Interchanging between Wall and Battery Power

XFactor · Post by **XFactor** » Mon Mar 27, 2006 8:27 pm

I am ready to wire up my N64 for battery power; however, I am confused/scared about the interchangablility between wall power and the battery.

I have a 7.4v battery and an 8.4v smart charger. My intention is to allow for the unit to operate on battery power and then once the battery gets low, switch the system over to wall power simply by plugging in the cable. On an earlier thread, someone (I think it was Niedo_64) said that diodes would have to be placed in such a fashion that it would not allow for the current to flow back to one or the other source when using wall power. I made this diagram to show what my interpretation of this was:
<a href="http://img377.imageshack.us/my.php?imag ... nge2ru.png" target="_blank"><img src="http://img377.imageshack.us/img377/2388 ... 2ru.th.png" border="0" alt=/></a>

The diodes are in blue, and the wires at the top of the picture lead to my DC-DC converter. This is where i am weary; because i am afraid that my DC-DC will fry because of the amperage.

These are my parts; the battery and the charger, respectivly:
http://www.batteryspace.com/index.asp?P ... rodID=2326
http://www.batteryspace.com/index.asp?P ... rodID=1230

codeman · Post by **codeman** » Mon Mar 27, 2006 8:41 pm

that's the way to do it, with one minor change. You don't need the diodes on the ground wires. Current is flowing in the opposite direction as through the "red" wire, so those diodes will stop the current flow! They're not needed anyway, you only need the diodes on the positive line.

Post by **Skyone** » Mon Mar 27, 2006 8:49 pm

I have never gotten the concept and difference of diodes. What diode are you using there?

XFactor · Post by **XFactor** » Mon Mar 27, 2006 8:51 pm

3A diodes. Codeman, what about the dc converter? Will it explode?

codeman · Post by **codeman** » Mon Mar 27, 2006 9:21 pm

I'm not sure what your concern is exactly. Are you worried that using the wall power will cause too much current to flow? If that's the case, don't worry about it. If your DC-DC converter is rated to supply the current the nintendo needs then you're all set. Current is "pulled" by whatever needs it, it's never "pushed" from a source. Is that what you mean?

Turbo Tax 1.0 · Post by **Turbo Tax 1.0** » Mon Mar 27, 2006 9:23 pm

the wall adapter only outputs 500 ma i dont think that its anything to worry about

so far i have wired it with no diodes just like that on my snesp and GCp and have had no problems. you gotta stop worrying

worst case is that you fry the DC-DC and you grab another free one

XFactor · Post by **XFactor** » Mon Mar 27, 2006 9:37 pm

Sorry Turbo about my anxiety; i guess i am too much of a perfectionist...

The reason behind my worry was that i think timmeh said that unless you put diodes on the positive ends of both those sources, the battery would explode.

This is not a worrisome question but more of a operational one: if at anytime during gameplay i want to plug in the wall adapter, all i have to do is plug it into that wiring style and it will not have any adverse effects like audio/video distortions or a power surge, right?

Also, i assume that with that configuration, the battery will charge while in gameplay right (when it is plugged into the wall without diodes)?

timmeh87 · Post by **timmeh87** » Mon Mar 27, 2006 10:51 pm

wha? i dont remember saying anything about diodes.

your concern about the system screwing up when you plug it in during gameplay seems legitimate... i guess you'll just have to see how it behaves.

the battery wont charge with diodes on the positive lines. come to think of it... why do you need diodes again?

JAY · Post by **JAY** » Mon Mar 27, 2006 11:06 pm

If your wall supply is the battery charger itself, then the diodes aren't really needed, since the charger is made to work with that particular battery, and so you don't have to worry about overloading your batteries. The diodes would be for situations where your batteries are 7.2 V, but the wall supply delivers a much higher voltage, like 9.6 V or higher (I don't know why someone would do that, though). Having that much voltage over the batteries may damage them.

XFactor · Post by **XFactor** » Mon Mar 27, 2006 11:11 pm

It must have been someone else who said that

...They said something along the lines of that if i tried to plug the wall charger in while the battery was being used, the battery would explode for some unknown reason.

I guess it would be wise just to play it safe and connect the power before i turn on the system so there is no sudden surge. I can live with saving my game and turning it off to reconnect the power supply; however, that would have been convienient without the risk of frying my system of course

Turbo Tax 1.0 · Post by **Turbo Tax 1.0** » Tue Mar 28, 2006 6:30 am

i asked the owners of battery space in an email and they said it was fine to charge and put a load on the batteries at the same time if you have a circuit and smart charger

Turbo Tax 1.0 · Post by **Turbo Tax 1.0** » Tue Mar 28, 2006 4:11 pm

im not sure about Ni-Mhs but i knwo li-polys can

timmeh87 · Post by **timmeh87** » Thu Mar 30, 2006 9:24 am

ti or maxim might have something similar.

codeman · Post by **codeman** » Thu Mar 30, 2006 4:58 pm

Is a battery charger chip not what you're looking for? Why can't you just get a wall power supply that can provide enough current, and put diodes on the power inputs to the charger chip to prevent feedback while you're playing and charging?

XFactor · Post by **XFactor** » Thu Mar 30, 2006 6:28 pm

It was mentioned on another thread that if you used an inductor on the input of the DC-DC, it would prevent serious oscillation. I theorize that of you used the method of wiring the battery and the wall adapter lines together, that once you plugged in the wall power, the inductor would automatically smooth out the power, preventing surge.