Adding an extra 18650 battery to Convoy C8

Hi all, I would like to add an extra battery to my Convoy C8 for longer life.

It currently is running a multi-coloured XM-L LED through a driver that has an input voltage of 3-4.2 volts, powered by a 3.7V 18650 cell.

I apologise in advance for what may scene naive, but am I right in saying I cannot just position the extra cell behind (in series)? Is it essential that I create a parallel circuit?

Many thanks,

Moss

That is correct. You would need the other cell is parallel.

Thank you. Because of the host, the batteries need to be positioned behind one another. I cannot find anyone who has really done this, it is always side by side. Do you thin that this is feasible / safe?

a bit like this ( except they're not 12v):

That design is accurate if what's needed.

Safe is relative.

But to make it work out youd need an extension tube that'd not just have the length for a second battery but also space to run wires plus hold a (ceramic) insulator between the cells.

By the time you're done, it'd be tough to say you'd be better off than just having a spare battery or going to a 26650 light instead.

I'm actually machining the host from scratch, I'm using the c8 as a reference for dims.

I'm worried that it could be hazardous making it a parallel circuit, is there another way? Do the 26650s have a longer running time?

Moss said:

I'm actually machining the host from scratch, I'm using the c8 as a reference for dims.

I'm worried that it could be hazardous making it a parallel circuit, is there another way? Do the 26650s have a longer running time?

Click to expand...

With 18650 you're going to max out at around 3000mah for the ultra high drain unprotected, or 3600mah for protected.

With 26650 you'll get 4200 for the former or 5200 for the latter. For a standard c8 you could use a protected 5200mah battery and be fine.

Not quite double a 18650 but you would get much more capacity with not much more size, and certainly less risk and failure points.

Thank you for your suggestions. It may sound silly, but as well as desiring a longer life, I was also interested in the battery tube be longer for how I wanted it to look/feel, a bit like the Jetbeam BC40GT. I've looked into finding RGBW leds with higher voltage but they are all around 3 something. Then it seems excessive to run 7.4V (2x18650 in series) if it only needs half, if that is even possible anyway.

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If I wanted to use 2x 18650 in series, would the answer be to find a different driver?

Yes, a buck driver would drop the voltage back down.

Or, while at it, you could swap the led to something like the xhp35 that runs a higher voltage yet. (I won't get into that but the various cree leds can take different input voltages.

As an idea if you making the host yourself then why not build a battery holder for 2x18650 in parallel. If you make this holder the dimensions of a 2x26650 batteries (it will inevitably be a few mm longer) then you have plenty of room in the holder to wire up a parallel circuit and then later down the line you can swap out driver and led for, let's say, an XHP-50/70 and 6-9v driver and run 2x26650 in series. You could even go as far as to make 2 heads. One for parallel 18650 use and one for series 26650 use.

Thanks Thom2022, that's a cool idea. The idea behind using the buck driver is that I could run the 2x 18650s in series without worrying about rigging up a parallel circuit. I'm not too keen to do the parallel circuit because it may complicate the charging of the device, also a bit nervous about it. I want the batteries to be behind one another which makes the circuit a bit more tricky also..

Do either of you know of a buck charger that I could run my CREE XM-L RGBW LEDs with?

I was looking at these:http://www.international.mtnelectronics.com/index.php?route=product/category&path=67_115 but none seem like they will work with the 4 chanels..

Also, does a high voltage RGBW LED exist?

To be honest charging never crossed my mind when suggesting the holder as I never use built in charging due to some bad personal experiences with some of my high end vaping devices. In my opinion the slight inconvenience caused by having a dedicated charger and carrying a spare set of batteries outweighs the risk of on board charging especially in something that is quite likely to get dropped once in a while.

hm, good point. It just feels awkward to make the parallel circuit, I enjoy taking the long route with my projects, but making the parallel circuit doesn't feel right for the design, perhaps I'm just not confident enough with circuitry, I'm more on the metal work side of things.

Ideally I would like the 2x18650 batteries in series running RGBW LEDS...

If you don't mind me dipping my proverbial oar in I will happily sketch up what I have in mind as its really simple. I wanted to make myself a parallel 18350 tube mod for vaping which required a similar holder to what I'm proposing but unfortunately I have no access to machining equipment so that cost put the brakes on for me.

Cool, that would be very much appreciated. I am also making a cad drawing right now but I don't know how to post the image, is there no way of posting an image straight from your computer?

Now I can't find any kind of driver for the XM-L RGBW, anywhere! Seriously, I think that I purchased the last one from Mountain electronics, but I need more quite urgently...

Do you know anyone who is selling them?

(maybe i need to start new thread)

kaidomain has a nearly identical driver to the MTN one. Although being shipped from China would negate any quickness you are needing. You might email Richard of MTN and see when he plans on restocking.

Thanks! I wasn't aware of this website. I sent an email to MTN too.

Generally speaking, is it possible to re programme these drivers so they could create different varieties of colour?

Moss said:

Thanks! I wasn't aware of this website. I sent an email to MTN too.

Generally speaking, is it possible to re programme these drivers so they could create different varieties of colour?

Click to expand...

I imagine I'm misunderstanding your question, but regardless this will at least give a bump...

The color of the beam is due to the LED type and bin combined with the reflector and glass. The driver can affect how hard it is driven and what modes you get, but the best way to get the color you want is to start with the right LED.

Google "cree xml2 data sheet" and you should find a document that shows all of the bins and color temp ranges that the xml2 led comes in. And while that one in bin t5 goes up to 8300K (very blue), there are bins in the neutral (4500K-ish) and warm (3000K-ish) ranges, too.

Thanks, I checked it out. A very good resource.

I think I am sort of happy with the LEDs, my wish is to be able to mix the colours. So to programme the driver to run the LEDs in different configurations, such as red and blue running together to make magenta..

I suppose I'm thinking of the manner in which stage lights are controlled, but in flashlight form. Have you ever seen this before?