Battery meter.

ShockSlayer · Post by **ShockSlayer** » Mon Mar 05, 2007 8:45 am

Well, In my portable, I'd like to be able to know when my battery is low. Is there some way I can easily install some type of meter or gauge to tell me when its low?

Battery specs:

3300 mah ni-mh rc battery

Powering:
N64 12v line
3.3 linear regualtor to n64 3.3v line
3 Led modded psoscreen
One 12v fan

SS

timmeh87 · Post by **timmeh87** » Mon Mar 05, 2007 10:03 am

if you just want a red light or something to come on at a certain voltage, codemaster had an opamp circuit he posted a while back.

they also sell analog vu-meter type chips, that light up a row of leds depending on the input voltage. i got one once and never used it...

the problem is that the voltage on nimhs is pretty constant, you wont know its dying till its already dead.

ShockSlayer · Post by **ShockSlayer** » Mon Mar 05, 2007 11:36 am

Well, Doesn't it steadily lose mah as it goes down? I don't know to much about powering stuff.

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vskid · Post by **vskid** » Mon Mar 05, 2007 4:48 pm

ShockSlayer wrote:Well, Doesn't it steadily lose mah as it goes down? I don't know to much about powering stuff.

SS

Yes, the drain is more or less constant, unless you turn the volume up or down or something. You can't really measure how many mAh's are left unless you check the voltage and compare it to the voltage drop chart. Maybe you could set something up to measure how many amps have been used.

ShockSlayer · Post by **ShockSlayer** » Mon Mar 05, 2007 4:58 pm

Can any mathmatician here tell me how much my current(kinda) setup wouild take?

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Kurt_ · Post by **Kurt_** » Mon Mar 05, 2007 5:45 pm

Well you can try this:

http://www.maxim-ic.com/appnotes.cfm/an_pk/3585

or this, but change the LED's a bit:

http://www.batteryspace.com/index.asp?P ... rodID=2775

timmeh87 · Post by **timmeh87** » Mon Mar 05, 2007 5:54 pm

i tried to use a ds2720 or something like that to make a battery fuel gauge, i failed pretty bad.