64458 6D Mag build... WOW!

[Battery Guy]

Newbie not up to speed here yet. It seems to me that using conductive copper/aluminum tape and/or possibly some solder wick could help out making a grounding strap to reduce the voltage losses.

If you are referring to the tail spring, a common mod is to solder a heavy gauge wire across the spring to reduce the voltage drop. However, it is hard to beat the copper braid in the tail cap, but that is only really effective if your cell stack is long enough to eliminate the need for a spring.

 

[FBsLights]

The cap across the drain to gate of the FET is a good way to do (negative feedback) it but with a bulb like the 64458, you have to be careful because the power dissipation in the FET during the soft-start turn-on can be HUGE! You wouldn't want >1sec soft-start.

I got the A123 cells from ebay from a guy selling pre-made packs of 3 cells for $10. The cells appear to be new and 1st quality. Great buy! Unfortunately, he doesn't seem to be selling them anymore.

If you don't have a host, how about (5) IMR 26500 in a 4D, or (5) 26650 IMRs (batteryspace.com) in a 5D?

FB

 

[Battery Guy]

If you don't have a host, how about (5) IMR 26500 in a 4D, or (5) 26650 IMRs (batteryspace.com) in a 5D?

I recently tested the AW IMR26500 cells and was unhappy with their performance at 10A due to the large spread in voltage, approximately 3.25-3.75 V for 80% of the discharge. This is kind of rotten if you compare this to the Molicel 26700 cells which have a window of 3.7-3.9 V for 80% of the discharge at 10 A.

The 26650 IMR cells at batteryspace.com are not high power. You can tell from the capacity, which is 4 Ah compared to 3 Ah for the Molicel 26700s. I have not tested them but would expect that they would perform poorly with a 10 A draw.

Cheers,
BG

 

[mat_the_cat]

The cap across the drain to gate of the FET is a good way to do (negative feedback) it but with a bulb like the 64458, you have to be careful because the power dissipation in the FET during the soft-start turn-on can be HUGE! You wouldn't want >1sec soft-start.

That's a good point, and one I had not thought of

I should probably play around with cap values and reduce the turn on time - maybe next time I mod it.

 

[FBsLights]

Battery Guy,

I've read many of your battery tests/reviews and would not question your battery expertise!

I have tested the batteryspace 3.3AH LiFePO4 cells and they do have more voltage sag than the A123 cells, but still performed OK. For best performance, it will be hard to beat the A123 26650 cells.
The IMR cells I was referring to don't seem to be available at batteryspace any longer. The 26650 cell they list now has a discharge rate of only 4.0 Amps. Definitely not what you want.

It can be hard to find a good, high discharge battery for a reasonable cost.

FB

 

[Battery Guy]

Battery Guy,

I've read many of your battery tests/reviews and would not question your battery expertise!

I have tested the batteryspace 3.3AH LiFePO4 cells and they do have more voltage sag than the A123 cells, but still performed OK. For best performance, it will be hard to beat the A123 26650 cells.
The IMR cells I was referring to don't seem to be available at batteryspace any longer. The 26650 cell they list now has a discharge rate of only 4.0 Amps. Definitely not what you want.

It can be hard to find a good, high discharge battery for a reasonable cost.

FB

Hi FB

Thanks for the info.

In my search for Molicel IMR26700 cells I learned that Molicel no longer makes these. They replaced the IMR26700 with IBR26700. The original Molicel IMR26700 was pure manganese spinel, which produced a beautifully flat discharge at high voltage. The new IBR cell has a different cathode formulation which gives the cell a sloping discharge curve not unlike the AW IMR cells. The trade-off is that the new IBR cells have substantially better cycle life and slightly lower internal resistance.

But the bad news for us is that the old Molicel IMR26700s that had that great flat discharge curve are no longer made and it does not appear that anyone makes anything equivalent.

I will definitely take a look at the batteryspace 3.3 Ah LFP cells and see how well they hold up at 10 A. I will also keep searching for a good source of the A123 26650 cells.

Cheers,
BG

 

[Mr Happy]

I will definitely take a look at the batteryspace 3.3 Ah LFP cells and see how well they hold up at 10 A. I will also keep searching for a good source of the A123 26650 cells.

BG,

Have you ever run any discharge tests on the K2 Energy LFP cells, such as the LFP26650P? Since I have some of these and also some of the LFP26650EV cells, I was wondering if it's worth me trying to run some tests. But I don't want to duplicate any work that has already been done.

(I have two LFP26650P cells driving a 3854-H very nicely. It is running pretty much at spec and not over driven, so although it is not super-bright it also should have a good life and a low risk of instaflashing.)

 

[FBsLights]

BG,

I live near Portland and have some of the cells that are discussed here. Maybe we are close enough to meet and you could borrow cells for testing.

PM sent.

FB

 

[Battery Guy]

BG,

Have you ever run any discharge tests on the K2 Energy LFP cells, such as the LFP26650P? Since I have some of these and also some of the LFP26650EV cells, I was wondering if it's worth me trying to run some tests. But I don't want to duplicate any work that has already been done.

