Wiring Batteries Together

[abigsmurf]

I should be getting a trio of these batteries sometime in the next week : http://www.batteryspace.com/index.asp?Page...ROD&ProdID=2332

However looking closely at the connectors it looks like the battery has a +, - and ground wire. When connecting them in parallel, do I ignore the ground wires? The charger I've got connects using a pair of crocodile clips, would it be safe charging them in parallel together?

Also, I assume if I connect the - and +'s to both sets of contacts in the battery compartment and it'll split the voltage between the two contacts and not fry the unit. I'd rather use the battery compartment then have a wire trailing into the power socket.

 

[luteijn]

I'd start with just one, without putting them in parallel. It is stated to be able to deliver 3A, GP2X 'needs' 1A (at most, as that is what the official power adapter would supply) so you don't need to complicate matters by putting these in parallel (800mAh means that you can run it for 1 hour while drawing 800 mA, or about 16 minutes while drawing the maximum 3A)

I'd try make sure the wires are actually doing what you think they do, maybe one is used to communicate the amount of power left ?


This might be a good read:
http://www.batteryuniversity.com/partone-24.htm

 

[carlgeorge]

Why? If this thing only delivers 800mAh it wouldn't last long, you still need to disconnect the battery to charge and then the big problem of working out how to butcher the case to make it fit. Why not spend the $10 on some cheap NiMH AA batteries? -- They'll last longer than this.

 

[Hanz™]

Why? If this thing only delivers 800mAh it wouldn't last long, you still need to disconnect the battery to charge and then the big problem of working out how to butcher the case to make it fit. Why not spend the $10 on some cheap NiMH AA batteries? -- They'll last longer than this.

​

Lithium polymer batteries will last longer than Nimh. But there are better battery packs.

 

[Squidge]

At a guess, I'd say two of those Polymer batteries (giving 1600mAh) would probably last about the same amount of time as two AA's that give 2700mAh.

 

[abigsmurf]

Why?  If this thing only delivers 800mAh it wouldn't last long, you still need to disconnect the battery to charge and then the big problem of working out how to butcher the case to make it fit.  Why not spend the $10 on some cheap NiMH AA batteries? -- They'll last longer than this.

​

Lithium polymer batteries will last longer than Nimh. But there are better battery packs.

​

Thats the biggest capacity that'll fit in the compartment, theorectically all three packs should fit with little or no modification of the case. However I'll settle for fitting two packs

 

[reaper79]

Also, I assume if I connect the - and +'s to both sets of contacts in the battery compartment and it'll split the voltage between the two contacts and not fry the unit. I'd rather use the battery compartment then have a wire trailing into the power socket.

​

Ummm, if I understand you correctly, you are thinking of wiring these batteries to BOTH sets of contacts? That is, you wish to split the battery negative to both compartment negatives and split the battery positive to both compartment positives? Depending on how you do it, your either going to fry something by wiring the polarity backwards OR you're going the hard way about wiring these in series which it turn will give you 7.2 volts and more than likely fry the unit. Remember, series equals twice the voltage @ the same amperage. Parallel equals twice the amperage @ the same voltage. Speaking in watt/hours (power), your going to get pretty close to 2600mah nimh's.

 

[abigsmurf]

I thought it was series splits voltage and current remains constant, parallel splits current with voltage remaining constant.

Wouldn't parallel supply 3.7V to each set of contacts for a total of 7.4 with series providing 1.85V to each set?

I'm not sure it's possible to supply to just one set of contacts, wouldn't the circuit be broken?

 

[Hanz™]

As far as I know in Series you would add the 3 voltages together and the current would stay the same.
In paralell you would add the 3 currents together and the voltage would stay the same.

The 2AA batteries that are you in the GP2X are added on in series I think. I think you might have to change something inside the GP2X in order that you can just use one battery (3 * Lithium cells in paralell) as otherwise the circuit will likely be broken.
I think it should be possible to make a switch that when used changes circuit - I don't know how though - and can't open a GP2X (as I don't have one) to see.

Edit: 2400mAh with lithium batteries at 3.7V will supply way more battery life than 2600mAh NiMh would at 2.4V.

Don't take my word on any of this though as I am atrocious at electronics.

Edit2: A much better Idea would be to connect them all in paralell and then wire them upto the DC plug, rather than having them go into the GP2X the other way.

Edit3: One of the pictures below should work.

