HI, i have a solar powered motion light designed for landscape lighting. Its made by Cooper Lighting. Model: MSL180w. It uses a 6V 15W g4 bi pin bulb that needs to be replaced. The bulb got shattered one day so i decided i want to replace it with a new one. After going to radio shack with no luck, i found some on ebay and purchased them. However the ones i purchased are 6V 20W bulbs.
When i install the bulb and turn it on, the relay buzzes. Which im sure is due to the lack of amperage. So to test my theory out, i inserted a 12V 5W bulb and turned it on, although it was very dim, it still lit up. So what i would like to achieve is to be able to use the 6V 20W bulbs. Im mechanically inclined and pretty good with electrical circuits, and im interested in modifying the circuit board components to make this happen.
Using the formula: W=VxA, the unit calls for 15W= 6V x 2.5A and if i want to use the 20W= 6V x 3.333A So i would need to increase the amperage by 0.833. Which component would i have to change/modify to increase the amperage to drive up the wattage output??? Any and all help is greatly appreciated. Thank You

Attached is a couple pics of the circuit board from inside the unit.

 

Pics of the circuit board from inside the unit

 

The sensor is supplied from a 6v 4aH battery backup, so it will take a 20 w bulb at 6v running for 4ah/3.333a = 1.2 hours,

or use the 15w bulb for 1.6 hours, or if you increase the battery capacity it will run for longer.

Looking at the pcb it has a relay for switching the light .

 

It could be the battery voltage "sags" when the higher power bulb is turned on. You could try a big electrolytic cap across the power wires, it might help.

 

I think ronv has nailed it, and you could confirm this by measuring the voltage across the relay coil.

A bigger battery should help, and I suppose a current limiting resistor in series with the bulb might also work. You might try it just for an experiment. It would waste your precious solar power, so I don't think it'd be a good long-run solution.

 

Yea ronv is correct about the voltage sag with the 20W bulb inserted. I checkd it with my DMM and it dropped down to 2V when it turned on with the 20W bulb.

 

It could be the battery voltage "sags" when the higher power bulb is turned on. You could try a big electrolytic cap across the power wires, it might help.

So what size cap would i use?

 

I no not think cap will help for more than a few ms.

 

shouldnt i be able to replace the 33ohm resistor with a lower value resistor??

 

Until you have a schematic you understand (with the help of folks here), don't bother swapping components.

You can't solve the basic problem that your bulb needs more power than the battery can supply without sagging voltage. You might try confirming this by directly jumpering the bulb to the battery.

 

Until you have a schematic you understand (with the help of folks here), don't bother swapping components.

You can't solve the basic problem that your bulb needs more power than the battery can supply without sagging voltage. You might try confirming this by directly jumpering the bulb to the battery.

LOL.... idk why i didnt think of doing that in the first place, brain fart... lol
ill go do it right now and be back in 5 min with the outcome. Thx for the help

 

ok so i checked the battery voltage and its at 6.20v so i jumped the 6v20w bulb directly to it and..... Nothing. lol not enough juice to light the bulb. so for shits&giggles i jumped a similar style 12v5w bulb directly to the battery and although pretty dim, it lit up.

 

Well maybe you should charge up (or replace) the battery before passing judgement on whether the new bulbs will work. Maybe a fresh battery will allow using the higher power bulbs.

 

Well maybe you should charge up (or replace) the battery before passing judgement on whether the new bulbs will work. Maybe a fresh battery will allow using the higher power bulbs.

Well thats the thing, the 6v battey with a full charge wont power the 6v20w bulb. when i turn it on, it causes the relay to buzz. if i unplug the bulb with the unit on, the relay stops buzzing. That why im thinking its gotta be a resistor thats not allowing enough power to pass through to the bulb

 

I think your battery is bad or needs to be charged.