DanMan4142
Newly Enlightened
- Joined
- May 18, 2004
- Messages
- 59
just got me a multimeter and wondering if measuring the voltage is a good way to guage how much life is left in a batt? if not then what is the best way, if any?
thanks
thanks
is voltage a reliable test of battery condition?
- Thread starter DanMan4142
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billw
Enlightened
Re: is voltage a reliable test of battery conditio
No. First, you'd always want to measure a battery "under load",
and second, a lot of modern batteries have a very "flat" discharge
curve, so there's a large part of the battery lifetime that looks
"about" the same from a voltage perspective, even if you measure
under load. Ie You know that a NiMH battery reading 1.3V is just
out of the charger, and you know one reading 1.0V is almost dead,
but if it's reading 1.2V, it could be either almost fully charged
or almost fully dead.
BillW
No. First, you'd always want to measure a battery "under load",
and second, a lot of modern batteries have a very "flat" discharge
curve, so there's a large part of the battery lifetime that looks
"about" the same from a voltage perspective, even if you measure
under load. Ie You know that a NiMH battery reading 1.3V is just
out of the charger, and you know one reading 1.0V is almost dead,
but if it's reading 1.2V, it could be either almost fully charged
or almost fully dead.
BillW
MrAl
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
Hi there,
I have to agree with the other posts that voltage by itself
can only tell you if the cell is dead or maybe just charged
but not anything else.
Here's some tests you can perform:
http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Number=693437&Main=692533#Post693437
Take care,
Al
Hi there,
I have to agree with the other posts that voltage by itself
can only tell you if the cell is dead or maybe just charged
but not anything else.
Here's some tests you can perform:
http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Number=693437&Main=692533#Post693437
Take care,
Al
PEU
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
I guess there is tests, but you cannot be completelly sure, because if you test the cell for its full capacity, I mean in time and in mAh, you end up with an empty cell...
Kind of testing fireworks, first time they allways work /ubbthreads/images/graemlins/smile.gif
Pablo
I guess there is tests, but you cannot be completelly sure, because if you test the cell for its full capacity, I mean in time and in mAh, you end up with an empty cell...
Kind of testing fireworks, first time they allways work /ubbthreads/images/graemlins/smile.gif
Pablo
DanMan4142
Newly Enlightened
- Joined
- May 18, 2004
- Messages
- 59
Re: is voltage a reliable test of battery conditio
thanks for the help guys. I suspected that voltage may not be a good way but i wasnt sure.
thanks for the help guys. I suspected that voltage may not be a good way but i wasnt sure.
koala
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
Lithium Ion full capacity is 4.20v and safe minimum discharge voltage is around 3.20v
You know when it's really full and when it's really empty but you can't gauge the rest.
IMHO best measurement is an online device that measures the cell capacity constantly.
I hope I don't confuse you...
Lithium Ion full capacity is 4.20v and safe minimum discharge voltage is around 3.20v
You know when it's really full and when it's really empty but you can't gauge the rest.
IMHO best measurement is an online device that measures the cell capacity constantly.
I hope I don't confuse you...
wptski
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
[ QUOTE ]
koala said:
Lithium Ion full capacity is 4.20v and safe minimum discharge voltage is around 3.20v
You know when it's really full and when it's really empty but you can't gauge the rest.
IMHO best measurement is an online device that measures the cell capacity constantly.
I hope I don't confuse you...
[/ QUOTE ]
Nominal voltage of a single Li-Ion is either 3.6V or 3.7V. Your saying that you can only go .4-.5V below that?
I emailed Pila a while back and they stated that their cells cutoff around 2.5V and I found that to be pretty much true but they often go lower. I've seen some go as low as 2.2V.
[ QUOTE ]
koala said:
Lithium Ion full capacity is 4.20v and safe minimum discharge voltage is around 3.20v
You know when it's really full and when it's really empty but you can't gauge the rest.
IMHO best measurement is an online device that measures the cell capacity constantly.
