Other Batteries for Power?

[Armada]

I've been brushing up on my N64 modding knowledge in order to start making my own. My question now is about power. So far I've read Li-ion cels are probably the best, and are standard. Since I can't seem to get my hands on any at the moment, I'm wondering how plausible it is to use AA batteries (1.2V). I'd like to known the disadvantages to using them (that aren't obvious) and if it's even possible. I have a few more specific questions as well:

1. Could I use 3 AA batteries (~3.6V) for the 3.3V source? If not, what issues would I encounter?
2. Will I still need to use a DC-DC step-down converter?
3. Could I use 2 different "sources" for the 12V and 3.3V power?
4. What would the approximate amount be? My minimum estimate is 6 to reach 7.2V. But since I plan to split them, maybe 9?

Anyway, thank you in advance for any answers.

[eurddrue]

aa's suck.

yes you still need a stepdown or it would fry your board

you could use 2 diff sources, but that would be kinda hard.

it would eat up double a's faster than the gamegear, you need some liions if you want decent battery life.

[thewise1]

I made a temporary power supply out of 5 rechargeable AA's at 1.2 volts just to test everything and make sure it's working. .1 Volt is dropped every 20 seconds, they suck, it won't even go a minute before the screen starts going down from low power.

[vskid]

1. Could I use 3 AA batteries (~3.6V) for the 3.3V source? If not, what issues would I encounter?
2. Will I still need to use a DC-DC step-down converter?
3. Could I use 2 different "sources" for the 12V and 3.3V power?
4. What would the approximate amount be? My minimum estimate is 6 to reach 7.2V. But since I plan to split them, maybe 9?

1. You could, but fully charged they would be about 4v all together, which would probably kill the N64. And the 3.3v line uses a lot more power than the 12v, so those batteries would die way before the others.
2. No, but see 1.
3. Yes, thats pretty much what you're doing with the DC-DC converter.
4. AAs just don't have the guts to power a N64p for a decent amount of time, if at all. You need to use at least sub-C batteries if you're using NiMH.

[Armada]

Well, what about the mAh. How would it effect the times. I was planning to use 2000 mAh. And by my calculations, I could get about 1 hrs 20 min into the 3.3V source (of course, that's in my homemade battery life calculator). However, that does squat when it fries the board. :\

How about a camcorder battery? Those are already 7.2V. I'd still need the stepdown converter either way. I know there are links around to one, but can anyone pass it on in this topic?

[jjhammerstein]

http://www.ebuybatteries.com/product/ca ... BP-911.htm

[Armada]

http://www.ebuybatteries.com/product/ca ... BP-911.htm

Thanks much for that! Since that's 7.4V, that'd work, correct? Around 10 hours too according to my calculator. Can't say it's the world's most accurate measurement.

[eurddrue]

...no. you would get around 3 hours.

[Armada]

...no. you would get around 3 hours.

That's right, I made a typo in my program. ^_^;;

[newguy24]

AA batteries will work if you use NiMH batteries due to there large capacity. Use one single source with a DC-DC step-down converter to run it, i do not recommend splitting the 3.3V line into a separate source as a DC-DC step-down converter will be required either way. I recommend either 6 in series for shorter life or 2 sets of 6 in parallel for longer life. (also there are higher capacity Nimh AA's that go up to 2800 mAh rather than 2000mAh)

I made a temporary power supply out of 5 rechargeable AA's at 1.2 volts just to test everything and make sure it's working. .1 Volt is dropped every 20 seconds, they suck, it won't even go a minute before the screen starts going down from low power.

What type of rechargeables did you use? Anything other then NimH or lithium ion do not provide very much power. And only 5 batteries?!? that's only 6 volts!

A note on NiMH AA batteries, they start charge at around 1.5Volts when fully charged (usually a little less). If you were to have 2000mAh = 2Ah batteries running in a n64 the speed at which the voltage drops is proportional to the rate at which power is removed from the battery. Example, an led modded N64 pulls approximately 1.76Amps of power (pulled that from a page somewhere) that means a battery would be discharging at 1.76/2 = .88 or 88% of the current rating. The lower that percentage is the slower the voltage will drop. In this case, all AA's (this will depend on the battery brand too) would discharge very quickly at first. Within 5-10% capacity usage all fully charged NimH AA's drop rapidly to around 1.3Volts. They then slowly drop to 1.2V, and in this case 1.2V will be reached when approximately a little over 85% of the battery discharges. So when about 1.7Amps have been used, the battery voltage will be around 1.2V and then will start dropping off much more rapidly. Please note that all AA rechargeable batteries will have an extremely fast voltage drop of .2-.3V initially before slowing for usage. So it pays to have higher capacity amps in batteries, as for instance if you hooked up the batteries in two sets in parallel and get 4000mAh. The discharge rate now will reduce to 1.76/4 = .44 or 44% of the current rating. Now the voltage will not drop off below 1.2Volts until almost the end of the battery capacity. All manufacturers have a discharge rate chart for there batteries which show voltage drop rate as a % of the rate of discharge capacity. NiMH do not store as much power per volume as lithium ion batteries but they are a good source for power if used properly. They are also much easier to install as a smart charger is all that is needed to charge the batteries and no built in protection circuit is required.

Depending on what battery mAh were used by thewise1, if that % of the power current becomes too great, the battery will lose voltage like it's its job. Also due to the high initial voltage (1.5*5Volts = 7.5Volts for all 5 batteries intitially fully charged) The N64 should run fine while the voltage will be dropping very quickly to 6.5Volts before leveling out (within the first few minutes) which is getting very low to even run a N64. This could have been your problem thewise1 with the voltage dropping very quickly and causing the screen to not be able to be powered.

My current N64p build will have 2 sets in parallel of 6-2500mAh Nimh AA's, This will give 5Ah of power, with a voltage range of 9V to a little less then 7.2V over the use of the system. NiMH batteries will work fine. If I run into problems with them I will keep everyone posted in my build thread. Thus far there have been none during testing. (12 AA's sounds like a lot, but it actually takes up very little space).

Hope this helps

[Life of Brian]

I really don't recommend AA's for just about any portable. They simply aren't able to handle the load for very long compared to larger cells. I used AA's for my first SNES portable, and even though I was using 2500mAh rechargeable Energizer batteries, I could barely get about an hour before my system started running out of power. That was with an LED modded screen and an SNES mini, so it's not like it was particularly power hungry. Larger cell batteries such as sub-C cell RC car batteries with an almost identical capacity ran the system for almost two hours longer.

[newguy24]

.... even though I was using 2500mAh rechargeable Energizer batteries, I could barely get about an hour before my system started running out of power.

wow that is not long at all. my info is just going off of the nimh battery technology... I'll have more concrete battery life testing when i finish up my n64p over the next 2 weeks. I'll post back when i do.

[timmeh87]

If you drain the batteries so fast that they heat up inside it kind of wastes a lot of power and makes the voltage go down.