battery/power draw question

newguy101 · Post by **newguy101** » Mon Sep 22, 2008 10:34 pm

ok so for my N64 project im going to use the 3 LED modded Zenith screen, along with the N64 and PTH08080WAH TI regulator. from what ive read i believe this is correct, but would a 7.4v battery power the n64 correctly? also does anyone know the power draw for the N64, so i know what expected battery life is. thanks in advance.... specifically looking at this battery which is 7.4v and 5200maH li-ion

evilteddy · Post by **evilteddy** » Tue Sep 23, 2008 12:59 am

My answer on a similar question asked below-

-7.2V*.1A = .72W(On the 12 V line)
-3.3V*1.5A = 5W (on the 3.3V line with expansion pack)
-7.5V*750mA = 6.5W(unmodded ps1 screen)
-2W (for a fan and other finishing touches and tolerances)

that's 14.5W. My Nintendo 64 has 2.4 Ah batteries at 11.1V that means that the current draw will be 1.3A in my case so my batteries should last for about 1:40 each (I have two and I swap them) which they did when they were new (but because I bought el cheapos from China one died and the other now does 1:30 run time).

If you want 4 hours of runtime then you'll need 60Wh of capacity. At 7.2V that is a bit over 8 Ah. There are very few 8Ah batteries so on to cutting load. LED modding the screen should around cut the consumption in half, say 400mA so the Wattage will be around 4W. Don't use an expansion pack and that cuts another 500mA at 3.3V so that will be 1.65W less.

With these energy cutting measures you can take power consumption back to 10W which means you'll need a battery which can do 40Wh as opposed to 60Wh. At 7.2V that is 5.5Ah which is perfectly manageable.

As for the battery you mentioned it looks good, 7.4V will work, it has great capacity in fact I would love to buy it but here in Australia everything is more expensive than can be accounted for by the exchange rate.

SonyPortableizer · Post by **SonyPortableizer** » Tue Sep 23, 2008 4:31 am

Yea, that'll work really well.
I now have a new place to get batteries thanks
Did I help supply the funds for this project?

EDIT: Yes Better spent on a car then a N64

Sorry, I like cars better

collinE · Post by **collinE** » Tue Sep 23, 2008 10:22 am

please put safety circuitry to your battery so that it doesn't esplode like gamelver's portable.

newguy101 · Post by **newguy101** » Tue Sep 23, 2008 1:15 pm

thanks for the info, hate to sped $50 on something and it not work right. and ill be sure to use the safety circuit as well, im sure ill have some questions about that. and actually sony, i spent your money on a new paint gun(for auto painting). ive had all the supplies for my n64 project(screen, speakers, console, fan, casing, buttons, etc...) for about 3-4 months now i just never bought batteries or got the regulator.

eurddrue · Post by **eurddrue** » Tue Sep 23, 2008 9:05 pm

anotherperson wrote:Have you folks thought about undervolting the 3.3V line? With that newfangled PTH-something DC-DC converter that replaced the older TI one in late 2006, All you need to do is jimmy with the resistor until you find the lowest voltage you can run at. I think Marshall posted a datasheet for the onboard N64 RAM, I remember seeing the voltage spec as 3.0 - 3.3v. I guess the limiting factor would be the CPU. Still, a small decrease in voltage will mean a big drop in power consumption (and heat! two birds with one stone there)

Bacteria ran his n64 advance at 2.89v and he said that if it had dropped .02 more of a volt he wouldn't have been able to use it.

HazmatB · Post by **HazmatB** » Tue Sep 23, 2008 11:18 pm

Also, Bacteria was never able to get the expansion ram running on that voltage.

Rekarp · Post by **Rekarp** » Wed Sep 24, 2008 7:35 am

Your forgetting to add in efficiency to your equations. Power in doesn't equal power out.

The PTN78000w is about 86% efficient at dropping 7.4V to 3.3V

For me this is how I would hook it up

7.4V*.1A = .74W(On the 12 V line)
3.3V*1.5A = 5W (on the 3.3V line with expansion pack)
7.4V*400mA = 2.98W(modded ps1 screen)
2W (for a fan and other finishing touches and tolerances)

Now if the 12V line can except a range from 12V to 7.2V I assume correct? Then you would really have to just wire the 7.4V lithium batteries directly to that line and the PSone screen.

86% efficiency on the 3.3V line gives you 5.81W of power in. So in total you have 11.53W assuming the 2W includes the cartridge and controller.

4 Hours of power gives 46Wh. This battery is ideal.

http://www.batteryspace.com/index.asp?P ... rodID=2847

Has built in protection pcb and uses flat cells so you can squeeze them into thinner places.

collinE · Post by **collinE** » Wed Sep 24, 2008 11:33 am

collinE wrote:please put safety circuitry to your battery so that it doesn't esplode like gamelver's portable.

I really like this battery you found. I was reading a little more and it said this:

"Built-in IC chip will prevent battery pack from over charge and over discharge and prolongs battery life"

so maybe you wouldn't have to build safety circuitry. it also says it recommends charging with their "smart charger." I don't think this is needed, but seems like if you are going the extra mile you could buy that for $25 and be extra safe

vskid · Post by **vskid** » Wed Sep 24, 2008 2:37 pm

collinE wrote:so maybe you wouldn't have to build safety circuitry. it also says it recommends charging with their "smart charger." I don't think this is needed, but seems like if you are going the extra mile you could buy that for $25 and be extra safe

It is needed. The protection is just to keep the extreme from happening (fire/explosion). A smart charger charges the battery at the correct rate.

newguy101 · Post by **newguy101** » Fri Sep 26, 2008 9:49 pm

so if i decide to grab this battery and this charger i wouldn't have to add any extra protection circuits correct? i really dont like the idea of wiring my own li-ions, not very mistake friendly from what ive seen. and it would run my system for about 4-4.5 hrs i think.

Rekarp · Post by **Rekarp** » Sat Sep 27, 2008 1:34 am

newguy101 wrote:so if i decide to grab this battery and this charger i wouldn't have to add any extra protection circuits correct? i really dont like the idea of wiring my own li-ions, not very mistake friendly from what ive seen. and it would run my system for about 4-4.5 hrs i think.

Correct.