Stupid questions...

[AndreasB]

As the title says I got a lot of stupid noob-questions.

Here's one:
1) How many mAh will an ordinary AA Duracell give me? :huh2:


AndreasB

 

[SilverFox]

Hello Andreas,

Welcome to CPF.

Capacity delivered is directly related to the load put on the cell. At a 500 mA load, the Duracell Copper Top Alkaline cells were coming it at around 1600 mAh.

Tom

 

[Doug S]

As Tom says above it various with load. It also varies with temperature, assumed minimum cutoff voltage, past discharge history, e.g. is load continuous or intermittant. Here is a link to the lastest Duracell AA datasheet. It should give you a bit of insight into some of these factors.
http://www.duracell.com/oem/Pdf/new/MN1500_US_CT.pdf

As the title says I got a lot of stupid noob-questions.

Here's one:
1) How many mAh will an ordinary AA Duracell give me? :huh2:


AndreasB

 

[AndreasB]

Ah ok. Thank for the replies.

So at most (all) loads my Sanyo 2700's will last longer than a common Duracell. I would have guessed it to be the other way around. :rock:

So as far as I can gather from various post here the common load to test the capasity of batteries is 500mAh ?

I there any "optimal load" or is it the lower load the more Ah'ers you'll get ?

AndreasB

 

[LightBright]

That's correct - the lower the load on the battery the more amp-hours you'll get.

For example, an Energizer D cell is rated at about 20 AHrs (WOW) - but that's at 25 milliamps, a pathetic output. At 500 ma it drops to about 10 AmpHours, so about a half watt for 10 hours.

A 500 milliamp (1/2 an AMP) load would be typical for a higher wattage LED flashlight.

 

[SilverFox]

Hello Andreas,

Here is some test data on Alkaline cells, and here is some data on NiMh cells.

Tom

 

[AndreasB]

Thanks for all your replies.

I got some other stupid questions:

Got this Li-on charger and protected LIR123A cells today:

http://www.qualitychinagoods.com/dsdreg-2bay-charger-plus-750mah-lir123a-protected-p-339.html

The package didn't contain a manual, so I'm gonna write the seller and have him mail me one.

When using protected cell in a "smart-charger" like this is there still any danger of explosions or other problems when charging and discharging?

Can I use protected Li-on cell in my DIY-lights without taking any extra safety precautions ?

How can I tell if the cells are really protected cells? Aren't there supposed to be some "venting-holes" in the ends? My batteries haven't got any holes.

Right now I'm using a batterypack of 10 NiMH AA's. Could I make a similar batterypack with say 4 protected 18650's ? And if so is there a place where I can get a batteryholder for such a pack?

Once again I'm sorry for all my tupid noob questions.

Thanks in advance
AndreasB

 

[LightBright]

Be careful with the Input Voltages to your flashlight - 18650's do not have the same range of output voltage as the NiMh. You should have a voltmeter for checking these packs.

 

[AndreasB]

One more stupid question to bump the other ones:

What will determine the current when directdriving a Cree?

Just tried to directdrive a Cree with 3 AAs and 3 AAA.
Using the AAs the current was around 460 mA. Using the AAAs it was around 380 mA.

Using I = R * U (or whatever way around it is) the current should depend on the resistance of the Cree. But then the current should be the same using either AAs or AAAs (the voltage is the same).

Hope anyone is up for education a noob a little.

AndreasB

 

[carbine15]

AAA sags under load more than the AA batteries becasue of their higher internal resistance? Try 9 AAA batteries 3 x 2 series / parallel and you'll see what I mean or better yet, 3 D cell batteries.

 

[LightBright]

When driving any Light Emitting Diode, the VOLTAGE across the LED (and the internal resistance of the power source) will determine the current running through the LED.

LED's do NOT have a linear response to voltage either, it's a curved line (on a graph of Voltage/Current). Take a look at the Datasheet for a Cree XR-E.

Every battery or voltage source has an "internal resistance". Yes the AAA's have a higher internal resistance than AA's.

and I = V/R where I = amps, V = volts and R = resistor value

 

[AndreasB]

Thanks for the replies.

In danish Ohms law (that whats its called here) is I = U / R
where U is the voltage.

AndreasB