM
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Julez's Avatar
Germany
Joined Dec 2003
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Get a VPX Pack, or 2 A123 1100mAh LiFePo4 cells, which is the same.

Solder the cells to a pack, then paint it thickly with clear spray paint, so that the paint goes ito every little gap, especially at the cell ends.
this should seal the pack sufficiently.
Afterwards, cover with shrink wrap.
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Old Oct 15, 2009, 07:42 AM
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Haralson County GA. USA
Joined Oct 2004
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You rally should use a balancer especially for the first 5 to 10 chrges and then from time to time. You can use a servo extension to make a balancing / charging lead as you only need 3 leads.

I use Goop to seal the ends of the cells and it works extremely well. I use to race nitro RC boats and we used ballons to bag / seal our batteries and receivers.

An old post showing how a 2 cell is wired for balancing. Disreguard the connector if you use a servo ext. . A standard servo ext is Black Red White. The Black and Red would be your standard rec, connector matchin leads and the White would be the center tap (where the cells series connection is).

http://www.rcgroups.com/forums/attac...hmentid=674433

Charles
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Last edited by everydayflyer; Oct 15, 2009 at 07:57 AM.
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Old Oct 15, 2009, 07:45 AM
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Perth Western Australia
Joined Jul 2009
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Hey Julez,

When charging the 2 x cells with my charger (it is a LiFePo4 charger) does it need to charge each cell or will it both through the leads?

Mike
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Old Oct 15, 2009, 08:01 AM
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Julez's Avatar
Germany
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Hi Mike, as the cells are wired in serial, both cells will be charged at the same time.
But be sure to balance them, als Charles wrote.
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Old Oct 15, 2009, 08:30 AM
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Perth Western Australia
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Ok, i am a newbe at this level, so correct me if i'm wrong, i need 2 x cells, 1 x 2s lead and 1 x servo lead (which i currently use on the Nimh packs i made?
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Old Oct 15, 2009, 10:18 AM
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Germany
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Yeah.

Just connect the cells in the way you would do it if you were to build a 2-cell 2.4V NiMH pack to supply the reciever. Use a normal RX battery lead to do this.

Additionally, you need a balancing cable. This has 3 wires. One connects to +, one to -, and one to the middle between the cells.
The outer wires are the + and -, the middle one is the middle one.

It connects to the balancing port of your charger.

If your charger has no such port, you have a problem.
But it can be solved by single charging the cells.
But I will not explain this before determining that this explanation is needed.
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Old Oct 15, 2009, 10:42 AM
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Haralson County GA. USA
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OK here is a link to a photo of receiber packs. The bottom one is a 2S LiFeP 1250 mAh size. It has both a receiner connector and a balancing connector on it.

You could use a 3 lead servo extension just as well.

http://www.rcgroups.com/forums/attac...mentid=2033421

Charles
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Old Oct 15, 2009, 05:11 PM
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Perth Western Australia
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Thanks guys, you have been of great help
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