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A123 Voltage Drop

Old 05-17-2011, 07:00 AM
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Default A123 Voltage Drop

So A123's are supposed to be fully charged at 3.6v per cell and dead at 3.3v per cell (from what I hear).

I recently bought a sweet Extreme Flight Yak 88" (the yellow and black version) that had two of these packs installed. I bought a A123 charger and charged the batteries last night. The charger has a display of the voltage, the second it quit putting volts in it started dropping like crazy. This morning one of the packs read 3.4v per cell. Is it normal for them to charge up and drop like that? Didn't seem normal to me.

I'll check the other pack when I get home tonight but this didn't seem normal, I was wondering what you Giant scale folks experiences were with A123's.
Old 05-17-2011, 07:12 AM
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Default RE: A123 Voltage Drop

PS - If there's a better forum to post this in let me know, but I figured the Giant Scale people probably had the most experience with this stuff
Old 05-17-2011, 08:04 AM
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Default RE: A123 Voltage Drop

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Old 05-17-2011, 08:05 AM
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Default RE: A123 Voltage Drop

rcfan,

I have A123 packs in my planes and they DO NOT drop like you describe. Actually I've heard they stay charged longer than nicads. I have not done any testing or paid close attention to my packs to be sure but I charge my packs when I come home from the field and the followiong weekend they are still at peak...
Old 05-17-2011, 08:28 AM
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Default RE: A123 Voltage Drop

Some reading material

http://www.hangtimes.com/a123rxsetup.html
Old 05-17-2011, 08:48 AM
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Default RE: A123 Voltage Drop

Thanks guys, kinda looks like I need to replace those batteries. I would like to convert all my rx packs to A123, it would be nice to eliminate some regulators.
Old 05-17-2011, 08:59 AM
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Default RE: A123 Voltage Drop

As far as I know the nominel voltage of A123 cells is 3,3V, freshly charged 3,6V and out of power at about 2,5V.

I have a Hyperion LiFe 2100mah pack in my TX, and it starts out at about 10V (3,33V pr. cell) of the charger, stays between 9,5 and 9,9 for about 8 hours before gradually dropping lower. The TX alarm goes off at 8,5V (2,83V pr. cell), but even then the pack should still be able to keep the TX running for half an hour or so.
Old 05-17-2011, 09:06 AM
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Default RE: A123 Voltage Drop


ORIGINAL: BarracudaHockey

Some reading material

http://www.hangtimes.com/a123rxsetup.html
I bought the Cellpro Multi-4 charger as shown on that website, seems to be a nice charger.
Old 05-17-2011, 09:09 AM
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Default RE: A123 Voltage Drop

[link=http://webhosting.web.com/imagelib/sitebuilder/misc/show_image.html?linkedwidth=actual&linkpath=http://www.hangtimes.com/sitebuildercontent/sitebuilderpictures/VM.gif&target=tlx_picrvg0&title=VoltMagic%20PLV%20 Trigger%20Points,%20Various%20Pack%20Types]Discharge Curve[/link]

According to that chart, I'm still in the safe range for voltage - but that chart is based on the fact that there's a load on the battery. My battery fell to ~6.8 volts after taking it off the charger. Hmm....
Old 05-17-2011, 11:22 AM
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Default RE: A123 Voltage Drop

So here's another question for ya: If I were to just go buy my own cells and weld them together, what is the best brand of A123's to go buy? And where? Links are always helpful.
Old 05-17-2011, 11:34 AM
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Default RE: A123 Voltage Drop

Look at the websites for Radical RC and Electrodynamics for information on packs, battery testers and so forth. You might also want to check the Battery forum on EZone regarding A123 packs and cells.
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Old 05-17-2011, 11:41 AM
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Default RE: A123 Voltage Drop

Hobbyking has genuine fresh A123 cells for $7.99. These have solder tabs for making your own packs. They are currently on backorder

http://www.hobbyking.com/hobbyking/s...dProduct=16575
Old 05-17-2011, 06:40 PM
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Default RE: A123 Voltage Drop


ORIGINAL: rcfan450

So here's another question for ya: If I were to just go buy my own cells and weld them together, what is the best brand of A123's to go buy? And where? Links are always helpful.
A123 is the brand name and trademark for for real A123 cells .... sold through many outlets.
Old 05-17-2011, 09:04 PM
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Default RE: A123 Voltage Drop

Very helpful folks, thanks! I checked and both my packs tonight are sitting at 3.4v per cell / 6.8v per pack. They seem to be steady at that point. Maybe they aren't bad?
Old 05-18-2011, 07:10 AM
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Default RE: A123 Voltage Drop

You could cycle them down and see how many mahs they have. That would be the safe way to see what their actual capacity was.
Old 05-18-2011, 07:16 AM
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Default RE: A123 Voltage Drop


ORIGINAL: Texastbird

You could cycle them down and see how many mahs they have. That would be the safe way to see what their actual capacity was.
That's a good idea, maybe I'll have a chance to do that tonight.
Old 06-03-2011, 06:39 PM
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Default RE: A123 Voltage Drop


ORIGINAL: Texastbird

You could cycle them down and see how many mahs they have. That would be the safe way to see what their actual capacity was.
So I am in the process of moving and therefore have been too busy to get to this... until last night!

