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Old 03-10-2005, 12:48 PM   #61
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PitCrew; This seems to fit nice with the latest charger generation, with multi phase charging, capasity-, delta-zero and temp cut off.

In other words, if the charge rate could be lowered at the end of the charge AND the cut-off is even more sensitive, we can charge at higher rates, because the batteries aint sligthly overcharged at high-amps.
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Old 03-10-2005, 12:58 PM   #62
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You know what-I just realized I did not give my thoughts on the DS issue-just what I saw in numbers.

Basically-I am thihnking that a DS pack screams on the track-especially up front. so you need to maximize those up front laps as the driver.

Now talking long-term here-the non deadshorted pack will eventually drop in capacity to the level of the DS pack-but all the while at a lower voltage.

So for me-for a GP3300 pack if I want the maximum voltage for "One" race-I will continue to DS. I dont DS any pack I plan on using for mod or 19t.
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Old 03-10-2005, 01:32 PM   #63
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Quote:
Originally posted by Cole Trickle
Hello Seaball.

What I would like to do, is to go out and buy 30 top notch packs, a discharger with PC interface and graph capabilities, and take some weeks off duty, and do some serious testing. But I dont have the cash, nor the time to do so.... So the analyze is done, thanksfully to all of you, who have helped me so far
i may have, both, the resources and the time. let me pursue this some...

though, i'll probably get distracted.
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Old 03-10-2005, 01:42 PM   #64
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Cole-

Not sure I 100% follow your post. I don't have a multi-phase charger, as in I can't set it up to change charge rates on its own during the charge.

I suppose I could start at a high amp rate, then lower it once the pack reaches 3000mah or so. (pulsar). But I am thinking that may defeat the purpose.

I didn't mention, but in the bench testing I have done, I also noticed that every minute that goes by between the end of charge and the start of discharge has a significant impact on the voltage output of the cells. I don't remember there being much difference in runtime however.

I think the main point that I am getting at is I believe (this may not be true) that when a cell "peaks" there is something chemically different or something has changed inside the cell. It has been my experience that when I stop a charge manually, say I am late for a race, the pack has better punch and more speed. This is amplified when you charge at a very high amp rate, such as 7-8 amps. When doing this, though, its bad I believe to let the pack peak on its own, because invariably one or more cells has reached full capacity before the rest of the pack, and those cells that are full will be getting more overcharged than if you charged at a lower amp rate, letting the pack peak (by charger cut-off) on its own.

I think overcharging is the #1 reason for cell failure, more so than heat. However, an overcharged cell generates a lot of heat too.

I also don't think that heat is that much of an issue as long as it isn't generated by overcharging of the cells. Heat quickens the chemical process inside the cells that produce electricity. The increased resistance of the metal I bet is negligable in contrast to the increase ability to produce current. Ever start your car on a very cold morning? Its harder to start (there are other factors in that too, but the main point is the batts ability to produce current at low temps is greatly reduced.)
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Old 03-10-2005, 02:07 PM   #65
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PIt Crew-everything I have said is opinion as is this. I too have noticed that it "seems" like when I am late for a race and have kicked up my charger to 7 to 8 amps and pulled the cell off before peak-car always feels fast and always runs the full race at speed. I always attributed it to anxiety form thinking your nt going to make the race and getting personally amped up. Maybe there is something to that.
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Old 03-10-2005, 03:15 PM   #66
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I am going to state my opinion here also. I have shorted and non-shorted packs. Testing shows everything that you all have stated here. However, on the track I find the unshorted packs have more punch. I do not let the non short packs just sit. I have a method I use but none the less, they are not shorted.

I too have felt the same power from packs that I have taken off the charger before they have peaked. In practice more so. I also repeak packs for practice and put it off before it is done.
When I go to race with the same motor and same gearing with a better pack it feels much slower. There is something to this battery deal that that no one has found yet, or they have found and are keeping to themselves.
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Old 03-10-2005, 04:49 PM   #67
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My statement isn't 100% opion.

I can say for certain that charging at 7-8 amps produces higher voltages for the duration of the race. I have not only felt that on the track, but seen it in my home testing as well.

However, Ray, like your saying, at times there is a mental factor involved. When my pack say only got 1800-2000mah charge, I often times drive more softly, trying to conserve power. Well, you know the old proverb: slower is faster. I think this is a manifestation of that. Your more cautious, and conservative driving style produces more consistent, if not faster lap times.

