Battery Voltage and Remaining Capacity Reference Thread

[kosPap]

hi all!

I admit this thread title is ambitius and maybe misleading but I am starting this thread as a reference point to any applicable "rules" and tips regarding the realtionship of Measured Battery Voltage and Remaining capacity.

For exmple I reall these from other members writings (if yuo are reading please raise your ahnd to receive proper credit)

Rechargable Li-IOn Voltage & Capacity
4.2V = Full
4.1V = 90%
4.0V = 80%
3.9V = 60%
3.8V = 40%
3.7V = 20%
3.6V = Empty
(voltage is measured open circuit, the DMM leads on the poles with no load on the battery)

at this point battery state at other voltages is needed (ie 2.5 volts = through away NOW)

Ni-Mh Voltage & Capacity
closed circuit (1-10 Ohm resistor)
1.4 V = Full
1.16 V = Empty, Recharge

Alkaline Voltage & Capacity
closed circuit (1-10 Ohm resistor)
1.6 V = Full
1.3 V = Empty ????

AA & AAA Lithium Voltage & Capacity
1.8 V = Full ????
V = Empty ????

CR123 & CR2 Lithium Voltage & Capacity
3.2 V = Full
V = Empty ????

So here it goes....Please feel free to add your input and I will integrated in this post...

enjoy, Kostas

 

[kosPap]

anyone?

 

[Mr Happy]

anyone?

An alkaline cell still has useful charge down to less than 1.0 V. It may be considered empty at 0.9 V, although some devices won't go that low.

A lithium ion cell reaches the knee of its discharge curve at about 3.3 V, though many may prefer to stop and recharge before that point.

 

[kosPap]

thanks....

now i need info on the CR123 (I believe it is 2.6 volts poractically for incandescent application)
And on the AA & AAA lithiums

and a general confirmtio of the info in my first post...

TNX, KOstas

 

[spencer]

I was actually looking for something like this. Thank you very much.:twothumbs

 

[spencer]

Assuming a 0.3C discharge on a large lithium ion cell, what would be the voltages at a given capacity? (say like 5%, 10%, 15%, and 20%)

 

[rmteo]

Battery voltage is a poor (and unreliable) indication of the state of charge - no matter what the chemistry. There are many fuel gauge IC's made that are designed for this specific purpose. In particular, a company called Benchmarq (acquired by Unitrode, then acquired by TI) specialises in this type of IC. They are used in laptops, cellphones, portable media/music players, etc., and are the only reliable way of determing charge state. Here is a list of 59 of these devices:
http://focus.ti.com/paramsearch/doc...log&familyId=412&uiTemplateId=NODE_STRY_PGE_T

 

[EngrPaul]

Keep in mind cheap DMM's are typically off by 0.1 or 0.2 V

 

[spencer]

Battery voltage is a poor (and unreliable) indication of the state of charge - no matter what the chemistry. There are many fuel gauge IC's made that are designed for this specific purpose. In particular, a company called Benchmarq (acquired by Unitrode, then acquired by TI) specialises in this type of IC. They are used in laptops, cellphones, portable media/music players, etc., and are the only reliable way of determing charge state. Here is a list of 59 of these devices:
http://focus.ti.com/paramsearch/doc...log&familyId=412&uiTemplateId=NODE_STRY_PGE_T

Looks very interesting. For my application I would need it to monitor 2 cells in series (7.4v) and then get it to light an LED. Looking at them I see they only do one cell (unless I'm missing something). I am thinking of making the first circuit on this site in my maglight and was wondering about what voltage I needed.

 

[Oddjob]

IIRC Silverfox did some testing on CR123's and found that voltage was not an accurate way to test its remaining capacity. I hope Tom or someone else can confirm this.

 

[VidPro]

Spencer

there was a device called BattSignal, it would beep for how many batteries were in series, then beep for how full it was, and holler a lot if the battery was going "critical".
it was for RC airplanes, weighed nothing, very tiny.
i couldnt find the link for that one , but tracking for it, i found another one.

http://www.customidea.com/shop/product_info.php?products_id=102&osCsid=vik5tpvdhecqqfh6inmgktm5i4


i bought a few,of the original battsignal but they only work for 2Xli-ion and more.

there are probably other similar devices for the same thing.