16A capable switch/connectors?

[Jarl]

Ok, I've got a plan. It involves 4IMR18650's, and on burst mode it'll be pushing them to the max with a 16A drain (8 MC-E's, 4 drivers each running 2 MC-E's, hoping to hit 9K warm emitter lumens, while maintaining full variable control right down to 1 or 2 lumens with a "cruise" setting of 300 lumens or so). I need a switch and a connector capable of taking doing this. It could either be a big, meaty switch capable of taking the whole 16A as a master on/off, or a multi pole switch, with each pole seeing a maximum of 2A, or anything in between. Suggestions?

Also, ideas for connectors; I want to be able to disconnect the battery holder and take it out, then remove the batteries from the holder. Again, I could go for 1 big 16A connector or 8 connectors which would see a max of about 2A (or 4 connectors seeing 4A, 2 connectors seeing 8A, etc)... obviously, the single big connector would be easiest to take out the holder quickly, but if it can't be done, it can't be done, and I'll use a load of small connectors.

This is my first dabble into high currents (never gone over 1.5A before, so 10x more is a big jump!), is what I describe possible or should I just forget it?

 

[TigerhawkT3]

What body? If it's a Mag (which I doubt because of the room required by eight MC-Es), you'll have much fewer options because of space and form factor limitations.

If it's an "anything goes" approach, you have many options. For the switch, you can just go to an auto parts store and get a big toggle switch. I have one (two, actually; one for the main switch, another for an internal safety) rated for 12V/50A in my LK12, handling 28V/22A. For the connectors, you can try an auto parts store or just get some RC connectors. Tamiya, PowerPole, etc. are often used to handle many tens of amps.

 

[Jarl]

Anything goes. There are limits to budget and size, but they're way up there, I just want to make a monster . I've purchased some 30A PowerPoles (overkill, but everything about this light will be!), and I'll pop into a car shop for a suitable switch.

If a switch is rated 12V/50A, could I run it 50V/12A (i.e, is the rating a function of power), or is it more complex than that?

Thanks!

 

[worldedit]

If you exceed the current specification the switch will get hot. If you exceed the voltage there might be sparks and the switch would be worn out sooner.

 

[LukeA]

Anything goes. There are limits to budget and size, but they're way up there, I just want to make a monster . I've purchased some 30A PowerPoles (overkill, but everything about this light will be!), and I'll pop into a car shop for a suitable switch.

If a switch is rated 12V/50A, could I run it 50V/12A (i.e, is the rating a function of power), or is it more complex than that?

Thanks!

You can't exceed either limit and have the switch last like it should. In extreme cases you can have contact welding.

Plenty of high current switches on Digi-key. I got some nice 12VDC/20A ones that I like a few weeks ago but I can't find them now (naturally).

 

[Gryloc]

What if you used a small relay or a mosfet to do the heavy switching so you can use any ordinary switch? I understand the large toggle switches are pretty large and require a bit more force to push the lever over. Well, the meaty switch could add to the "meaty" feel of a 9000 lumen light, or the feeling of switching a device of a mad man. :naughty:

A relay is simple to wire up, as is a mosfet (or a good, low Vf hexfet to run really cool). Ask around for the simple circuit diagram for such a mosfet based solid state swiching circuit. There are a lot of incan guys that propably add a mosfet switcher to their modded mags, so they can keep their stock switch. The circuit can be made to be small if needed. Good luck. I hope you will present your finished project. Just because the light uses 8 MC-E emitters means that it is instantly awesome! :twothumbs

I hightly respect the lower modes as well due to the super efficiency! Just dont forget that the efficiency will actually start dropping if the current levels are too low. They peak between 10mA-40mA per die. I do not have any charts on me to show you, but jtr1962 and evan9162 (no relation) have lumen/current charts that show this strange phenomenon. The efficiency drop may not mean much since the total power is so low on your low mode, but it would be neat to see you utilize this max efficency current level in one of your modes! ...Actually, now I think of it, it looks like that was what your "cruise" mode was for. I have a feeling that you thought about this already. If so, good job. Oh well...

-Tony

 

[LukeA]

Here's one CPF MOSFET switch.

