Trying to find out is this a rumor or fact and if fact does anyone have any idea if the newer ones have started shipping; if so are there specific manufacturing codes or dates to look for?
Fenix TK70; Is this fact?
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Trying to find out is this a rumor or fact and if fact does anyone have any idea if the newer ones have started shipping; if so are there specific manufacturing codes or dates to look for?
Honestly I am not sure how they would pull that off.
Alkalines simply don't do well at high current levels, and turbo requires 3 Amps PER EMITTER at a forward voltage of 3.0 I think....maybe higher for 3 amps since the wattage is estimated at 35+Watts (which 9x3 does not equal). So we need at least 9 Amps at 3.1 volts. Likely more.
4 Alkalines in series = 6 volts, so each battery would need to pull a good 1 Amp and that would get you a whopping SIX Watts. 4 amps per battery would get you up to 24 watts, assuming no inefficiencys in the driver, etc. And we still aren't there.
So I would expect if they did make a new version, it would either detect the lower current and have a "turbo-lite" mode for alkalines, or simply fail more gracefully. I wouldnt hold my breath for a true Turbo version.
Why would you pay 200 bucks for a flashlight and use cheap leak-able alkalines with it? 4 Accuevolution D cells and universal smart charger are only 60 bucks...a small fraction of the flashlight cost.
Alkalines simply don't do well at high current levels, and turbo requires 3 Amps PER EMITTER at a forward voltage of 3.0 I think....maybe higher for 3 amps since the wattage is estimated at 35+Watts (which 9x3 does not equal). So we need at least 9 Amps at 3.1 volts. Likely more.
4 Alkalines in series = 6 volts, so each battery would need to pull a good 1 Amp and that would get you a whopping SIX Watts. 4 amps per battery would get you up to 24 watts, assuming no inefficiencys in the driver, etc. And we still aren't there.
So I would expect if they did make a new version, it would either detect the lower current and have a "turbo-lite" mode for alkalines, or simply fail more gracefully. I wouldnt hold my breath for a true Turbo version.
Why would you pay 200 bucks for a flashlight and use cheap leak-able alkalines with it? 4 Accuevolution D cells and universal smart charger are only 60 bucks...a small fraction of the flashlight cost.
tre
Flashlight Enthusiast
I don't know anything for a fact but running turbo mode on alkalines has got to be nearly impossible. My guess is that this is a flase rumor.
Personally I wouldn't run alkalines - but if the above were true then perhaps there would be some advantage to finding out - perhaps not.
samgab
Flashlight Enthusiast
The calculations above aren't correct. When cells are connected in series (as in the TK70) to make a battery, each cell puts out the the total current drawn.
(It's parallel battery connections that divide up the current.)
On turbo, the TK70 draws as much as 9.5 Amperes, depending on the battery voltage.
So, if under load all 4 cells are measuring a combined potential difference of 3.7 Volts, the current draw of the TK70 would be 9.5 Amperes.
That means each of the 4 cells would be running at 9.5A, (and 0.925 Volts, if all 4 cells are equal).
At 6 Volts on turbo, the TK70 only draws 5A.
So at 6 Volts, the power consumption is 6V*5A=30 Watts.
At 3.7 Volts, the power consumption is 3.7V*9.5A=35 Watts.
However, no D cell currently in existence can maintain 1.5V at 5A draw, so the current would almost certainly run higher than 5A all the time on Turbo due to voltage drop under load.
So with Alkaline cells being what they are at present, there is no way any Alkaline can run the TK70 on Turbo for extended periods, period.
If a very good NiMH D cell can maintain 1.125V under 7.5A load, then the following would apply:
4* D cells @ 1.125V = 4.5V. Draw at 4.5V = 7.5A (per cell).
4.5v*7.5A = 33.75 Watts.
To really make it work better, they'd need to go up to a 6 D cell battery tube so the higher Voltage would mean lower currents could be drawn, and the whole setup would work better. The current 4D setup is really dependent on very good cells in very good condition that can maintain more than 1V under very high current loads.
(It's parallel battery connections that divide up the current.)
On turbo, the TK70 draws as much as 9.5 Amperes, depending on the battery voltage.
So, if under load all 4 cells are measuring a combined potential difference of 3.7 Volts, the current draw of the TK70 would be 9.5 Amperes.
That means each of the 4 cells would be running at 9.5A, (and 0.925 Volts, if all 4 cells are equal).
At 6 Volts on turbo, the TK70 only draws 5A.
So at 6 Volts, the power consumption is 6V*5A=30 Watts.
