-1
\$\begingroup\$

I have a 9,6V 2000mAh Ni-Mh battery (with charger) and I was wondering how to use it to build a portable spotlight (= flashlight for video.)

I need 30 to 60 minutes of battery so if I remember my lessons from high school I have approximately 18 W of power available. Most LEDs seem to come in 3/6/12/24V etc. I saw some videos where they convert 5 V to 12 V with boosters so my guess is they exist for 9,6 V battery.

So my question is what kind of booster would you recommend for my spotlight? (I don’t need a dimmer and I guess I only need passive cooling.)

\$\endgroup\$
  • \$\begingroup\$ LEDS don't 'come in' 3/6/12/24V at all. Your 9.6V battery will power a LED quite nicely with no 'booster'. First you need to choose a LED (presumably white). Then the LED data will give the forward voltage (Vf). BUT if you want to power a LED LAMPBULB such as MR16, then just connect your battery directly. The MR16 LAMPBULB already contains a driver chip and will probably work fine from 9.6V. but you'll need to check. That's the easiest route. If it doesn't illuminate or is dim, then you do indeed need to think again. What's this 9.6V battery btw ? GIVE DETAILS IN YOUR QUESTION !!! \$\endgroup\$ – Graham Stevenson Oct 10 at 21:03
  • \$\begingroup\$ Thanks for your answer ! The battery looks like a RC car battery, it has 8 cells and the brand is Bakth (Ni-MH) \$\endgroup\$ – gilou gilou Oct 10 at 22:52
  • \$\begingroup\$ OK. 9.6V is probably the 'nominal' voltage in that case. The simplest method is probably for you to use a 12V MR16 LED LAMPBULB and power it via a voltage regulator board that you might find on ebay. I'll post an answer now, \$\endgroup\$ – Graham Stevenson Oct 10 at 23:06
3
\$\begingroup\$

I have a 9,6v 2000mAh Ni-mh battery ... I need 30 to 60 minutes of battery so if I remember my lessons from high school I have approximately 18 W of power available.

Not quite. You have 18 Wh of energy available. (Energy = Power × Time.)

So, for a discharge to 50% of capacity (safety margin) you have 9 Wh available. To use that in one hour means your lamp and booster can draw 9 W max. If your booster is 80% efficient you can use a 9 * 0.8 = 7.2 W LED.

So my question is what kind of booster would you recommend for my spotlight?

Find a module that has the required input and output voltage specifications and adequate current rating for your lamp. Ideally it should have an automatic shutdown feature on low input voltage to avoid completely discharging the battery should you leave it on. Shopping recommendations are off-topic so you won't get a product recommendation here.

| improve this answer | |
\$\endgroup\$
  • \$\begingroup\$ Thanks a lot for your help ! If I ever win an Oscar for best cinematographer I’ll thank you Transistor (it may never happen) ! Have a nice day \$\endgroup\$ – gilou gilou Oct 10 at 6:45
0
\$\begingroup\$

I think the simplest answer is to use an 'off the shelf' MR16 LED lampbulb such as any of these ....

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=mr+16+12v+led+bulbs+-halogen&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=mr+16+12v+led+bulbs

And step up the battery voltage a bit using something like this ...

https://www.ebay.co.uk/itm/DC-DC-Adjustable-Boost-Buck-Step-down-Converter-Voltage-Module-Power-Regulator-N/311696275301?hash=item48928bb765:g:zm4AAOSwvt1WRCJb

The 12V rating of the lampbulbs is A.C. but they will run on DC. It's simply a case of adjusting the output voltage of the regulator board.

You should be OK with up to 10W load.

| improve this answer | |
\$\endgroup\$
  • \$\begingroup\$ Thanks, but I think I will go with a brighter led like a Samsung LH351D (or cree equivalent) which can be powered by a single 18650 so I won’t have a problem with my 9.6v battery (I want to use it as a film noir kinda spotlight) \$\endgroup\$ – gilou gilou Oct 13 at 9:47
  • \$\begingroup\$ The Vf of that LED is ~3V. As your 18650 discharges, a resistor in series will result in the LED dimming with use before recharging. Best to use a 'constant current' driver. \$\endgroup\$ – Graham Stevenson Oct 13 at 10:18
  • \$\begingroup\$ Thanks a lot I think that s what I’m gonna do ! \$\endgroup\$ – gilou gilou Oct 13 at 10:41

Not the answer you're looking for? Browse other questions tagged or ask your own question.