Govert

Hi guys,

I'm planning to purchase some A123 cells and I really need some advice about the batteries itself and some good chargers.

Here's my thing: I'm planning to switch over from sub-c cells to A123/Life cells because of the ease of use aspect. Lipo's don't fit my needs, because of a few things: expensive, 1C charge for lipo, A123 lasts 10 times longer than lipo, A123 delivers higher C-rates and all the other lipo disadvantages lipo-lovers don't like to talk about (no flaming).

Some A123 specs: 4600mah, 6.6V, maximum (advised) charge rate of
18AMPS.
The cells come in 3.3V, 2300mah. So what you need to do is connect 4 cells to make to whole pack 6.6V, 4600mah. So 2 sets connected in series and those 2 sets connected parallel (If I'm wrong, please do correct me).

Now here's the thing. What I know is:
You CAN balance the cells, not really necessary.
Charge up to 18AMPS.
Maximum voltage under charge (volt cut-off value) 3.6V per cell. (makes
7.2V for the whole pack).

Most of the chargers that are able to charge lipo's have a cut-off of 4.20-4.25 per cell. Obviously this is to high. Luckely there are a few chargers that are able to charge A123 cells, because they have a variable volt cut-off setting.

My questions:

-Which charger charges with 10 AMPS or more and is reasonably priced (preferably with display!)?
-Do you really need to balance the cells and how do you do that?
-How do you connect (if needed) the balance cables if soldering my own cells?
-Some other tips and tricks or facts?? All are very welcome!

-Right now I use a MM Cell Master (not suitable for A123) and I have access to a Robitronic Overloader 1. Is this one suitable??


A lot of questions, but I hope most of them will be answered.
Just to be clear, I'm not looking for a lipo versus A123 or Sub-c discussion, becauce my mind is set on these cells because of the earlier mentioned specs.

Additional information: car: Tamiya TRF416, LRP Sphere TC.

Thank you in advance!

Eddie_E

The Onyx 230 does A123s at 7 amps for around $80.

DLS II

Hi, I'm using MEC SPT's with my A123 cells. No soldering! I don't balance-if the cells do go out of balance I can break the packs down in 2 minutes and balance the cells individually. I charge using a Astroflight 110D and Dapter. My 4600 6.6 volt pack charges in roughly 30 minutes @ 8 amps. They are great cells. Have fun! Don

Juanchoyo

What about an Hyperion???

Govert

Thank you for your reactions so far,

Hyperion looks good and is reasonably priced.
@ DLS II: Could you be a bit more specific please? What do you mean with MEC SPT? When I google it, looks like something with De Walt...I know that De Walt uses A123 cells, but are these usable?
@ Eddie_E: looks like a good charger, but would still like to charge with higher amp rate.

Any more suggestion or any other complementary information?

Thanks.

DLS II

MEC -www.modelelectronicscorp.com. They sell SPT's- solderless power tubes. They are kits made up of clear "shotgun" tube( like what is used on preassembled NIMH stick packs), molded plastic end pieces, 2-56 threaded rod,bicycle spoke nipples,a battery bar and a set of wires with a metal connector on one end(that fits into the molded end piece) and a Powerpole connector on the other. They also sell turned aluminum pieces that take the place of a cell in case you want to make a pack with an odd # of cells. All in all with a 4 cell kit you can configure it 4s(13.2 volts). With 2 extra battery bars(the kind used to make NIMH sub c side by side packs), a foot of 2-56 rod and an extra piece of "shotgun" tube you can also make 2s2p(6.6 volts) or 2s(6.6 volts). If you get that turned aluminum "dummy" battery, you can also make a 3s(9.9 volts). A very versatile and useful battery system! Yes the Dewalt packs can be broken down and the cells utilized. Don

Itchy

iTrader: (1)

Hi,

Most chargers that do 10A are not particularly cheap. I got the A123 charger. It doesnt have a display, but you can get good deals on ebay.

To really take a profit from A123 capabilities i would consider the new Hyperion EOS 0720i (check specs here)

Because of their tolerance to overcharging, it is not completely clear if balancing is necessary with A123 cells. In any case, its probably a good ideia to balance them.

The overloader 1 doesnt have a life mode. You can ask robitronics to upgrade the software so it is A123 friendly.

You can also use diodes to lower the voltage from the overloader, and charge at a maximum of 8A in li-on mode. I did this and it works, but i would advise to get a proper A123 charger.

