[hardware Subforum]f200 Internal Liion Battery Mod

[Squirrel61]

* Mods, please delete my other thread about this subject; it was in the wrong subforum. *

The GP2X range of handhelds has been designed to work on 2 AA-sized batteries (preferrably rechargable but Alkaline type batteries are also supported) or on external power from an AC adapter. Since it's release, people on this board or elsewhere have been studying on ways to improve battery life and/or efficiency.

After I studied the datasheets of the voltage converter chips used in the F100 and F200 some time ago for repair purposes, it turned out that the main voltage converter operates most efficiently at an input voltage of 3.7V. Other people have also experimentally discovered this, by modding the GP2X to run off 3 AA rechargables (the thread still can be found on this board, use "search" if you want to read it back) and getting more than the expected 50% lifetime increase.

Inspired by this knowledge, I've been looking for ways to extend my F200 with a 3.7V battery. The most important conditions for me where that:

1. The F200 should look completely normally from the oudside. No loose batteries, no cables, no bulges
2. It should still be possible to operate the F200 from AA batteries
3. It should be easy to recharge the battery. Preferrably in the F200 by using the AC adapter, but an external charger is good too.
4. It should not fry my F200

After studying several possibilities and comparing several batteries, it seemed the NDS Lite battery suited my needs. I bought a 2000 mAh battery from Dealextreme.com and an external charger (USB or NDS AC adapter powered) from Psxboy.com (Psxboy didn't have powerful replacement batteries and Dealextreme didn't have the charger anymore ). However, the battery didn't exactly fit in the F200's battery space and I needed spring contacts. Because the battery had to be removable, soldering the battery was a no-go.

So this is what I started with: the battery, the charger and the F200

Here's where it goes wrong, the battery is slightly too large.

So I have to cut away some plastic to make the NDS battery fit. Here the F200 is still unharmed...

After cutting a slot, the battery fits smoothly.

The slot when looking at it from the inside and outside of the case.




The contacts for the battery already in place. I used battery contacts from an old cellphone.


To establish a contact between the new battery contacts and the existing ones (the most convenient way imo to do it), I used two strips of thin copper that I placed in the slots for the "official" battery contacts. I soldered the wires from the new contacts to these strips. After reassembling the F200's case, the battery contacts on the motherboard will establish the contact with these strips.

Here's some details.





As you can see in the next pic, one of my most important conditions have been met: the AA batteries still fits snugly.

In the next pics, the difference between AA and NDS shows up clearly. Both batteries have been fully charged, but because the GP2X on-screen battery gauge has been calibrated for the input voltage of 3.0V (produced by the AC adapter or 2 alkaline type batteries), it's showing only 2/3th with NiMH batteries. The increased voltage of the NDS battery makes it jump to 100%, where it's supposed to be after a full charge.


I've just finished this mod and haven't done any testing, so there's still nothing I can say about the lifespan of a charge. But I will keep you informed, as soon as I've done some playing. I'm not a frequent player, though, so it could take some time before I'm back with results.

Btw. the strange tuby thing you can see just above the battery space is a stylus holder, made from a piece of rigid air hose. It's holding a DS stylus, which I like much more than the F200 auto-retracting-whenever-you-touch one.

Oh I forgot a condition for the mod. When I decided to use an NDS Lite battery, I also decided that it prefferably had to stay unmodded. So I could use the same battery as a spare for my NDS Lite, in case that one would run out of power. Or otherwise, use the NDS's battery in case the GP2X would run out of power, far more proable.

(Btw. the automatic post-merging of this board is fantastic! It allows you to use more than 6 pics in a single post )

 

[Manjuu]

Impressive!

Would like to do this also... but I don't like to "damage" my F-200 in any way. :lol:

Hope the battery life would be great; keep us informed.

Good work, and thanks for sharing.