At 3.7 Volts, the power consumption is 3.7V*9.5A=35 Watts.
However, no D cell currently in existence can maintain 1.5V at 5A draw, so the current would almost certainly run higher than 5A all the time on Turbo due to voltage drop under load.
So with Alkaline cells being what they are at present, there is no way any Alkaline can run the TK70 on Turbo for extended periods, period.
If a very good NiMH D cell can maintain 1.125V under 7.5A load, then the following would apply:
4* D cells @ 1.125V = 4.5V. Draw at 4.5V = 7.5A (per cell).
4.5v*7.5A = 33.75 Watts.
To really make it work better, they'd need to go up to a 6 D cell battery tube so the higher Voltage would mean lower currents could be drawn, and the whole setup would work better. The current 4D setup is really dependent on very good cells in very good condition that can maintain more than 1V under very high current loads.
samgab
Flashlight Enthusiast
This graph was done by cpf user HKJ and is the source of my figures on current/voltage on turbo mode:
For further info see his review of the TK70.
For further info see his review of the TK70.
samgab
Flashlight Enthusiast
It would be cool if we could buy extra 1*D extenders, like the one that comes with it. Then we could buy 2 extra extenders, and use anything from (3,) 4, 5, or 6 D cells.
I'm thinking of getting 3 x LiFePo4 32650 cells. It will fit. And although the fully charged voltage will be a little higher than usual, I don't think it will be high enough to cause any damage... 4 brand new Alkalines might be 6.4V. 3 fully charged LiFePo4 cells might be ~10.6V, which would quickly drop to something like 9V as soon as the device is turned on to turbo.
Good LiFePo4 cells can discharge at high current rates, like >8C, and are fully discharged at ~2V (or 6V in a *3S battery), so the current would never go above about 5A running 3 LiFePo4's.
So it could work out pretty good.
I don't recommend it, because I haven't tried it yet, and I'd hate someone else to try it and find that the voltage fries their TK70, but I'm keen to give it a go.
They'd ideally be LiFePo4's with a protection circuit.
Possibly a better solution would be 2x LiFePo4 32650's and a dummy cell. Or even better, a 2D tube for the TK70 and no dummy cell.
I'm thinking of getting 3 x LiFePo4 32650 cells. It will fit. And although the fully charged voltage will be a little higher than usual, I don't think it will be high enough to cause any damage... 4 brand new Alkalines might be 6.4V. 3 fully charged LiFePo4 cells might be ~10.6V, which would quickly drop to something like 9V as soon as the device is turned on to turbo.
Good LiFePo4 cells can discharge at high current rates, like >8C, and are fully discharged at ~2V (or 6V in a *3S battery), so the current would never go above about 5A running 3 LiFePo4's.
So it could work out pretty good.
I don't recommend it, because I haven't tried it yet, and I'd hate someone else to try it and find that the voltage fries their TK70, but I'm keen to give it a go.
They'd ideally be LiFePo4's with a protection circuit.
Possibly a better solution would be 2x LiFePo4 32650's and a dummy cell. Or even better, a 2D tube for the TK70 and no dummy cell.
Um, what did I say that was wrong exactly? I said 4 Ds in series = 6 volts. If each battery pulled 1 amp that would be 6 Watts, which is way short of the 35ish watts needed. Even 4 amps per battery would be insufficient.
You don't need 9 amps from the batteries because they are at 6 volts instead of Vf of 3.1+. So a boost/buck circuit would turn the 6 volts times 5ish amps = 30Watts into 9 amps at 3.2 volts (30ish watts).
I think we both agree that this is absolutely impossible with alkalines.
You don't need 9 amps from the batteries because they are at 6 volts instead of Vf of 3.1+. So a boost/buck circuit would turn the 6 volts times 5ish amps = 30Watts into 9 amps at 3.2 volts (30ish watts).
I think we both agree that this is absolutely impossible with alkalines.
I am just guessing here. Fenix don't want to sell extra extender could be due to damage control. Fenix is selling a lot accesories so there is no difficulties for them to sell extender battery tube. But there will be cases some owners start experimenting with higher voltages or different configurations. If those owners are not careful and not honest or not knowing much about flashlights, damage the flashlights and start complaining to Fenix or in this forum, it will not be worthy to sell extender if it creates more disputes. Of course, people can fabricate extender if they want, but that will be limited of people. A few posts in this forum talk about some flashligths problems can do big impact and reduce sales, even the problem is not fully investigated or understood.
