a123 or lipo.... and other ?s

[BrianG]

The A123's seem to be a good choice if safety, charge time, and discharge C are your major concerns. It would just be nice if they were available in a flat pack instead of round...

[GorillaMaxx360]

arent they comming out with a flat pack soon.

[MetalMan]

Originally Posted by GorillaMaxx360

arent they comming out with a flat pack soon.

I'm not aware of any.

Lately I've been using my ICE to charge my 5s2p A123 pack. Believe it or not, but in 10cell NiMh mode, the ICE WILL charge up to the 18v that 5s A123 needs to be charged to to get a full charge. In fact, the ICE will even go over 19v! (it was an accident, I swear!) The ICE does have a 120watt power output limit, so when a 5s pack is approaching the end of a charge it can only put out about 6.7amps (but at 15v it can still do the full 8amps).
You do need to cut the charge off manually, though. Or, you can get a "LipoDapter" that will cut the charge off at 3.6v/cell.

[starscream]

I'm not sure what you mean by a "flat" pack. Are you referring to the A123 3S packs?

I am testing a prototype 3S flat pack from modelelectronicscorp.com (same size as the 4S pack)
I am running 7S on my maxcim system and am happy with the the initial results. I charged them in series using my Lipodapter and Astroflight 110D. The funny thing is that the 110D cuts off the charge before the LipoDapter.
I am going to really put them to the test this weekend when I head down to the track so I'll have a better idea on actual track results then.

I really don't know why anyone would want to solder these cells together.
The Solderless Power Tubes are, IMHO, the best way to go. The M1 cells stay in balance very well so using a balancer on every charge is really over kill and not necessary IMO.

[BrianG]

I meant A123 should make flat packs like lipos are so they'll fit better and make more efficient use of the room they do take. Probably wouldn't have a metal shell, but that would save weight.

[starscream]

I don't think it wise not to have these in a metal casing. It seems like an expensive and messy risk and I'd assume much easier to puncture than LiPoly.

The A123 "round" casing is quite light, I think its something like .5oz at most
I've held an empty cell and its almost un-noticeable.

[t-maxxracer32]

flat pack would be sweet. but i guess you pay for what you get!

thanks guys! im just going to bnuy the a123 cells!

[MetalMan]

Originally Posted by starscream

I really don't know why anyone would want to solder these cells together.
The Solderless Power Tubes are, IMHO, the best way to go. The M1 cells stay in balance very well so using a balancer on every charge is really over kill and not necessary IMO.

I chose to solder because of the extreme (IMO) cost of the SPTs. I just made up a shopping cart of everything I would need to do one 4s2p setup (2 x 2s2p), and it would cost $40 without shipping. The current setup on my Revo is 5s2p (3s2p + 2s2p), and to make a pack like that using SPTs would cost $52. Obviously the Silver Power Paste is a one-time buy sort of deal, but for me to make another 5s2p pack it would still cost $36.

The only cost for my soldering method is the copper braid, which cost something like $7 and will make almost two packs (the cost of the solder is almost negligible). And with as many car projects as I have on the budget I'm on (12hrs/week at $6.75, half of that goes to savings, and then $20/week allowance), the method I'm using is so much easier to afford.

A123 cells aren't perfect, and won't perfectly maintain balance. When using the Dewalt packs, sometimes (even with brand new packs) there might be a low cell or two. One cell in one of my Dewalt packs was at something like 1volt while the rest were at ~3.30v. Even if you don't use the Dewalt packs, balancing is a very good thing to at least be able to do.

[starscream]

Originally Posted by MetalMan

I chose to solder because of the extreme (IMO) cost of the SPTs. I just made up a shopping cart of everything I would need to do one 4s2p setup (2 x 2s2p), and it would cost $40 without shipping. The current setup on my Revo is 5s2p (3s2p + 2s2p), and to make a pack like that using SPTs would cost $52. Obviously the Silver Power Paste is a one-time buy sort of deal, but for me to make another 5s2p pack it would still cost $36.

The only cost for my soldering method is the copper braid, which cost something like $7 and will make almost two packs (the cost of the solder is almost negligible). And with as many car projects as I have on the budget I'm on (12hrs/week at $6.75, half of that goes to savings, and then $20/week allowance), the method I'm using is so much easier to afford.

A123 cells aren't perfect, and won't perfectly maintain balance. When using the Dewalt packs, sometimes (even with brand new packs) there might be a low cell or two. One cell in one of my Dewalt packs was at something like 1volt while the rest were at ~3.30v. Even if you don't use the Dewalt packs, balancing is a very good thing to at least be able to do.

