A123 Batteries for Dummies.

[Kiwi]

A123 Batteries for Dummies.

Well the thread title is aimed at me. It seems that there is a very good alternative to the power setups we are using in some of our planes these days. Hidden way down in the bowels of another thread on the site is a discussion on the pros and cons of the A123 battery technology.

These things may be just what the doctor ordered so I hope the likes of Dick Hanson and anyone else who is experimenting with these packs or cells can enlighten us all here.

Fire away please guys. I need to know more about them and I prefer to learn it here.

[sprice50]

Never heard of this... interesting. Can't wait to see what it is all about.

[F3AFlyer7]

I've used them in a modified electric E-maxx and they work great! They are surprisingly light for their size and seem to perform much like a Li-po. They are still heavier than Li-po's for their capacity and take up more space. I know some people are running them on 90 sized helis with great success. But thats as far as my knowledge goes.

[krashmaster81]

Standing by to be enlightened...

-Matt

[tobytorkn]

I would love to hear the following.

a. where can we get them outside of a123 racing, (ie. supporting hobby distributor)? i think horizon just did a deal with them? cost per battery/pack?

b. what kind of chargers can i use? will a triton,hobbico elite, etc, work by doing a little programming?

c. what are some actual field reports.

d. for people making larger packs are you doing balance charging or is this even necessary.

by what i've read you litterally can do a dump charge while your fueling and they'll take the abuse.<---lets here some actual field reports.


thanks for the info.... toby silhavy
www.silhavyaerosports.net

[toprudder]

The topic in the other thread was about using A123 cells instead of Li-Ion for powering rx/servos. One advantage is the lower voltage per cell of A123, no regulator is needed.

I've heard some people buy the A123 cells by purchasing Dewalt tool batteries on eBay. I don't know which model number battery, and I know a lot of the Dewalt tools use Nicad packs, so the model number would be useful information.

Bob R.

[Kiwi]

Here's what I do know about them.

They are a nominal 3.3 volt cell so by putting two cells together you get 6.6 volts. Definitely no need for a regulator.

They are capable of delivering 70 amps pretty much continuously with a burst for 10 seconds at 120 amps with voltage loss. That humongous amperage for a 35% plus sized plane with these new 8711 type servos.

The ability of the cell to take such a whopping load yet hold voltage is one of the key advantages.

You can charge them at 8 amps and in 15 minutes your fully charged and ready to go flying again (talking electrics here but the same for flight packs I suppose)

You don't need fancy chargers, 100 dollar charger from FMA Direct is available now.

I will get the De Walt battery number but the 36 volt De Walt pack on Ebay runs for around $100. That must have ten or twelve batteries in it.

I will find more this weekend but I know Dick is using them and swears by them.

[exeter_acres]

Toby has a good question... as I don't do business with FMA...
is that a special a123 charger... or can we use our current LiIon/LiPo chargers?

[hybris]

You don't have to buy the Cellpro from FMA but I like it the best. There is also a new Astro A123 charger coming out. The are some other chargers also. You cannot use a regular Lion/lipo charger, it will overcharge the cells. 3.6v per cell is full charge vs. 4.2 volts for lipoly. Check out my thread:

http://www.flyinggiants.com/forums/f...ies-today.html

Now up to over 2.5 hours on them in my Extra.

[hybris]

Tanic packs sells them: www.tanicpacks.com

I got mine from ebay. Dewalt DC9360 battery (36v) for about $110 delivered.

Instruction on taking apart a Dewalt pack: http://www.slkelectronics.com/DeWalt/packs.htm

[GoeKeli]

I have some ideas of how I would like to use these cells but am watching and waiting. The weights are not far off from nickel batteries. If I were to get into them today I'd buy off ebay and or http://www.tanicpacks.com , that guy knows his stuff from what I can see. I use a mix of futaba receivers and JR servos and am not sure they like anything over 5.5 volts together. There is also IMO a lack of real easy and cheap chargers right now that will show up later if these cells get popular. The price of them is steep for what they do IMO.
Good luck Kiwi.

Joe

[toprudder]

A standard LiIon or Lipo charger will not work, it must have a special charge mode programmed in with the different cell voltage. The charge algorithm is the same (current limited, constant voltage) as Lipo/LiIon, just a different voltage. As I understand it, the FMA charger will handle Lipo as well as the A123. Most chargers could be modified by the manufacturer with updated firmware, but whether they do it or not....???

I'll probably do what Dick Hanson talked about, build a charger with a simple three terminal power supply regulator, like the LM317. Should be easy to do.

Bob R.

