A123 Batteries for Dummies.

[hybris]

I posted pictures of home built packs:

http://www.flyinggiants.com/forums/252301-post16.html

[toprudder]

	Quote: Originally Posted by Kiwi
	Thus my thoughts are any variable voltage supply set to the right voltage will be the perfect charger.

That is my understanding. BTW, you can also do that with Lipo and LiIon. Set the correct voltage on the power supply, limit the current, and away you go. This is how I did my 4 cell Lipo before I had a real charger that would handle 4 cells.

Most programmable power supplies allow you to program the max current. Until the battery voltage rises to the level you have set for the power supply voltage, the current will be limited to this max current amount. Once the voltage level of the cells reaches the programmed voltage, then the current starts to drop while the voltage stays regulated.

If you watch most Lipo chargers (like the Accucycle Elite) this is exactly what they do, only you can't pick the charge voltage different from the ones programmed into the firmware. You simply pick the number of cells, and the cell chemistry, and it picks the proper voltage. Like I said, a firmware upgrade would allow them to handle A123 cells, but most chargers are not field upgradeable.

Bob R.

[Kiwi]

As most of you know I love to tinker with stuff. It could be better termed pulling things to peices and most times never getting them back together again. Its been an affliction since childhood.

Well I packed all my testing bits and pieces in a bag and brought them home to play over the weekend. Its going to be cold so no flying possible anyway.
I have a big project in mind testing all the regulators made by Smart-Fly to build up a data base on capacity, regulator characteristics etc etc.

My first round of tests was to define the limits of a 2400 Mah Li-Ion pack under maximum sustainable load. Well I near fell off the chair tonight. The 2400 packs are falling over with a constant eight amps load after 14 seconds. The 4800 packs repeat the same result with 16 amps load. Guys I'm not scare mongering yet because I set the cut off voltage in the test to 4.5 volts.

Tomorrow with a lot more caffiene in the blood and a smarter outlook on life (with luck) I will get some solid results.

However the real eye opener was the packs ability to completely fail. Sure they recovered as soon as the test shutdown but I did not expect that sudden death spiral under load.

Keep posted. This might be fun. A123 batteries just took a real turn for the better in my books. De Walt pack, here I come.

[airbike]

Just some more field experience...

I got a 10 cell 36v Dewalt pack from ebay and configured a 3S2P pack for use as a motor pack. The left over cells will become 2S Rx packs for my 33% & 35% planes.

On my electric LR-1 pylon plane with an Aveox motor, I measured 86 to 90 amps at WOT. A 3 minute WOT flight got the batteries warm but still cooler than Lipos at similar discharge rate.

Then, I tried the 3S2P pack in my hotliner. I used a clampmeter to measure the current and was surprised to see that it was delivering OVER 200 amps to my motor.
I flew for about 45 minutes with about 7 climbs of 5 or 6 seconds each. (gets small really fast). Upon landing, I checked the battery and it was barely warmer than before the flight, and it STILL put out OVER 200 amps.

[GooseF22]

Guys, Im converting all my stuff over little by little. evenutally I will have all 2S packs with common plugs. This lets me interchange if needed, which isn't needed. But it lets me move packs from plane to plane and get the exact same performance. For instance. 2300 packs times 4 wired in 2 parallel harnesses makes for a great 40% double pack for any setup. for the smaller 33-35%, twin 2300's will work. for the sub GS, one pack. KEeps my setups simple, and reliable and powerful. if you have a servo go bad, the 2S pack can still get you down without dropping out below 4 volts. Guys this is just the beginning of a new wave. We will be wondering why others dont do this later. The only limitation right now is availability. I read where several hundred of these were put together on a motorcycleand it was pretty fast, something like 180mph. The turbine guys will be jumping on these soon. they are great starter batteries too.

Here is my thought. Hook up 2S2P times 2 to the power distro block, whatever brand doesn't matter. Power everything, smoke, Seiko p50, 10 digitals, matchboxes. whatever.... everything and not worry about under volting or overheating ever again. Plug em in when refueling, and walla. continuous flying. Let me see, last meet I say how many guys charging late in the day? there is always one guy with the big battery that is gassing and going allday. Lets be him on the GS side of the house.

Guys this is just the beginning of the wave. I dont know how much more strongly Dick and I can say that. I caught the idea from him. I spent some time over at Radical RC messing with these batteries, and they rock. AND they are stable like a rock.

[Kiwi]

Goose,

I just wish the rest of you guys would stay away from Ebay and let me win a pack or so for $80. Durn it all every time I get close some other RC pirate ups the price.

If you other Ebay guys are reading this then let ALLANCITO have a go please. JK!!!!!

I already have my dream setup planned. Plus I found a 0 to 30 Volt power supply on a certain site with a variable output to 30 amps. Less than $200 so thats going to be my charger for sure plus it is super useful in my shop for testing equipment. I'm not telling you the name or supplier or a thing until I get one. Then its fair game for young and old.

[krayzc]

wow win u one and then get out of our way lol

[GooseF22]

Go for it,
Im taking a few months off...........not by choice. Uncle sammy grabbeth me up.

[sprice50]

Great thread guys. Thanks for all the info.

[aerobob]

Okay....just "won" my pack on e-Bay.... so I'll have some extra cells. Now I'm going to "join the Revolution"... and play with fire. Should be fun.

Any words of wisdom from anyone about configuring connectors, since I'm only using these for Rx/Servo packs in my gassers???

[klhoard]

.
I posted some discharge curves for my 2-cell A123 pack on another thread. 15 amp discharge and the pack held right at 5.9 volts.
.

[toprudder]

	Quote: Originally Posted by aerobob
	Any words of wisdom from anyone about configuring connectors, since I'm only using these for Rx/Servo packs in my gassers???

If you are using a power expander, use whatever high current connector they use (Deans Ultra, for instance). If plugging directly into the receiver, I would use two or more standard battery pigtails since each connector is only rated for about 3 amps.

Bob R.

[Kiwi]

Ahhhhh,

The gods have finally smiles on me and my New DeWalt pack is on the way. No lets see what all the fuss is about as I have very high expectations for these batteries using them as flight packs.

Once I get them we will start playing.

[aerobob]

I'm actually thinking of dual output leads on each of my 2S packs, so that demand current is divided between two output connectors, and two switches into the two power connections of the RX for just that reason. Don't want any current limiting going on before the individual servo connections at the RX.

I'm not running these for e-power motors; just the Rx packs to servos/Rx in my planes. Good advice about reducing current loads on the power connectors, for sure.

[aerobob]

Okay.... so my stuff is on it's way. I will be using an FMA CellPro w/ balance to keep things on track. Will make packs using 20 ga, HD, 3 wire JR-style connectors/cables, using the orange wire for the "center tap" so the balance thingy works on 2S packs. Which, I have discovered, means the current crop of "charge switches" are history. They ONLY make/break the RED wire, with the orange and black wires tied through.

So - I'm thinking I'm in new territory here to permit in-plane charging, and that means "custom" switches which have mechanical redundancy and make/break both the red and orange wires. Which means finding 2A contact rating (or better) 4PDT slide switches that may meet mil spec.

ANYONE have any suggestions for this? Other than un-plugging the battery to recharge it (very inconvenient in my birds)....