Here is some useful information by Squidge:

The 2X expects 3.3V, but has a switch mode psu to increase the voltage if you use batteries which only output 2.4V for example.
-
@ 2.5V = 410mA. = 1.025 watts/hr
@ 2.9V = 340mA. = .986
@ 3.3V = 300mA. = .990
@ 3.4V = 290mA. = .986
@ 3.6V = 280mA. = 1.008
@ 3.7V = 270mA. = .999
@ 3.8V = 260mA. = .988
@ 4.0V = 260mA. = 1.040
-
@ 2.5V - upto 850mA = 2.125
@ 2.9V - upto 690mA = 2.001
@ 3.1V - upto 650mA = 2.015
@ 3.3V - upto 590mA = 1.947
@ 3.7V - upto 530mA = 1.961

As you can see at 3.7V the GP2X needs less current.
Therefore 3 of the lithium cells mentioned above should give 2400mAh @ 3.7V. Which should be much more efficient. Or we could use 2 cells : 1600mAh @ 3.7V.
2 * 1.5V Ansmann 2600mAh batteries should have a power of 6.24 watt/hours.
3.7V Lithium batteries (3*800mAh) should have a power of 8.88 watts/hours.
Also (and more importantly):

If you increase the battery voltage, you increase the efficiency as the vreg in the 2x isn't wasting energy boosting the voltage for you. Also, li-ion's don't loose there charge over time as the AA's do (therefore needing further voltage boosting, and therefore even higher current drain...)

 

[reallynotnick]

Yes in series the voltage of all the power supplys will add up (In other words you don't want to do this)
In paralell you will add the amps together causing a longer battery life (good)

This would be pretty interesting if you could get this to work with 3 batteries being that they are lithium and they are of a much higher voltage you could get some VERY nice battery life.

 

[abigsmurf]

people are getting confused with the arrangement I'm talking about. The batteries themselves will be connected in parallel but then that will be connected to the battery contacts in series:

However I'm not sure how the battery contacts themselves are organised, it's possible that may short it.

I'm possibly considering the following arrangement where only 1 set of contacts is actually powered and the other is just bridged.

 

[Hanz™]

That should work. I think.
I didn't realise before that you would have a wire going in between two of the battery contacts.

 

[abigsmurf]

which one?

 

[Hanz™]

Thats what I am not sure about.

 

[nubie]

You've got it all wrong.

If you look at your (or pictures online) GP2X you will see one end is simply a metal strip connecting the AA batteries in Series.

Try connecting them like this to your packs.

You might not want to attempt this anyway as a beginner project.

 

[luteijn]

This reminds me of the Darwin awards... Order some stuff (either some JATO bottles, v14gr4 knockoffs, LiIon battery) over the intarweb, wire it up, press go button...

Just because it's 'only' a few volts DC, doesn't mean it's not dangerous. (I never understood why you're allowed battery operated gear (including high-power radiotransmitters) on a plane, but not your nail-clippers-with-integrated-nail-file (also made in Korea))

Anyway, Good Luck , and let us know how it turns out.

P.

 

[Hanz™]

If you look at your (or pictures online) GP2X you will see one end is simply a metal strip connecting the AA batteries in Series.

Yeah I thought it might have been done like that.
But may I add surely the -ve wire of the battery should be attached to a positive terminal?
I know that normally AA batteries attach +ve to +ve, but I thought this was just because they mislabeled it for stupid people to understand? I presume they mislabel the batteries and not the actual inside compartment.
Do they mislabel the wires on a lithium polymer battery - so that you attach the +ve wire to a +ve terminal?

 

[Hanz™]

This reminds me of the Darwin awards... Order some stuff (either some JATO bottles, v14gr4 knockoffs, LiIon battery) over the intarweb, wire it up, press go button...

Just because it's 'only' a few volts DC, doesn't mean it's not dangerous. (I never understood why you're allowed battery operated gear (including high-power radiotransmitters) on a plane, but not your nail-clippers-with-integrated-nail-file (also made in Korea))

Anyway, Good Luck , and let us know how it turns out.

P.

​

Thankfully Lithium Polymer does not explode.

 

[abigsmurf]

You've got it all wrong.

If you look at your (or pictures online) GP2X you will see one end is simply a metal strip connecting the AA batteries in Series.

Try connecting them like this to your packs.
*snip*
You might not want to attempt this anyway as a beginner project.

​

bleh I didn't actually look at the case when drawing the diagram (didn't have the console with me). I would've made sure about the polarity before wiring up

In terms of an electronics project, it doesn't get much simpler than this.

Luteijin : Lithium polymer cells are extremely safe compared to Li- 's, they don't blow up (which is why they're not in thick metal cases). Also these come prewired into protection circuits. As long as I wear gloves, goggles and put it on a heatproof surface, the worst I'd probably do is some melted wires. Also, I've access to mediumly decent electronics equiptment to make sure i'm not gonna connect a 50V 10A power unit to the console.

That and my dad's an electrician with 40 years experience if worse comes to worse.

 

[Series-8]

Get out your multimeter, TEST EVERYTHING!

If you don't have one/know what one is stop now.

I have seen external battery packs that provide 10K mAh, but they ain't cheap.