Mountain Bike Reviews Forum banner
1 - 20 of 44 Posts

·
Registered
Joined
·
192 Posts
Discussion Starter · #1 ·
Dear All,

I have just ordered one of Trouties 7UP kits from Cutter and have a couple of questions to ask you.

Apologies for the questions but I am not particularly electrically minded


I have ordered the PCMCB so that it is populated as follows: 4 x XPG R5 and 3 x XPE R3. The battery ordered for this build is a Lithium Polymer Battery pack - 18.5V @ 4500maH.

[1] Based on the above specification, in your opinion/experience, what should be the Maxflex be driven at 1000mA, 1200mA or 1300mA and what are advantages/disadvantages of these various current settings?

[2] Can you provide me with a brief schematic on how to wire the attery status led to the maxflex? – refer to diagram

[3] I would like also to use an illuminated LED momentary switch (just because I like to have an illuminated on/off switch). Is it possible to use such a switch and again, could you provide me with a brief schematic on how to wire the status led to the maxflex? – refer to diagram

[4] Based on the LED board setup of 4 x XPG R5 and 3 x XPE R3, what is the hypothetical vs real light output at the current settings per [1]

[5] Again based on the above specification, to what point would you set the temperature sensing cut off

[6] Battery status LED – noting the use of a LiPo battery, at what point would you set the warning light to activate? - ½ discharged or nearly fully discharged and forced off (or warn only).

Many thanks
 

Attachments

·
Registered
Joined
·
752 Posts
Both the unconnected end of you battery status LED and the (-) terminal of your switch indicator LED should be connected to the GND terminals on the maxflex.

Since I assume you want the switch indicator light to be illuminated whenever the light is on, you'll have to draw the power for that LED off the main LED output of the maxflex (LED+). You'll need a current limiting resistor in series with that connections so just a few milliamps of current will divert off to drive the indicator LED and the rest of the current will go to the main LEDs. 10ma is enough to drive most small LEDs. The voltage of the main output terminal will always be around the sum of the Vfs for the 7 XPG/XPEs. 7 * 3.2V = 22.4v will be the nominal voltage at the LED+ terminal. It'll vary some, but that won't make enough difference to matter. So the current limiting resistor will need to be (22.4 - 1.4) / .01 = 2100 ohms. The 1.4 is the typical Vf for a small indicator LED. So a 2k resistor in series will work fine.

So, the LED+ terminal of the maxflex will connect both to the +terminal of your main LEDs and one side of the 2k ohm resistor. The other side of the 2k ohm resistor will connect to the +terminal of your switch indicator LED.
 

·
Registered
Joined
·
2,707 Posts
I've been emailing cutter about trying to see if they sell the kit w/o the housing so I can build my own. They still won't reply to me.
 

·
Registered
Joined
·
344 Posts
chelboed said:
I've been emailing cutter about trying to see if they sell the kit w/o the housing so I can build my own. They still won't reply to me.
hey, go to trouties website - he is selling the housing there!!
 

·
Drinkin' the 29er KoolAid
Joined
·
1,542 Posts
18.5V battery might be too much

I'd be really careful with that 18.5V battery. Assuming were talking about a 5 x lithium ion battery, it will actually put out 21V when fully charged (5 x 4.2V). Problem is the MaxFlex has a maximum input voltage of 20V, and in comments I've seen from the George @ TaskLED that 20V was considered a hard limit. So with that high a voltage you run the risk of blowing up the driver... expensive and somewhat difficult to replace once "permanently" bonded to the housing with AA.
 

·
Registered
Joined
·
608 Posts
I see you're using Lipo... I have plans to do the same. What are you going to do in regards to low voltage cutoff?
 

·
Registered
Joined
·
1,781 Posts
kwarwick said:
I'd be really careful with that 18.5V battery. Assuming were talking about a 5 x lithium ion battery, it will actually put out 21V when fully charged (5 x 4.2V). Problem is the MaxFlex has a maximum input voltage of 20V, and in comments I've seen from the George @ TaskLED that 20V was considered a hard limit. So with that high a voltage you run the risk of blowing up the driver... expensive and somewhat difficult to replace once "permanently" bonded to the housing with AA.
I took the risk with an 18.5v on my home made 7up (7 xpg though) and have had no problems and it has had lots of use. Fresh of the charger it's on the limit but as soon as the light is switched on (700ma and above) the under load voltage of the battery drops instantly to well under the safe 20v.

