Game Gear - Parallel Lithium Ion batteries ?

I don't know much about batteries, so bear with me if I've written anything retarded as a result of my 10 minute self-education. I'm planning to build the following configuration using six 3.7v li-ion 4000mAh batteries. I will take 3 of them, and put them in parallel, and will do the same to the other 3. Then, I will put these two configurations in series.

I think this should give me 7.4v at 12000mAh (minus some accounting for self-discharge). The setup will look like this (ignore the dots):

..............+- (neg) 3.7v li-ion 4000mAh (pos) -+
Negative <----+- (neg) 3.7v li-ion 4000mAh (pos) -+--+
............. +- (neg) 3.7v li-ion 4000mAh (pos) -+ .|
. . . . . . . . . . . . . . . . . . . . . . . . . . .|
............. +- (pos) 3.7v li-ion 4000mAh (neg) -+ .|
Positive <----+- (pos) 3.7v li-ion 4000mAh (neg) -+--+
..............+- (pos) 3.7v li-ion 4000mAh (neg) -+

edit: fixed, thanks TPSNT

So now for my questions:

1)
I'll be charging them with an appropriate charger that won't overcharge and allow it to blow up), but is using them dangerous at all?
i.e. Will this possibly just blow up in my hands one day?

2)
Is the self-discharge going to be a huge issue?

3)
Would it be a good idea to label each set of 3 so I always use the same 3 in the same parallel set so as to minimise self-discharge?

4)
I don't plan on charging the batteries like this, they will be taken out and charged individually using an appropriate a li-ion charger. In light of this, will I need to have a protection board inserted in this setup? (if so, how?)

The reason I am choosing this method (as opposed to using two higher capacity 3.7v cells in parallel, or using a 7.4v cell on its own) is largely because the 6 AA sized batteries will be a perfect fit (physically) for what I want this for (a game gear with the battery connectors re-wired for this configuration). Thanks in advance for any advice.

 

You can get high quality aa rechargeables as they are these days. I use Energizer branded but Eneloop is supposed to be good as well. Should get quite a few hours out of them.

 

Yeah, I could. But from what I hear, they're nowhere near as good as the best li-ion batteries in terms of capacity. Also, my Energizer rechargeables have gone downhill since I first got them. I guess I'll see how long they last once I LED mod my GG and see if it's worth looking into this.

My aim is to create a gamegear that will last as long as possible without having to significantly modify the case (a few battery connections and some wiring is pretty simple). Size 18650 li-ion batteries appear to be exactly the same size of AAs which is why I had the idea / thought I'd ask.

 

All 6 batteries are in parallel here, so this will only provide 3.7V.

According to your description you want it like this:

..............+- (neg) 3.7v li-ion 4000mAh (pos) -+
Negative <----+- (neg) 3.7v li-ion 4000mAh (pos) -+--+
............. +- (neg) 3.7v li-ion 4000mAh (pos) -+ .|
. . . . . . . . . . . . . . . . . . . . . . . . . . .|
............. +- (pos) 3.7v li-ion 4000mAh (neg) -+ .|
Positive <----+- (pos) 3.7v li-ion 4000mAh (neg) -+--+
..............+- (pos) 3.7v li-ion 4000mAh (neg) -+

 

If you are going to the trouble, take the next step and do a DSi backlight mod for better light distribution. http://www.smspower.org/forums/viewtopic.php?t=13132

 

Hi,

as i have changed the lithium cells on one of my old laptops i think i can answer a few questions.

I used 18650 Cells from Panasonic (bought from ebay)

1)
Lithium Cells are dangerous as shit if handled wrong. They can burn and they can explode if shortened.

2)
The cells need a circuit (usually the electronics in the laptop battery) that shuts down the power at a certain discharge level. If not a exhaustive discharge will occure. This will kill the cell permanently.

My advise. Buy a laptop battery that has the voltage you need. So you have the full electronic in it so it can´t be discharged completely and you can charge it safely also.

 

Thanks, that is what I meant. I got carried away with the ASCII art and messed it up.

I have a lot of bright LEDs and some perspex lying around. I'll try putting in some sanded perspex to see if that works first. I definitely don't want the "2 really bright sections" that commonly results from the LED mod because, IMHO it looks like total crap.

Thanks a lot for this - it was very helpful. It looks like I'll need to learn some more before I consider this.

If I still go down the same path (of using 18650s in the configuration I wrongly described and TPSNT fixed then I will need to get a safe charger the batteries (probably don't want to trust Chinese made products for this one) and get a protection circuit inside the gamegear to prevent over discharge. I'll also put a diode at both the anode and cathode end of ever single battery. While I don't think I'll ever put the batteries in the wrong way - someone else might, and an exploding li-ion isn't the nicest of things as I've just been watching on youtube.

 

removed my previous post in favour of this one.

SANYO Li-ion 18650 7.4V 7800mAh Battery Pack 6 cells to 2S3P W/PCM & Plug
http://www.ebay.com.au/itm/221042909069
this seems to be exactly what I need (but it's all together instead of in 2 halves which I would need)

SANYO Li-ion 18650 3.7V 7800mAh Battery pack 3 cells to 1S3P W/PCM & Plug
http://www.ebay.com.au/itm/221043530503
here's each half..

Does anyone know how these would be wired up?

Would the first (six cell, 2S3P) pack essentially just be 2 of the second (three cell, 1S3P) packs but wired in series?
or is there some special consideration that needs to be taken care of in the Protection Circuits to do this?

 

I think Li-Pos are safer than Li-Ions and dont need the safety circuit. Dont take my word on that though

 

If you want to DRAMATICALLY increase the battery life of a Game Gear console, get rid of that stupid cold cathode fluorescent lamp. Put white leds there and be happy.

 

I don't know about you but the white LEDs leave me far from happy. I'm tempted to fit a brand new LCD in there and wire in a board for RGB output. Should be enough space inside.

 

Have a browse through this thread, have done this. With GG games you will get a smaller screen due to it's resolution.

http://www.smspower.org/forums/viewtopic.php?t=12954