Upgrade a Mag85

VegasF6 said:

The thing with the most common lithiums most of us are using (ones with PCB protection) is they don't limit voltage, they limit current, or amperage through the cell. I guess it is only safe to pull about twice the rated capacity through the battery at once. So, if you have 1, or 2, or however many batteries stacked together in series, you can still only pull about that same amount of current at once. In addition, the quality of that PCB depends on the maker of the battery.

So, if you are using for instance an ultrafire 18650 rated at 2400 mAh, you could theoriticly draw 4.8 amps at once. A 6 volt bulb * 4.8 amps = 28.8 watts. But, there is more to consider. When we overdrive the bulbs at higher voltages, the effective wattage is also raised, hence the current used is higher as well. In addition, the ultrafire being a "budget" cell odds are the PCB is going to be of lower quality and just not allow that amount of current out. And, the way they work, they seem to limit it even more so from a sudden rush of power going through them, I guess because to the PCB it appears to be a possible short circuit. So, you see people talking about "soft starts" and "NTC's" and such, because they allow a gentler start on the batteries, less voltage to begin with that ramps up. (I don't know exactly how long, but I am thinking less than a second) There are other reason's they work as well, having to do with heat generated and the resistance caused by that heat, thereby actually allowing less current to pass. So you see people talking about a light that may not start on the first click starting after 3 or 4 clicks.

Now in the case of safe lithium cells, the lower voltage ones, there is no protection circuit so you don't have those same problems. But, even with the safe chemistry cells you should still follow the 2C rule for the sake of the battery itself. If you don't, it isn't as dangerous because if a safe chemistry cell vents, it doesn't vent with flames and cause your light to explode and vent poison fumes. But, you still run the risk of venting.

Now in the case of other types of cells, the emolis, and A123's, those rules don't apply. They are perfectly safe to use at very high current levels, I don't know the exact specs, but over 40C in a lot of cases, probably more. In fact, they are designed for it.

So, in the case of very high voltage cells, like the 6x3.7 volt setups you are talking about, you would have to find a bulb that is high voltage, but low wattage, and no examples come to mind for me except HID's. Or, use emoli cells or A123's. Or, you could use 6 cells but in series parralel configuration. So for instance, you have 6 cells, but only 2 of them in series. Now you have doubled your voltage, to 7.4 volts. But, because you have 2 stacks of 3, you have tripled your capacity from 2400 mAh's to 7200 mAh's.

Those are the basics of the batteries, but to get answers from someone who REALLY nows what they are talking about, unlike me, you might be better off posting in the battery forum. As for a light choice, best off finding a combination someone has already made and following there recipe exactly. One light you may enjoy reading about is the mag623. Apparently it is quite a step up from the mag85.

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VegasF6 said:

It's not that it can't be done, you just need to be aware of certain safety stuff in advance
The plus's of the lithiums are they hold their voltage quite well under load, very little self discharge, they are light, and dollar for dollar and volt for volt they are pretty reasonable.
According to luxluthors destructive tests, at 10.8V the 1185 should give 1100-1200 bulb lumens. I know mine running on 9 eneloops is my brightest light, out flooding and out throwing my P7's. But, I would love to see a well driven D bin P7. Maybe soon
Have you read up on the mag 35 on 8 cells? Rather on old build now, but a 6V bulb overdriven that high sound interesting and the bulbs are less than 5 bucks apiece It is a 35 watt bulb driven to nearly 70 watts, should be interesting.
Here is a link that recently surfaced again:
http://candlepowerforums.com/vb/showthread.php?t=107571&highlight=mag35-8

Otherwise, I guess there is always HID or a 6 emitter R2 build.

