read the "Conditioning new cells or packs" section here..
http://www.camlight.com/techinfo/techtips.html

It may not be necessary, but I like to individually discharge each cell down to 0.5v at 100ma (as low and slow as the Triton will go) before charging them up as a pack.. if the triton would go to 0, I'd do it to zero, since you cant hurt the cells by going to zero while they are seperated (rather than in a pack). That way you know each cell is equally flat before charging them.

If you charge them slow enough (<.1C) then the discharge equalisation may not be necessary since at that slow a charge rate, any cells that reach full first will just generate small amounts of heat as the rest catch up, but I'm just being picky..

Read all of Johns (Camlight) pages in detail, they're the best collection of factual Nicd/Nimh tech info I've seen yet..
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Great minds discuss ideas. Average minds discuss events. Small minds discuss people

Thanks i couldent find the part about conditioning cells

Btw how long dose it take to discharge a cell at 100mah when its new or i asume 0.9v?

Cos 60 cells will take a long time
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Tim Team Reaper.

If i charge the pack at 100mah so the cells cathch up would it help to set the peak sensitivity to a lower setting like 0.5mv? myn is on 0.9 at the moment.
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Tim Team Reaper.

Individually discharging each cell down to 0.5V (or even zero) can help with matching the cells but might not be necessary if the cells are from the same batch (and were formed/conditioned/tested the same way and at the same time by the manufacturer or dealer).

But, it won't hurt to discharge them individually to 0.5V or even zero.

If you have, let's say, 3300mAH cells and you want to condition them by charging at a 100mA rate, it will take 3300/100=33 hours. Way too long IMHO and your charger might have a backup timer that will turn off the charge long before that. You can slow charge at up to 1/10C without problems and even higher for a lot of cells. If you had 3300mAH cells, you can safely and effectively condition them at a 300mA charge rate. It will then take about 10-11 hours to charge them. Be sure that doesn't exceed your charger's safety timer too. You might have to bump up the charge rate to 350mA-400mA to keep the time below 10 hours (a value that a lot of chargers use for slow-charging timeouts).

Set your charger's delta-peak detection voltage to the value recommended by the cell's manufacturer or dealer. NiMH cells need a lower value to avoid over-charging compared to NiCd cells, but the lower the value the greater the chance of false-peaking during the charge....especially with new cells. You might have to occasionally re-start the charger.
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John Muchow, CamLight Systems
http://www.camlight.com

Thanks john

I think ill discharge them all as i have alot of batts and have spent allot of $ and i want the best performance out of them
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Tim Team Reaper.

Going back a couple of posts to where Jake and John were discussing self-discharge of a pack possibly driving some cells into reverse polarity..

At first glance, I'm on Jakes side, with no circuit from one end of the battery string to the other, I cant immediately see how any of the cells could be reverse charged..

The self-discharge-to-zero yes, since there is an obvious leakage path within the cell itself, but there is no current path for the electrons to flow from one end cell to the other end cell, so no way for a conventional current flow to be pushed backwards through the middle cell.

I presume john, that you mean that the presence of the left and right cells attached to the middle cell offers somewhere for the electrons to flow, even although those cells have no circuit on their other end either ?

Is it that the self-discharge reactions in the end cells somehow absorbs ions from the center cell as part of their self-discharge ? I still dont completely see it though.. wouldnt the polarity be wrong for that sort of flow to occur ?

I dont think we need the precise chemical reactions just yet until we understand where the current is going and why..

Heres a diagram of what I think you mean is happening, perhaps you can tell me if I'm on the wrong track here.

Blue is conventional current flow, red is self discharge flow, green is my guess at this not-understood across-the-cells discharge flow


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Great minds discuss ideas. Average minds discuss events. Small minds discuss people

quote:

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Originally posted by Spockie-Tech:
At first glance, I'm on Jakes side, with no circuit from one end of the battery string to the other, I cant immediately see how any of the cells could be reverse charged

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mmm i was going to put my two bobs worth in a while ago but the neuron bit was beyond my understanding of current flow ....
So i deliberatly discharged two cells in a string in between two fully charged cells down to 0 volts and left the 2 shorted over night to make sure they were 0 volts.
I then unshorted them and left the string for about week and one was still at o volts with no polartity showing on the meter and the other was at about .01 of a volt with the corect polarity so i guesed it stil had a small amount of residual chemical activity in the cell i further discharged it by shorting it over night again and left the pack another day both discharged cells still showed 0 volts i will moniter them for a couple of weeks and post the results (these are just cheap drill packs) but should still sufice for the experiment

That last post isa little confuseing
I have one charged cell followed by a discharged cell then another charged cell followed by the second discharged cell then the rest of the charged cells in a 12 volt pack with no circute between the cells

I thought some really funky physics was about to take place. Guess I can back to using normal battery theory again

try not to sound too disapointed ;-P
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Mechanical engineers build weapons, civil engineers build targets

quote:

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Originally posted by colin:
I thought some really funky physics was about to take place. Guess I can back to using normal battery theory again

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depends on your background i guess

yes when i first read Johns post i was also going to disagree.. but not being a chemist or any thing else qualified i only had my own experiances to rely apon so thats why i set up the experiment the only time i have noticed any sort of batteries that were reverse polarity has been in situations where they have ben under load and have been discharged for long periods in series ... i have come acros it mostly in lead acid batteries where a truck has had the ignition left on or lights on and had had two batteries of diffrent curent rateing s or age in series for 24 volts ...the quickets way it usualy gets noticed is when a battery charger blows a fuse or burns out trying to charge the reversed battery .

In Addition to my last post ... my theory of the reverse polarity of the lower voltage cells not conected in a circute was more along the lines of a weak electro magnetic induction in the cans of the still discharging cells either side of the cel that had gone 0 volts and this induction some how induceing a reverse voltage flow in the suspect cell..........

I was going to try and test this with a accelerated experimet by starting off with one cell at 0 volts betwen two charged cells and seperatly load the two charged cells with a high discharge current to force the(theoreitic) induction to a measurable current flow in the dead cell.....
Now that reverse polarity in open circute cells has been disproven by more knoledgable persons i can just spend the time chargeing the rest of my batteries instead of pondering lol