PSOne screen battery recommendation

forrest · Post by **forrest** » Mon Jan 02, 2006 3:04 pm

I just picked-up a new PSOne screen off ebay and am planning on powering the screen and an Atari 130XE computer (runs off 5V DC) off batteries. Size isn't much of a concern, as I'm placing the batteries in a 7 5/8 x 4 3/8 x 2 3/8 inch project box - which will also double as a base for the PSOne screen.

Judging from the info on these boards, RC batteries seem to be popular and it looks like they work well for high current applications. The computer has a 5V 1.5A power supply and I think someone mentioned an unmodified PSOne screen draws around .75A at 7.5V.

The question for you experienced users is should I use one or two battery battery packs? Should I use NiMH 7.2V, 8.4V or 9.6V packs or use a Li-Ion 7.2V or 7.4V. I know NiCd batteries drop in voltage as they run down. Does the same thing happen with NiMH or Li-Ion?

Thanks for your help.

sniper_spike · Post by **sniper_spike** » Mon Jan 02, 2006 3:33 pm

9.6V batteries have too much voltage for the PSone screen, I tried running it with them just an hour ago. I had an image, but a lot of artifacting, so I quickly removed the battery to avoid any damage. Most people say 7.2V - 9V is acceptable, but I'm not quite sure about 7.2V, as the screen itself originally takes 7.5V. You'll need to get a 7805 linear regulator to attach between the battery and Atari to drop the voltage down to 5V.

Ni-Cad batteries do not drop voltage untill they're almost dead, that's for sure, and neither do Ni-MH or Li-Ions.

The only battery type that drops (noticable) voltage right off the bat is Alkaline.

timmeh87 · Post by **timmeh87** » Mon Jan 02, 2006 3:43 pm

not many people choose too use two separate battery packs for the screen and the system. its easier as far as size, weight, and ease of charging to just go with one. that said, heres a brief description of each type:

nicd
- lowest energy density (power per weight)
- slightly sloped discharge curve, averaging around 1.2 volts
( http://www.rcbatteryclinic.com/Hofffig1.jpg )
- easy to charge/discharge (no danger involved)

nimh
- high energy density
- surprisinly flat discharge curve, averaging around 1.2 volts
( http://muss.cis.mcmaster.ca/~bernast/img/nimh.gif ) <- i took this curve myself with two cells in series
- easy to charge/discharge

li-ion and li-poly
- very high to incredibly high energy density
- slightly sloped discharge curve, averaging around 3.6 volts
( http://www.buchmann.ca/chap2_files/image007.gif ) look at the "graphite" curve
- very dangerous to charge/discharge, dedicated protection circuitry is needed.

i personally reccomend using a 7.2V nimh battery pack. you can hook that directly to the screen, and then use a regulator or a dc-dc converter to bring the voltage down to 5v. be warned, the dc-dc converters from TI need 9v to operate properly, despite some early speculation on the forums that they would operate at 7.2v

forrest · Post by **forrest** » Mon Jan 02, 2006 4:14 pm

Thanks for the info. How long do you think a single 7.2V NiMH battery pack will last assuming it just powers the PSOne screen (unmodified).

segasonicfan · Post by **segasonicfan** » Mon Jan 02, 2006 4:58 pm

I think people overlook the greatness of Li-Ion way too easily. Lithium Ion are THE MOST powerful batteries on the market (next to lithium polymer) if you judge the size/weight/power ratio. They way light as a feather compared to NIMH and are ideal for all portable projects. The only reason I would ever consider not using them is if I was investing in something I didn't plan on spending a lot of time and money on, and that is not the case when I make portables.

Additionally, despite popular belief you do not need protection circuitry for li-ion batteries. It's nice to have (and fairly cheap) but not necessary. If you use a proper li-ion ONLY battery charger your batteries will discharge and charge properly just fine.