Definitely worth it. I have not purchased any of the K2 Energy LFP cells yet and I am unlikely to have a chance to test these anytime soon. I would love to see some discharge curves for these, especially at 6 A and 10 A, as these are the discharge currents that I am usually interested in for hotwire mods (6 A is a pretty close match for the CL-1909 bulb and 10 A is similar to many of the higher voltage Osram bulbs).

(I have two LFP26650P cells driving a 3854-H very nicely. It is running pretty much at spec and not over driven, so although it is not super-bright it also should have a good life and a low risk of instaflashing.)

Great to hear that you did that mod. I know you were talking about it in another thread. But I thought that you were going to push the limits and try the 3853-H bulb with three LFP cells. Did you ever give that a try? I was curious to know if that combination would instaflash.

Cheers,
BG

 

[NightKids]

Let's see some long range beamshots! Like across a football field or something...

 

[Justin Case]

If you can wait, you might consider using the JM-PHD-D1 incan regulator to run your 64458. It appears that JimmyM is gearing up for another run of 100 drivers. Presumably with the driver, the AW IMR26500 voltage spread won't matter as much.

 

[Mr Happy]

Definitely worth it. I have not purchased any of the K2 Energy LFP cells yet and I am unlikely to have a chance to test these anytime soon. I would love to see some discharge curves for these, especially at 6 A and 10 A, as these are the discharge currents that I am usually interested in for hotwire mods (6 A is a pretty close match for the CL-1909 bulb and 10 A is similar to many of the higher voltage Osram bulbs).

There are some discharge curves on the data sheet, which probably you have seen: http://www.battlepack.com/LFP26650P.pdf

The 5 A curve looks like a stroll in the park, while 20 A and higher apparently cause the voltage to sag a bit at the beginning and then rise later on, presumably as the cell warms up. The 10 A curve is missing, but by interpolation it would probably remain above 3 V for most of the discharge.

I can only do constant resistance discharges, but I might see if I can do one at some point to verify the manufacturer data.

Great to hear that you did that mod. I know you were talking about it in another thread. But I thought that you were going to push the limits and try the 3853-H bulb with three LFP cells. Did you ever give that a try? I was curious to know if that combination would instaflash.

Well, I'm a conservative soul at heart and when I looked at the charts I got the feeling that a 3853-H on three cells would be pushing it just a bit too close to the limits. I was looking for something on safer ground as a first experiment. I do have a 3D Mag on hand, so I will try three cells soon. I'm afraid I'm still inclined to be conservative and try an 1185 at first though. What I'd really like to do is run the 3853-H with a regulated driver so I can soft start it and fine tune the voltage below the flash point. But that will have to wait until I can get my hands on an incan regulator.

 

[Mr Happy]

If you can wait, you might consider using the JM-PHD-D1 incan regulator to run your 64458. It appears that JimmyM is gearing up for another run of 100 drivers.

That's good to know. I'm definitely in line for one of those.

 

[EMC2]

The EV cells pulse @11C and a 3C continuous rate
The P cells pulse @ 50C and a 20C continuous rate.
The resistance could be in your batteries

Why stop @ 90W?
Is there a preferred FET device or circuit?

 

[FBsLights]

The A123 cells are very low resistance.

The 64458 is 90W at 12V. At these voltages, it is >150W. That is enough power to get things HOT fast enough.

You need a FET with a nice low Rds ON and high power handling. The part I used is rated to 75 Amps with an Rds of 0.009 ohms.
If you are not electrically inclined, I recommed buying a driver, like the JimmyM mentioned above. 10+ amps of these bulbs can get tricky!

FB

 

[Eddie-M]

I'm running an Osram 64458 in a 6d mag off of 21AA duraloops in a 21>6d odd mods battery adapter with an AW 3 was soft start switch and an FM 3x head. I have to let the batteries rest for over an hour off the charger or I will (and have) blown bulbs. I then ramp it up from low to medium for a few seconds then high. It is bright as hell, but pretty much a battery toaster at this point for the duraloops. I later plan to run some AW IMR batteries once I have the funds, but I built this a few months ago while I was still afraid of Lithium battery chemistries. I had orginally wanted Titanium AA's or simililar but battery guys testing of the newest batch proved less than stellar if I remember correctly, and just decided on ruining my older used duraloops in the mean time. I love this bulb and the axial filament and it's sure is bright as hell !

 

[Battery Guy]

I'm running an Osram 64458 in a 6d mag off of 21AA duraloops in a 21>6d odd mods battery adapter with an AW 3 was soft start switch and an FM 3x head. I have to let the batteries rest for over an hour off the charger or I will (and have) blown bulbs. I then ramp it up from low to medium for a few seconds then high. It is bright as hell, but pretty much a battery toaster at this point for the duraloops. I later plan to run some AW IMR batteries once I have the funds, but I built this a few months ago while I was still afraid of Lithium battery chemistries. I had orginally wanted Titanium AA's or simililar but battery guys testing of the newest batch proved less than stellar if I remember correctly, and just decided on ruining my older used duraloops in the mean time. I love this bulb and the axial filament and it's sure is bright as hell !

The new Elite 2000 AA cells from cheapbatterypacks.com are quite good for high current applications. I have posted test results here. They are certainly going to hold up better than the Duraloops under a 12 A load. If you are blowing bulbs with the Duraloops hot off the charger, then you might actually need to put a dummy cell in the holder if you switch to the Elite 2000s.