 

[peelie]

nice mod;

should be possible to get a li-ion battery that is correct size so that there is no need to cut battery compartment?

also i am not sure i understand how you connected the new contacts?

cheers

 

[Squirrel61]

Would like to do this also... but I don't like to "damage" my F-200 in any way. :lol:

I didn't want any damage either. But I still wanted the mod, so I decided that as a compromise, the mod shouldn't be visible from the outside. (The stylus holder comes off easily without any remains, since hot glue doesn't keep to well on the slick surface of the F200 case)

Btw. I realise I was talking about an internal charging possibility. After deciding for LiIon, I completely dropped that part, since LiIon charging can be fairly complex. And I don't want to risk the battery overheating or even exploding when inside my F200 :blink:

also i am not sure i understand how you connected the new contacts?

The pics are supposed to tell most of the story, but I'll try to explain it a bit more.
The new battery contacts are ripped from an old cellphone. I soldered two wires on the contacts, one for + and one for -. I had to connect these wires to the F200 in some way.

When you take the F200 apart, the battery contacts slide out of the slots in the case, because they have been soldered to the motherboard. When looking at some pictures of the motherboard eg. the ones you can find in the wiki, you can clearly see this. Of course I could simply solder the wires to the normal battery contacts, but then assembly and disassembly of the F200 will be slightly harder, because you always have to desolder the wires. No big deal if you never intend to take it apart again, but I wanted it easier.

So I took two strips of thin copper that I slit in the slots originally intended for the normal battery contacts. Because the copper is so thin, the original contacts will still fit in the same slots, thereby establishing an electrical contact with the copper strips. So by soldering the new battery contact's wires to these copper strips and assembling the case, the new battery is connected through the wires, copper strips and original battery contacts, to the motherboard.

should be possible to get a li-ion battery that is correct size so that there is no need to cut battery compartment?

Maybe there is. I've been searching, but haven't been able to find a suitable one. But probably some cell phone batteries will fit without modding. But they have 2 disadvantages, the first being that they usually have a much lower capacity (usually even below 1000 mAh) and the second being that they're usually charged using a cellphone as a charger. When you can find a battery that fits and is supported by a desktop charger, you're lucky. But you probably need to use two or three in parallel in order to get the capacity needed and then again, the battery lid won't close anymore.

 

[Manjuu]

Would like to do this also... but I don't like to "damage" my F-200 in any way. :lol:

I didn't want any damage either. But I still wanted the mod, so I decided that as a compromise, the mod shouldn't be visible from the outside. (The stylus holder comes off easily without any remains, since hot glue doesn't keep to well on the slick surface of the F200 case)

Btw. I realise I was talking about an internal charging possibility. After deciding for LiIon, I completely dropped that part, since LiIon charging can be fairly complex. And I don't want to risk the battery overheating or even exploding when inside my F200 :blink:

Having the exterior intact is definitely a plus.

From what I can see, it wouldn't rattle around... would it? :lol:

How hard is it to remove and charge the Li-ion battery?

Also, do you have to remove the original battery contacts to insert the Li-ion battery and put them back in when switching to AA batteries?

 

[Squirrel61]

From what I can see, it wouldn't rattle around... would it? :lol:

The battery fits perfectly after cutting the slot. It won't rattle but you don't need any force to insert it either. On the inside, there's just enough space to add the new battery contacts and the spring pressure is keeping the battery steady in place.
QUOTE
How hard is it to remove and charge the Li-ion battery?

It's as hard as removing and charging the AA batteries. Just open the battery lid, pull the string to get the battery out and drop it in the external charger. However, using an NDS as external charger (which is an option when you can't find an external charger) will complicate the process, unless you've replaced the NDS battery lid with one that doesn't need a screw
QUOTE
Also, do you have to remove the original battery contacts to insert the Li-ion battery and put them back in when switching to AA batteries?

No, everything can stay in place. It's just a matter of opening the battery lid, pull the string to get the NDS battery out, insert the AA batteries and close the lid. And from AA to NDS: Open the lid, pull the string to get the batteries out, insert the NDS battery and close the lid. Since the AA batteries have no side contacts and the NDS battery has no top contacts, there's absolutely no danger for short circuits.

Maybe I'll try to upload a short video later, but I'm on my work now, where Youtube has been blocked

 

[Manjuu]

Cool, thanks for the clarifications.

