Getting More Out of Your Batteries Idea

[Erlex]

So I was thinking of a way to extend the play time you can get out of your batteries and I had an idea. I am not sure if this is a common problem or if anyone has thought of this before, but when my battery pack gets down to about 6.8V the image on my PSone screen gets so distorted that it becomes unplayable. Now my idea is to use a boost DC-DC converter to hold the voltage at a near steady 7.4V to squeeze extra usable time out of one charge. This is a similar circuit to the one that most everyone is familiar, which is the switching regulator used on N64 portables to drop the voltage to 3.3V. This one just works in reverse.

I made this horribly crude graph in paint to try and illustrate my point.



Notice that the overall lifespan of one charge is shorter with the converter on it due to it needing to pull more power as the voltage drops (and the effiency of the converter comes into play aswell); BUT in theory, the playable time on one charge should be longer. Also, a reminder, this is a rough graph. The time scale on the x-axis is relative and loosely based on percents. Its the concept I am trying to convey.

So is there anything fundamentally wrong with this that I am overlooking? Or will this work?

[Rekarp]

No reason is shouldn't work but when you do boost the voltage it's going to draw lots more amperage so your going to get negative returns at an almost exponential rate. You might be able to squeeze 15 minutes at max. I would be loved to be proven wrong however.

I say go for it.

[Erlex]

You might be able to squeeze 15 minutes at max.

Hmmmm. I was worried about that. But yeah, ill give it a shot anyway. At least I wasn't met with...

No, that will explode.

Or something like that.

[Rekarp]

You might be able to squeeze 15 minutes at max.

Hmmmm. I was worried about that. But yeah, ill give it a shot anyway. At least I wasn't met with...

No, that will explode.

Or something like that.

[cint]

mmm..useful info...

[timmeh87]

Lithium batteries shouldnt ever go below 3 volts per cell.

If you converter is only 90% efficient (this is realistic. could even be less), then you are going to have to be able to get enough power back to make up for the 10% you lost before the situation pays back in any way.

If you are already getting close to your "theoretical" life then there's probably no point.

For example, I can tell you that there is very little power in a cell between 3.3 and 3.0v. Check the curves
http://www.gmbattery.com/upload/editorf ... 4_5817.jpg" onclick="window.open(this.href);return false;

So... figure it out.

[Rekarp]

Ti boosters run roughly 85% to 90%. Again tho I see very little performance gain from this.

[Erlex]

Alright. Thanks for the input guys.
Looking at that graph, there looks like there might even be a possibility that it may hurt the battery life some. I don't know, I still may try though. I would prefer the whole system to shut off rather than just having to stop playing due to not being able to get video after a while.

[Mario]

Maybe try using a low-battery indicator that actually turns on the booster. Then it would really only be running when you need it.

[timmeh87]

Do you really want to cycle your batteries that deep? Im sure they would be happier if you didnt.