I have my temp @ 70*

Medium v = 18v Low v = 16.4 Cut off v = 15.6v

Remember that the maxflex takes a minute from sensing the low voltage to cutting the power that's why I have set the extra .6 v on the cut off voltage as a lot can happen in a minute with lithium batteries at the end of discharge if one forgets to dim the light.

I run mine @ 1000ma for high, any more and you produce a lot more heat but hardly any more light(if any), also a lot less run time just to produce more heat.

I have had no problems with this set up in the UK weather with my housing, Trouties housing looks like it should run cooler than mine, though I have never actually seen one for real.
 

·
Drinkin' the 29er KoolAid
Joined
·
1,542 Posts
Yetibetty, is your 18.5v battery a Lipo pack or something made of up 18650 cells? Reason I ask is I originally made myself a 14.8v pack with four 18650 cells and noticed that the battery voltage sagged significantly under the load of the 7up on high... like in the order of 1 - 1.5v. I've since changed to a cheapie RC Lipo pack (12C) which sags .3v under the same load. Recently tried a friend's more expensive Lipo pack (rated at 20C) and it sagged only .02-.03v with the same load!

So depending on the battery type and instantaneous current capability you could still be above 20v with an 18.5v pack.
 

·
Registered
Joined
·
1,781 Posts
kwarwick,

True it will, or could matter if you use realy good batteries that don't sag much under load.

Mine is a 5 cell 18650 pack that I made my self due to having the same problem as you with the 4 cell.
 

·
Registered
Joined
·
291 Posts
The real issue with the 20V max input rating of maxflex is due to the 2 input FETs. The 1st one is for reverse polarity protection and has a 20V max gate to source rating The second FET is for power management to the switcher IC and it has a max source to drain rating of 20V.

So, what you are risking is damage to either/both of those FETs. The next 'weak' link is the input cap to the switcher IC and that's rated at 25V.

The problem is that even with no load (driver electronically off), both FETs are going to see the battery voltage and that's when the damage will be done. The rest of the switcher core doesn't see the battery voltage until the driver is 'clicked' on and that circuitry can handle 25V and the battery voltage will have sagged at that point anyway...

cheers,
george.
 

·
Registered
Joined
·
344 Posts
Hi george,

is it possible to flash the battery warn(low voltage) levels by the main leds in case i have no stat led connected?:eek:

Or can these warn levels only be indicated by the stat led (which i dont't want to use)
I was not able to get that point out of the descriptions:confused:
 

·
Registered
Joined
·
2,005 Posts
Whitedog1 said:
Hi george,

is it possible to flash the battery warn(low voltage) levels by the main leds in case i have no stat led connected?:eek:

Or can these warn levels only be indicated by the stat led (which i dont't want to use)
I was not able to get that point out of the descriptions:confused:
Yep
See page 20-21
http://www.taskled.com/leds/maxflexuni_v4.00.pdf

8.5 FiveClicks–VoltageWarningStatus
How (and how often) the circuit reports the low and medium voltage conditions is configured using this Menu option.
The circuit reports the low voltage condition via the STAT pin on the PCB. STAT will drive high (~2.5V) to light the status LED and drive back to 0V to turn the status LED off. The STAT pin can drive a single 3mm or 5mm (at approximately 20 mA). If this feature is used, wire the 3mm or 5mm LED between STAT and GND. A red or amber LED is recommended for this use.
Note: The STAT pin will light the status LED (if affixed) if the input voltage is greater than the V Low Setting but less than the V Med Setting. The STAT pin will pulse (flash the status LED) once per second when the input voltage is less than the V Low Setting. The STAT pin will double pulse (flash the status LED) once per second if the input voltage is less than the V Cut Off Setting.
The STAT pin is pulsed once every time the light is turned on as a self-check that the status LED is functioning correctly.
If the user does not want to wire a status LED to the STAT pin but still wants an indication of low voltage occurring, then the main LED can be set to flash at a specific interval to give a visual warning. How the main LED flashes is dependent on whether the light is in constant or strobe mode.

