Real Time A123 review

[Chris_The_Battery_Man]

Originally Posted by JohnRobHolmes

Even with a lower cutoff the a123 woudn't hit 2300mah at 20 amps.


On larger rigs a 2p setup is needed. An emaxx would be pretty fast on 6s2p a123.

No I will give A123 that... They will hit near 2300 mah even at 30C but it is such a low voltage sag(2.6-2.4volts) that its pathetic....

And for the Emaxx.... Yeah even an A123 at full volt sag will put out 15 volts at 6s.... yeah thats alot but put in a 6s lipo and under full sag you be around 21 volts..... HOLD ON!!!!!

[Chris_The_Battery_Man]

Here are some pix of what we are testing and what with

Using 8mm bullets




The equiptment... thats a 100 amp amplifier with dual 10 awg leads to 8mm bullets hooked up to a turbo 35 tester which is was more accurate than a CBA annalyzer.... It also reads voltage through a seperate set of leads to keep the voltage read out in the graph while under load more accurate...

[NickRummy]

How much would a 20C 6S 4600mah or equivalent lipo cost?

I'm running a 6S1P A123 setup in my E-maxx with a 10XL and Monster Max. 22/66 gearing and my cut off is set at 15V. I'm dumping 1300mah in a 5m minute qual and it's never hit the cutoff. It'll run strong until it uses up around 2100mah. With the 15V cutoff I'm getting a resting voltage of 18V when I go to charge them.

Here is a test run while the pack was still being broke in. I think it might have only had 1-2 full cycles on it. Running some heavy wheels too. GPS'd at 39mph. I could easily gear up but it's already a handful on the track.

[Chris_The_Battery_Man]

A 6s 30C Elite 4500mah pack would be 240

[NickRummy]

Originally Posted by Chris_The_Battery_Man

A 6s 30C Elite 4500mah pack would be 240

Not bad. I have $160 in my two 6S1P packs. I do like the hard casing of the A123 though and I can charge the 6S1P in under 20 minutes.

[mattnin]

Some temperature measurements would be great too

[Chris_The_Battery_Man]

What relevance would temps be to you? I can say that last night The A123 was barely holdable after it was done discharging... Havent got to re testing the Lipo yet.

And on a side note what setups are the guys you're racing running?

[mattnin]

I feel temps are important because a battery can be run to where it is destroyed due to temperature.

The guys I race against use all sorts of different motors, most run brushless, Novak, LRP mainly, I am the only oddball with Tekin, and they run motors ranging from 7.5 to 4.5. Stock is Novak 13.5. Their batteries are some nimh, but most run the carbon spec race pack lipo, or the new 3800 mah race pack lipo.

[Chris_The_Battery_Man]

Yeah true they could be ruined but generally that happens people build them wrong or ask too much of them. Were testing them within their rates so if they're getting too hot then its because of them not being able to handle the current. But I will try and throw the heat gun on them to monitor temps when I get back to testing. They didn't seem hotter than they could handle to the hand though.

[NickRummy]

I've notice that their best performance comes from a slightly warm pack also.

[mysharona]

More heat(freshly charged pack)=less resistance= more POWER

[Chris_The_Battery_Man]

Yeah very true... But in a situation where there is alot of current being drawn the pack will warm up regardless. Look at the graph on the first page... the blue curves dip then climb when theyre warming up...

[BritCrawler]

To prove it makes little difference Chris, could you charge, then discharge while it's warm, one A123 cell for us a couple of times and compare it's warm start to it's cold start characteristics? It's not likely to make a fat lot of difference but it'd be interesting.

[OldShovelhead]

Probably all I can do here is interject my lack of real data, but want to share my working experience.
I recently purchased a Proboat Formula Fastech. Bought 2 DTX 4200mAh NiMH stick packs from my LHS at the inflated price of $80 for both. Also, bought for the same price 4 4500mAh Tenergy stick packs. So, I've got $160 worth of crap stick packs. But nonetheless they're all new and will withstand a little abuse before crapping out.
With the NiMH packs my run times average about 5 minutes. My Raytech reports temps around 145-180 between the cells and the wiring. Most FE boats are water-cooled now and if you check out this model you'll note it's a full aluminum cooling sleeve on the motor and not a cheese-d!&^ coil affair. The ESC is also water cooled.
With my a123 packs which for the boat are 4 cells in 2s giving me 2 packs at 4600mAh each.
Testing the a123 packs this past Weds eve I ran the boat for 3 mins, brought it in to check heat etc, back in for about another 3 mins to check, and again for about 4 mins.
ALL components were normally warm- not hot. Even the deans were warm to the touch but not hot....unfortunately I forgot the temp gun so I can't produce factual data for these temps. But it was clearly cooler running than with the NiMH.
With the a123 cells I got 2' of cavatation which I've never experienced with the NiMH cells. All of the running characteristics are different now- the boat is overall faster and accelerates faster and gets to top speed faster. The packs are a bit larger than the NiMH packs BUT they're lighter as I can see this in the ships attitude as it sits on the water. I need to shift weight to the rear for better CG with the NiMH packs but the a123 packs clearly show a higher bow = less weight in the same place as the NiMH packs.
So as I'm reading this real time evaluation I felt I wanted to chime in with my practical experience with these cells.
I'm also running a 2cell 1100mAh pack in my Scorpion - plenty of torque and one helluva lot less weight.
just my twocents

[mattnin]

There is no doubt A123 are high performing cells. Do I really have to bring a copy of the scoresheet of this Sundays upcoming modified touring car race?

