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Discussion Starter · #1 ·
With the 3800 and 4200 cells, all the information and advice I've seen say to discharge your pack on a tray, down to about .8V to 1.1V per cell, just before charging them.

I understand the concept of keeping some charge in the pack for storage, and discharging it down just before charging again.

My question is, does it really need to be discharged on a tray, doing each cell individually? Years ago with NiCd's, the individual cells were discharged down to close to zero volts to empty each cell, and equalize them all down to zero before charging them up again. But since we're not equalizing them down to zero, does each cell really need to be discharged down to the same level, whatever it may be - .8V, .9V, 1.0V, 1.1V, etc.?

What would the effect be if I were to just discharge the whole pack, at about 4 or 5 amps, just before charging? Would this be bad for the health of the pack? Would performance suffer? Would I get the same results and performance as if I trayed the pack?

Just wondering - thanks.
 

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The trays are not for discharging.. they are now for equalizing the cells..Thats why the adjustable voltage cutoff trays are all the rage.. the non adjustable ones can disharge the pack down to much.. this will reduce runtime, nd possibley damage the cell... This way all of them start out at the same voltage.. This way they have a better chance of charging more evenly..

discharge on a t 35 down to 3.6 then throw them on the tray..

Ask Corey Heft next time you see him at a race.. He will give ya the right info..
 

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Discussion Starter · #3 ·
Ok - so, by starting them all at the same voltage just before you charge, you'll get a better charge into them, and a more even charge over all of the cells in the pack, correct? Actually sounds like the same concept as we used to have with NiCd's, just not going down to zero volts, and doing it just before you charge up the pack.

BTW - burbs, were you 'bumbles' at His and Hers Hobbies on the 26th? I was going to say hi, but wasn't sure if it was you or not.

Thanks.
 

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Yes, if you "Equalize" each cell before charging, you should have "As Close to As Possible" perfect equal charge if your cells are properly matched....

I "guess" you could compare that to dead shorting, since All the cells started out at zero volts and charged equally...

If you know of someone with a Spintech, or Futaba Charger you can run a test and monitor each cell in a pack with both Equalized and Non equalized packs.... :thumbsup:
 

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All this battery maintainance stuff has gone absolutely crazy .

Something else to sell the racer.

With 3800's or 4200's ,, charge them up and use them and leave at least 1000 mah in the pack untill next use .

The night before discharge pack down to 1.0 volt per cell and most of the time your absolutely fine to charge from there.

I usually pull the pack down at 30 amps , then 20 amps , then 10 amps.

Equalizing has its theorys but as nimh cells progress it seems less important as run times aren't really a problem anymore.

Even the top battery tray manufactures say not to equalize everytime.

You'll see a lower pack peak temperature when their not equalized.

Even after 20 yrs in this sport , battery maintainance equipment is a good profit center for the RC suppliers.

All depends how serious your are and how much time you have , you touch the wall once and all this is a waiste of thought.
 

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I'm just glad I can go for 4 mins (usually) without touching the wall now,I feel better about the time and money I spend on all the little extra's.
 

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Bill Johnson said:
Yes, I agree with you, after 21 years in the hobby, things have changed.....
BUT, if you don't equalized, and you overcharge one cell, after 5 or 6 charges you WILL have that one pack with a cell that will be weak.....

Your packs are only as good as the weakest cell... :thumbsup:

All these tests from all the Matchers are tested, I can't think of a matcher that doesn't race themselves, they don't have deals with Discharge tray manufacturers, they have nothing to gain but repeat customers...


The guy asked a question about equalizing and the effects of equalizing, he didn't ask if it was a myth or not..... :rolleyes:
Thanks for the compliments Bill .

If you don't want to listen to other opinions then get off or try and be more open minded.

Talk to your battery supplier and I 'm sure he'll agree with most of what I stated .

Well ,, lets think about this for a minute ,, as a pack gets used and looses some of its match , if you bring all the cells down to an equal voltage point then when you charge the pack it gets hotter than it should because the cells have different capacity levels, hmmmmmmmmm.

Where if you bring them down to 1.0 volt per cell x # of cells , your starting at an even discharge point and will peak better and stay cooler.

If you don't agree , then thats fine , just don't be such a _________. :eek: :thumbsup:
 

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I have been pretty fanatical about discharging equalising cells since the new IB's, even going as far as to discharge each cell on my T-35 on each pack after each run for months! I have done every test I could think of to try to get the most out these cells and what i have found is that it doesnt make a bit of difference. Generally cell voltage depletion is not a good thing, more so on the track say dumping in a mod car, but lately i have been traying on the 0-30 tiull all the lights go dark so I know I am starting with empty cells, then within 5-10 seconds start charging. Cells charge longer and take more mah then when I discharged to 4.00, this has had zero effect on runtime loss as well. these cells are naturally unstable, the matchers can only do so much with the IB's I'm convinced the care issue is overrated. Buy 4 packs every 3 months and dont sweat it. This is only for American cells, the canadien cells may react differently!

And johnson , stop being an A...........!:)
 

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marig said:
.

BTW - burbs, were you 'bumbles' at His and Hers Hobbies on the 26th? I was going to say hi, but wasn't sure if it was you or not.

Thanks.
Yep thats me...
 

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Mayhem said:
lately i have been traying on the 0-30 tiull all the lights go dark so I know I am starting with empty cells, then within 5-10 seconds start charging.
I dont know... when I discharge on my 0-30 till the lights go off and then place it on my discharge tray (DPD or Novak tray) to equalize, the cells continue to discharge for quite a while before they hit .90. I believe the matchers want you to equalize at a low (2-5 amp) discharge rate. :)
 

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ANY battery pack is only as good as the worst cell in it,specs,nicads,nimhs.If there is a cell in a pack that has more run time left in it and it is not equalized before recharging,when that pack is charged again,that cell will dictate the peak detect that your charger reads.This is easily seen on the dpd,just look at the discharge times.
 