If you are used to 5 cell, for A123 the ideal ratio will be one or two pinion up

Good luck.
If you can please post pictures of your future setup. Im strugling to fit these cells on my HB Cyclone, but i suspect the Tamiya will be more friendly

linger

iTrader: (1)

Hi Govert,
If you are planning to make a pack with the A123 cells, here are a few tips.
Connect two cells in parallel first, then connect them in series. The cells connected in parallel will self balance. If you connect in series first, you will have a balancing nightmare.

Concerning balancing - you probably don't need to balance A123. They are actually pretty good about absorbing overcharge while Lipo doesn't.

yes, the Dewalt packs use the A123 M1 cell - 2300 mAh.

If you get the cells with a welded on tab - Do not break off the tab since you need to solder onto them! The can of the A123 cell is aluminum and impossible to solder onto. If you are able to find Aluminum solder - it's incredibly weak.

And finally - since you have a 416 (I have one) - good luck fitting A123 cells (I have a bunch of those too) into that chassis. There isn't much room.

Good luck.

Govert

Thanks people,

I have learned a few things. I didn't know the A123 can is made of aluminum. So if I don't buy the De Walt cells, I have to buy the cells with a soldering tab I understand. And thank you for the balance cable tip, very helpfull.

@ Itchy: That Hyperion EOS 0720i is actually exactly what I'm looking for. Capable of charging every type of battery with a charging rate of 20AMP!
One thing though, it's hard to find stores that sell the 720, I have only found one or two. Are there any asian stores that have this charger in stock? Does anybody know?

And Itchy, are you sure about the one or two pinions up? Since I drive 5 cell
(6 Volt) and A123 is 6.6 Volt, shouldn't I go down with my pinion instead of up?

I'll try to make some pictures this week, since a buddy of mine has a brand new A123 stickpack. He's driving a Xray T009, that shouldn't be a problem fitting the battery in, but I'll see how it goes with my trf416WE.

Oh and Itchy, if you have the time and patience to inform me about the diode you replaced in your Overloader, that would be very helpfull. Even though you're not a big fan of replacing it. No pressure though

Buggy Brad

Here are a few more things to consider,
Dewalt puts the 2300mah(26650) cell only in the 36 volt pack all the rest use the 1100mah cell(18650) in a 2p setup. Another thing to know about the 2300 is the button is negative and the can is positive, the 1100mah cell is a steel can and normal as far as the button and can for polarity. I think you will enjoy the 123 cells, I switched over a couple of years ago and now all my planes, heli's and cars are powered by 123. Some use the 1100mah and others use the 2300mah cells........BB

Itchy

iTrader: (1)

Hi again,

I think EOS 720i was released a month ago or something. In the next weeks its availability should improve.

I drive mod in BIG tracks. Your mileage may vary, but i have found A123 like small ratios. I think it is because they drop a lot of voltage under load (but dont be mistaken, with the proper motor and gearing they are very fast and smooth )

The diode is not inside the charger!

You just have to put the diode between the aligator from the charger and the cells.

I will take a picture when get home, it will be much more clear

Govert

Ok Buggy Brad,
I'll avoid the De Walt batteries that aren't 36 Volt. Funny thing the flat end is positive and the button is negative. Something to pay attention to. Thanks for the usefull tip.

@Itchy: I'll play a little with the gearing, and start with your suggestions.

If you could post a picture of your charger and diode combination any of these days, that would be great and might help many other people to switch over to these cells.

Thanks for all the help so far. All your help is very usefull!

Itchy

iTrader: (1)

Hi again.

Here is a picture of my setup. I used 6 diodes in paralel, of 3A each. Thats because those were the only available at my local electronics store at the time :P



They still get hot at 8A charging. In summer it would be advisable to use a fan or bigger diodes.

In this setup the negative clamp of the charger conects to the 6 diodes wich conect to negative pole of the batery.

The diode(s) will drop the voltage by about .6v. So in Li-on mode the overloader will stop the voltage at 8.2-0.6=7.6v (or 3.8v/cell).

The diodes i used are P600K.

nexxus

iTrader: (315)

I was sold by all this too, spent big $$ on 2 * Hypersonic A123 2s2p packs, a 3s1p pack and a 2s1p pack and their "Hypersonic" charger (after they advised it was the only one that could balance the packs correctly).

The packs all had dead cells within 5 months.

A123's customer service became non existant.

I charged everything by the book.

My advice, avoid these like an ex girlfriend!

gortan

iTrader: (1)

rc-mushroom seem to have the i720 in stock.