xen0s
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Hi hi smile
I just modded my GB Pocket with a backlight and the screen looks quite good. At first I did not use a separate resistor as the backlight should have internal one, however I noticed that while playing the lower left corner of the gameboy would heat up a bit too much for my taste. So I added a 39 ohm 0.25w resistor and it heats up less now. However I also noticed that my batteries only lasted about 2 hours (with the resistor added) of playing Pokemon Gold (mid contrast, max volume). It is true that I have charged those batteries about a week ago, but I have used them very slightly before, so they should have lasted more than 2 hours, way more - those are 1100mha batteries >_<.

Have any of you experienced heavily reduced battery life after installing a backlight? Would adding a stronger resistor (say 100ohm) fix the heat and battery life?

I dont really know the model of the backlight, it appears to be made by ASM and has 4 LED`s (for reference it is from gameboymodsuk).

Any suggestions are welcome.

Last edited by xen0s (Aug 1, 2014 6:13 pm)

seatrash
Offline
seattle

at one point i had a MGB that i modded with a 3xLED panel from kitsch. i didn't bother with adding any resistors because the kitsch panel had one built in, but i did get some pretty terrible battery life (not more than 2-3 hours)

eventually i stole the battery out of a GBA SP, duct taped and zip tied it to the back, and played my first gig with it. i had to end early because it kept crashing. haha

i'd say if the heat problem is gone and the brightness isn't too bright, keep the current resistor. bad battery life is just one of those things.

arfink
Offline
Minneapolis
xen0s wrote:

Hi hi smile
I just modded my GB Pocket with a backlight and the screen looks quite good. At first I did not use a separate resistor as the backlight should have internal one, however I noticed that while playing the lower left corner of the gameboy would heat up a bit too much for my taste. So I added a 39 ohm 0.25w resistor and it heats up less now. However I also noticed that my batteries only lasted about 2 hours (with the resistor added) of playing Pokemon Gold (mid contrast, max volume). It is true that I have charged those batteries about a week ago, but I have used them very slightly before, so they should have lasted more than 2 hours, way more - those are 1100mha batteries >_<.

Have any of you experienced heavily reduced battery life after installing a backlight? Would adding a stronger resistor (say 100ohm) fix the heat and battery life?

I dont really know the model of the backlight, it appears to be made by ASM and has 4 LED`s (for reference it is from gameboymodsuk).

Any suggestions are welcome.

Yeah, it does reduce battery life significantly. The best reults I ever had was actually with an LED backlight from an old iPod. It wasn't as blinding bright as the ones from Kitsch (only had one LED), but it consumed less power and I never had any heat issues.

That lower left corner you're talking about is where the voltage regulation circuitry is, and IMO, backlight modding a Pocket has always been a problem because that circuitry really wasn't built to handle the extra load from 3 really bright LEDs, even when current limited by a resister. But I'm not enough of an engineer to design a proper solution, though I have pondered it.

xen0s
Offline

Thanks for the input.

The voltage board still heats up, it gets less hot, but still hotter than normal. Also I got a pair of Duracell turbomax batteries that can show you how much charge is left. The after about 2 hours the gameboy powered down, yet the batteries themselves show 100% charge which is very strange. 2 hours of battery life is pretty abysmal, I expected some reduction but this is way too much and Im seeing people claiming they get about 7-8 hrs...

I guess I will buying various resistors and testing them out today or tomorrow and update with the results. Meanwhile if someone has any ideas Im all ears (or rather eyes).

arfink
Offline
Minneapolis
xen0s wrote:

Thanks for the input.

The voltage board still heats up, it gets less hot, but still hotter than normal. Also I got a pair of Duracell turbomax batteries that can show you how much charge is left. The after about 2 hours the gameboy powered down, yet the batteries themselves show 100% charge which is very strange. 2 hours of battery life is pretty abysmal, I expected some reduction but this is way too much and Im seeing people claiming they get about 7-8 hrs...

I guess I will buying various resistors and testing them out today or tomorrow and update with the results. Meanwhile if someone has any ideas Im all ears (or rather eyes).

I don't know if you're aware of this, but alkaline batteries in particular are not able to push that much current. The chemistry of the battery simply can't keep up if you make too much demand on them for current. This is especially true of AAA batteries. So you could well be starving the MGB of power without having fully drained the batteries.

Some of these longer-life alkaline batteries get their higher maH ratings from altering the chemistry or the construction of the layers inside the battery in such a way that you lose the ability to discharge rapidly in exchange for being able to hold more power overall. Trying a cheaper (I know, sounds crazy) brand of battery may actually make a difference in this application. Of if you're really desperate, you could try out some of those lipo batteries that have a high C rating.

Last edited by arfink (Aug 2, 2014 4:45 pm)

xen0s
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I had no idea about this, it sound very possible considering the behavior I am experiencing.
Today I installed a 300ohm resistor and the heat was reduced again, additionally I was able to power the gameboy for about another hour and a half using the same pair of duracell batteries. They are still far from fully drained after the gameboy powered down.

Currently the backlight is connected to the 5v line on the cartridge slot and it runs on 2.3v with the resistor, but I saw there is also 3v line around the voltage regulator, so tomorrow Im going to try connecting to that one and see if there is further improvement.

Using a LIPol battery is an interesting alternative, but I kinda like being able to swap the batteries, so for now Im gonna stay away from this.

Last edited by xen0s (Aug 2, 2014 5:19 pm)

lw
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Since this looks like a thread about backlights, let me ask a question:
What resistor should I use with my Kitsch GBC frontlight to have low-to-medium luminance and medium-to-high battery life.
Thanks for the input beforehand and sorry if my English is kind of clunky, it's not my native language.

Last edited by lw (Aug 3, 2014 10:19 pm)

xen0s
Offline

Ok I did tests with various resistors and with fresh batteries. I got optimal results (brightbnes/battery life) using the 5v line and a 300ohm resistor. The light runs at 2.3v and is bright enough. With a fresh pair of alkaline Duracell (mn2400) batteries I get about 6 hours and 30 minutes of play time. With rechargable Fujicell batteries (1100mha fhr 4uex) I get about the same play time. Note that the rechargeable ones run at 1.2v (I noticed that just now).
Judging by the voltage reading I get from the batteries after the GameBoy turns off it seems that they are pretty close to empty so I will stick with this setup.

@lw I think testing with various resistors would be the best solution. For example you can start with a 200ohm resistor and depending on the results go up or down.