I hope I don't confuse you...
[/ QUOTE ]
Nominal voltage of a single Li-Ion is either 3.6V or 3.7V. Your saying that you can only go .4-.5V below that?
I emailed Pila a while back and they stated that their cells cutoff around 2.5V and I found that to be pretty much true but they often go lower. I've seen some go as low as 2.2V.
koala
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
Two types of lithium ion electrode, coke and graphite. While the older graphite electrode has a higher end of discharge voltage(3.0v) the newer graphite2 has an end of discharge voltage 2.5v which is the same as coke electrode.
Most devices that employs lithium ion technology cuts off at 3.2v. The reason being there's a sharp voltage drop at the end of charge. Lithium ion has a pretty flat dischage curve so there's nothing to worry about.
Two types of lithium ion electrode, coke and graphite. While the older graphite electrode has a higher end of discharge voltage(3.0v) the newer graphite2 has an end of discharge voltage 2.5v which is the same as coke electrode.
Most devices that employs lithium ion technology cuts off at 3.2v. The reason being there's a sharp voltage drop at the end of charge. Lithium ion has a pretty flat dischage curve so there's nothing to worry about.
MrAl
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
Hello again,
Pablo:
In all my infinitesimally small wisdom i eloquently
overlooked the use of any battery that isn't an NiMH
type battery <font color="red"><red faced></font> /ubbthreads/images/graemlins/smile.gif
If you measure alky cells at roughly the same temperature
you can get SOME idea (not too exact) by using the
same cell manufacturers i bet. 1.65 is fresh, 1.1 is very
used, anything inbetween is roughly just that: inbetween,
but you might make some sense out of it in that one that
is 1.5 is still better than one that is 1.3 .........
although it's not fresh.
Hope this helps this time around :-)
Take care,
Al
Hello again,
Pablo:
In all my infinitesimally small wisdom i eloquently
overlooked the use of any battery that isn't an NiMH
type battery <font color="red"><red faced></font> /ubbthreads/images/graemlins/smile.gif
If you measure alky cells at roughly the same temperature
you can get SOME idea (not too exact) by using the
same cell manufacturers i bet. 1.65 is fresh, 1.1 is very
used, anything inbetween is roughly just that: inbetween,
but you might make some sense out of it in that one that
is 1.5 is still better than one that is 1.3 .........
although it's not fresh.
Hope this helps this time around :-)
Take care,
Al
Re: is voltage a reliable test of battery conditio
You can use voltage to determine the quantity of charge remaining in a cell provided you apply a load (to ensure you are not simply reading open circuit voltage) and know the characteristics of the type of cell. With NiCd / NiMh and alkalines there will be a fairly linear voltage decay as capacity is used up however it is important to remember that the discharge curves for the two will be different. That is why a battery level indicator on an appliance that uses its own built in rechargeable pack will accurately indicate charge level, yet on a digital camera may read a full charge that suddenly drops off without warning... the charge level indicator will be set up for disposables (alkalines or Zinc carbon/chloride).
With lead acid batteries you also need to apply a load to the battery to get an accurate reading, however in this instance such testing is usually used to determine the condition of the battery (refered to as drop-testing) and the load will usually be several amps or more.
You can use voltage to determine the quantity of charge remaining in a cell provided you apply a load (to ensure you are not simply reading open circuit voltage) and know the characteristics of the type of cell. With NiCd / NiMh and alkalines there will be a fairly linear voltage decay as capacity is used up however it is important to remember that the discharge curves for the two will be different. That is why a battery level indicator on an appliance that uses its own built in rechargeable pack will accurately indicate charge level, yet on a digital camera may read a full charge that suddenly drops off without warning... the charge level indicator will be set up for disposables (alkalines or Zinc carbon/chloride).