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DK47 said:
ANY battery pack is only as good as the worst cell in it,specs,nicads,nimhs.If there is a cell in a pack that has more run time left in it and it is not equalized before recharging,when that pack is charged again,that cell will dictate the peak detect that your charger reads.This is easily seen on the dpd,just look at the discharge times.
Thank you.... :thumbsup:



Mayhem...Canadian Cells, thats a good one.....Your American Cell supplier has you Brainwashed very nicely... :thumbsup: Nice to see your still "against the Grain" in ALL aspects of life... :D

NCFRC...Again, this thread is not about that....Read the first post, or don't write anything at all......
I think you've started a thread on this once, if not, start one, and will be happy to indulge your argumentative comments... :rolleyes:
 

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Man I've got some deep south cells that just don't seem to be up to par,maybe I'll request some canadian cells next order,LMAO.
 

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Discussion Starter · #17 · (Edited)
Thanks for all the feedback, everyone.

So, I think the ideal situation - from a performance standpoint - for charging any pack would be for each cell to reach its peak at exactly the same time, so as to avoid both overcharging any cells and damaging them, and undercharging other cells. If you have a pack of matched cells, this problem goes away or is at least minimized, because cells are matched by their discharge capacity, which is related to their charge capacity.

So equalizing each cell down to some fairly low voltage before charging makes sense to me. Since each cell has the about the same capacity, it's voltage level at rest should be a good indicator of it's current capacity - how full or empty it is. If you bring all the cells down to the same voltage, when charging them they should - if they are closely matched - reach their peak at the same time, and you have the ideal situation.

But part of my original question was, instead of equalizing each cell individually down to 1.0V per cell (or whatever voltage your matcher recommends) just before you charge, what is the difference if I discharge the pack as a whole, say at about 4A, down to 1.0V per cell? It seems to me that if the cells are matched, if my pack is at 4.0V, each cell should be at 1.0V, especially if I'm discharging at say only 1A per cell. I guess what it boils down to is, do I really need the tray to do this?

I'm not trying to argue with what anyone has said so far. I'm just trying to understand, and I really appreciate everyone's thoughts and facts. I don't mind buying an equalizing tray - it's not a major investment like a dyno or something. I just want to understand in a little more detail why I need it.
 

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marig said:
If you have a pack of matched cells, this problem goes away or is at least minimized, because cells are matched by their discharge capacity, which is related to their charge capacity.

But part of my original question was, instead of equalizing each cell individually down to 1.0V per cell (or whatever voltage your matcher recommends) just before you charge, what is the difference if I discharge the pack as a whole, say at about 4A, down to 1.0V per cell? It seems to me that if the cells are matched, if my pack is at 4.0V, each cell should be at 1.0V, especially if I'm discharging at say only 1A per cell.
If you have ever tried testing individual cells on a sincle cell cycler (like a Turbo35) you would find that matching by discharge capacity does not mean they are matched as well by charge capacity.

Another "mismatch" area is that cells vary in their self-dischage rate, no matter how well they are matched for a 35A discharge. You will see this if you take a pack that was partially discharged and let it sit for a week then discharge the cells individually.

A low discharge rate as you suggest will compound your problem because 3 cells might still be at 1.25V while one is at .25. The problem could be worse with a 6-cell pack. You could reverse a cell.

So the answer is, in my opinion, yes you need a tray for the current cells. I long for the day when a company will make high performance cells as durable as GP3300s.
 

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Discussion Starter · #19 ·
ta_man said:
Another "mismatch" area is that cells vary in their self-dischage rate, no matter how well they are matched for a 35A discharge. You will see this if you take a pack that was partially discharged and let it sit for a week then discharge the cells individually.

A low discharge rate as you suggest will compound your problem because 3 cells might still be at 1.25V while one is at .25. The problem could be worse with a 6-cell pack. You could reverse a cell.

OK, ta_man, this makes sense - during storage, the self-discharge could cause each cell to have very different voltages when you go to do your "pre-charge discharge". So in that situation, I could see where it's better to bring each cell down individually.

I checked the three IP3800 packs I have, to which I added 500mah for storage about 4 days ago, and the individual cell voltages varied as follows:

pack 1: high cell - 1.314V, low cell - 1.306V, 8mv diff.
pack 2: high cell - 1.325V, low cell - 1.307V, 18mv diff.
pack 3: high cell - 1.321V, low cell - 1.298V, 23mv diff

The recommendation I've seen for peak detection is about 7mv drop per cell, so I can see where you'd be better off getting each cell down to the same voltage level individually before you charge them. With the differences from low to high cell above, discharging the pack as a whole - even if it took the same amount out of each, equally, would seem to leave you with a big difference between your low and high cell just before you charge. This difference would seem to carry through to the end of the charge, resulting in some cells overcharging at least a little.
 

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ta_man said:
I long for the day when a company will make high performance cells as durable as GP3300s.
That would be great... I doubt they can make a cell that has the best of both worlds.... everything is a comprimise.... low IR and high voltage with a greater chance of losing a cell... or lower voltage with a higher IR and a more durable cell.
Every one has great memories of the 3300's... but to be honest they varied so much from batch to batch you had to look at date codes to find the good ones and they cost more than the IB's. Now they did last a long time and you could DS them. But for me DS was a pain... now days I run a race and put them away until either the next run or the next week then I equalize and charge... really pretty simple.
 
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