Discharging Mathematical Function of Rechargable Battery

[odense]

Hi all
I am working on aspects of energy for mobile robots so I would like to model a discharging or charging mathematical function of rechargable battery. Actually, as seen from datasheet of most rechargable battery, I can only find discharging diagram that may be probabilisticaly established. I have not yet found a mathematical function or way to model a discharging function of rechargable battery.
If any guy knows how to create a discharging function or any idea to do that, please help me.
Odense.

 

[Oznog]

All batteries (not just rechargeable) are effected by something called the Peukert Effect, which is a formula which tries to predict how a battery capacity is reduced at higher currents.
https://en.wikipedia.org/wiki/Peukert

Now understanding charge state vs voltage varies wildly depending on which type of battery is involved. Lead acid is easy, NiCd/NiMH is virtually impossible.

 

[odense]

All batteries (not just rechargeable) are effected by something called the Peukert Effect, which is a formula which tries to predict how a battery capacity is reduced at higher currents.
https://en.wikipedia.org/wiki/Peukert

Now understanding charge state vs voltage varies wildly depending on which type of battery is involved. Lead acid is easy, NiCd/NiMH is virtually impossible.

First, thank for quick reponse.
Anyway, I cound not find how voltage effects to capacity in Peukert's equation. It only obtains Time and Current and its derivation depending on time. We know that change of Capacity would be depended on two varying elements of Current & Voltage because the two elements will decide whether the electronic systems is still working or not.
Further, the Peukert' exponetial number is quite hard to determine, except using empiritical data. It seems to be impossible to do an algorithm to calculate for all cases.

Now I am coming back to some real examples we can see in the electronic world. Regarding to portable e-devices such as Laptop or Mobile phone, the question is how it can show us the current state of battery capacity on percent columm. What element is real-time measured and What equation is used to do the performance. To my best understanding, they can use Peukert's equation if the battery is Lithium because the Voltage would be stable at a constant value until current is dropped off. But What can we do if it is NiNM/NiCd since its voltage is not stable?

Please clear me up for the questions mentioned above.
Cheers,
Odense

 

[Oznog]

Now I am coming back to some real examples we can see in the electronic world. Regarding to portable e-devices such as Laptop or Mobile phone, the question is how it can show us the current state of battery capacity on percent columm. What element is real-time measured and What equation is used to do the performance. To my best understanding, they can use Peukert's equation if the battery is Lithium because the Voltage would be stable at a constant value until current is dropped off. But What can we do if it is NiNM/NiCd since its voltage is not stable?

Please clear me up for the questions mentioned above.
Cheers,
Odense

First you need to decide what battery technology you're asking about. Determining charge on lithium, lead-acid, Ni-MH, Ni-Cd are completely different things!

Peukert's is primarily for high current discharges. It has a lesser effect at slower discharges and is often neglected.

 

[odense]

My question mentioned an element Voltage because I think it is also important for electronic devices. Peukert's equation does not obtain the element. Why?
Actually, I wish to measure state of NiMH battery to generate state for my robots but I am not sure how to precisely obtain good measurement. Could you give me detail description of measuring Discharging state of Portable device usign Lithium or NiMH?
Thanks!