Constant Mode: If the input voltage is greater than the V Low Setting but less than the V Med Setting, the main LED will briefly flash off once at the flash rate chosen with this Menu option (5 sec, 10 sec, 30 sec or 60 sec). This warning will time out after five sequences so the remaining battery capacity can be used without annoyance. As a reminder, the V Med warning sequence will repeat if the light is turned off/on, or if a higher level is chosen. The STAT pin will remain active with no timeout. If the input voltage is less than the Low Setting the main LED will flash off twice at the flash rate. This V Low warning sequence will continue until the Cut Off Setting is reached or recharged to above the V Med Setting. If the input voltage is less than the Cut Off Setting the main LED will flash off three times at the flash rate. This Cut Off warning sequence will continue until the light turns off (Cut Off enabled) or indefinitely (Warn Only enabled), see Sec 8.6. These sequences were chosen to give an obvious indication of battery status while still allowing use of the light for navigation.

Strobe Mode: If the input voltage is greater than the V Low Setting but less than the V Med Setting, the main LED will do a slower strobe sequence for ~1 second at the flash rate chosen with this Menu option (5 sec, 10 sec, 30 sec or 60 sec). This sequence will occur five times as a warning, and then time out so as not to be annoying during use. As a reminder, the V- Med warning sequence will repeat if the light is turned off/on, or if a higher level is chosen. If the input voltage is less the Low Setting the main LED will do a faster strobe sequence for ~1 second at the flash rate. This V Low warning sequence will continue until the Cut Off occurs (if enabled) or indefinitely till the battery is discharged (Warn Only enabled) or recharged to above the V Med Setting. These sequences were chosen to give an obvious indication of battery status while still allowing use of the light for navigation.
 

·
Registered
Joined
·
192 Posts
Discussion Starter · #15 ·
Hi All,

Have just finished the build and am wanting to configure before I post shots.

(Wiring the maxFlex is a chore but damn space is at a premium in the actual housing. Had to cut wires and resolder x 2 :madmax: I know we all want smaller lights, but .....)

I have populated the PCB with

3 x XPE R3
and
4 x XPG R5

and am running at 14.8v Lipo with 5200mah on tap

Noting the mix of LEDs what is the optimal safe maximum current to run the maxflex at?
 

·
Registered
Joined
·
192 Posts
Discussion Starter · #17 ·
znomit said:
XPE are only rated at 1A, its a good place to start :)
Many thanks.

It was what I thought based on the CREE spec sheets, but always good to have the confirmation
 

·
Registered
Joined
·
3,062 Posts
Fury25 said:
Hi All,

Have just finished the build and am wanting to configure before I post shots.

(Wiring the maxFlex is a chore but damn space is at a premium in the actual housing. Had to cut wires and resolder x 2 :madmax: I know we all want smaller lights, but .....)

I have populated the PCB with

3 x XPE R3
and
4 x XPG R5

and am running at 14.8v Lipo with 5200mah on tap

Noting the mix of LEDs what is the optimal safe maximum current to run the maxflex at?

Alot will depend on your ambient temperatures when you want to run the light
max I would go to is 1 amp anyways any higher and the heat will mount fast for little light gain .

and dont forget to set the thermal protection to 60 or even 70 degrees
 

·
what a joke
Joined
·
2,280 Posts
Fury25 said:
Hi All,

Have just finished the build and am wanting to configure before I post shots.

(Wiring the maxFlex is a chore but damn space is at a premium in the actual housing. Had to cut wires and resolder x 2 :madmax: I know we all want smaller lights, but .....)

I have populated the PCB with

3 x XPE R3
and
4 x XPG R5

and am running at 14.8v Lipo with 5200mah on tap

Noting the mix of LEDs what is the optimal safe maximum current to run the maxflex at?
I went with the 7 x XPG R5.

I need a suitable battery, what is the details of yours?
 

·
Registered
Joined
·
344 Posts
I just got one from the big auctions house in the internet!

€ 34 shipped! 14.8v 5000mah 30c Brand name: Winforce

It arrived completely balanced, didn' had time to solder connections and charge it - so no info on that!
We will see how the quality goes after a couple of cycles!

the dimensions are perfect to fit into a water bottle/toolbox!
 
1 - 20 of 44 Posts
Top