Battery Basics 101

Namuna said: Just to put some perspective on that; Charging a 150mAH battery at 5,000mA is like baking a cake (that's suggested at 375°) at 12,500°!!!

Oh, that sounds like my wife's rule of thumb.
Just add a little, it will make it bake faster.


-Nox

[novastar512]

I found an ac adapter which gives 800mA dc at 3 volts to a battery. Do you think that would work ok on a 150mah battery at 1.2 V?

Also, the adapter does not say it in mah, but rather just in mA, it is one of those radioa shack ones like this: LINK.

[nrmcj]

i think 800mA might be a little high... i think 300-400 is max.... for not blowing out the battery..

[SuperFly]

A friend and I built AC chargers. I first used an 800mah 3v adapter, but my friend had a 1000mah adapter, and we concluded that a double charge from the 1000mah adapter was better than the 800mah adapter. In fact, a double charge off of the 1000 was better than a triple charge on the 800. This is all with stock NiCads in the cars. Haven't noticed any ill effects on the batteries.

[nrmcj]

whoa... that's scary... lol, hmm i guess they Wont burn the batts out then

[novastar512]

What length of charge are you giving them? and how long are they running?

Because I was wondering if the 800ma adapter is not millamp hour. What's up with that? Is it like ma per second or instant?

[Namuna]

I can only imagine they didn't give AC Adapters the 'mAH' rating so as to keep folks from being confused...Even though that's what it means...

An 800mA AC Adapter, means it'll charge to 800mA in 1-hour

So just do the math if you want to know by minutes (800/60 = 13.33mA per minute)

[novastar512]

sweet, thanks. Stupid radio shack. Oh well, I think I have a few different adapters at home.

[SuperFly]

So Namuna, given your maH equation, would you conclude that a 3v/8oomAH adapter would need 11 minutes and 15 seconds to fully charge a 150mA NiMH battery?

[BabyKiller]

basicly a AA battery puts out 1250mah acording to your past (4xAA=5000mah) and considering the charger puts out 2500mah at 1.5 v and doing qfm's duel cell chager mod on the controller dosnt change **** but volts and you said volts dont really matter am i correct?

[hogjowlz]

1250mah means total capacity of the battery. it doesnt dump it all at once.

[BabyKiller]

errr could someone set this straight how much mah does a AA put out

[hogjowlz]

volts do matter somewhat(depending on internal resistance of the batteries. they have to hit a certain thresold(i belive roughly 1.5x of what you want to charge). thats why 3v doesnt charge 2.4v batteries.

[Namuna]

Originally posted by SuperFly
So Namuna, given your maH equation, would you conclude that a 3v/8oomAH adapter would need 11 minutes and 15 seconds to fully charge a 150mA NiMH battery?

The math is right, but charging batteries ain't an exact science...So add like 20% to your final time and I'd say you're fine with 13 to 14 minutes.

As far as the AA ratings...I haven't tested a single Alkaline AA, but I'd say 1250mA would be about right.

Let's use the classic Water to Electricity comparison, hopefully this helps with understanding what's going on...

If Electricty was water; Current (mA) would be the volume or amount of water flowing and Voltage would be the pressure or how fast it was flowing at.

For comparison sake, using an AC Adapter at 3v/500mA would be like getting shot by one of those big Super Soaker guns...Whereas using a 4xAA Alkaline battery pack would be like getting shot by a Firehose...They'll both get you wet, but one hurts less...ESPECIALLY over time.

So, the hog is right in saying that Voltage matters (somewhat)...But you need to be careful with the Current

[hogjowlz]

also i did a big battery no-no by adding a 3rd battery to my toys-r-us truck and its not the same capacity or brand as the other two. no problems so far so maybe its pretty close.