With lead acid batteries you also need to apply a load to the battery to get an accurate reading, however in this instance such testing is usually used to determine the condition of the battery (refered to as drop-testing) and the load will usually be several amps or more.
wptski
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
Don't Li-Ion chargers use constant current then constant voltage at the end of the cycle using 4.1V-4.2V as a cutoff? Doesn't this mean that as far as a Li-Ion goes, voltage may be a decent check of battery condition?
On lead acid batteries. There are conductance type checkers now that are more accurate and faster than doing a load test. Midtronics is the leader in this field. Lots of good reading at their site too!
Don't Li-Ion chargers use constant current then constant voltage at the end of the cycle using 4.1V-4.2V as a cutoff? Doesn't this mean that as far as a Li-Ion goes, voltage may be a decent check of battery condition?
On lead acid batteries. There are conductance type checkers now that are more accurate and faster than doing a load test. Midtronics is the leader in this field. Lots of good reading at their site too!
PeLu
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
[ QUOTE ]
wptski said:
Don't Li-Ion chargers use constant current then constant voltage at the end of the cycle using 4.1V-4.2V as a cutoff?
[/ QUOTE ]
No, depending on the start current and the differences in between cells, most of the charging may take part at constant 4.2V (or 4.1V). I do have cells which have less than 3% capcity charged when reaching the 4.2V.
The very first rechargeable Li cell, the Molicell almost two decades ago, had an almost linear discharge curve and you could tell the remaining capacity with better than 5% accuracy.
Nowadays it is usually said that cell volatge only gives a very corse estimation.
[ QUOTE ]
wptski said:
Don't Li-Ion chargers use constant current then constant voltage at the end of the cycle using 4.1V-4.2V as a cutoff?
[/ QUOTE ]
No, depending on the start current and the differences in between cells, most of the charging may take part at constant 4.2V (or 4.1V). I do have cells which have less than 3% capcity charged when reaching the 4.2V.
The very first rechargeable Li cell, the Molicell almost two decades ago, had an almost linear discharge curve and you could tell the remaining capacity with better than 5% accuracy.
Nowadays it is usually said that cell volatge only gives a very corse estimation.
wptski
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
I hope that I still have links to the pages at home but I've read that charging to 4.2V as compared to 4.1V means a good increase in capacity.
One of the changes made in the JSB 123 Li-Ion charger from the earlier version was to charge to 4.2V.
That same change was also made in the MAHA MH-C777PLUS-II over the PLUS model.
In watching my Triton charger, it starts charging at a lower voltage than 4.2V and doesn't reach that value till towards the end as current drops. I'll look at the manual tonight, as it gives a explaination of the cycle.
I hope that I still have links to the pages at home but I've read that charging to 4.2V as compared to 4.1V means a good increase in capacity.
One of the changes made in the JSB 123 Li-Ion charger from the earlier version was to charge to 4.2V.
That same change was also made in the MAHA MH-C777PLUS-II over the PLUS model.
In watching my Triton charger, it starts charging at a lower voltage than 4.2V and doesn't reach that value till towards the end as current drops. I'll look at the manual tonight, as it gives a explaination of the cycle.
jayflash
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
A heavily loaded alkaline cell will sink around 6 - 8 amps. As the cell is used the available current goes lower - eventually to an amp or two. At that point they may still show 1.1 - 1.3 volts but can't power a heavy (1+ amp) load.
With rechargeable cells it's more of a guess. They, too, should provide at least 8 or more amps into a short but they can do that right up until they die, so it's not a good indicator. A NiCd or NiMh showing less than 1.25 volts may need recharging.
A heavily loaded alkaline cell will sink around 6 - 8 amps. As the cell is used the available current goes lower - eventually to an amp or two. At that point they may still show 1.1 - 1.3 volts but can't power a heavy (1+ amp) load.
With rechargeable cells it's more of a guess. They, too, should provide at least 8 or more amps into a short but they can do that right up until they die, so it's not a good indicator. A NiCd or NiMh showing less than 1.25 volts may need recharging.
wptski
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
My memory was correct! The Triton uses constant current during the initial stages of fast charge till the battery reaches approx. 4.0V per cell and then switches to constant voltage at which time the battery dictates the current it wants. When the current drops below 100ma, charging is halted.
