Powering Gp2x With An Nds Lite Li-ion Battery


bacteria

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Not even turned on my GP2x for ages now, I recently tried some NDS Lite Li-ion batteries to power a PSone screen and some plug'n'plays; didn't prove a great choice as I only got 50 mins from them whatever I did (2 of them in series as each cell is 3.7v), even when two sets of series cells were in parallel, same result. Used some camcorder Li-ions instead.

This left me with some unused NDS Lite batteries with the tabs soldered to, and I don't have an NDS Lite...got me thinking...

Each of the NDS Lite batteries are rated at 1800mA and 3.7v and rechargable via USB (charger adapter).

Connected GP2x to two batteries in parallel - booted fine, green LED on nice and bright. Tried a single battery - also booted fine, green LED on nice and bright.

No idea how long they will run for, not tested. I remembered reading here a while back that the GP2x runs happily on 3.7v and uses less amperage at this voltage.

Relevance of this find you ask?

* No need to use NiMH cells, which don't always power the GP2x after batteries are newly charged (NiMH cells are crap).
* NDS Li-ons are slim, 6mm thick and also 34mm x 49mm dimensions. This means with an adjustment to the battery compartment, it would be not too difficult to incorporate one, or two of these Li-ions into the unit. In fact, one of these Li-ions nearly fits into the existing battery compartment - only needs a bit of shaving off the battery compartment and all done! The battery can be removable or hard wired in.
* Li-ions keep their charge up until the last 20% of power, so far better, more powerful and far more reliable. How many times do you charge a few sets of batteries at the moment and find some of them don't even power the GP2x, or if they do, almost straight to the red light?? not a problem with Li-ions.
* These Li-ions have built-in protection circuits and of course no memory effect.

Got lots on with other projects at the moment, considering when I get breaks between (many) projects, doing a better GP2x modded system, with a PS2 8" Joytech screen I have; it is 12v but with a step-down regulator can also provide 3.7v or lower for the GP2x. This will be far better for playing movies and games!

...or I might just experiment with slipping in an NDS battery into the GP2x. Either way, a future project...
 

sam fisher

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So you've got approximately 3.6Ah there? It wouldn't be prudent for me to estimate how long that will last as the GP2x doesn't seem to have a static current draw.
 

bacteria

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1 battery 1800mA, two in parallel 3600mA.

Might be a lame duck, only by testing until the GP2x dies will a definitive answer be gained. Might give this a go in a week's time or less, to find out. Just need to solder the battery wires to the GP2x connectors and let it run.

Point is that if the Li-ions sucked the GP2x wouldn't boot; however it does boot quite happily, which is encouraging.

Either the batteries will disappoint (again) or I might have hit on something quite useful! (TBC).
 

nubie

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Hey guys, don't forget the protection circuit, Li-Ion doesn't like being fully discharged.

As luck would have it 3.6 or 3.7 volts is perfect for the GP2X, I think Squidge put a bench power supply on one and tested it to be the best at that voltage.

I was able to use 3 NiMH to get the 3.6 volts, but it was a bit bulky, (now that I am trying the bigger NAND I am wondering if I can put the third AA inside by moving the SD slot off to the left or right ;)).

2xLi-Ion sounds nice, but maybe try a PSP battery first, that way only one battery is needed. (I don't know if it fits, but you can mock it up without buying one.) I know bacteria has his batteries already, so this doesn't apply to him.

I would try to flatten the battery bulge and make the GP2X sleek and slim, but that might not be possible.

If this works, please post pictures :).
 

bacteria

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Sure, will let you know if this is good to go or not. Will probably test tomorrow or following day, to see.

With one of these batteries, it could be made to fit into the existing 2 x AA cavity, so the back plate can be shut as per normal. Trick is the battery life, which is the important thing. They might well prove to be a dud; i'm actually expecting this and hoping these cells prove better than I think.

These cells have protection circuit inside - the idea is to stop the cell overcharging and exploding after all.
 

