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Old 01-04-2006, 01:40 AM   #1081
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i ususally only let them sit for 2 weeks or less. can i get away with that or should i really put some charge back
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Old 01-04-2006, 01:43 AM   #1082
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Quote:
Originally Posted by PitCrew
If my battery doesn't care what rate it is discharged at, then what are we doing wasting all this time with 30amp dischargers.

Why not just throw on like a 100 amp load and make it dead in like 1 minute?

In all seriousness though, I am curious to know if you charge at say 10 amps, but don't let the pack peak at that amperage (like you take it off the charge early, or reduce the amp rate near peak mAh) then will that cause any deterioration to the cells. THis is considering they are NOT overheated during the charge.
I am talking within LOGICAL limits.
Lets not get carried away.

Remember that there is a chemical reaction taking place...and there are limits.
Just so that you know, we have used IB3800s in applications that demand 100 continous amps for a very short time.
We worked on a submarine project were this was the case. The batteries did not last long, but they performed as needed.

Every application has its needs and limits, and we work within them.

In electronics there are laws, and one of them is OHMS LAW.
Power is equal to CURRENT SQUARED TIMES RESISTANCE....Do you see what happens? P=I^2*R and P is HEAT...

Quote:
In all seriousness though, I am curious to know if you charge at say 10 amps, but don't let the pack peak at that amperage (like you take it off the charge early, or reduce the amp rate near peak mAh) then will that cause any deterioration to the cells. THis is considering they are NOT overheated during the charge.
I am sure you can charge your battery for the first 2400mah at 10A, the cut the current down to 3 amps and it will work.

I have not done enough tests to give you a YES or NO answer regarding the deterioration of the battery...
I would assume that the life of the cell will be shortened, but by how much, I have no idea.

But I tell you this, I will do some tests and figure out what happens...

Isaac
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Old 01-04-2006, 01:54 AM   #1083
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Quote:
Originally Posted by fjm9898
i ususally only let them sit for 2 weeks or less. can i get away with that or should i really put some charge back
I don't think that there is a RIGHT or WRONG answer.
However, I would put 1300mah on the pack just for safety reasons.
This will keep the batteries from overdischarging, which can happen. I see it all the time with packs that are not taken care off.
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Old 01-04-2006, 02:20 AM   #1084
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Quote:
Originally Posted by BATT_MAN
I am talking within LOGICAL limits.
Lets not get carried away.

Remember that there is a chemical reaction taking place...and there are limits.
Just so that you know, we have used IB3800s in applications that demand 100 continous amps for a very short time.
We worked on a submarine project were this was the case. The batteries did not last long, but they performed as needed.

Every application has its needs and limits, and we work within them.

In electronics there are laws, and one of them is OHMS LAW.
Power is equal to CURRENT SQUARED TIMES RESISTANCE....Do you see what happens? P=I^2*R and P is HEAT...



I am sure you can charge your battery for the first 2400mah at 10A, the cut the current down to 3 amps and it will work.

I have not done enough tests to give you a YES or NO answer regarding the deterioration of the battery...
I would assume that the life of the cell will be shortened, but by how much, I have no idea.

But I tell you this, I will do some tests and figure out what happens...

Isaac
Yes, I am familiar with the laws. I know them all.
Obviously you are pumping much more watts through the cells. How much of that, that gets turned into heat, I don't think is as simple as just knowing what the resistance of the cells is.

AS far as extremes go, I like to look at things in extremes to get a better idea of the big picture sometimes.

Like, if we can discharge at 30 amps, why can't we CHARGE at 30 amps. Yeah, I know it would blow the cells up. WHY is what I want to know.
I am not a battery chemist.
Why is it that the crud moving from one electrode to another in the cell can go more rapidly in one direction than the other..?? I guess there would be a huge Hydrogen and Oxygen build up in the cell faster than it could get out.

Kaboom.
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Old 01-04-2006, 05:02 AM   #1085
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Quote:
Originally Posted by BATT_MAN
When a battery starts to loose its power and charge we cycle them at LOW CURRENT to bring them back to life...
A battery doesn't have a brain but it can sleep and back to life/awake? You said need to cycle after a battery starts to loose its power.

Quote:
Batteries can not be trained.
This is from your website : We can match per request at rates up to 80 Amps. Our engineers will work with you to get the best possible power for your application...This is GREAT for competitive STOCK and 19T racing

I have a conclusion from it, so if you want most power from a battery you match them up to 80 Amps?

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Old 01-04-2006, 05:12 AM   #1086
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Quote:
Originally Posted by daniz24
This is from your website : We can match per request at rates up to 80 Amps. Our engineers will work with you to get the best possible power for your application...This is GREAT for competitive STOCK and 19T racing

I have a conclusion from it, so if you want most power from a battery you match them up to 80 Amps?

I believe the reason for matching cells at even higher rates is to weed out more cells and get the best of the best.
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Old 01-04-2006, 08:07 AM   #1087
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Quote:
Originally Posted by XrayFK
I believe the reason for matching cells at even higher rates is to weed out more cells and get the best of the best.
Dude, if you matched it at 80A, nothing will come out
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Old 01-04-2006, 09:24 AM   #1088
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Quote:
Originally Posted by BATT_MAN

In electronics there are laws, and one of them is OHMS LAW.
Power is equal to CURRENT SQUARED TIMES RESISTANCE....Do you see what happens? P=I^2*R and P is HEAT...

