Monday, October 13, 2014

Battery Life in the 8-bit Game Boy Line

When the Game Boy was released in 1989, it was the first portable video game system using interchangeable cartridges.  (While the Microvision had been released in 1979, the games themselves attached to the base and provided controls and CPU as well as program code).  In the palms of the player's hands they had much of the power of the NES.  However, its rivals the Atari Lynx, Sega Game Gear & Nomad and the NEC Turbo Express, could have easily eclipsed it with their color screens.

The Game Boy had two huge advantages over its rivals.  First, it came with the killer-app pack-in, Tetris.  Second, it had far superior battery life to any of its rivals.  In this post, I will discuss battery life among the four members of the 8-bit Game Boy line, the original DMG Game Boy, the Game Boy Pocket, the Game Boy Light and the Game Boy Color.

1.  Game Boy DMG-01

The DMG-01 takes four AA (LR6) batteries and there was an official Rechargeable Battery Pack, DMG-03, available at launch, that could provide portable or AC power.  Regular Alkaline AA batteries are rated to provide a nominal 1.5 volts and 1800-2400 milli-amperes per hour (1A = 1,000mA) depending on the energy drain of the powered device.

The DMG doesn't tell you directly everything you need to know about its power requirements.  On the back of the DMG, the text states that the DMG is rated for 6 volts and 0.7 watts.  If you look in the Game Boy Owner's Manual, (p.12) you will see that this is not the maximum power consumption for the device, just the approximate usage.  Power consumption depends on what game is used and what it is doing.  The manual gives approximately 15 hours on 4xAA, but I have seen other estimates of 35 hours.

Four out of five of the launch titles for the DMG, Alleyway, Baseball, Tennis, Tetris would have required fairly little power.   These small (32-64KB) games only tend to animate a small portion of the screen, leave lots of undrawn "white space", do not use extra RAM in the cartridge, are often silent or do not always have music playing and rarely scroll the screen.  The fifth launch title, Super Mario Land, is a substantially more complex game and would have a greater power draw.  Larger (128-512KB) and more complex games after these launch titles would almost certainly draw more.

Back to our DMG, we need to determine the amperage the device requires.  Fortunately the relationship between volts, amps and watts is simple :

W = V x A

Dividing the wattage, .7, by the voltage, 6, we get .11666A, or 116.66mA.  If we look at the rechargeable battery pack specs, we see that it provides 150mA, confirming the ampere requirements for the DMG.

The DMG and its successors connect its batteries in series so that the output voltage is the sum of the output voltage of each individual battery.  So four 1.5v AA batteries will give a voltage of 6v.  Unfortunately, the mAh available to the Game Boy does not increase with extra batteries.  If the batteries were connected in parallel, it would increase but the voltage available would only be 1.5v, which is nowhere near sufficient to drive the device.  Thus you get a tradeoff, either you increase the voltage or the current that can be provided, but not both.  

The rechargeable battery pack also tells us that it provides 4.8v to the Game Boy.  Rechargeable AA batteries like NiCd and NiMH batteries provide a nominal 1.2v per cell.  NiMH was just coming on the market in 1989, and the rechargeable battery pack used NiCd batteries. However, the Game Boy is fairly tolerant of the variance between 6v and 4.8v, probably because it uses 5v logic.  Besides, depending on the quality of the Alkalines being used, that 1.5v per cell may be very nominal indeed.  Moreover, the voltage of an alkaline declines over time, whereas a modern NiMH battery's voltage remains much more constant until it reaches the point of discharge.

Now we come to the issue of mAh.  Consider the following datasheet :

http://data.energizer.com/PDFs/E91.pdf

As we have determined, the Game Boy requires an average of 116.66mA to operate.  According to the Milliamp-Hours Capacity, at that amperage requirement the battery can provide approximately 2400mAh.  If we divide the mA by the mAh, we get 20.57 hours.  Nintendo's estimate may have been a bit conservative here, but they could have been thinking ahead for the more complex games to come.

Nintendo was not only introducing a new video game console, it was introducing a new video game concept. It had to convince buyers that they should buy an expensive hand-held video game machine and its cartridges.  It also had to show that the simple games from Tiger Electronics simply were not good enough.  First impressions counted a great deal, and Nintendo could not afford to fudge the battery life figures too much.  This was especially true because of how crucial battery life was to the hand-held video game market.  Nintendo's success rested in no small part on its battery life.  You could get 15-20 hours out of a Game Boy on a fresh 4-pack of batteries.  Its competitors required 6 batteries and could give you six hours at best.

