Hotwire Dimming Problem

[Aircraft800]

I have a 3D M@g running a WA1111 using new Titanium 1800's. After approx 3 min. the light starts to dim down a bit, and yellows a bit. If I let it cool, it goes right back to full power.

I guess it's a Resistance problem or something. I don't believe it's the cells, because it will do this anytime even after a full charge.

Does anyone else see this? Where is the most common place to find the Resistance, the switch, the slider, the spring, tail spring, the filament? Does the Resistance go up when there is a lot of heat, or is the tower growing and leaving me with poor contact between the slider and the slug?

Thanks for the help!

 

[Valolammas]

I may be wrong, but it could be nothing more than the voltage of the cells dropping under load, especially if the light recovers after a while. I'd think if it was just extra resistance, it would be more constant.

You see, even with high current cells the voltage will drop when the cell is supplying current, and it will drop more under heavy drain like a ROP. Once you turn the light off, the cells will recover back to their normal resting voltage. E.g. let's say a cell has a normal no-load resting voltage of 1.3 Volts. Under heavy drain that voltage may drop down to 1.1 Volts or even less, but once the drain is gone, the voltage will return to 1.3 Volts (assuming the cell wasn't drained so much that it's resting voltage is now lower).

As for resistance fixes, I've heard that the tailcap spring and the sliding contacts are the worst culprits. The spring is perhaps the easiest to fix, just solder a flexible wire from top to bottom, so the current doesn't have to flow through the spring itself. For rest, see this thread

 

[thezman]

Check each cell. One bad one can cause a problem.

 

[Aircraft800]

Check each cell. One bad one can cause a problem.

Check the voltage of each cell with a Fluke, or do you mean I need to somehow load each with something and check the Current?

You may have something here, I may have seen a little wettness near the vent hole on one cell alfer charging, but I don't remember which one.

 

[Icebreak]

Cell size, type, configuration and number please.

WA1111 is usually a six NiMh or two Li-Ion set-up. The 3D host is throwing me off.

Also, can you measure using the hundredths place? 1.39V is a good start but 1.32 is not a good starting voltage.

I think thezman and Volalammas have you going in the right direction.

 

[lctorana]

Check the voltage of each cell with a Fluke, or do you mean I need to somehow load each with something and check the Current?

Test the battery with a multimeter under load - anything will do - a 1.2V torch globe is good, as is a 5W resistor of anywhere between 1.5 and 5.6 ohms.

Test the no-load voltage, then see how far it drops under load.

This test is effective for any NiMH/NiCd/Alkaline/Zn-C/Zn-Cl cell.

 

[Aircraft800]

Cell size, type, configuration and number please.

WA1111 is usually a six NiMh or two Li-Ion set-up. The 3D host is throwing me off.

Also, can you measure using the hundredths place? 1.39V is a good start but 1.32 is not a good starting voltage.

I think thezman and Volalammas have you going in the right direction.

Sorry, I guess I never explained my setup. I'm running 12 Titanium 1800's in a 6X2 series/parallel FM Adapter setup in a quad bored Mag, so I shouldn't have any problem with voltage sag, but maybe testing each cell under a load will find something.

I've been looking at the resistance fix mod. I didn't find any resistance (Almost none) in any parts, but that was not under a load or hot or anything. I didn't know that there would be such a difference loaded or not. I'm unsure how to check resistance under a load of the switch and springs.

Test the battery with a multimeter under load - anything will do - a 1.2V torch globe is good, as is a 5W resistor of anywhere between 1.5 and 5.6 ohms.

Test the no-load voltage, then see how far it drops under load.

This test is effective for any NiMH/NiCd/Alkaline/Zn-C/Zn-Cl cell.

lctorana,

I'll give this a try when I get back to work, Thanks!

 

[LuxLuthor]

With 12 cells, the proper cell designation of what you have is 6s2p giving you 7.2V at 3600mAh. You did not say what your battery holder setup is as well as whether you have made any resistance changes, nor how you are charging them, or what charger you are using, and what setting is used.

My guess with what I have read so far is either you have a bad contact, a bad cell, or you have not "conditioned" the cells, and 1 or more is terminating the charge at typical higher voltage early, and is dragging down the pack after a few minutes, because it is not properly charged.