I discharged the batteries down to 2.1v/cell (4.2 volts).

I then charged them, let them sit for five mintues, put them in a plane, wiggled 4 digital servos (5645's and 5625's) for 11 minutes, charged again back to full.

Here's the results:

Battery A
- input 850mah from dead voltage to full
- lost 15% capacity while sitting on charger in five minutes but then settled around 6.8v (3.4v/cell)
- input 61mah in three minutes to go back to full after plane usage (on ground of course)
- charger said it was at 71% capacity after the plane usage (and before charging it the second time)

Battery B
- same as above except it too k 910mah from dead voltage, used 57mah after 11 minutes of use in the plane, and charger said it had 79% capacity after the plane use.

I'm tempted to use them, one for ignition and one for servos, but wouldn't dare go more than two flights. I'm still debating just buying new ones but I have limited funds right now (read above, I just bought a new house and am moving). These are aparently 1100mah A123's, not the 2300's which is what I was told they were. I'd much rather have the 2300's and I'm thinking Hobbyking is the way to go on that, with solderable tabs ya know.

BTW, servo response seemed no more crisp and responsive than my lipo setups, regulated.

Old 06-03-2011, 06:46 PM
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Default RE: A123 Voltage Drop

Could someone please tell me the difference between these two cells?
[link=http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=6444]http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=6444[/link] $11.99
[link=http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=16575]http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=16575[/link] $7.99
Old 06-03-2011, 07:05 PM
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Default RE: A123 Voltage Drop

rcfan
I fly the EF yak and I use 2 1100 mah A123's for the rx. I charge after 3 flights, I can fly as many as 5 flights but why risk it. 2 1100's weigh as much as 1 2300 and I get redundancy. For ignition 1000 mah nicad. very simple and effective. I charge my batteries with a jump box that you start your car with, it takes about 4 minutes to charge 1 battery. So by the time the next guy is done flying you are ready to go again. FMA makes very nice chargers, I own the 10S. Having said that the battery fuel percentage is a worthless reading on the A123's it is more accurate with different chemistry types. Just do the math and figure out how much you are taking out per flight and how many mah are going back into the battery. On a side note: depending on how you fly it might be a good investment to get a fromeco Dcup, its really cheap insurance. I was doing some testing with the fromeco cricket and I was seeing the voltage on the rx bus drop down below 4 volts( not good). With the Dcup it always stays at 6 volts (good).
Old 06-03-2011, 07:15 PM
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Default RE: A123 Voltage Drop

I've got an XPS tattle tail, it's basically the same thing as the fromeco DC-up, but much smaller. Good idea though, maybe I'll stick that on and see what it says. I did have a volt meter hooked to the plane too when I was playing with things and never saw the voltage go below 6.5 or so.

My guess is that I'll be fine for a flight or two - but that's it! Charge! If I do end up trying it, I'll charge after every flight.

I'm not a big fan of redundancy, never had an issue with that - some day that may bite me but for now I'm fine. This is my 4th 50cc plane in the hangar, but first with A123's. The guy I bought the plane from flew it quite a bit with this setup w/o issue. I just think the batteries have sat around long enough that it's time for new ones.

Still curiuos about my question a couple posts back.
Old 06-03-2011, 07:22 PM
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Default RE: A123 Voltage Drop

where was your volt meter installed?
Old 06-03-2011, 07:25 PM
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Default RE: A123 Voltage Drop

ORIGINAL: weezle

where was your volt meter installed?
plugged right into the rx

still curious if anyone knows the difference between the Hobbyking A123's I posted links to above..........
Old 06-04-2011, 03:19 AM
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Default RE: A123 Voltage Drop


ORIGINAL: rcfan450

So here's another question for ya: If I were to just go buy my own cells and weld them together, what is the best brand of A123's to go buy? And where? Links are always helpful.

The only type of A123's are A123 Racing cells, there is no other. There are other types of Lithium Nano Phosphate on the market, but technicaly they are not A123 cells.
Old 06-04-2011, 01:08 PM
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Default RE: A123 Voltage Drop

A great source for real A123 packs, cellpro chargers and info is Richard at WrongWayRC,, [link=http://www.wrongwayrc.com/]Click here[/link]

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