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Old 04-09-2006, 07:15 PM   #1
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Default Equlizing trays are bad for your packs. what you think?

it is well accepted that you should equalize after each use.

But when I think about it, it doesnít make sense to equalize them. Yes it does bring the cells down to equal starting levels but its really irrelevant the starting point of the cell. As each cell will accept different levels of charge anyway.

What I do is to equalize on the charge process.

I charge the pack up in series about 80% of the way.
Then what I do is to peak each individual cell. Do this for each of the 6 cells. Then your packs are equalized. Let it rest for a few hours to let the cells go to its natuaral voltages, and discharge about 80% of its capacity. And now your packs are ready to be charged for racing.




Think of it as water tanks.

We have 6 water tanks and they are all rated as 3000litres. Some tanks vary in size. Some are 3100, 2900, 2950Ö. Etc

If we were to equalize them by draining the tanks all to zero, then filling it up tank 1 will be under-filled by 100litres, tank2 over-filled by 100 litres etc etc.

However if we were to Fill them up to around 2800litres then, we top up each of the tanks individually then we will fill its tank full, no overfilling and no under filling.

Then when we use the cells, so long as they donít dump they would all use the same amount of energy, so why not just fill up what you used. Rather than take each cell individually down to its initial levels and make them unbalanced.

Anyway, I been thinking about It for a while now, and donít see the need for a tray as all it does is bring them all to equal initial levels, however the ending value is what is important.

Anyway this is just my theory on why a discharge tray may not be good. Opinions appreciated
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Old 04-09-2006, 07:31 PM   #2
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My opinion is that it seems you're slightly confused. When cells discharge under race conditions, they dont all discharge at the same rate and have different voltages and capacities after the race.

Throw a pack on a Novak Smart Tray some time after a race. You'll see that not all cells get to the cutoff voltage at the same time, hence different capacities remaining.
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Old 04-09-2006, 07:32 PM   #3
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The only problem with charging each individual cell is that the first cell charged will end up having less charge than the rest because it will sit there the longest. If you charge each individual cell at the same time it will work better than a discharge tray but not if you don't charge them at the same time.
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Old 04-09-2006, 08:12 PM   #4
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The problem is that buying a $50 EQ tray is much cheaper than buying a charger capable of charging six single cells at the same time (which would be necessary for the sake of convenience - your method might be too time-consuming for most). I don't think a charger like that even exists, but if it did it would probably be the best way to charge a pack -- and expensive, too.
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Old 04-09-2006, 08:13 PM   #5
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I thought most of us run matched cells. All the cells (water tanks in your story) are indeed same in voltage, capacity, etc, etc. As described above, under race conditions, there are some differences in each cells discharge. We use qualizer trays to level them off, then fill each one to the same(close enough anyways) amount during charge.

If your cells are unmatched and way unequalized, you'd be surprised how differently each cell gets discharged AND charged! Some cells dump while others still got lots of juice. OR some cells get COOKED and other cells get 2/3 full.
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Old 04-09-2006, 08:22 PM   #6
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Quote:
Originally Posted by BobbyDoyle
I don't think a charger like that even exists, but if it did it would probably be the best way to charge a pack -- and expensive, too.
ICC from Spintec is under development I believe
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Old 04-09-2006, 08:24 PM   #7
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lets assume your water tank theory is correct. your not over filing the first tank in order to reach the full level of the largest tank, BECAUSE, if your delta peak set correctly, then when the first tank reaches capacity the water shuts off. the tanks that didn't get topped off don't effect voltage, only run time, and with most of our packs getting over 7 minutes of normal run time. well you get the point. just a different opinion
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Old 04-09-2006, 08:37 PM   #8
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I can see how your logic might work for unmatched cells but for matched packs, I believe your theory holds no water as each cell in a pack is essentially the same. Each cell of a matched pack is the same "size" as you put it. They all will hold the same amount of juice and they will all discharge at the same rate rate for the same amount of time.

If were a perfect world, we would not have to use or rely on equalizing trays through. Even though cells are matched, not even the best, most accurately matched cells will remain equal. Some cells will always hold more energy than others, and some will discharge faster than others in the pack. An equalizing tray helps to train your cells and maintains them so that they stay equal or closer in performance over the long run. These trays also ensure that when you do start charging, each cell has the same amount of charge in it as the rest of the cells in the pack.

Even though chargers today peak detection is based on the overall voltage of the pack, we do not have to worry about frying cells do too overcharging for this same reason...the cells in a matched pack are the same and an equalizing tray helps ensure they stay the same. They all start off charging at the same voltage, they all hold the same amount of juice and all have the same amount of resistance so all the cells should peak at around the same time as well. Assuming you use good solder and battery bars, along with having a solid solder joint, the charge should flow into each cell equally helping ensure an even charge of all cells in the pack.

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Old 04-09-2006, 09:12 PM   #9
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This is like "having no motor heatsink to cool down a hot motor is better than using a motor heatsink to cool a hot motor."
Even if they're not perfectly equalized after equalizing as some cells tend to rebound differently, its still better to charge them at that point atleast you wont overcharge some cells. This is how sensitive IB get damaged when some of the cells have peaked but still get charged. Same goes for discharging. If you discharged the whole pack to x volts, chances are some cells are over discharged hence the individual cell discharge is preferred.
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Old 04-09-2006, 10:36 PM   #10
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Quote:
Originally Posted by koabich
I believe your theory holds no water
I'm sure there was no pun intended, but man thats a bad one!
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Old 04-10-2006, 12:49 AM   #11
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Quote:
Originally Posted by koabich

Id thear waers a perfeact worlkd the trays youlld alwwwyaayayysadgash cdlkm man sinng trays also ensure that when you do start charging, each cell has the same amount of charge in it as the rest of the cells in the pa.



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Old 04-10-2006, 02:42 AM   #12
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This all really just begs the question, "Why is ROAR so P-whipped about LiPos"? Get on with it already. Sub-Cs are like typewriters, like brushed motors, etc....
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Old 04-10-2006, 06:12 AM   #13
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InYourFace,

I like your ideas about batteries and I have been thinking the same way for a long time. I run all matched packs and after a couple of cycles they are not even close to matched anymore. On a novak tray my packs will be different by several minutes and that is after only a couple of runs (5 or so). Before 3300's came out, I didn't have this problem. I ran sanyo 2600 NiMH cells and even to this day they stay closer in runtime to each other than my 3800's do. In my opinion the best setup for charge discharge would be this.

Charge each cell individually at the same time, i.e. a charger that can charge 6 single cells.

Run the pack

Use a individual dump tray where each cell is dumped down to 0.9V at 30A.

Do not use a low amp tray afterwards!

Let pack rest

Start the process over.
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Old 04-10-2006, 07:31 AM   #14
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#1 Buy the Spintec I.C.C. charger is this is a major concern with you.

#2 that is why you pay extra for matched batteries, batteries are matched according to their actual capacity, not their rated capacity. It would be like buying water tanks matched according to their actual tested capacity instead of their rated capacity.

#3 batteries charge at an exponential rate, as they get closer to their peak, the charge rate slows down (voltages rises faster at the beginning of the charge than it does at the end), having batteries that start out at a different point of charge would, over time, continue to get further away from them being matched.

with a Spintec Individual Cell Charger, and a Tekin discharge tray, your all set.
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Old 04-10-2006, 07:51 AM   #15
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discharge trays are good as long as they are used correctly
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