For example with brand new Elite 2/3A 1500 mAh NiMH cells, when charged at 1 to 1.5A some of them will prematurely give the voltage drop that triggers the termination before they were fully charged. However, if I charge them at 0.2A, they will all fill up properly, and behave normally thereafter with charges.

Others have already told you ways to test the cells under load....and it may be that 1 or more cells are not actually bad. They may just need to be slowly charged.

 

[Aircraft800]

@ Lux,

Thanks for the info. I'm using one of the junk Universal Smart Chargers, and I break my adapter in half while charging, so I only charge 6 series at a time at the high rate. I didn't know that I could use the slower rate, I'm a newbie.. I really need a Triton2 or a Supernova Charger, but I'm holding out for a AC charger so I don't have to use a car battery or a AC/DC adapter. Only problem, are a lot to expensive for me! Big purchases like this means the kids skip another dentist appointment (Just Kidding, you get the point).

I have only done the resistance fix to the spring under the bulb, I'll finish the rest this week, the slider, the tail spring. Maybe a Kiu socket would help also.

I'll also check the cells, It's possible I have a bad one, I think they got too hot once while trying to charge all 12 (6X2) at the same time, previously started another thread about this.

Thanks again for all of the help! I hope I can find my problem!

 

[LuxLuthor]

Keep in mind that with borderline overdriving where you are on the verge of flashing, doing too many "resistance fixes" can end up flashing the bulb on a full charge if you tip the scales too much.

The dimming indicates one of the issues I mentioned rather than resistance. If that were the problem it would never be bright. Given your charger, the prospect of improperly conditioned cells (rather than one of them being defective or damaged) moves into the #1 probability IMHO.

 

[Aircraft800]

Keep in mind that with borderline overdriving where you are on the verge of flashing, doing too many "resistance fixes" can end up flashing the bulb on a full charge if you tip the scales too much.

The dimming indicates one of the issues I mentioned rather than resistance. If that were the problem it would never be bright. Given your charger, the prospect of improperly conditioned cells (rather than one of them being defective or damaged) moves into the #1 probability IMHO.

Lux,

Now that I'm using a decent charger, is there a possibility of conditioning the cells now, or is it too late? I'm using a SuperNova and am charging at the slowest rate 0.1A.

I'll have to do a voltage sag test for each cell once I cycle them a few times, but I did check the total load, let me explain. I put my 6s2p FM adapter in with the tail jack plugged into my DMM and read 8.34v. As soon as I turn on the lamp (WA1111) the voltage sags WAY DOWN to 6.0-7.0v and drops off rapidly in the hundred ts place.

I noticed that you also use the Titanium 1800's, have any problems? I've got 4 that spewed out some junk when charging at a 1.0A rate. They seem fine 1.39v, but may be contributing to my problem. It also caused some corroding (green) of a contact in my adapter, cleaned it up with a pencil eraser.

 

[LuxLuthor]

Lux,

Now that I'm using a decent charger, is there a possibility of conditioning the cells now, or is it too late? I'm using a SuperNova and am charging at the slowest rate 0.1A.

If batteries have not been condition charged at 0.1C (where C is the mAh rating on the battery label...so 0.1C of an 1800mAh cell would be charging it at 180mA--call it 200mA), you can still do it. Usually a good idea to discharge them at say 0.5C down to about 0.9V to 1.0V, then let them rest for 30-45 mins before starting the 15 hour 0.1C slow charge....however....see below

I noticed that you also use the Titanium 1800's, have any problems? I've got 4 that spewed out some junk when charging at a 1.0A rate. They seem fine 1.39v, but may be contributing to my problem. It also caused some corroding (green) of a contact in my adapter, cleaned it up with a pencil eraser.

Titanium 1800's are nice high current output cells...but you don't need them for the 3-4A scenario with your 1111 bulb.

OK, now the "however" from above....if you have 4 cells that released battery acid, it is a pretty likely scenario that those cells are ruined...and moves into the #1 most likely slot of what is causing your problem. Either the cells are defective, or you somehow damaged them...with the charger a possible cause since so many leaked. I would replace them, and learn the lesson. I'm assuming you adequately cleaned out any residual acid from your contact.