DVD Player Battery?

[2Lincolns]

Long time visitor to the forum, first time poster. I've been wanting to make a portable NOAC NES for awhile, and my girlfriend got me a Dremel for my birthday, so I figured now is as good a time as any!

Anyway, I have a question regarding batteries. I was interested in using a DVD Player battery like the Polaroid BT41 that was used in the L64 portable (7.4V, 4200mAh I believe). (See: http://forums.benheck.com/viewtopic.php ... light=bt41)I'll be powering a PSOne Screen in this setup. If I've read correctly, as long as I have 7.2V or more, I have enough to power the screen, and the 7805 Regulator will give me my 5V needed for the NOAC and the other 5V hookup on the screen.

So as far as voltage, 7.4V should be fine then, right? As far as mAh are concerned, I'm not sure of the exact draw of the whole system, but I've heard the NOAC alone is only 50 mA. Assuming the whole setup takes less than 700 mA to power, I can get at least 6 hours play time from 4200 mAh. So, if my logic is correct, either of these batteries are okay, correct?

BT41: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... :IT&ih=019

BT46: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... :IT&ih=020

...or any other model of these batteries being 7.4V, right? I'd assume I'd want a minimum of 2000-3000 mAh to make it worth it. On a side note, Corscaria mentioned that the BT42 battery was recalled in the L64 post (page 10, explained here: http://www.cpsc.gov/cpscpub/prerel/prhtml06/06060.html), so I'm excluding that one from my search.

Also, Marshallh had stated "You just plug in any old 9v wallwart with >1amps and it charges itself." implying that any old 9v wall plug adaptor works with these batteries. Can someone elaborate?

Lastly, what are any downsides to using these batteries? From what I understood from Marshallh's posts, you can charge while playing, and they have the protection circuit built in, which is what makes me interested in them.

Thanks for the help! Glad to join this forum of highly talented people!

[CronoTriggerfan]

Should be just fine, so long as you power the NOAC via a 7805. As far as the 9v comment, I'm not sure, but I'd generally advise against random wall plugs for lithium batteries of any kind; you should probably use the original charger if you can, or at least a smart charger of some sort. We've had all too many horror stories here about these things exploding, even one that destroyed a beautiful GCp and nearly burned down a house!

[2Lincolns]

Should be just fine, so long as you power the NOAC via a 7805. As far as the 9v comment, I'm not sure, but I'd generally advise against random wall plugs for lithium batteries of any kind; you should probably use the original charger if you can, or at least a smart charger of some sort. We've had all too many horror stories here about these things exploding, even one that destroyed a beautiful GCp and nearly burned down a house!

Thanks for the quick reply Crono! Yeah, I agree about the wall plug. I was pretty weary, that's why I asked. I'll probably search for the original adapter for that DVD player.

[Aguiluz]

We've had all too many horror stories here about these things exploding, even one that destroyed a beautiful GCp and nearly burned down a house!

WHERE!? CAN I READ?

[Rekarp]

There is a picture floating around somewhere of a melted portable.

[Valium]

It was a GCp. One of the best ever produced here. I think it was Gamelver's

[Life of Brian]

Ohhh yeah, that one was a mess! I remember that pic... Yes, it was gamelvr's portable.

I'm so glad you did your research, 2Lincolns! You are exactly right on every single question/point you made. Goes to show what a little bit of reading will do.

By the way, would you rather we call you 2Lincolns every time or something else? Maybe Link?

[2Lincolns]

Here's the link to Gamelver's woes:

http://forums.benheck.com/viewtopic.php ... light=fire

To Life of Brian: You can call me Link if you want. My name is Jeff, so whatever works for you. I chose 2Lincolns because it's the name of my blogging site that I'm working on (almost done). Check it out if you want:

http://www.2lincolns.com

Feedback is always welcome. I'm sure you guys are the same way, but I'm becoming the king of 85% complete projects.

Brian, btw I loved the portable SNES you did (the black one). Great work.

I'm so glad you did your research, 2Lincolns! You are exactly right on every single question/point you made. Goes to show what a little bit of reading will do.

EDIT: Forgot to address this. Thanks, I appreciate the acknowledgement. I've basically been searching the forums for anything I hadn't figured out on my own. Whether you realize it or not, you've all probably helped me already with a previous post. I have a degree in Computer Science, and even though it's software focused, we did have to take a decent amount of computer and electrical engineering. Despite that, after 3 years out of college, you tend to start forgetting things.

It takes a lot of patience and digging to find things on the forum (phpBB's search tool isn't exactly robust), but there is enough information on here to write an encyclopedia on console hacking, if not electronics tinkering in general. I'm glad to join both such a talented and enthusiastic community.

[Mario]

Here's the link to Gamelver's woes:

http://forums.benheck.com/viewtopic.php ... light=fire

Oh my goodness! That's horrible!

