Hotwire Problem

[daBear]

I have a tri bore Mag 85 which uses 9 LiIon 17500 cells in 3 separate FM holders. It has an AWR HD hotdriver of course with a low resistance KIU socket. My problem is the light will not come on unless you actually click it on then work the tail cap back and forth a couple of turns. Then it will come on and work fine. While warm you can click it on and it comes right up and works perfectly. But take it cold off the shelf and no way will it start without screwing the tailcap back and forth.

I have a copper wire on the tail spring to lower resistance, I have applied liquid gold to every possible joint and the batts are fully charged.

The only thing I can think of is one of the 17500 cells is weak and I am not getting enough amperage at the start. voltage checks out within range of 4.2 =/- .1 with no load for each battery pack. (three)

 

[LuxLuthor]

I have a tri bore Mag 85 which uses 9 LiIon 17500 cells in 3 separate FM holders. It has an AWR HD hotdriver of course with a low resistence KIU socket. My problem is the light will not come on unless you actually click it on then work the tail cap back and forth a couple of turns. Then it will come on and work fine. While warm you can click it on and it comes right up and works perfectly. But take it cold off the shelf and no way will it start without screwing the tailcap back and forth.

I have a copper wire on the tail spring to lower risistance, I have applied liquid gold to every possible joint and the batts are fully charged.

The only thing I can think of is one of the 17500 cells is weak and I am not getting enough amperage at the start. voltage checks out within range of 4.2 =/- .1 with no load for each battery pack. (three)

IMHO, the tipoff in your trouble shooting is the response to twisting the tailcap. That makes it a connection issue. I have several of those FM lights, and here are the things I would check:

1) Check the length and position of the threading rod. It is easy for it to have moved in the plastic.

2) Check the battery contact pads. I highly recommend you lightly abrade off the oxidation surface with a pencil eraser or fine grit sandpaper.

3) Then coat with Progold and wipe off with single swipe. (Not supposed to leave a wet coating of Deoxit or Progold after application)

4) Lightly sand the top (contact) surface of tailcap spring, AND make sure there is exposed aluminum in tailcap where spring fits in.

5) Clean off edges of Mag body tube and mating edge of tailcap....to make sure there is not a lubricant interfering.

My likely guess is on the battery holder contact points. Been there, seen that.

 

[mudman cj]

You may have fried the hotdriver. IIRC, hotdrivers do not like the switch to be turned on while the tailcap is put on. They also do not like rapid clicking of the switch or reverse battery polarity. I hope I am way off base here for your sake. I will try to find the source of this info, but I think it was well over a year ago when I saw it.

 

[daBear]

You may have fried the hotdriver. IIRC, hotdrivers do not like the switch to be turned on while the tailcap is put on. They also do not like rapid clicking of the switch or reverse battery polarity. I hope I am way off base here for your sake. I will try to find the source of this info, but I think it was well over a year ago when I saw it.

Thankfully the hotdriver is fine. The normal indication of a failure is the light will not turn off at the switch. Once this one is on for a while it continues to work fine. Lux is right on target I feel and I will check these fixes out in a bit.

Thanks.

 

[mudman cj]

I asked Andrew about your problem, and he said it may be a case of protected cells shutting down in combination with a high voltage setting on the hotdriver. Before he could be sure he would need to know if your light starts blinking when you multi-click the switch, or only with jiggling the tailcap.

If that is the issue, there is a fix for that involving adding a sense wire to limit startup current, but it involves taking it apart. So, by all means try the other suggestions here, but if you still find it not working there may yet be hope.

Of course, if you want to reduce the startup current from the cells you could also lower the hotdriver voltage, but then this would drive the lamp at a lower level. BTW, what voltage is the hotdriver set for?

Edit: Oh, and I found that info about hotdriver failures caused by attaching the tailcap while having the switch on. That is one of the main causes for blown FETs in 100W hotdrivers, but I suppose that doesn't apply to your case.

 

[daBear]

mudman cf,

Thanks for the reply. There is no blinking when you multi click. In fact nothing at all happens when you rapidly click the switch. The ONLY way the light will come on is to click the switch to the on position then unscrew the tailcap and screw it back in several times. I have been tied up with a busted computer and installing a new one for the past several days and I will try LuxLuthor's advice tonight. Unless something else gets in my way.

 

[mudman cj]

I heard back from Andrew. Provided you are using AW protected cells, he is 95% sure it's the current limiting of the battery protection circuits kicking in, and can be fixed by changing the hotdriver itself. If you want to try this option, you can email Andrew to swap your hotdriver for one with the fix. PM inbound.

 

[daBear]

Just finished charging the cells individually rather in the FM holder placed in in a 4 D cell battery tray I fabricated. That way I am sure each cell is toped off. The batteries and FM holders had plenty of excess ProGold on it. I never knew you were supposed to wipe the excess off. I used an eraser to clean every contact which there are plenty of, put it all back together and it blinked briefly. Then on the second click of the switch it came on. Now that everything is warmed up the light will turn on and off fine. I will let it cool back down for a while and see how that works. I am still not convinced the HD is at fault. I think is is the huge amount of resistance accumulated by using three separate battery holders with three cells each. That adds up to a lot of contacts and resistance. I am operating the same HD setup in other lights with welded battery packs soldered directly to the bottom of the Mag switch and all is well and they work perfectly.

If all this craps out I will contact AWR and work something out. I sincerly appreciate all input and help.

 

[LuxLuthor]

Just finished charging the cells individually rather in the FM holder placed in in a 4 D cell battery tray I fabricated. That way I am sure each cell is toped off. The batteries and FM holders had plenty of excess ProGold on it. I never knew you were supposed to wipe the excess off. I used an eraser to clean every contact which there are plenty of, put it all back together and it blinked briefly. Then on the second click of the switch it came on. Now that everything is warmed up the light will turn on and off fine. I will let it cool back down for a while and see how that works. I am still not convinced the HD is at fault. I think is is the huge amount of resistance accumulated by using three separate battery holders with three cells each. That adds up to a lot of contacts and resistance. I am operating the same HD setup in other lights with welded battery packs soldered directly to the bottom of the Mag switch and all is well and they work perfectly.

If all this craps out I will contact AWR and work something out. I sincerly appreciate all input and help.

Yeah there was a thread about Progold not too long ago, where I gave links to Caig's website...it's kind of buried in their instruction PDF's. Wondering if you would benefit with fine sandpaper rub on outside of battery holders contact points.

 

[daBear]

I should have known it could not be a simple fix. I'm back to screwing the tailcap off and on with the switch on for the light to work. Still think it is a resistance issue though. I sure hate to set asside $75 worth of FM batt holders and $90 worth of 17500 cells and install a welded NiMh pack. Think I will give AWR an opportunity to look at the hotdriver before I do that.

 

[mudman cj]

I think you are right about it being a resistance issue. It sounds like you may have temporarily had just the right amount of resistance to limit startup current enough to prevent the cell protection circuits from kicking in.