Voltage Monitor for Mag?

Hi there!

I must do another mod...! :devil:

For that I need a voltage monitor that fits inside a 4D Mag and is capable to show me the battery status with 1 or 2 leds. It needs to work with 4 Ni-MH down to 0,9V/cell.

I didnt found any on the internet yet. Or maybe someone has a circuit diagram for such a voltage monitor that I can build it myself.

Look here Low battery level circuit
Norm

I am doing one on my 1d mag project but I am using lipo cells.

This voltage monitor is only 6-30VDC.

The_bad_Frag said:

( Or maybe someone has a circuit diagram for such a voltage monitor that I can build it myself.

Click to expand...

The_bad_Frag said:

This voltage monitor is only 6-30VDC.

Click to expand...

I thought you were looking for ideas?
Norm

That was maybe a little misunderstanding. Im not an electronics specialist so I need a circuit diagram of a voltage monitor that only needs to be soldered together. I have no idea how to modify that circuit to get it working with 4 NI-MH.


Edit: I found a battery monitor but it only works down to 4,3V http://www.robbe.de/akkumonitor-8-led.html. It would be better when it would go down to 4V or 3,6V.

By changing a resistor in Norm's circuit you can go down to 2.5 v or by using a bandgap reference instead of what's in there you can go down to about 1.3v. Post all your desired specifications - current draw, voltage range, etc. At 3.6 v the LED will probably need it's own power supply, otherwise look for a 'grain of wheat' incand. lamp that works on 2v or less.

Tschuss!

http://en.wikipedia.org/wiki/Bandgap_voltage_reference

I cant post accurate values now because I not have bought all the parts. I have a good spare boost driver laying around which I want to use.
It will be a triple XM-L running at 1A on 4 D cells. The boost driver Im using is currently connected to 3xXP-G and draws about 2.2A on 4 full C cells.
Its a very efficent setup because the driver is barely getting warm even without a heatsink. The XM-Ls will only consume about 8,94W at 1155 lm! (calculated)


The problem is that this boost drivers input ampere must not exceed 3A. It has no protection on it so it will drain the NI-MHs as hard as it can, go over the 3A and destroy itself. You dont notice to light getting dimm when running on too low input voltage because its a boost driver. On 0,9V/cell its just about to hit the 3A mark and the cells are at the correct voltage to be charged.

The_bad_Frag said:

Hi there!

I must do another mod...! :devil:

For that I need a voltage monitor that fits inside a 4D Mag and is capable to show me the battery status with 1 or 2 leds. It needs to work with 4 Ni-MH down to 0,9V/cell.

I didnt found any on the internet yet. Or maybe someone has a circuit diagram for such a voltage monitor that I can build it myself.

Click to expand...

Your Triple XM-L mod had battery monitoring down to 4 volt built into the PWM dimmer you used (nice build BTW...:thumbsup. How about using 5*NiMH 'C' cells in a PVC sleeve?

Yeah I know but its 28.95€+shipping

This build should be a bit less expensive after the last 250€+ build. And I want to use 4xNI-MH because of the ~4 hour runtime. Mag 5D is too long to fit inside my Audi door compartment and under the shelf at my bed where my flashlights stand.

Is is that hard to get a simple voltage monitor?

Marketplace member Cottonpickers sells solar setups that include a voltage monitor, (although i think it needs at least 1 lithium cell to display voltage)

They fit nicely in the tail cap of D-mags ill post an image of the prototype i made a bit later.

A SPDT relay with a 5 vdc coil may drop out at 3.6 vdc or you can use a variable resistor in series with the coil adjusted to make it drop out at this voltage.
Hosfelt.com has some for $0.45 and up but the low coil resistance may be a problem and I don't know how repeatable the dropout voltage will be.
You put the indicating light in series with the NO contact.

If you have some old VCRs the relay will be free.

UberLumens said:

Marketplace member Cottonpickers sells solar setups that include a voltage monitor, (although i think it needs at least 1 lithium cell to display voltage)

They fit nicely in the tail cap of D-mags ill post an image of the prototype i made a bit later.

Click to expand...

This could be a nice solution! :thumbsup:

xul said:

A SPDT relay with a 5 vdc coil may drop out at 3.6 vdc or you can use a variable resistor in series with the coil adjusted to make it drop out at this voltage.
Hosfelt.com has some for $0.45 and up but the low coil resistance may be a problem and I don't know how repeatable the dropout voltage will be.
You put the indicating light in series with the NO contact.

If you have some old VCRs the relay will be free.

Click to expand...

I guess the relay is active all the time when the light is on, right? How much current does it need?

The_bad_Frag said:

I guess the relay is active all the time when the light is on, right? How much current does it need?

Click to expand...

No, the light goes on when the relay drops out due to low voltage. The current draw depends on the relay and series resistor you use.

I always wanted to put one of these in a 2d li-ion maglite. I just could never figure out how to exactly do it. Would that not be cool to have this displaying voltage at all times while in use or maybe a second button or switch to push to trigger the monitor.
Hobby king also has a 1s battery monitor that has a buzzer that sounds off when low voltage is reached. I think that it would probably be easy to unsolder the buzzer and solder on a led maybe with a resistor to limit current. I would have to get one and play with it to see if it would work. Description says the buzzer goes off at 3.2v but this could probably also be changed with a value better suited to your needs. At hobbyking look under battery chargers & Acc., then under accessories.

xul said:

No, the light goes on when the relay drops out due to low voltage. The current draw depends on the relay and series resistor you use.

Click to expand...

Sorry for my bad english. Thats what I wanted to say.

moderator007 said:

I always wanted to put one of these in a 2d li-ion maglite. I just could never figure out how to exactly do it. Would that not be cool to have this displaying voltage at all times while in use or maybe a second button or switch to push to trigger the monitor.
Hobby king also has a 1s battery monitor that has a buzzer that sounds off when low voltage is reached. I think that it would probably be easy to unsolder the buzzer and solder on a led maybe with a resistor to limit current. I would have to get one and play with it to see if it would work. Description says the buzzer goes off at 3.2v but this could probably also be changed with a value better suited to your needs. At hobbyking look under battery chargers & Acc., then under accessories.

Click to expand...

Yeah I saw that one with the buzzer. I had the same idea to change the buzzer to a led but I have no idea to get it lighting up at 3,6V. 3,2V is a lot too low for me.

The_bad_Frag said:

Yeah I saw that one with the buzzer. I had the same idea to change the buzzer to a led but I have no idea to get it lighting up at 3,6V. 3,2V is a lot too low for me.

Click to expand...

Post its schematic.
"You have questions, we can help"

...btw this is the battery monitor were talking about -> http://www.hobbyking.com/hobbyking/store/__14520__Hobby_King_Battery_Monitor_1S.html

The_bad_Frag said:

...btw this is the battery monitor were talking about -> http://www.hobbyking.com/hobbyking/store/__14520__Hobby_King_Battery_Monitor_1S.html

Click to expand...

Is $2.94 correct?

Yes. Hobbyking has really cheap stuff.