whats a good battery?

[stuntpenguin007]

I'm looking to power a retro duo and a ps1 lcd screen (might add led mod)

Anyways does anybody have recommendations? I'm looking for something to last at least 2 1/2 hours, but if that would cost $500 I guess I could always go for a not so long lasting battery.

- In the mean time I'll be looking through past portables to see what what batteries they used.

[snowpenguin]

I don't have any specific recommendations, but, I think I remember reading that the retro duo draws very little power, and that an LED mod'd psone screen will draw around 450 mAh, correct me if I'm wrong. So let's just say 700 mAh draw, total. Correct me if I'm wrong.

Then for 2.5 hours you should need about 2100-2200 mAh.

So, might be smart to go li-ion in that situation, as a 2200 mAh battery can be found at radio shack for $20 with charger, but it is about .75 inches thick and like 6 inches long, 1.5 inches wide or so, as it is a ni-mh.

Meh, if you're okay with a slightly larger battery, go with the nimh on such a small battery, cheaper, easier, blah blah blah. IMO though, just my 2 cents.

[Kurt_]

That's not exactly how it works.

I bought two 3.7V Lithium Polymer batteries for my SNESp. It was a mini snes, LED modded PS1 screen, a separate audio amp, and used a switching regulator in place of the 7805s.

The 7.4V, 4000mAh pack lasted me 6 hours before I stopped testing. It was still running fine at this point, I just figured I'd never actually want to play for more than a few hours straight.

Keep in mind the discharge curves of Lithium are much more shallow than Ni MH or anything else. This means that it can use more of the battery's life before the voltage drops below usable levels. The batteries, charger, and protection circuitry shouldn't run you more than $100, being quite generous with money. Think <$50 with some deal hunting.

[snowpenguin]

Ummm... Remind me exactly what I got wrong?

[stuntpenguin007]

so lets see if I'm getting this...

So a typical 7.4V lithium battery with 4000mah will last around 6+ hours. (shouldn't matter if it's dual batteries like you or just 1)

does li in a batteries name indicate lithium? like li-po or whatever those batteries are called?

[Kurt_]

Well, it does matter, because a 7.4V battery doesn't exist. Within reason, it's impossible to create a half decent battery with a potential difference of more than 5 volts. Current battery technologies top out with Li-Ion at 3.7V (Typically around 4.2V when fully charged.)

What I'm saying is any 7.2/7.4 volt battery you get will be two cells taped together, essentially.

Snowpenguin:

You can't just add the current draw of a system and divide it by the milliampere-hours of your battery to get the duration your battery will effectively power your system for. As charged cells transfer electrons to the other side, the rate and energy of these transfers decrease. There are discharge curves that show this nicely. Once the energy drops below usable levels (Say, 6 volts), your battery will still have some energy, but not enough to power your system.

Get it?

Lithium Dischrage curve for different power draws. 1 coulomb is a lot, more than we will need to be concerned with.


Nickel Metal-Hydride technology


Lead Acid


Electrolytic Capacitor

[stuntpenguin007]

My screen came today, and I tested it to be working on my psone... so here it goes. I'm going to try solder it onto my snoac now...

[Kurt_]

Don't forget to connect the ground of the screen and the ground of the system.

[stuntpenguin007]

Yeah I remembered the gnd.

yes! It works! I can't believe all it took was 2 wires. Anyways I'll be adding left and right audio pretty soon here.

edit: can left and right audio be soldered together?

would two 3.7V 1000mah batteries make a 7.4V 2000mah battery or a 1000mah battery?

[Kurt_]

Soldering left and right audio will give you mono sound. I recommend living with an extra wire. But you can if you want.

As far as adding batteries, think of it like this.

Batteries have a certain power. Volts multiplied by Amperes gives you the power (in Watts) of a system.

A 3.7V 1000 mAh (1Ah) battery has 3.7 watt hours.
A 7.4 2000 mAh battery has 14.8 watt hours.

If that doesn't make sense, disregard it altogether. The point is that 3.7 * 2 <> 14.8.

Attaching batteries in series (positive to negative) will increase the voltage. Attaching them in parallel increases the effective amp hours of the battery.

[stuntpenguin007]

So hooking a 7.4V pack up to a retro duo shouldn't fry it right? It says 5V but on the board it says 8V.

So I could probably get 2 of these http://cgi.ebay.com/Li-Po-Lithium-Polym ... 286.c0.m14" onclick="window.open(this.href);return false; (or something similar)

And what exactly is the protection circuitry? As for a charger... Can I just find something close, like a generic 12V charger and hook it up to the + and - of the battery?


Thanks for all your help so far


edit: woah! there's a whole batteries board. I'll look at this for the protection circuitry. http://forums.benheck.com/viewtopic.php?f=43&t=30962" onclick="window.open(this.href);return false;


I could get this to save myself some soldering. http://www.batteryspace.com/polymerli-i ... witch.aspx" onclick="window.open(this.href);return false;

I'm guessing that should last at least a good 3 hours. Plus its got protection circuitry built in.

If Someone can confirm that the above battery looks good and would get at least 3 hours of use I'm definitely buying it.

Also if I do need to regulate the power down to 5V I could always just use a 7805 regulator thing right? I'm guessing The Shack has 'em

[Kurt_]

In my experience, the huge batteries I used barely took up any space. Their low profile (~5mm) allows you to put them side by side without any significant increase in thickness. They also make a good separator for the screen and system boards.

[stuntpenguin007]

So your saying it might be better to solder two of these side by side? its 8.7mm
http://www.batteryspace.com/polymerli-i ... arate.aspx" onclick="window.open(this.href);return false;
With the protection circuitry of course.

-I could just buy what I put above and tear it apart, then put the batteries side by side. It would be slightly cheaper, plus I'd only have to order one thing instead of 4 or 5.

What do you think of that battery though? Good enough for 3 hours?

Also before I hot glue down my composite video, audio and gnd wires, does the audio just come out a little fuzzy because that's just the way it is, or should I check for shorts?

I think I should use a switching regulator... Would that save me much power/heat or could I use a 7805?

[Kurt_]

The protection circuit goes side-by-side too.

2000mAh should last around three hours. A mini snes with an LED modded PSOne screen draws around 700mA maximum.

A switching regulator would save you power and heat. But I recommend not screwing around with that on your first try. I mean, you can always do it later once you get a feel for things.

Fuzzy audio: Check speakers for dirt that's been magnetized to the speakers. What audio amplifier are you using? What source? What speakers?

[stuntpenguin007]

If I get time I'll order that battery tomorrow.

I have a 7805 regulator on hand from an old broken noac I can desolder.

As for fuzzy audio, I'm just using the ps1 lcd screen speakers. I cleaned them up, but I didn't find any dirt to begin with. Next I tried to see if removing composite video would make it not fuzzy, but there's no audio if you remove the video. The screen did become discolored (I couldn't see exactly because the screen was upside down) I think it be came black and white, then the audio was perfect... but since I was just touching the desoldered (video) wire to the pad it was hard to tell what I did.

Am I going to need any heat protection for that 7805? Can I just encase it in hot glue?