[dick hanson]

Hybris info on the models I fly on 123-- is much the same as I experienced .
Here are some pics of testing I have been doing and a basic pic of wiring. actually a good wiring job done with parallel leads to two switches then to two rx inputs is a very easy way to get best current flow with over the counter pieces. Depending on your own servo loads, this may show up as increased servo performance.
I made a simple discharger from two 1157 taillight bulbs -which on the two cells pulls about 3.7 amps . using this setup and a very inexpensive Harbor Freight Voltmeter -- you can entertain yourself and find out what the cells actually do under loads
well worth a few hours of charging /discharging / measuring etc.. you don't need to wait for cells to cool just test and go
If you like ,use a heavier discharge load - but for use as a receiver /servo pack , this simulation is fine.
the bulbs are from any auto parts house .
a 2 cell pack for planes up to inc 33% size -weighs 5.5 ounces and how long they fly on a charge is ,bluntly put - Your responsibility to measure and deal with. Plug n play can only go so far --
Why should one use these vs NIMH- well - weight difference is the only good answer I have in this comparison. The ability to supply current under high loads is about the same as a properly formed, 4200ma 5 cell extremely low impedance NiMh pack. (but not for as long a period)
How about vs LiIons .
Different story altogether .
The LiIons need a regulator and they also have nowhere near the ability to discharge huge spikes of power .
So what?
In many cases the LiIons and regs work very well -proven -no sweat -until you really jamb the load to them --then if the regulator -usually a linear type gets HOT-- look out . Not trying to frighten anyone - If you don't fully understand your LiIon reg capability - get in touch with your supplier and find out what loads it will reasonably handle.
I have seen some which are simply awful and some good ones too.
The 123 cells are really a fairly constant power output -without a reg.
Why?
simply put - they can supply current at minimal voltage depression, faster than you can use it --very important
On my electric modes, I start with 14 v (4 cells) apply over 40 amps load and the volt meter stays above or on 11 volts .
LiPos will do this too -untill you run em too low -- then it's bye bye $$.00 pack.---
On my 123 cells - I can run em to almost 2 volts per cell- (no load measurement) then just recharge em -
The least expensive way to get the cells is -at the moment -EBay - 10 cells in a 36VDeWalt battery case. -split the cost with a pal or two and the cells are REALLY cheap. Packs go from $100-$125.
New cells are also on the market singly - from $20.00 apiece on down to $10.00-- you have to do your own bird dogging on this--Horizon also has new ones I buy them too -all are tabbed and all 4 I have purchased were perfect. at at exact same voltage --you store em at full voltage not fussy at all.
I bought one pack from EBay -- cell voltages were all over the place on each cell. I was unhappy --till I started charging em - the strange -really strange part was that ALL cells - once cycled -- went -right to 3.6 v . and all work perfectly the same
they do -really -- self balance -this is simply done by running em down to 3 v then recharging.-- My CellPro gets antsy if you start with two cells which are over .15v DIFFERENCE when you start a charge with "almost full" batteries - this bugged me - It went into safety mode -- charged in a balancing act for an hour - a pain in the ass . I found that by simply discharging down to 3 v- the cells zipped up and rebalanced . My four cell power packs for my electric models -get charged on a non balancing charger - and --they end up all the same -every time.
The Cell Pro was originally developed for LiPos and is a great charger . The 123 cells really don't require all the features in that charger -but I still think it is a great one for this use
Why?
it does tell you what each cell is doing - when you do a battery test -in your model ,once settled down, takes a couple of minutes . It shows voltage level in each cell AND an extrapolated % of full charge "85% charge" as an example or "100%" charge . etc.. Essentially, the charger is also your battery checker . I just plug into th charge switch during refueling.

[Kiwi]

Wow,
This thread lit up like a neon sign in no time.

Guys from what I can understand all you need to charge these things is a source of voltage and current that matches the cell. I am not an electronics guy at all. I got left in the dark in that respect years ago. I still battle with the remote control for the tele so go figure??

If you could get a variable voltage supply rated at say 8 to ten amps then all you need to do is set the voltage. The charge current will sort itself out as the voltage equalises between the pack and the power source.

Dick Hanson gives an idea of that by showing that the 36 volt De Walt pack can be hooked directly to three car batteries in series and the pack is charged in 15 minutes. No regulated feed, fancy trickle charge top off etc etc.

Thus my thoughts are any variable voltage supply set to the right voltage will be the perfect charger.

If I'm wrong let me know. I like things with nuts and bolts. That tricity stuff is invisible and I know it bites you if there's enough of it. That's my total sum of knowledge when it comes to electronics. Oh and if the remote for the TV does not work, change the batteries.

[Kiwi]

Here's the data sheet direct from the A123 web site. You have to admit they seem to have a huge potential and are surely the answer for those 14 servo setups with potential 3 amp loads.

The voltage on these things just does not flatten off at all. 70 amps continuous is whopping big. 120 amps burst for ten seconds is going to melt your on board avionics anyway so you cant blame the batteries any more.