I tested out my 7S setup (with a SPT phantom cell) at the track yesterday and am very pleased with the performance. The extra cell made all the difference in the voltage drop I saw with the 6S setup and I plan to use the 7S config for racing.

Budget restrictions are always a factor. The SPT kit is a one time purchase and gives you the ability to make x-1 cell configs (x being the max cells for the kit). These packs are easy to take apart and put together, so if/when you chose, you can replace or balance cells. In terms of balancing, I don't see these cells much different than NiMh packs. After 20+ cycles, I believe Pete's 6 cell pack was within a few one hundredths of a volt of each other.

I got my Eagle Tree system the other day so I am eager to do some testing, if it ever stops raining that is. I didn't realize they are based right over in Bellevue :027: I could have saved a few bucks on shipping. :007:

[MetalMan]

I agree that the SPTs are great to use, and if I had some extra cash I might have gotten them. But for me, soldering works and I know that the joints between the cells are very strong, and so now the weak links are the tabs that are welded to the cells (I soldered to these tabs instead of directly to the tabs).

However, my soldering setup offers something that the SPTs cannot offer - I can have a 2p setup where there are groups of 2 cells in parallel that are then connected in series. With the SPTs, you would have to have two groups of cells in series that are then put in parallel, which IMO, is not as good of a way to do a 2p setup. Of course if you aren't doing a 2p setup like I am (and I know you are doing a 1p setup, starscream), then SPTs would work perfectly.

As for balancing, my packs are built for this. I had read that A123 packs would come into balance better after the first few cycles are completed, and at this point my packs seem to have done that.
You would be able to balance your SPT'd A123 packs, but it would still require soldering. You would cut slits out of the plastic tubes for each cell, and then you would use aluminum flux to solder wires onto the cells.

[Scoob]

I have a question. Couldn't you set the ICE to the Li-Ion mode and charge the cells? Hasn't anyone done this?

From what I can tell it will charge them (CC/CV mode) to 3.6v per cell. You can charge at up to 8 amps. The Ice will not let you charge more than 1C
but you can fool the charger by setting the capacity to 8000mah and get the 8 amp maximum that the ICE can give. It wouldn't effect teh peaking of the battery at all. It would be just a little slower than the 10 amps that the A123 charger delivers but still very fast.

I'm asking because I have two ICE chargers and was thinking about getting some of the batteries but don't want or need another charger. I could charge two packs at once with my ICEs.

[MetalMan]

Originally Posted by Scoob

I have a question. Couldn't you set the ICE to the Li-Ion mode and charge the cells? Hasn't anyone done this?

From what I can tell it will charge them (CC/CV mode) to 3.6v per cell. You can charge at up to 8 amps. The Ice will not let you charge more than 1C
but you can fool the charger by setting the capacity to 8000mah and get the 8 amp maximum that the ICE can give. It wouldn't effect teh peaking of the battery at all. It would be just a little slower than the 10 amps that the A123 charger delivers but still very fast.

I'm asking because I have two ICE chargers and was thinking about getting some of the batteries but don't want or need another charger. I could charge two packs at once with my ICEs.

That 3.6v for Li-Ion is the nominal voltage. It actually charges to 4.1v/cell, which for the most part is too high of a voltage.

You can use the ICE to charge A123 cells, but you need to stop the charge manually at 3.6v/cell (7.2v for 2s, 10.8 for 3s, 14.4v for 4s, and 18v for 5s). You could even do a manual CV phase of the charge by decreasing the current to keep the pack at 3.6v/cell.
One way to do this automatically would be to get the LiPoDapter:
http://slkelectronics.com/lipodapter/index.htm
It will automatically stop the charge when the pack reaches 3.6v/cell.

[BrianG]

The only bad thing about the lipodaptor is that it stops the charge as soon as it sees the 3.6v/cell peak, which would be the very end of the CC phase of charging. You'll lose whatever the CV stage would put into the battery. It's not much by comparison, but if you're using 1p A123s with fairly low 2.3Ah runtime, it could make a difference...

Personally, I'd do the manual CC mode thing MetalMan suggested. It just involves you to watch it carefully and make quick adjustments quite often. Also, this assumes your charger will let you adjust the charging current on the fly...

[Scoob]

Got it. So the CV mode doesn't kick in untill 4.1v. It would be a lot of trouble to keep the V constant on two packs at once. I was going to run them in series for a M-truck. I'll just have to stick to lipo. Thanks.

[t-maxxracer32]

so if i just bought a lipo dapter my ice would charge them automatically liek it does with a normal batt? how long would the charge time be?