 

[mash.m]

you can use the circuit i used at my BigMag³:

http://www.candlepowerforums.com/vb/showthread.php?t=186673

scroll down to shematics and give them a try. it is capable to switch more than 50A with steppless dimming. if you need more you can change the fet or add one or two but then you need a driver for the fet´s.

markus

 

[Oznog]

Yeah... don't switch 16A with the switch. Terrible idea.

MOSFET. You need a very low rd-on MOSFET and this is a bit of selection work. The biggest package may not be the best candidate. There are plenty of teeny tiny switches that can handle a lot of current because the on-state resistance is so low they do not generate a great deal of heat.

There's going to be a power supply, right? You wouldn't even want an external switch but rather something which enables/disables the supply.

How are you getting 16A, anyways? An 18650 cannot safely put out 16A. Well it might as a stunt but it'll surely degrade the cell and for all I know I couldn't completely rule out a battery fire. A series string does not increase the current capability just the voltage. Putting them in parallel is probably a terrible idea unless they're welded together, otherwise if the voltages are even the smallest bit different then large currents can flow from cell to cell. There are no great isolation solutions to fix that.

AFAIK an 18650 1.5C discharge is what's seen as "safe". The Tenergy protected cell for example will shut off the cell at 1.5C, 2.4AH=3.6A max. So 3.7v x 2.4AH x 1.5C x 4 cells = 53.3W, * 80lumens/W = 4.2Klumen. I would wire the MC-E as parallel dies, put 3x in series, and drive it at like 3.5A with a buck converter. Then it won't run out of voltage and dim until the battery's pretty low. Actually a buck converter does put out more current than it takes in when Vin>Vout, so maybe 4A, but as cell voltage drops Vin will near Vout and cell current will increase. I'd use protected cells too since it's a series string and could stay running when a cell drops below 2.5v.

I would use an HV9910B controller chip since 4x li-ion provide enough voltage for that chip. But you gotta consider the inductor and transistor selection very carefully.

 

[divine]

http://www.candlepowerforums.com/vb/showthread.php?p=2257729

Darn, luke beat me to it. =\

 

[LukeA]

http://www.candlepowerforums.com/vb/showthread.php?p=2257729

Darn, luke beat me to it. =\

Better two than none.

Interesting that the links are different and still go to the same thing though.

 

[effulgentOne]

Better two than none.

Interesting that the links are different and still go to the same thing though.

It looks like one links to the thread, and the other links to the first post.

 

[Daravon]

If you can't/don't want to find a mosfet, you can get 30A automotive relays at car stores; very common part. They are big though.

 

[Jarl]

grlyoc: You're right, that's what cruise mode is for. I plan to get a lightmeter to get the low level done as efficiently as possible... it'll probably end up with 6 controlled by 3 sharks with a master pot, with the minimum level from these 240ish lumens, then an independantly controllable MC-E with a floodier beam and buckpuck wired 2s2p, running at anything from 1 to 500 lumens, and some fancy switching that should turn on a small red LED when I have both the flood and the other 6* LED's on so I don't waste power.

*Had to drop to 7 MC-E's due to changing my mind about reflectors used. So now it's going to be just off 9K lumens and just off 50k lux lol. Still a long way from shabby, mind

Oznog: Check out this. While I can point out new technologies for li-ion, I have no idea what a HV9910B is! Looks like I've got some reading to do!!

Thankyou everyone else for idea's of mosfets. Never even knew what a mosfet was 15 minutes ago*.... hopefully ignorance isn't bliss!!!!

*Still don't!


If anyone has any more to add; please do. Bear in mind I will be using the mosfet as the master on/off between the source (16.8V to 12V, with 4 cells though I might use 6 cells which would be 25.2V to 18V) and the 3 sharks (wired in parallel). Max current would be definitely <15A, potentially could be brought to <10A with the 6 cells if that helps, though max draw would most likely hover between 10 and 15A.

edit: Just had a read.... and I still can't quite figure it out. What is a mosfet? I mean, what's an LED. A light emitting diode, it emits light and behaves as a diode. Simple, right? What's a resistor? Something that adds resistance to a circuit... what's a mosfet? Something that fets my moss? lol. The fact that it's currently nearly 1AM doesn't help my understanding much, but I'm normally pretty good at this kind of thing >.<

 

[LukeA]

grlyoc: You're right, that's what cruise mode is for. I plan to get a lightmeter to get the low level done as efficiently as possible... it'll probably end up with 6 controlled by 3 sharks with a master pot, with the minimum level from these 240ish lumens, then an independantly controllable MC-E with a floodier beam and buckpuck wired 2s2p, running at anything from 1 to 500 lumens, and some fancy switching that should turn on a small red LED when I have both the flood and the other 6* LED's on so I don't waste power.