Isaac
Just a note*

P=I^2*R

In this equation, P = "Power" as in "Work" performed, not heat. Heat can be a by product of the work being performed or a by product of "Power" being "wasted" as heat. It can also be the "work" being performed but in and of itself, P does not equal "Heat".
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Last edited by Advil; 01-04-2006 at 09:51 AM.
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Old 01-04-2006, 09:46 AM   #1089
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Quote:
Originally Posted by Advil
Just a note*

P=IR^2

In this equation, P = "Power" as in "Work" performed, not heat. Heat can be a by product of the work being performed or a by product of "Power" being "wasted" as heat. It can also be the "work" being performed but in and of itself, P does not equal "Heat".
Good info, but definitely over my head. I'll have to come to this in a few months.
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Old 01-04-2006, 12:32 PM   #1090
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Quote:
This is from your website : We can match per request at rates up to 80 Amps. Our engineers will work with you to get the best possible power for your application...This is GREAT for competitive STOCK and 19T racing

I have a conclusion from it, so if you want most power from a battery you match them up to 80 Amps?
Did you read the UP TO... that does not mean that we continuously test at those rates. We rarely do that. Please do not misinterpret what I wrote...
We match at 24amps for some oval racers because they ask. Our equipment can go from 150ma to 100A.

Now that I see how some may interpret that I will rephrase that on the website. (THANKS )

We match at a reverse ramping rate that goes from 40 down to 30 Amps linearly...to try to simulate a resistive load like a motor.

The reason is that there are customers that want to have their batteries tested at that rate. If I am going to discharge at that rate, I might as well do it once while it is being matched.

These are cells for boat racing, and our customers ask for that (80 A matching) Itís for a drag race that lasts only a few seconds.

In my opinion, it does not make any difference as long as the cells work.

We perform another test called PPDM and that tests alone gives me the quality of the cell. It is a very quick test that takes a battery from x-y amps and that dictates the cell quality.

Matching or testing at different currents HAS NOTHING TO DO WITH THE WAY A CELL WILL PERFORM (as long as we do not do it at very low currents) however it will eliminate weaker cells... but not by going up 5 amps, you need to go at much higher rates to detect the weak cells, and for r/c cars, testing at 30 to 40 is more than enough.

When we test at higher rate we run the chance of damaging the cell while testing. That is why this is done only for specific applications that will demand that current draw.

20 years ago we used to match at no more than 10 amps because the majority of the batteries could not handle the continuous current at that rate.
Batteries have improved and we can push them to the limit.

We have tested IB3800s at 100A for a submarine project that we worked with with a University. The application demanded that, and we needed to screen the batteries that could hold the charge for the desired time.

Last edited by BATT_MAN; 01-04-2006 at 01:01 PM.
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Old 01-04-2006, 12:36 PM   #1091
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Quote:
Originally Posted by Advil
Just a note*

P=I^2*R

In this equation, P = "Power" as in "Work" performed, not heat. Heat can be a by product of the work being performed or a by product of "Power" being "wasted" as heat. It can also be the "work" being performed but in and of itself, P does not equal "Heat".
Advil,

I KNOW that...

You know the explanation I gave earlier regarding POWER and YOU ASKED ME TO KEEP THE ENGINEERING STUFF OUT, right?

I have been told to keept things simple ( by you).
I think it's on this thread, if I am not wrong.

I am not teaching physics here... The by product that they see from the power generated by the cell is the HEAT... as in waisted energy...

I kept in management language, as you asked before

I used the KISS analogy.
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Old 01-04-2006, 01:14 PM   #1092
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Quote:
Originally Posted by BATT_MAN
Advil,

I KNOW that...

You know the explanation I gave earlier regarding POWER and YOU ASKED ME TO KEEP THE ENGINEERING STUFF OUT, right?

I have been told to keept things simple ( by you).
I think it's on this thread, if I am not wrong.

I am not teaching physics here... The by product that they see from the power generated by the cell is the HEAT... as in waisted energy...

I kept in management language, as you asked before

I used the KISS analogy.
True enough....I did say keep it simple. Fact of the matter is, when you quoted Ohms Law and equated P with Heat, you confused ME! LOL
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Old 01-04-2006, 02:02 PM   #1093
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Quote:
Originally Posted by Advil
True enough....I did say keep it simple. Fact of the matter is, when you quoted Ohms Law and equated P with Heat, you confused ME! LOL
Advil,

Thanks,
I was just following your suggestion to keep it simple and short.
I used ohms law just so that they could see the relationship between current and resistance. Since POWER (WATTS) is not linear in relation to current v resistance, I thought it would be OK to throw in the equation without due explanation.

Last edited by BATT_MAN; 01-04-2006 at 04:29 PM.
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Old 01-04-2006, 02:58 PM   #1094
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I have been looking for a way to equalize 3800's other than using a smart tray, and decided to try a Tekin tray. The pack was new 3 normal cycles on race days only. Cycled pack on T-35 for data and then placed on the Tekin for 24hrs. Recycled on T-35 and was a little suprised at the numbers. I know runtime may change and it did by 45 seconds 467/422, the avg. voltage went from 7.22 to 7.30. Similar change to what I normally found with GP's. What I found interesting was that the time that the pack took to reach 7.0 volts was almost unchanged 370/364 seconds. Anyone have any thoughts why a pack would loose 45 seconds of runtime with almost all of the change happening on the tail end of the cycle after voltage curve drops below 7.0 volts?
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Old 01-04-2006, 07:21 PM   #1095
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i think your problem is that you left it on the tray for 24 hours. this actually brings the cells down to .5v/cell on the tekin tray i believe. and as every one has said with these cell, you should not store them at that low of voltage. you can bring them down to that just before a charge but to hold them for 24 hours at that level will reduce runtime.
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