 

[palmertech]

Hate to break it to you, but those dealextreme batteries are lies. Not only are they not the stock 1000mah ones, they are only about 900-950mah.

Here is my suggestion: Sand away the battery bulge, hook up TWO ds lite cells is parallel, take the itty bitty charging circuit from the ecternal charger, and wire that to the USB port and the batteries. Bondo over the hole, and you have a bulge-less gp2x with internal li-ions!

 

[Squirrel61]

Hate to break it to you, but those dealextreme batteries are lies. Not only are they not the stock 1000mah ones, they are only about 900-950mah.

It's not 1000 mAh, it's 2000 mAh. I've taken into account that it actually is a fake battery that doesn't produce it's rated capacity. But I think even after subtracting the lies, there's enough left for some nice playing time. Users of the battery have reported that it lasts longer than the original one, so it shouldn't be too bad.

It's one of the reasons I wanted to keep the battery swappable, so when a better battery pops up somewhere, I can use that instead.

QUOTE
Here is my suggestion: Sand away the battery bulge, hook up TWO ds lite cells is parallel, take the itty bitty charging circuit from the ecternal charger, and wire that to the USB port and the batteries. Bondo over the hole, and you have a bulge-less gp2x with internal li-ions!

That collides with some of my main goals. I still wanted to be able to use AA's and I wanted the GP2X to be as unmodded as possible. At least from the outside. But indeed, I've been thinking about removing the inner part of the battery bay so only the lid remains. That should provide enough space for 2 or 3 NDS or cellphone batteries stacked. But it's far beyond what I wanted. Maybe in the future, when get in need of real long battery life, I'll do it. But I'm a bit afraid of connecting LiIon batteries in parallel and charging them all at once, I believe it's better to let each battery have it's own charging circuitry. That would mean a lot of electronics.

 

[Tag5]

Awesome looking battery mod! Nice feature that you can still use AA's without any further tweaking.

I might give this a try if a high enough (3000+ mAh) battery is available to be used. Wishful thinking...

 

[DaveC]

Interesting. I would like to find out the play time though. You can get 2500 NiMH AA batteries. The voltage is lower yes but by the time you factor in the lower voltage but higher MAh it may come out to be close to a wash. Look forward to your tests though.

 

[grahf]

I'm interested in play time also. Please share your results !

 

[Squirrel61]

Interesting. I would like to find out the play time though. You can get 2500 NiMH AA batteries. The voltage is lower yes but by the time you factor in the lower voltage but higher MAh it may come out to be close to a wash. Look forward to your tests though.

A simple and not really correct calculation (but it should be good to give an indication):
2 AA batteries give 2.4V. 2.4 x 2.5 = 6 Watts of total power.
1 Li-Ion battery gives 3.7V. 3.7 x 2 = 7.4 Watts of total power, assuming the battery produces a real 2000 mAh.

Considering the better efficiency of the main voltage converter (there are 4 or 5 in the F200) when running from 3.7V, I expect lifetime to be roughly equal to that of 2500 mAh AA's. If I was sure about the 2000 mAh of the Li-Ion, it would be far better. But I'll keep you informed.

 

[palmertech]

Here is the problem: I was not saying they were 1000mah because they are not real. REAL, genuine DS Lite cells are only 1000mah! These 2000mah labels are only a chinese marketing tactic. Believe me, they are decent cells, but not made of magic or anything. I doubt that some rip-off artists have somehow managed to make Nintendo's design twice as good with no increase in size, all while maintaining a very low cost; if they had, Nintendo would be using them.

I have personally bought and tested these "2000mah" batteries, and they are ALWAYS around 900-950mah. The reason people give good feedback about "Longer battery life"? Well, part of it is the placebo effect, where they think there is a difference, but there is not. The other reason is that most people buying a replacement battery have one that is currently defective/worn out, so of course a new one is better.

 

[Squirrel61]

You're probably right about the batteries. But to date, I've found no particular disadvantages in using the NDS battery. I think the advantages of the higher voltage and the LiIon technology compensate for the lower capacity.