What to build with these bits?- Mtbr.com

# Thread: What to build with these bits?

1. ## What to build with these bits?

Hi all
I'm running a single MC-E helmet light with a Fraen reflector at the moment and want something with more power using some bits I've got.
My list of bits is:
hipFlex driver
7.4v battery
A couple of MC-E's
maxFlex v5
A couple of RED xp-g's

I don't mind buying some LED's/optics/reflectors but would like to use up some of the other bits. Maybe even putting the red LED's on the back for a bit of added safety/visibility from the back.

Any suggestions as to what I can do?

Steve

2. Would the maxFlex run a 7-up XP-G off the 7.4v battery? According to the gumpf it will take an input of 2.5-24v and output upto 24v.

vF @ 1.2a = 3.2v x 7 = 22.4v
vF @ 1a = 3.15v x 7 = 20.05v
vF @ 0.7a = 3.05v x 7 = 21.35v

I'm not too desperate to get a huge throw or runtime as I only tend to do 2 hour rides.

3. Originally Posted by deesta
Would the maxFlex run a 7-up XP-G off the 7.4v battery? According to the gumpf it will take an input of 2.5-24v and output upto 24v.
Technically the maxFlex can handle 7 XPG no problem, but the problem is at 7.4V input it has to boost the voltage so much that it will be drawing above the recommended maximum 3A input current and the driver will overheat very quickly. For 7 XPGs you pretty much have to use a 14.8V battery to avoid cooking the maxFlex.

4. How about 2 x XM-L with the hipFlex? vF 6.7v @ 3a.
Input V = 7.4, output V = ~6.7

5. IIRC the HipFlex max output is 2.8A, but that's close enough to 3A that you'll not notice. Your 7.4V pack will run 2 XMLs. They will drop out of regulation part way through the run after the battery voltage drops some. That won't hurt anything, but the light will slowly dim as the pack voltage continues to drop. Some like that as an indicator that it's time to wrap up the trip. An 11.1V battery would be the ideal for a 2S XML and HipFlex setup.

6. hipflex technical says it maxes out at 2.8A, which should be fine for driving XM-L. It says it only needs .5v overhead @ 2.8A, so you're right on the edge.

7. Hmmm, seems like I have a bag of non-compatible bits. Maybe change to a bigger battery?
I do like the 2 cell one tho as it's nice and light on my helmet..

Any other options to keep the battery and maybe change LED's and driver?

How about an LFlex and 2 x XM-L @ 3A?

8. Originally Posted by deesta
How about an LFlex and 2 x XM-L @ 3A?
That works fine also but you will still go out of regulation partway through the runtime. That's the setup I am using on my latest go at a helmet light. I used the Lflex just for the smaller size over a B3Flex which I would prefer.

BTW, no double XML @3A will get your 2 hour runtime on a 2 cell battery. You would have to drop to ~1.5A to get 2 hour runs

9. Originally Posted by Vancbiker
BTW, no double XML @3A will get your 2 hour runtime on a 2 cell battery. You would have to drop to ~1.5A to get 2 hour runs
I wouldn't be running full power for the whole time, probably about 1/2hr max. Would have it set up in tri mode and @ 2A. That would give me approx 1700 lumens and about 1.4hrs @ full power from my 2.8aH battery. Sound about right?
That would be way more than my current MC-E single..

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•