The batteries should be fine if I don't take off the circuit that came with it?
Here's a pic of mine:


If I leave it like that, and charge it through that board, they won't explode, right? (The bottom of the board has a few small ICs and some surface mount components)

[Gordon1]

Hi, and welcome to the forum. I used the bt41/42 in my first portable. The 41 and 42 are practically the same thing. I contacted Marshallh and he said to use a 9v wall wart that puts out at least 500ma (.5a). I did so and it works just fine. The actual circuit board on the battery pack is about 2" by 3" and has a built in protection circuit and charge circuit. Just be very careful pulling the cells off of the plastic case DO NOT USE A KNIFE TO GET THEM OFF. A lithium cell that has been slit acts in a similar fashion as an overcharged one.... fire!

Also, you load goes on the top terminals and your charge goes on the the bottom two.

Mario: I have no idea what that circuit is from but the bt41/42 has two cells side by side.... not stacked. As for that circuit I have no Idea where it came from.

[2Lincolns]

Gordon,

Thanks for the reply. Very useful information. I haven't received the battery yet (just ordered today), so I can't look at what you're talking about with the leads. Any chance you could whip up some sweet paintbrush action to illustrate?

Also, you load goes on the top terminals and your charge goes on the the bottom two.

Just looking for a clarification on that statement. I haven't drawn up all of my wiring diagrams. I'm just not sure what you mean by that statement. I've worked with electronics enough, but never with a rechargeable battery system before. Usually it has just been a 4AA battery pack or a power supply from the wall.

[timmeh87]

A 9v 500ma, adapter is more like 12v open-circuit. If the over-voltage cutoff didn't catch it, it would certainly damage the cells.

Generally I would advise against using protection circuit like a magical anti-exploding device. For at least two reasons.

1) The over/under-voltage limits in certain circuits are set slightly outside what is generally considered as the safe operating range (3v - 4.2v). For example, one circuit I looked at in the past had its limits set to around 2.7v - 4.35v. The protection in this case is a last resort if your charger/device somehow fails.

Also less dangerously, letting your portable drain the batteries to 2.7v every time you play isn't going to be very good for them in the long run (most of your consumer electronics shut down at 3V).

2) Some circuits cannot be [easily] reset. The idea here is that if something bad happened, the cells should not be used until they are at least looked at by some kind of technician. However, some may not even need resetting.

With that said, If someone has tried it before and it works, I guess you cant really argue with that. Marshall knows what he is talking about. If it was me though, Id keep it away from flammables when its charging.

I would recommend looking up the datasheet on any protection ICs you plan on using like a charger. If you understand how it works you can make the right decision.

[Gordon1]

A 9v 500ma, adapter is more like 12v open-circuit. If the over-voltage cutoff didn't catch it, it would certainly damage the cells.

Generally I would advise against using protection circuit like a magical anti-exploding device. For at least two reasons.

1) The over/under-voltage limits in certain circuits are set slightly outside what is generally considered as the safe operating range (3v - 4.2v). For example, one circuit I looked at in the past had its limits set to around 2.7v - 4.35v. The protection in this case is a last resort if your charger/device somehow fails.

Also less dangerously, letting your portable drain the batteries to 2.7v every time you play isn't going to be very good for them in the long run (most of your consumer electronics shut down at 3V).

2) Some circuits cannot be [easily] reset. The idea here is that if something bad happened, the cells should not be used until they are at least looked at by some kind of technician. However, some may not even need resetting.

With that said, If someone has tried it before and it works, I guess you cant really argue with that. Marshall knows what he is talking about. If it was me though, Id keep it away from flammables when its charging.

I would recommend looking up the datasheet on any protection ICs you plan on using like a charger. If you understand how it works you can make the right decision.

I'm just going to put this straight. There is a built in charger, there is even an LED so, just give it some voltage (9v) and let it charge until the light turns to green and unplug it, done. SO, I am NOT using the protection circuit as a charge cut off so, don't think that.

[2Lincolns]

Good to know Gordon, thanks.

I do have a few more questions though, this one aimed at those who have used the BT41 battery.

I'm making some progress with my NOAC, and the scary reality of wondering how everything is going to fit in my case is setting in. First question:

Q: Can I cut off the area in the picture marked below in red off the PCB that comes with the battery?



It doesn't seem to serve any purpose other than to extend the PCB to the screw holes. I tried to look for traces that run through there, but they seem to be pretty well hidden if there are any.

Second question...

Q: I'm kind of weary desoldering the + and - cables currently on the batteries. Any tips for this? Sticking a soldering iron, even for a few seconds, to these leads doesn't sound like a great idea.

Also, is there a certain gauge wire I should use for the +/- connecting to the batteries?

Any advice on how to fit these batteries in a case would be much appreciated.

Thanks![/img]

[Aguiluz]

Q: Can I cut off the area in the picture marked below in red off the PCB that comes with the battery?

Sure! As long as there are no traces or components on that part, obviously.