NIMH is the next best alternative but its HEAVY. You also need more cells to achieve higher voltaged (1.5v per cell and li-ion is 3.6v per cell). I use 2 li-ion cells in serious for my PSOne screen for a perfect 7.4v nominal voltage.

In conclusion: Choose Li-Ion for a QUALITY portable you plan on putting a lot of work and money into. If you don't care that much and you want to save $$, use NIMH.

-Segasonicfan

Post by **marshallh** » Mon Jan 02, 2006 5:21 pm

segasonicfan wrote:despite popular belief you do not need protection circuitry for li-ion batteries.

I wouldn't agree with that. Have you had a li-ion battery explode onto your carpet? I used the charger that was made for the battery. It turns out I removed the protection circuitry, and discharged a little too much.
It exploded when my charger started charging.

Exercise caution with them, and if you do use them, note they disintegrate starting the day they are made. The average expected lifespan is about 2 years for a li-ion cell. There are exceptions, but they do go downhill fairly quickly.

segasonicfan · Post by **segasonicfan** » Mon Jan 02, 2006 5:25 pm

I've NEVER had an li-ion battery explode. I use them without protection circuitry all the time and my chargers work great with them. I've also been using them for almost 2 years now and I doubt they'll die anytime soon...

Don't get my wrong though, I do recommend the protection circuits. I just can't always use them when I have, say, an 8A li-ion battery pack

-Segasonicfan

forrest · Post by **forrest** » Mon Jan 02, 2006 6:12 pm

I'm cheap and weight doesn't matter. Anyone care to guess the life of a PSOne (stock) running on a single 7.2 V NiMH (3300 mAh) pack?

sniper_spike · Post by **sniper_spike** » Mon Jan 02, 2006 6:26 pm

Someone mentioned that the (unmodded) screen's drain was ~600mAh so the battery will last ~5.5h (3300/600).

forrest · Post by **forrest** » Mon Jan 02, 2006 6:50 pm

5.5 hours - that's excellent. Thanks for the info.

Post by **marshallh** » Mon Jan 02, 2006 7:04 pm

If you LED mod the screen, then it only draws 350mA. Of course that doesn't include the game system (if you'll be using one.)

superdeformed · Post by **superdeformed** » Mon Jan 02, 2006 7:26 pm

forrest wrote:I'm cheap and weight doesn't matter. Anyone care to guess the life of a PSOne (stock) running on a single 7.2 V NiMH (3300 mAh) pack?

I measured mine at about 850mA with brightness/volume up all the way, and 180-200 mA with the backlight disconnected. Even at 850mA it will still last a considerable amount of time on that battery (almost 4 hours).

timmeh87 · Post by **timmeh87** » Mon Jan 02, 2006 7:33 pm

segasonic has probably been saved so far by the fact that the hardware cuts out at a relatively safe voltage, somewhere above about 2.7v per cell. this would have a sort of "protection effect", preventing the batteries from getting below the threshold for explosion (which i would put somewhat unprofessionally at about 2 volts or so).

the exposion is apparently caused by the development of crystals within the cells. it totally rips them apart

anyhow, im warning everyone here: DONT DO THIS!. after leaving them on the shelf at 2.5 volts, you may find that they have dropped to 2 volts over a month or two. once the cells get down to 1.5 or 2 volts, they can discharge considerably (like an entire volt) just when you try to unsucessfully start your hardware. i had one go from .85v to .66v just with the current the multimeter was drawing.

and yeah. at that poitn even a proper charger will make them explode. almost guaranteed

JeffMan · Post by **JeffMan** » Mon Jan 02, 2006 8:40 pm

Since I don't wanna make a new topic and I don't have my PSOne screen on hand, I just wanna know one quick thing: do both of the voltage regulators on the screen drop down to 5V? I wanna desolder the 7805 from my SNES, and put a wire from a regulator on the screen to the +5V on the snes where the 7805 was, without things blowing up.

daguuy · Post by **daguuy** » Mon Jan 02, 2006 9:15 pm

yes they are both 7805s