New 540C-7XL pics dissected,

[BrianG]

Originally Posted by zeropointbug

Yeah! A123 cells are GREAT! They have fantastic power, it seems like its 100% right until they dump too! They simply suddenly slow right down. And charging! It's great, i have a 5s2p pack (developer kits) that i charge on a lab quality BK Precision power supply with all programmable features and CCCV;

Do you balance your cells at all?

[zeropointbug]

I do yes, after 10 or so runs through them, i just tap each cell in the pack and do a precise 100% charge. But here is the kicker, they are only ever off by like .02 volts at the most.

DO invest in these batteries, for a given runtime, you need less A123 cells because they are more efficient than LiPo's and they give you 100% performance right until you they dump.

[mtucker]

I do the plastic bag trick like Metalman when I put a flat spot on the shaft.
Slide your pinion on and see about where the pinion set screw is going to go and then mark that place on the shaft with a felt marker. Cut a small hole in a plastic bag and slide it over the shaft. It only takes a few seconds with the Dremel cutting tool to make a flat spot on the shaft.

You pinion will likely wind up spinning on the shaft if you don't.

Matt

[zeropointbug]

I think I will do that at a later time, when i am done making my new chassis. And then i know where the pinion has to be. I think i will make a crater from a drill bit, it seems that will work better, and better balancing...

[BrianG]

Originally Posted by zeropointbug

I do yes, after 10 or so runs through them, i just tap each cell in the pack and do a precise 100% charge. But here is the kicker, they are only ever off by like .02 volts at the most.

DO invest in these batteries, for a given runtime, you need less A123 cells because they are more efficient than LiPo's and they give you 100% performance right until you they dump.

I guess I should have phrased the question: How do you balance them? Or what do you use?

I'm still not totally sold on those A123 cells yet. Even though they have high discharge rates, the runtime isn't great unless you parallel them. And then, the voltage isn't quite as high normal lipos. I guess I'm still waiting for the Holy Grail of batteries to arrive...

[zeropointbug]

Well, the only way to know for YOU, is if you buy them, now they aren't cheap, but they are not as expensive as LiPo's. The voltage issue is irrelevant though, i mean they are a different type battery altogether. I personally, LOVE them. I would never go back to Li-Po.

You ask about the holy grail of battery tech........


Europositron technology

This company is based out of Finland, and received a Frost & Sullivan award for 2005, for good reason, well VERY good reason. They say 1-2 years market. :)

Energy Density/Volume: 2100 Wh/litre

Energy Density/Weight: 1330 Wh/kg (Standard LiPo: 140Wh/kg)

Cycle Life: 3000+ cycles

Minimum Working Temperature: - 40C

Maximum Working Temperature: +70C

Life: 10-30 years

Discharge Rate: Adjustable

[MetalMan]

Originally Posted by BrianG

I guess I should have phrased the question: How do you balance them? Or what do you use?

I'm still not totally sold on those A123 cells yet. Even though they have high discharge rates, the runtime isn't great unless you parallel them. And then, the voltage isn't quite as high normal lipos. I guess I'm still waiting for the Holy Grail of batteries to arrive...

I justify the lower capacity/higher weight of the A123 cells when compared to LiPo by comparing them to NiMh - more power, more runtime, higher voltage, faster charging, etc. for less weight. I'm pretty much converting everything over to A123 cells - Rustler is getting a new, A123-specific chassis, Revo will have batt mounts made to hold them, and the Savage will also get batt mounts. What really draws me to these cells is that they physically can't puff up - I had to send my Maxamps 4s3p pack of 2100HV cells back for a replacement when one of the parallel groups puffed up for no apparent reason (with the use of a Dimension Engineering CellShield LVC and a balancer on every charge). My only LiPo-powered cars will be my 18t (still need a Mamba and LiPo pack), Dark Impact (have 2 Lipo packs for it), and my X-Terminator (getting the replacement Maxamps pack).

[BrianG]

MM, believe me, I'm not trying to downplay your choice! Comparing them to NiMH, there are advantages. I think the trouble I have with them is the size. They are kinda difficult to stack in a space-saving way. Makes for an oddball package IMO. I could see maybe running these in my Jato at 3s1p. But to run them in my Revo, I'd have to 2p to get any amount of runtime out of them (I like at least 15 minutes) and then 6s for the voltage. That's 12 rather large cells.

Now, if they had a solid 4 or 5Ah, then runtime would be higher and would only need 1p for most applications. The cells would of course be larger, but the footprint would be less than two of the current sized ones together. If only the M1 cells were flat, it would be a no-brainer!

Believe me, I'd like to covert to one super battery chemistry for everything. Maybe the Europositron technology stuff might be what I'm waiting for. My Hyper8 buggy is still sitting around because I can't decide whether to go for lipos or not.

[MetalMan]

Originally Posted by BrianG

MM, believe me, I'm not trying to downplay your choice! Comparing them to NiMH, there are advantages. I think the trouble I have with them is the size. They are kinda difficult to stack in a space-saving way. Makes for an oddball package IMO. I could see maybe running these in my Jato at 3s1p. But to run them in my Revo, I'd have to 2p to get any amount of runtime out of them (I like at least 15 minutes) and then 6s for the voltage. That's 12 rather large cells.

Now, if they had a solid 4 or 5Ah, then runtime would be higher and would only need 1p for most applications. The cells would of course be larger, but the footprint would be less than two of the current sized ones together. If only the M1 cells were flat, it would be a no-brainer!

Believe me, I'd like to covert to one super battery chemistry for everything. Maybe the Europositron technology stuff might be what I'm waiting for. My Hyper8 buggy is still sitting around because I can't decide whether to go for lipos or not.

Aren't you the one who's running one NiMh pack on top of the other in your Revo? :005:. These cells are slightly taller, but that wouldn't do much to the COG of your Revo since they're lighter.

[BrianG]

:p

Yeah, only because I had sized the batt-tray for a 5s2p pack of the TrueRC 8Ah packs, but then decided against it. So, I remade a few of the 3300 packs I already had laying around until I could find something else. That "until I found something else" was longer than I anticipated. Believe me, it's not my ideal choice!

Besides, the M1 cells are quite a bit bigger really; ~4mm wider and ~20mm longer than NiMH cells. They are actually roughly the same size (a little smaller) than my emoli cells and those are a pain to stack in an economical way! I dunno. Maybe if a pack fell into my lap I might try to finagle them in there. I think it would be clunky though...