*Had to drop to 7 MC-E's due to changing my mind about reflectors used. So now it's going to be just off 9K lumens and just off 50k lux lol. Still a long way from shabby, mind

Oznog: Check out this. While I can point out new technologies for li-ion, I have no idea what a HV9910B is! Looks like I've got some reading to do!!

Thankyou everyone else for idea's of mosfets. Never even knew what a mosfet was 15 minutes ago*.... hopefully ignorance isn't bliss!!!!

*Still don't!


If anyone has any more to add; please do. Bear in mind I will be using the mosfet as the master on/off between the source (16.8V to 12V, with 4 cells though I might use 6 cells which would be 25.2V to 18V) and the 3 sharks (wired in parallel). Max current would be definitely <15A, potentially could be brought to <10A with the 6 cells if that helps, though max draw would most likely hover between 10 and 15A.

edit: Just had a read.... and I still can't quite figure it out. What is a mosfet? I mean, what's an LED. A light emitting diode, it emits light and behaves as a diode. Simple, right? What's a resistor? Something that adds resistance to a circuit... what's a mosfet? Something that fets my moss? lol. The fact that it's currently nearly 1AM doesn't help my understanding much, but I'm normally pretty good at this kind of thing >.<

A mosfet (metal oxide semiconductor field effect transistor) is a device that allows very fast switching of high current loads with no moving parts and a small signal current.

That's my (basic) understanding.

 

[Jarl]

ok, so, here's a few (probably very noob) questions:

If i'm not bothered by high speed switching, is a mosfet still fine to work with? (guessing yes)

Above, petrev uses a 10K resistor. He also puts a 4.7K in if the voltage becomes very big.... I'm guessing this is to limit the current, and 2 resistors are used because 10K and 4.7K are both common values, unlike trying to find a 15K resistor to put where the 10K resistor is in this diagram. However, I might be wrong; does the mosfet go by voltage or current at G?

Thanks in advance!

 

[VegasF6]

Also, ideas for connectors; I want to be able to disconnect the battery holder and take it out, then remove the batteries from the holder. Again, I could go for 1 big 16A connector or 8 connectors which would see a max of about 2A (or 4 connectors seeing 4A, 2 connectors seeing 8A, etc)... obviously, the single big connector would be easiest to take out the holder quickly, but if it can't be done, it can't be done, and I'll use a load of small connectors.

For connectors you may want to check in RC hobby store stuff. You can easily find connectors rated this high. Just for instance one of the popular models, Deans Ultra plugs I find rated at 100 amps! I dunno if that is continous, but my goodness thats a lot of power. Switch, relay or mosfet etc this isn't really very much current for large switches, like automotive use. One trick I have seen done that I thought was pretty neat was a key switch. Kinda serves two functions, yah know.

 

[Oznog]

ok, so, here's a few (probably very noob) questions:

If i'm not bothered by high speed switching, is a mosfet still fine to work with? (guessing yes)

...However, I might be wrong; does the mosfet go by voltage or current at G?

Yes it's fine to work with a MOSFET. It will actually not switch very fast anyways with the circuit presented but more than fast enough.

A MOSFET switches based on gate voltage. The gate itself draws no DC current and would show up as an open circuit on an ohmmeter. It has a very small capacitance that shows up when designing high speed switching, like hundreds of KHz, or with a lot of resistance in series with the gate.

MOSFETs have 3 basic states, off, saturation region (throttles current), and ohmic region (closed switch). We want to avoid that middle one because it's not acting like an open or closed switch and generates a lot of heat. Just getting the voltage high enough for the max current drawn by the circuit avoids this.