Here's a good link about batteries/charging: Here
My memory was correct! The Triton uses constant current during the initial stages of fast charge till the battery reaches approx. 4.0V per cell and then switches to constant voltage at which time the battery dictates the current it wants. When the current drops below 100ma, charging is halted.
Here's a good link about batteries/charging: Here
brightnorm
Flashaholic
- Joined
- Oct 13, 2001
- Messages
- 9,027
Re: is voltage a reliable test of battery conditio
[ QUOTE ]
wptski said:
...I've read that charging to 4.2V as compared to 4.1V means a good increase in capacity....
[/ QUOTE ]
It's a bit puzzling that the PILA chargers usually charge to only 3.8-3.9+ in the experience of many users including myself. No one seems to know why and I find it quite frustrating.
Brightnorm
[ QUOTE ]
wptski said:
...I've read that charging to 4.2V as compared to 4.1V means a good increase in capacity....
[/ QUOTE ]
It's a bit puzzling that the PILA chargers usually charge to only 3.8-3.9+ in the experience of many users including myself. No one seems to know why and I find it quite frustrating.
Brightnorm
Billson
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
Aren't the Pila chargers dumb chargers so it means the protection circuit in the cell is the one determining when to terminate charging.
Aren't the Pila chargers dumb chargers so it means the protection circuit in the cell is the one determining when to terminate charging.
brightnorm
Flashaholic
- Joined
- Oct 13, 2001
- Messages
- 9,027
Re: is voltage a reliable test of battery conditio
The indicator lights turn from red to green when charged so they must be smart, but there are many variations on smart.
I don't have the tech knowledge to answer more than that.
Brightnorm
The indicator lights turn from red to green when charged so they must be smart, but there are many variations on smart.
I don't have the tech knowledge to answer more than that.
Brightnorm
wptski
Flashlight Enthusiast
Re: is voltage a reliable test of battery conditio
[ QUOTE ]
brightnorm said:
[ QUOTE ]
wptski said:
...I've read that charging to 4.2V as compared to 4.1V means a good increase in capacity....
[/ QUOTE ]
It's a bit puzzling that the PILA chargers usually charge to only 3.8-3.9+ in the experience of many users including myself. No one seems to know why and I find it quite frustrating.
Brightnorm
[/ QUOTE ]
Like Billson stated, I thought that the cell determines the charging cutoff voltage.
I use a Triton charger on my Pila cells and they charge to 4.1V-4.2V. I've used a MAHA MH-C777PLUS and PLUS-II on Pila cells and at times, it may depend on how run down they are, the MAHA will take forever. I've just stopped it. This never happened with the Triton though.
If you checked that link I provided, it stated at 3.8V, it's approx. 50% charge. That's not very good! /ubbthreads/images/graemlins/thumbsdown.gif
The MAHA chargers charged to 4.1V-4.2V even when they hung up too!
[ QUOTE ]
brightnorm said:
[ QUOTE ]
wptski said:
...I've read that charging to 4.2V as compared to 4.1V means a good increase in capacity....
[/ QUOTE ]
It's a bit puzzling that the PILA chargers usually charge to only 3.8-3.9+ in the experience of many users including myself. No one seems to know why and I find it quite frustrating.
Brightnorm
[/ QUOTE ]
Like Billson stated, I thought that the cell determines the charging cutoff voltage.
I use a Triton charger on my Pila cells and they charge to 4.1V-4.2V. I've used a MAHA MH-C777PLUS and PLUS-II on Pila cells and at times, it may depend on how run down they are, the MAHA will take forever. I've just stopped it. This never happened with the Triton though.
If you checked that link I provided, it stated at 3.8V, it's approx. 50% charge. That's not very good! /ubbthreads/images/graemlins/thumbsdown.gif
The MAHA chargers charged to 4.1V-4.2V even when they hung up too!