[BritCrawler]

So, in conclusion, well at the very least I'm gonna try and create some kind of summary...

A123 does not perform as well as true LiPo packs. I think Chris has provided us with ample evidence to prove this. The only unknown here is starting temperature, but I feel, from what Chris has said, that this won't make a *significant* difference. I'm not saying it's not gonna make *any* difference, but it's not going to be *significant*.

A123 is lighter, more powerful, and almost as safe as a NiMH battery pack. Actual dimensions are an issue for some and not for others, and A123 is a bit awkward to fit in some spaces, but overall I think it's got the upper hand on NiMH for performance per gram, and it's almost as safe. I'm pretty sure a 4s1p A123 pack would kick a near equivalent 10 cell 12V NiMH of the same mAh into touch in most applications.

A123 is not the be-all and end-all of performance. A123 is not perfectly safe either. I've heard nothing about safety issues with A123, but I've read no less than 3 stories on forums in the last week of NiMH popping cells, so even 'safe' packs aren't totally safe. Any battery contains a large amount of energy in small place. It's dangerous to some extent. Be careful with any battery pack, charger etc. A123 is no a LiPo replacement technology. A123 requires an appropriate charger, like LiPo, with a balancer and LiPo enabled.

A123 *is* safer than LiPo. A123 is better than NiMH in almost all respects apart from physical size. A123 charges faster, MUCH faster, than LiPo. A123 *is* perfectly adequate for 99.9% of Rock Crawling applications.

Feel free to contradict anything above. I am just trying to draw some sense from this thread!

[JohnRobHolmes]

I would choose LiFe (a123) over NiMH any day for high drain or weight savings, that is for sure. Less cells to go bad in a pack, much longer expected life, and a lot lighter for the same Watt/hour of energy.

Interesting setup Mattnin. Is that two packs of different capacity in parallel?

[Chris_The_Battery_Man]

Originally Posted by OldShovelhead

Probably all I can do here is interject my lack of real data, but want to share my working experience.
I recently purchased a Proboat Formula Fastech. Bought 2 DTX 4200mAh NiMH stick packs from my LHS at the inflated price of $80 for both. Also, bought for the same price 4 4500mAh Tenergy stick packs. So, I've got $160 worth of crap stick packs. But nonetheless they're all new and will withstand a little abuse before crapping out.
With the NiMH packs my run times average about 5 minutes. My Raytech reports temps around 145-180 between the cells and the wiring. Most FE boats are water-cooled now and if you check out this model you'll note it's a full aluminum cooling sleeve on the motor and not a cheese-d!&^ coil affair. The ESC is also water cooled.
With my a123 packs which for the boat are 4 cells in 2s giving me 2 packs at 4600mAh each.
Testing the a123 packs this past Weds eve I ran the boat for 3 mins, brought it in to check heat etc, back in for about another 3 mins to check, and again for about 4 mins.
ALL components were normally warm- not hot. Even the deans were warm to the touch but not hot....unfortunately I forgot the temp gun so I can't produce factual data for these temps. But it was clearly cooler running than with the NiMH.
With the a123 cells I got 2' of cavatation which I've never experienced with the NiMH cells. All of the running characteristics are different now- the boat is overall faster and accelerates faster and gets to top speed faster. The packs are a bit larger than the NiMH packs BUT they're lighter as I can see this in the ships attitude as it sits on the water. I need to shift weight to the rear for better CG with the NiMH packs but the a123 packs clearly show a higher bow = less weight in the same place as the NiMH packs.
So as I'm reading this real time evaluation I felt I wanted to chime in with my practical experience with these cells.
I'm also running a 2cell 1100mAh pack in my Scorpion - plenty of torque and one helluva lot less weight.
just my twocents

Well you werent putting them up against good Nimh packs. Pm me and I will send you a good pack to compare with and I would be interested in knowing your results. Tenergy and Duratrash betteries are not a good test subjects. I would have to go out on a limb and say with the exception of maybe off the line punch... A good Nihm would give LiFe a good run for its money. That being a 9.6v Nimh versus a 9.6v Life... Again PM me and I will set you up and let me know what you think.

If I had to guess a 9.6v Nimh under a hard load will hold around 8.5-9 volts and the Life would hold around 7.5-8 volts.... The Life would just be lighter...

[mattnin]

Originally Posted by JohnRobHolmes

Interesting setup Mattnin. Is that two packs of different capacity in parallel?

No, it is one pack. The cells are in parallel, not the pack in parallel. I can't remove the 1100mah cells from the pack if that is what you mean.

Because a 2300 mah A123 won't fit under the top deck of the Xray T2 007, and a 2S1P 2300mah pack off to the side of the top deck barely had enough capacity to finish a 5 minute heat/main, I had to make a 2S2P pack using the 2300 & 1100 mah cells. I charge it just like before, just one balance tap and at 10 amps.

I know some people may say that won't work because the cells aren't matched, but they auto balance during charge/discharge because the cells themselves are in parallel.

[JohnRobHolmes]

Thats what I was getting at, 2s2p using different capacity cells. Cool setup.