DaveC

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I don't know if this is good or not.

Li-ion cells say 3.6V nominal but in reality they go as high as 4.2 V when fully charged. I would like to hear from someone that is an electrical engineer as to whether there may be a problem powering something made for 3.0V with a battery that can reach 4.2V. Any excess voltage in the unit will be dissipated as heat. You may or may not fry the voltage regulator boost circuit in the GP2X with 4.2V. Even if you don't fry it immediatly, you may drastically shorten it's life span.

Any expert opinions about that?
 

sam fisher

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I have been told before that the GP2x has an excellent and high quality voltage regulator. Plus Dave while you are right that the increased voltage means an increase in the amount of energy carried per unit of charge but it's likely that the GP2x will draw less current at that higher voltage. As Power is the product of current and voltage then it is entirely possible that the energy draw may be the same or even less while at a higher voltage (as the voltage regulator may be more efficient at that voltage).
 

nubie

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DaveC said:
I don't know if this is good or not.

Li-ion cells say 3.6V nominal but in reality they go as high as 4.2 V when fully charged. I would like to hear from someone that is an electrical engineer as to whether there may be a problem powering something made for 3.0V with a battery that can reach 4.2V. Any excess voltage in the unit will be dissipated as heat. You may or may not fry the voltage regulator boost circuit in the GP2X with 4.2V. Even if you don't fry it immediatly, you may drastically shorten it's life span.

Any expert opinions about that?
Look up an old thread of Squidges, he has tested it on a bench pretty high, I don't think it has a problem with Li-Ion, even fully charged.

The regulator is pretty high quality, and I am sure it doesn't generate excess heat like a linear regulator. I think it is PWM, and since it is making 3.3 volts it is better to start with more voltage than the 2.4-2.8 volts of NiMH.
 
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Squirrel61

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DaveC said:
I don't know if this is good or not.

Li-ion cells say 3.6V nominal but in reality they go as high as 4.2 V when fully charged. I would like to hear from someone that is an electrical engineer as to whether there may be a problem powering something made for 3.0V with a battery that can reach 4.2V. Any excess voltage in the unit will be dissipated as heat. You may or may not fry the voltage regulator boost circuit in the GP2X with 4.2V. Even if you don't fry it immediatly, you may drastically shorten it's life span.

Any expert opinions about that?

From the docs for the F100 voltage converter:
QUOTE
Wide Input Range: 0.5V to 5V

From the docs for the F200 voltage converter:
QUOTE
Vin Voltage ................................................. –0.3V to 6V

Although it produces output from 1.8V up and it seems to like not to be fed more than 4.2V
 
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Squidge

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4.2V is also the most efficient, going by the diagrams. Going higher than that shouldn't damage the device, as long as it's < 6V, but operation isn't specified.
 

bacteria

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Squidge said:
4.2V is also the most efficient, going by the diagrams. Going higher than that shouldn't damage the device, as long as it's < 6V, but operation isn't specified.
Ah good, I was about to post to ask the question. Li-ions have a stated voltage (under load) eg 3.7v; but a voltage which is higher when not under load, or little load; yes, the NDS Lite cells can get to 4.2v after recharge.

I was going to ask if 4.2v would fry the GP2x, the fact Squidge says it won't is fine by me.

I find it surprising that when the system was designed they didn't make the battery compartment designed for 3 cells instead of 2, as the worst case is 4.5v and the normal case is about 3 - 3.6v with three cells. Don't know about you guys, but many of my NiMH AA cells lose their ability to hold power after only several charges.
 
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DaveC

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Squidge said:
4.2V is also the most efficient, going by the diagrams. Going higher than that shouldn't damage the device, as long as it's < 6V, but operation isn't specified.
Ok that is good.

I always wanted to mod my GP2X to use 2 cylindrical li-ion cells in parallel and put in an adaptor to use regular AAs as well. Thanks for the info.
 
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