ILIKEFLASHLIGHTS
Enlightened
- Joined
- Aug 4, 2011
- Messages
- 652
Protactical19 off of ebay told me that Fenix was coming out with a newer version of the TK70 that will work with Alkalines on the turbo mode. That's all I know.
I wonder how well the body can screw together and what's the limit to it? the Thailand Special edition has extra 2 cells tubes, together with the 3+1 on the standard body that makes it 6 cells-capable right out of the box, and after all these times hasn't anyone tried to use 6 alkaline D cells?
Also I wonder if the current 3+1 cell extension tube is purely for packaging and shipping, I don't see any situation where 3D cells would serve a purpose, I mean D cells usually comes in packs of 2, so if you're in an emergency and could only find alkaline cells, would you be better served by just using 3 cells or 4that'd barely run as it is? the weight/length penalty is minimal. Okay maybe for taking on planes and such where you could disassemble and makes the whole thing less intimidating/club-like
Also I wonder if the current 3+1 cell extension tube is purely for packaging and shipping, I don't see any situation where 3D cells would serve a purpose, I mean D cells usually comes in packs of 2, so if you're in an emergency and could only find alkaline cells, would you be better served by just using 3 cells or 4that'd barely run as it is? the weight/length penalty is minimal. Okay maybe for taking on planes and such where you could disassemble and makes the whole thing less intimidating/club-like
Some good stuff has been said and some less good stuff as well:
More batteries = higher voltage = less current CORRECT.
Put more batteries in the current TK70 = you might end up with more voltage than the flashlight was designed to handle (poof), so Fenix will certainly not sell extra extenders.
IF Fenix releases a version that can use Alkies to power up the turbo, it will be a different revision that uses a longer tube with more batteries. No only the tube will be longer (at least double, so they might scratch the whole tube part and make it into something else) but, most importantly, the driver will be different.
And to put my personal grain of salt into this: I bet this is just a rumor and nothing more. Fenix usually comes out with a different product altogether rather than modify something that already exists.
More batteries = higher voltage = less current CORRECT.
Put more batteries in the current TK70 = you might end up with more voltage than the flashlight was designed to handle (poof), so Fenix will certainly not sell extra extenders.
IF Fenix releases a version that can use Alkies to power up the turbo, it will be a different revision that uses a longer tube with more batteries. No only the tube will be longer (at least double, so they might scratch the whole tube part and make it into something else) but, most importantly, the driver will be different.
And to put my personal grain of salt into this: I bet this is just a rumor and nothing more. Fenix usually comes out with a different product altogether rather than modify something that already exists.
If batteries are put in parellel, it will be same voltage, and less demanding on current per cell. And maybe driver will not change.
I wonder will it help to reduce chances of batteries go below 0.8V while others are still 1V. For example 8D cells 4S2P, will the D cell help equalize each other?
I wonder will it help to reduce chances of batteries go below 0.8V while others are still 1V. For example 8D cells 4S2P, will the D cell help equalize each other?
I've tried powering the TK70 from the power supply up to 10.5V. Above 8-9V you will loose low modes and above 10V it will go to direct drive even in turbo mode. So using 3x Lifepo4 cells could be risky.
2D tube and two Lifepo4 is a safer solution than three cells, some dealers offer this as optional accessory.
samgab
Flashlight Enthusiast
Cheers for the info. As it turns out, I've ordered 2 x "F size" LiFePo4 cells, AKA 32900's. They are the size of 1.5 D cells each. Two of them together is exactly the same length as 3 x D size cells. So it's a perfect solution, seemingly. The voltage will be right, and I won't need an adapter or dummy cell, and because they're larger in size, they have good capacity: 5Ah each. And they are capable of at least 5C continuous discharge rates.
Kitchen Panda
Enlightened
Energizer's excellent Web site gives a data sheet for a D alkaline that says its internal resistance is between 100 and 300 milliohms when fresh. Even at the low end of this range, if you try to pull 7.5 amps from the cell, you are dissipating as much power *inside* the battery in waste heat, as you are getting out of it - and you're dropping half the 1.5 volts across the internal resistance of the cell, leaving only .75 V for making lumens. So, anything that loads D cells to several watts/cell is going to be horribly inefficient. And if you have 300 milliohms internal resistance, you can't get more than 5 amps out of the cell on a short-circuit, delivering zero usable power to a load.
I have new respect for NiMh cells since buying a TK 70. Mind you , I wish all the NiMh's I saw in stores weren't just AA cells in a D shell...the real 10 AH D cells seem to be a mail-order item only.
Bill
