zax

oh ok..then what is the difference between a higher amp diode and lower amp diode for the cut off?

XrayFK

iTrader: (1)

Nothing, the voltage drop is the same (rated, actual value may vary) The amp ratings are exactly that, how much current the diode is rated at.

zax

if i am using 0.4ohm resistor and a 5A diode on each cell..what is the discharging current and the cut off voltage?

loopedeloop

Cutoff voltage will vary depending on diode type, but standard rectifier diodes are generally 0.7v . This is the cut-off Voltage.


I thing the current is worked out like this( sticking my neck out here )

1.2v(cell)- 0.7v(diode)= 0.5v drop over the resistor.

Ohms law= I(current)= V/R so,

I= 0.5v/0.4r= 1.25A

Now, power(watts) = VxI so, 0.5x 1.25=0.625w so a 1watt 0.5 ohm resistor should be sufficient


Now I'm no expert so someone tell me if i'm wrong

XrayFK

iTrader: (1)

loopedeloop has the correct equation, but is slightly off.
Whatever the cell voltage, it directly affects the discharge current. So at 1.2v, the current is 1.2/.4= 3A. The cells will equalize closer to 0.6v if you leave them on long enough, and that rate would be 1.5A
If the diode has a forward voltage of 0.7v, that doesn't necessarily mean that anything under that has no flow. The current to voltage graph of a diode is extremely exponential before and after the drop point. So anything above 0.7v goes up so high that pretty much the same amount will pass through. Under 0.7v the current decreases just as quickly, but does not go immediately to zero. I hope I've explained that correctly/clearly. Either way, diodes aren't perfectly accurate anyways, so small but noticeable variances between even the same model numbers exist.

sup

with all that said.. ill think ill save up for a novak smart tray (or anything like it). im no electrician and what i currently have is a trinity realtime 2.5 tray. im beginning to stack up on IB cells, and as i have read, they dont want to be discharged to 0 volts like the GP cells.

Alfalfameister

iTrader: (1)

So the Tekin Battery Doctor is a good tray then, yes? I think it draws at 2 amps all the way down to .9 volts or something, and much lower current that s_l_o_w_l_y brings it down to .5 volts (took several hours from .7 to .5 volts).

BringItOn

the teamwave lightning takes overnight to get it to 0.7volts at the slowest setting.

zax

how do i check for the forward voltage on the diode? and if i want the cell to cut off at 0.9volt, which resistor and diode should i use??

killingtime

iTrader: (3)

Even so, this is all good to know. With batteries changing and the ideas on how to care for them always changing, it's nice to know who to configure your dischargers to accommodate the changes without having to buy new ones each time. Any information that can save some money in this hobby is valuable knowledge! But I understand where sup is coming from, a lot of this info can get confusing quick.

XrayFK

iTrader: (1)

The Trinity trays uses just resistors, so all you would have to do is solder a diode inline with each resistor and you would have a safe cutoff to use on IB cells.

XrayFK

iTrader: (1)

Yes, the Tekin tray works very well with IB cells. I don't know know exactly when, but they have a digital tray in the works.

sup

killingtime & xrayFK, quite confusing actually for individuals like me that does not know a thing about electronics. but, its a good read. with what xrayfk explained, all i need now is the guts to do it myself. ill just backread a little and find the parts i need from the local electronics supply. will see, i might get inspired to do this project this weekend. again, thanks a lot guys for your input.

BringItOn

so anyone know if its possible to get diodes to get the zero-thirty to cut off at 0.95v/cell?

killingtime

iTrader: (3)

let us know how it works for you sup. I'll be trying it out on my Integy Zero-6S and Zero-6M trays.