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Old 03-24-2006, 04:38 PM   #46
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Originally Posted by BringItOn
so anyone know if its possible to get diodes to get the zero-thirty to cut off at 0.95v/cell?
Just out of curiosity, why 0.95v? Germanium diodes have a much lower forward drop of about 0.3v, so you could use a combination of those to get 0.9v
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Old 03-24-2006, 05:17 PM   #47
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Just out of curiosity, why 0.95v? Germanium diodes have a much lower forward drop of about 0.3v, so you could use a combination of those to get 0.9v
then i can do 30amps down to 0.95 (allowing for some tolerance in diodes) then use my equilizing tray and tray them down to 0.90v
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Old 03-24-2006, 05:26 PM   #48
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ok, now for the stupid question...... what's the diff. between a diode and a transistor? Don't both regulate voltage? I can't believe I'm going to need an electrical engineering degree to mod a discharger!
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Old 03-24-2006, 05:33 PM   #49
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A diode will gradually decrease the discharge rate, where as a transistor will stop discharging immediately.
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Old 03-24-2006, 05:37 PM   #50
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Diodes will not "cut-off" the discharging, but merely decrease the rate at which they discharge at a certain voltage. Putting a diode on the o-30 will decrease the discharge amperage to approximately 1.5 amps as they add a great amount of resistance to the circuit. Not to mention there are quite large variances on the voltage that they start decreasing the discharge rate.
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Old 03-24-2006, 05:38 PM   #51
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Quote:
Originally Posted by BringItOn
then i can do 30amps down to 0.95 (allowing for some tolerance in diodes) then use my equilizing tray and tray them down to 0.90v
No, the lower value and the higher value diodes do not work like stacking batteries to get a higher voltage. One diode with a .7 forward voltage then the .3 forward voltage diode will still allow down to the .7 forward voltage diode, then it will cut-off. If you are looking to do a .95 cut-off you will need to find a diode with a .95 forward voltage. People are using multiple diodes in these circuits to get the amperage levels to a point where they don't kill the diodes due to pulling too many electrons through at once... They are wiring them in parallel, not series.
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Old 03-25-2006, 01:52 AM   #52
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Many questions are surfacing about diodes.

Regarding a 0.95 volt diode... Well, as far as I know there is one Schottky diode made that has a 0.98 VF, IF=160amps, it is a TO-249AA package. It measures about 2"x1"... For example, a standard TO-220 package is about 1/5 the size of the 249AA
This diode costs around $65 USD....and they are not easy to get. It is made by IR for those might be interested.
If anyone is interested in them I do have about 25 of them in my lab.

The majority of the high speed diodes fall in VF range of 0.25v to 0.8+

Diodes have also leakage current but is minimal for this application...

Quote:
what's the diff. between a diode and a transistor?
A transistor is nothing more than two diodes wired together...well it gets a bit more complicated but that is the basic way is made. A model of a transistor is two diodes wired together. Thus you have three connections, the BASE, COLLECTOR, and EMITTER. The BASE is at the junction of the two diodes. The BASE is used to control the current flow through a transistor.

A diode is like a ONE WAY VALVE, it allows current to flow in one direction (IF)... a transistor is a CURRENT AMPLIFIER, and an FET is a VOLTAGE amplifier. This is in the most elementary form.
Depending how you connect a transistor (or FET) you can control the way they operate. A diode has two states, ON-OFF.

The current that flows through a TRANSISTOR is equals to Ie=Ic+Ib ... that means that the current that flows through the EMITTER (Ie) is equals to the total of the COLLECTOR (Ic) and BASE (Ib) CURRENT (again,in it's simple form)

A diode passes the current (when FORWARD BIASED) that the load demands... you should not exceed the current and power limits of the diode, or else... BOOM

Another important thing to consider is that if you are discharging EACH CELL individually you do not have to worry about the 0.9 volt cut-off.
There is NO RULE that states that a cell should be discharged to 0.9 volts. This is just a safe voltage that is used when cells are put together in series in order to avoid what is known as VOLTAGE REVERSAL.

There is NO difference whatsoever if you bring a cell down to 0.9 pr 0.85volts... 5 millivolts is NOTHING.

The main thing when discharging a cell is to keep it within a safe operational range and that includes the voltage and current.

For good equalization, the lower the current the better the equalization. You just need to decide at what voltage you want to equalize your cells at and make sure that all of them cut-off at the same voltage.

I do NOT RECOMMEND discharging cells at high current (above 20 amps) because of the temperature and inner cell pressure that is reached. If you want your cells to last longer discharge them at a lower current.

The other thing that you need to consider when selecting and using diodes to control cut-off voltages is thermal drift. If the temp of diodes increases it will change its characteristics...

I hope this helps

Last edited by BATT_MAN; 03-25-2006 at 02:16 AM.
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Old 03-25-2006, 02:01 AM   #53
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hey do you have them 0-30 kits forsale cutoff at 0.85 and 20amp discharge?
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Old 03-25-2006, 06:09 AM   #54
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They have the cut-off kits for sale. As for the 20 amp discharge, all you have to do is take out one of the resistors one each cell slot.
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Old 04-04-2006, 06:26 AM   #55
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i am using 0.4 ohm resistor and 5A diode on each cell..if i leave the battery there to continue discharge for 1 week..will it drop to zero volt?
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Old 04-04-2006, 10:12 AM   #56
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Quote:
Originally Posted by zax
i am using 0.4 ohm resistor and 5A diode on each cell..if i leave the battery there to continue discharge for 1 week..will it drop to zero volt?
No
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Old 04-09-2006, 05:38 PM   #57
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Quote:
Originally Posted by killingtime
They have the cut-off kits for sale. As for the 20 amp discharge, all you have to do is take out one of the resistors one each cell slot.
Do they actually have these kits in stock? How much are they? And where do I get one from?
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Old 04-15-2006, 08:00 PM   #58
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OKay Ive been looking through this thread countless times and trying to figure out what to get.

I currenty have a Real Time 2 Trinity Tray, with 0.2ohm resisters (10watts), which equals to 6 amps discharge for one cell.

My question is what diodes to get.. I pretty sure all I have to do is solder the diodes I need to the tray chip. I have no idea what I need.. I understand i need something that can handle the amps/watts. I am trying for a .7 cut off voltage.

What will me discharge current be after I install the diodes? can i get these Diodes at a local Radio Shack, or somewhere like Fry's Electronics? ANd what would the estimate price be?

Thank you
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Old 04-15-2006, 09:15 PM   #59
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The diodes that have been mentioned throughout this thread have a resistance of .7ohms, so if you were to use a .2ohm resistor, your discharge rate would be reduced to approximately 1.3amps.
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Old 04-15-2006, 09:28 PM   #60
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wow that really eats it up huh.. 1.3 amps..
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