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mudman cj said:

Well, I know what you mean about the loss of amazement over a light that only puts out less than 1000 lumens. :devil: But especially for a duty light you have to weight that against size, weight and runtime. It's hard to beat the 1185 bulb overall in these categories. However, you could certainly get more runtime and even a smaller size with the 1185 by switching to AW Li-ion C cells. They fit in an extended 3C or a cut down 4C (or you could use a spacer instead of cutting it down) and provide about 50 minutes of light. Less runtime than that gets into the realm of questionable practicality IMHO. And you could use your 3D host that you already have as well (with appropriate spacer), I just prefer the smaller size and weight of the C bodies.

For improved throw you could look into Fivemega's alternative reflector options such as the 2" deep version and various larger diameter ones that require replacing the head as well. These cells should be charged one at a time or in parallel or in series with balance taps controlled by a balancing charger. Do not charge them as a series pack.

The reason I recommend C cells instead of D cells is because D cells cross the threshold for instaflashing the 1185 without soft starting. Also, there are still no protected D cells of a quality that I feel comfortable recommending. A cheaper option is using 3 protected 18650 cells (again, I recommend AW cells) in a 4C host to make a great 1185 with just over 30 minutes of runtime.

If you really want brighter than the 1185, then I suggest stating another requirement such as maximum size or minimum runtime to help narrow the field of candidates.

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VegasF6 said:

Sure, it is safe to run the 3 lion's in series. In fact, even though conventional wisdom had sad so, I still had the same question I posed. It was answered by LuxLuthor in this thread:
https://www.candlepowerforums.com/threads/197823

Of course, you want to charge them separately, use quality cells, quality charger, and it is important to keep them in balance. You have a meter, correct? If not, please pick one up, a cheapie will do fine. Check your voltages before running the light and try and get them within .1 or .2 volts of each other. (the closer the better)

So lets say you have a mag85 in a 3D with 3x18650 (which fits great by the way) and you remove one of the cells to run in your MRV for awhile. You wouldn't really want to put that cell back into the series setup before charging everything again. Otherwise the run down cell risks the chance of attempting to reverse charge by the others, and that can lead to venting. I THINK the protection circuit should stop that, as long as it is polarity protected, but it is recomended to follow safe procedures anyways and try not to rely on the PCB as it could fail.

For the mag85 or another hotwire you are surely going to need high quality cells like AW's, and you will need to have a charger with separate charging channels to keep your batteries in balance. (make sure it has 2 leds)

For budget concerns you could probably use a cheaper cell like a Trustfire for your MRV, though many will recomend AW cells for everything. But I can understand being on a budget. Many use the Trustfires and you don't hear about them blowing up every day or anything like that.

In the case of the hotwire you would probably prefer AW C cells anyhow for both better runtime, and the possiblity of a hotter hotwire. You can sustain higher current with the larger cells.

If you have a particular build you want, feel free to post it in this thread. If you still just want to learn more about the batteries I think you are going to be better served posting a new thread in the battery forum and getting the advice of the real experts. I am just regurgitating what I have already learned from the board, but others have done the research and can pass on better information than me.

I look forward to seeing your build whichever you may choose, good luck!
VegasF6

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eyeeatingfish said:

Thanks for the link, it was very informative. My MRV has an attachment where it can take a second 18650 cell for more runtime and a little more brightness and i was thinking about getting the extender, so i guess I should buy AW batteries if im going to do that, or get the MVP.

I didnt see any mention of a problem of using a larger number like 9 AA size LiIon batteries. Im not sure if i understand exactle how the juice runs throught PCB cells yet. So the voltage of one battery doesnt run through the second one, it runs past it on PCB lights and thats why the battery doesnt have too much juice flowing through it?
The thing about making sure the batteries have a similar charge I dont understand too well. It sounds as if one is a bit lower it will act as if it is being charged by the other batteries or the other batteries will want to charge it or something? Is it not the case that a flashlight will naturally draw energy out of batteries differently? When i charge my mag 85 cells i notie some of the AAs charge quickly as if they aren't all draining at the same exact rate. Cant remember if ive ever gone to measure it yet.
Maybe i should jsut resurect your old thread, or at least link any new thread i make to it.

Thanks for all the info so far, I hope its not a bother.

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