2.  Game Boy Pocket MGB-001

The Pocket was the second iteration of the Game Boy line, released in 1996.  This was a comparatively slimmer device, as its name implies.  The Pocket takes 2xAAA (LR03) batteries and has power requirements of 3v and 0.7W.  Thus, although the Pocket's logic may require fewer volts to operate, it requires double the amps, 233.33mA.  Therefore the actual power to operate the Pocket is unchanged from the DMG.

The official Game Boy Pocket A/C Adapter from Nintendo, MGB-005, outputs 3v and 300mA.  A similar third-party adapter from Hori outputs 350mA.  The Pocket A/C Adapters are to be used with the Game Boy Light and Color.  In Japan there was a rechargeable battery pack for the Pocket.

The use of AAA batteries kills the battery life of this machine.  An Alkaline AAA battery has the same voltage as an AA battery, 1.5, but only provides 850-1200mAh.  There is only about half the energy available to the Pocket as there is to the DMG.  I have seen quotes of battery life of 8-10 hours for the Pocket.

If we take the datasheet here as a guide :

http://data.energizer.com/PDFs/E92.pdf

We can see that at 233.33mA, we are only going to get about 700mAh out of our good AAAs.  This gives us a pathetic 3 hours.  Perhaps Nintendo was measuring it against the titles that were available in 1994-1995, such as Kirby's Dream Land 2 and Donkey Kong.  The strict approximation doesn't seem to hew to the reported battery life, which demonstrates that the Nintendo or the battery makers were treating the issue of battery life very conservatively.

3.  Game Boy Light MGB-101

The Game Boy Light, released only in Japan, functions like the Game Boy Pocket with a switch to activate an electro-luminescent backlight.  The Light uses 2xAA batteries and boasts 20 hours of play without the backlight and 12 hours with it on.  The power requirements have also decreased slightly to 3v, 0.6w.  Thus it requires an average of 200mA to run.

According to the datasheet, at 200mA we have approximately 2000mAh.  If we divide the mA by the mAh, we get about 10 hours on a pair of AAs.  One hopes that the stated power requirements were taking the backlight into consideration.

4.  Game Boy Color CGB-001

The Color has the specs of the Light without the backlight.  I have seen quotes of battery life of 20-35 hours.

Now the Color has the same power ratings as the Light, but this time it has a color screen, three times the RAM and a CPU that can run twice as fast as the Light, Pocket and DMG.  The games themselves are typically larger, from 1-4MB.  I suspect that the battery life is more impressive if it runs monochrome Game Boy games than if it is running Color Game Boy games because those extra features are not being used.

Compared to the original DMG, the Color seems to have less life.  However, the Color can run on 2 AAs whereas the DMG requires 4.  I would say that with 4 AA batteries (meaning you need to replace the batteries once), you can probably get the same amount of playtime as you would with a DMG.

The videos here may be very instructive :

https://www.youtube.com/watch?v=XsU4AcYhjy8

https://www.youtube.com/watch?v=VgKdEa06qUs

The video maker in his first video gives a battery life of 31hrs 12mins for a DMG and in the second video 35hrs 45mins for a Color.  In the later video, the relatively short time for the Game Boy is because one of his children turned it off prematurely.  However, both systems were running monochrome Game Boy games, and I cannot tell for certain what game was in the DMG, but it appears both videos used the same game in the DMG.  I think it is Super Mario Land.  (For the Color it was Top Rank(ing) Tennis).  Super Mario Land has an attract mode, but Top Ranking Tennis has animation and music on its title screen, so the cartridges seem pretty fair.  However, if a true Color game were being played, I would certainly think that the time would be significantly shorter.

5 comments:

Raifield said...

You never fail to post interesting articles. I had the original Game Boy in early nineties, but as a kid I wasn't aware the battery back was a portable rechargeable unit. I thought it was just for sitting next to the wall.

In my defense I was eight years old.

I still have the Game Boy, plus a Color unit. I use them to play Link's Awakening a few times a year.

Great Hierophant said...

If you liked Link's Awakening, make sure to try Oracle of Seasons and Oracle of Ages, both worthy successors.

Elizabeth J. Neal said...

The Game Boy had two huge advantages over its rivals. First, it came with the killer-app pack-in, Tetris. Second, it had far superior battery life to any of its rivals. In this post, I will discuss battery life among the four members of the 8-bit Game Boy line, the original DMG Game Boy, the Game Boy Pocket, the Game Boy Light and the Game Boy Color. batteriser

James M said...

Excellent work, very thorough, this helped me out a lot because I am currently making a DMG gameboy rechargeable from the internal DC jack. I have already successfully made a gameboy pocket rechargeable from the internal DC jack, and I was needing to know the power rating for the DMG, and now I have information for all of the classic models! Thanks.

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