However, I will drive hard as long as I have over 2500 mah in a pack whether it peaked or not. Knowing this, I can attribute higher speeds when charged at high amp rate and being cut-off early to an effect on the battery, and not my driving style.
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Old 03-10-2005, 05:23 PM   #68
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wow i learned a lot of info on this thread, thanks everyone
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Old 03-10-2005, 11:33 PM   #69
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Quote:
Originally posted by rayhuang
You know what-I just realized I did not give my thoughts on the DS issue-just what I saw in numbers.

Basically-I am thihnking that a DS pack screams on the track-especially up front. so you need to maximize those up front laps as the driver.

Now talking long-term here-the non deadshorted pack will eventually drop in capacity to the level of the DS pack-but all the while at a lower voltage.

So for me-for a GP3300 pack if I want the maximum voltage for "One" race-I will continue to DS. I dont DS any pack I plan on using for mod or 19t.
Thanks.

This sounds to me, like the discharge voltage curve is steeper, meaning more voltage at the beginning compared to a non-DS pack, and then droping relatively fast.

I find your observation about long term very interesting, seems like several people experience good performance from DS packs, when it's about long term use.
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Old 03-10-2005, 11:48 PM   #70
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cr250 and Seaball, let me see if I've understood the average voltage thing correct: When a pack is deadshorted, the last bit of runtime is removed. In this part the voltage drops. But in the opposite to a non-DS pack, in the "new" last runtime the voltage aint decreased, instead the pack voltage dumb very sudden. Is this right?

PitCrew: WHat I'm trying to say, is that a higher charge rate IS an advantage, IF we're able to cut off at the correct point.

And you're probably very right about cell tolerances, one, maybe two cells, WILL peak before the others.

If this hypothese is correct, wouldnt it be nice with a charger, whuch were capable of charging and cut off cells individually, while all 6 cells is still soldered together in a serie ? Then we probably could charge at an even higher rate and still have packs with a reasonably lasting. And even better, we dont have to wait so long for a pack to finish...
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Old 03-11-2005, 12:04 AM   #71
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A NiMH battery when charged is using electrolysis to generate oxygen and hydrogen gases from water. These gases are absorbed by the Nickel at the positive and negative sides. As the cell peaks, the gases being generated are not able to be absorbed any further by the metal.
This causes a buildup of pressure from the gas created in the cell, which generates heat. The cells will explode eventually if charged at a high rate.
The cells have seals that will vent the gases, which causes a loss of capacity.
Heat will damage the seals and increase venting.

The chemical reactions in the batteries are not accelerated by heat, except they must be above very low temperates where the water is close to freezing.

Heat is a side-effect. It is like a person having a temperature. In the dark ages, some doctors thought if people get hot when sick, it must help them to get better, and the smart doctors artifically increased their patients temperatures to make them better.
The reality is heat is destructive to the human body (well if above freezing..) But some people sweared it was their cure...
In most all cases, you'll get better after a few days no matter what you do!
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Old 03-11-2005, 04:49 AM   #72
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Quote:
Originally posted by Cole Trickle
If this hypothese is correct, wouldnt it be nice with a charger, whuch were capable of charging and cut off cells individually, while all 6 cells is still soldered together in a serie ? Then we probably could charge at an even higher rate and still have packs with a reasonably lasting. And even better, we dont have to wait so long for a pack to finish...
there is such a charger, but it's not available yet!

http://www.spintec.nl/ICC.shtml
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Old 03-11-2005, 04:55 AM   #73
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Thanks, Billtc3, I'll be following this charger very close. Seems like I've found my next charger
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Old 03-11-2005, 06:05 AM   #74
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Default Dead shorted batteries

I not a battery guru, just a guy who learning o become a better driver, that being said, this is what I learned last nite.

1. you can only run them one time after DS.

2. you are faster but not for the whole race.

3. I running fusion batteries
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Old 03-11-2005, 10:15 AM   #75
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Nimble, your right that hydrogen gas is produced in the cell during charge, however, I dont think its responsible for voltage production on the discharge side. It is a by product of the chemical process inside the cell.

However you are incorrect in saying that heat does not quiken the chemical process in the cell. If that is the case, shouldn't a batt put out more power when cold due to decreased resistance of the constituent compents within the cell? Resistance increases in all materials with heat.

And, a fever is the bodys natural way of killing pathogens within the body. Thats a bit off topic..

But, we are batteries, according to the Matrix.
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