Topic: newby question, what do i need to know about mA or mAh? Also, powering a SonyD3?

[Big Muff]

Ok,
  So I'm getting used to the idea that I don't really know what i'm doing with re-chargable batteries, yet.
 
 I've got a Sony D3 That I've been using standard alkalines with for the past few years. (made a unit with a 6 D cell battery sled). Now I'd like to switch to something more economical/enviromentally friendly.

 I feel certain the 8.4v NiMH packs would be best for the Sony D3(9v). But what do I need to know about mA? or mAh?
 the wall adapter for the D3 says it puts out 9v @ 700mA.. Should i be looking for the highest possible mA or mAh available on NiMH batteries for longer life or am i missing something?
What to do? Thanks!
-Mike

[leegeddy]

Ok,
  So I'm getting used to the idea that I don't really know what i'm doing with re-chargable batteries, yet.
 
 I've got a Sony D3 That I've been using standard alkalines with for the past few years. (made a unit with a 6 D cell battery sled). Now I'd like to switch to something more economical/enviromentally friendly.

 I feel certain the 8.4v NiMH packs would be best for the Sony D3(9v). But what do I need to know about mA? or mAh?
 the wall adapter for the D3 says it puts out 9v @ 700mA.. Should i be looking for the highest possible mA or mAh available on NiMH batteries for longer life or am i missing something?
What to do? Thanks!
-Mike

mA = mili ampere or simply mili-amp (1/1,000th of an ampere).  this is the current draw (usage).  all electronic equipments need current to operate.

mAH = mili amp hour (mA multiplied by a unit of time in Hours).  this is a measure of power source's capacity yielded by its discharge curve/rate.  higher the number, the higher the battery's capacity

if you like your 6 D-cell sled, why not just use NiMH D cell batteries in replacement of the alkalines?  

marc

[caymanreview]

you can get 4000mah D cell batterys at a few online retailers, and 4000mah is higher mah than any rc packs out yet

[Brian Skalinder]

First, I'd check with a multimeter the actual voltage of the wall wart.  Just because it's rated at 9v doesn't mean that's what it's putting out.

Second, if it were me - and the wall wart voltage tests around 9-10v, I'd just go with 9.6v RC batteries.

FWIW, 6 D-cell rechargables will only get you to 7.2v, possibly not enough.

[Big Muff]

I thought about that.. There were a few of those RC packs for sale last week in the yard sale section.  I've got two that i use to power my MX-100 which needs 10v. So, freshly charged my Radio shack 9.6v 1600mAh batteries were putting out almost 11v!  I don't think I want to put that through my D3..
also, concerning rechargeable D cells.. they only put out 1.3v a piece. So it seems that a rechargable 8.4 might be the way to go..

Do i want a battery with the highest possible mAh? Does that just mean longer life? or would too much mAh possibly ruin my deck?

[dklein]

mAh reflects how long they'll go (3000 mAh implies 3000mA for one hour).  You can start playing around with the #s - like 1000mA for 3 hours, just be aware that it's not linear, meaning it won't work exactly as the math would suggest.  I believe that you get less performance from high current draw situations.

If your wall wart puts out 700mA (no need to measure it) you can safely say the DAT will not draw more than that and very likely a fair bit less because the power supplies are always over spec'd for the application.

Voltage is always changing.  
Alkalines start at 1.5 and work their way down over the life.  
NiMh batteries fully charge at just over 1.4 and hold a pretty steady voltage until about 1.2 - once it starts to drop below 1.2 the end comes quickly.  Note that this is one of the great features of NiMh - holding the voltage til the end.
NiCad batteries I'm not as familiar with.  I think they charge to about 1.25 volts.  I don't use NiCads since the NiMhs have come along.

I'm sure your DAT has an acceptable voltage range (in the manual or by experiment) that can work with a NiMh pack.

*wait* *googling*
http://www.solorb.com/dat-heads/digests/V2.800/D851#Msg1
Sounds like 6 - 9v is OK and current draw varies with voltage.  You can do the math to figure out what batteries you need for a given run time.  Only count on getting say, 80% of the rated capacity to be conservative.

Here - this guy did a NiMh pack with 5 cells (range 6-7 volts depending on charge state).
http://members.cox.net/barryklein/dat.htm

When looking at RC packs, you really  want NiMh, not NiCad.  You generally get twice the capacity from the same size pack and as tapers, we usually need the extra juice.