Useing 2 batteries.

rahilb · Post by **rahilb** » Fri Apr 14, 2006 11:38 am

I thought this would make the wiring a lot easier, give more playing time etc.

would it be possible, more importantly, would it be easy?

toby dawg · Post by **toby dawg** » Fri Apr 14, 2006 11:48 am

you mean for the 3.3 volt line?

superdeformed · Post by **superdeformed** » Fri Apr 14, 2006 12:05 pm

It's certainly possible, but there are a few things you will want to take into consideration. The major one is that hooking up batteries in parallel without any sort of protection is generally a bad idea. If the batteries discharge unevenly (which would be pretty hard to avoid), then when one drops down far enough below the other you will get a massive current spike as the battery with more charge tries to charge the other. Needless to say this could cause a lot of problems.

An easy fix to avoid that would be to place diodes on each battery to prevent reverse current flow. If you're only using a 7.2V battery then you'll run in to more problems from the voltage drop across the diodes. You could either use a battery pack with a higher voltage, or try and find a diode (probably a schottky) with a very low forward voltage drop. One other thing to take in to consideration is that the voltage of the two batteries might not be the same, although I'm not sure if that would actually be an issue with anything other than NiCds.

Another way you could go about using two batteries is to wire them in series, then use dc-dc converters/switching regulators to drop the voltage down to 7.5V (or whatever voltage you're using) and 3.3V. This would have pretty much the same effect as wiring them in parallel if you used high-efficiancy regulators, as the current draw would be half as much with twice the initial voltage.

edit: just saw Toby's post, and wasn't really thinking of that. If you just mean to use a different battery for each input, then yes it is possible. You probably won't get any more play time out of it though, because the battery on the 3.3V line will empty out much faster than the one on the 12V line due to the higher current draw. You will still have to stop and recharge/replace that one just as often.

rahilb · Post by **rahilb** » Sat Apr 15, 2006 8:30 am

You misunderstood my question, i meant using 2 batteries, one for each component, one for the screen, one for the N64...

Neildo_64 · Post by **Neildo_64** » Sat Apr 15, 2006 8:59 am

short answer - Yes, you could. Someone else can give a long answer.

Dont feel up to it.

Warrior_Rocker · Post by **Warrior_Rocker** » Sat Apr 15, 2006 9:11 am

I did this with version 2 of my portable, bad idea.. simply because it will add weight, and it makes it harder to charge 2 different power batteries, not only that but it causes greif in wiring and everything else, better to just strap a 3.3v regulator to the n64 and have it run off 12v

timmeh87 · Post by **timmeh87** » Sat Apr 15, 2006 9:16 am

yeah but psone screens cant do 12v. so youre even BETTER off with a 7.2v RC pack

Warrior_Rocker · Post by **Warrior_Rocker** » Sat Apr 15, 2006 9:50 am

No problem supplying the n64 with 7.2 to the 12v in, and getting a regular from ti for the 3.3 as it goes from 4.5v to 14... once again 1 battery ftw...

however i dont reccomend supplying the lcd with only 7.2 , as soon as the battery dips lower it will go funky

superdeformed · Post by **superdeformed** » Sat Apr 15, 2006 12:13 pm

I (along with pretty much everyone else it seems) have used 7.2V batteries with no problems at all powering the screen and system. I'm not sure what the drop out voltage is on the 7805's on the board, but everything else that runs off of 7.5V can go as low as 7V without any problems. It's even less of an issue if you're using NiMH batteries, as their voltage stays pretty constant until they're just about dead anyways.

timmeh87 · Post by **timmeh87** » Sat Apr 15, 2006 3:37 pm

yeah, everyone uses 7.2v batteries, i didnt just make that up

ive ran the n64 off 5.6v before... but i didnt have sound hooked up. this leads me to believe that the 7805 is only used for sound?? i dunno.