A123 Batteries for Dummies.

[dick hanson]

parallel cell charging is simply too risky for those who have no equipment to correctly sort out that the cells being charged are exactly matched .
the theory is fine . the actual application is a potential disaster as the A123 cells wil NOT stop at full charge rating - buy some A123 cells and try this before suggesting how how easily they will charge in parallel.
If one cell is at more than .1 volt than the other -you can get in trouble if you don't understand the A123 cell . I ran actual tests on this.
best bet - don't charge in parallel-and don't diddle around trying to top off fully charged cells -- these cells are NOT like LiPos

[Rolling Thunder]

I trust your testing and I will follow your advise.

[Kiwi]

The brown box has arrived, there will now be peace in the world while I bury myself learning about these things.

[Pale Rider]

If you plug these into a regualar JRHD switch that has the charge jack, can you charge/check them through the jack in the switch ?

[aerobob]

I followed Dick Hanson's lead on this, and using the FMA CellPro 4S, I wired a "center tap" charge lead, which mounts in the fuse with a Ernst mount. On the "output" of the battery, only the + (red) and - (black) are connected. This permits the JR switch to function normally. Yes, you can use it for checking voltage. Should not be used for charging because the orange wire is connected straight through the switch. If you did it that way, in the "on" position, the orange center tap voltage would be seen by the orange pin connection in the Rx. Not good. Drawing attached.

[Pale Rider]

So the center tap lead is used for charging and or checking ? What if you eliminate that lead and just plug the pack into the switch as you would a regular pack? Then you should be able to charge through the switch ?

[aerobob]

	Quote: Originally Posted by Pale Rider
	So the center tap lead is used for charging and or checking ? What if you eliminate that lead and just plug the pack into the switch as you would a regular pack? Then you should be able to charge through the switch ?

Yes, but doing so won't permit using the balancer function of the CellPro charger. I don't know about others.
Still searching for my dwg, will update when I find it.

[Pale Rider]

Got it...this the one Im looking for right ?

http://www.fmadirect.com/products.htm?cat=45&nid=4

[aerobob]

	Quote: Originally Posted by Pale Rider
	Got it...this the one Im looking for right ? http://www.fmadirect.com/products.htm?cat=45&nid=4

Yep. It will work. I added the schematic of my setup (except that I have dual switches, with dual leads from the battery for current handling/redundancy)

[Pale Rider]

	Quote: Originally Posted by aerobob
	Yep. It will work. I added the schematic of my setup (except that I have dual switches, with dual leads from the battery for current handling/redundancy)

Dual switches was the what I was thinking as well..

[aerobob]

BTW - I've been using these now for about 3 weeks in 3 airplanes. Perfect. Cellpro lets me measure current consumption by displaying total recharge current to the pack. Nice feature.

[hybris]

	Quote: Originally Posted by dick hanson
	parallel cell charging is simply too risky for those who have no equipment to correctly sort out that the cells being charged are exactly matched . the theory is fine . the actual application is a potential disaster as the A123 cells wil NOT stop at full charge rating - buy some A123 cells and try this before suggesting how how easily they will charge in parallel. If one cell is at more than .1 volt than the other -you can get in trouble if you don't understand the A123 cell . I ran actual tests on this. best bet - don't charge in parallel-and don't diddle around trying to top off fully charged cells -- these cells are NOT like LiPos

I don't know how two cells connected in parallel can be off .1 volts. I am not suggesting connecting separate pack in parallel for charging. I am suggesting that a pack can be built with parallel cells. What testing did you do to to prove this unsafe? What was the result? Another option is to build two 2s packs and use a Batt Share. this would also give you twice the capacity.

[Kiwi]

Guys,

I have taken the plunge and the cellpro 4S is on the way.

But I downloaded the manual for it off the net last night and I think I learned more reading those 11 pages about Litium cell technolgy and care than I read in 1000 pages of bullsh!t here on the internet.

If you want a quiet five minutes reading go download the manual, it makes for some extremely interesting reading.

[klhoard]

	Quote: Originally Posted by hybris
	I don't know how two cells connected in parallel can be off .1 volts. I am not suggesting connecting separate pack in parallel for charging. I am suggesting that a pack can be built with parallel cells. What testing did you do to to prove this unsafe? What was the result? Another option is to build two 2s packs and use a Batt Share. this would also give you twice the capacity.

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The idea behind using A123's is to de-complicate the electrical system in the plane, so adding a "Batt-share" would just replace regulators with another dead weight box in the plane.
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I think the problem with parallel batteries Bob is talking about is what happens when one cell develops problems. If one cell develops an internal short, then the parallel batt will go right down the tubes with it. If the parallel batt fails open, then you won't know about it until you take the pack out of the plane and do a capacity test, and the good cell will be overcharged every time.
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I agree with Bob, the best way to treat these packs is to have two independent packs, and charge them with a balancing charger like the CellPro.
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Another advantage of using the CellPro is that every time you charge you are also doing a "health check" on each individual cell. If every cell the CellPro is charging doesn't come up equally, then you will get an error message from the charger letting you know something is wrong. If the cells were paralleled, a bad cell would be masked.
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[Kiwi]

Good advice,

I was looking at the way to have all the charging system etc work as per the cell pro yet still fand a way to run 4600 MaH packs on my 40%. I think I have the answer and it seems neat and again absolutely bullet proof.

I figure if I use one of these FMA parallel connector boards I can make four two cell packs and plug them into this thing. Then its just a short jumper to the Power Expander. That way I get my longevity of flight for the day without having to recharge, I have wads of potential for any type of aggressive servo power demand and at the end of the day, unplug them and charge them at my leisure.

I don't know maybe I'm off base with this idea but it seems simple and doable.