Moteur de recherche de fiches techniques de composants électroniques
  French  ▼

Delete All
ON OFF
ALLDATASHEET.FR

X  

Preview PDF Download HTML

BQ78412 Fiches technique(PDF) 7 Page - Texas Instruments

Click here to check the latest version.
No de pièce BQ78412
Description  Pb-Acid Battery State-of-Charge Indicator With Run-Time Display
Download  36 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Fabricant  TI [Texas Instruments]
Site Internet  http://www.ti.com
Logo TI - Texas Instruments

BQ78412 Fiches technique(HTML) 7 Page - Texas Instruments

Back Button BQ78412 Datasheet HTML 3Page - Texas Instruments BQ78412 Datasheet HTML 4Page - Texas Instruments BQ78412 Datasheet HTML 5Page - Texas Instruments BQ78412 Datasheet HTML 6Page - Texas Instruments BQ78412 Datasheet HTML 7Page - Texas Instruments BQ78412 Datasheet HTML 8Page - Texas Instruments BQ78412 Datasheet HTML 9Page - Texas Instruments BQ78412 Datasheet HTML 10Page - Texas Instruments BQ78412 Datasheet HTML 11Page - Texas Instruments Next Button
Zoom Inzoom in Zoom Outzoom out
 7 / 36 page
background image
=
Discharge Learn Accumulator
FCC
Derating
bq78412
www.ti.com
SLUSAA0 – OCTOBER 2010
Gas Gauging After a Reset
During normal operation, the last learned full charge capacity (FCC), elapsed time and other important variables
are stored in permanent memory. If, for some reason the battery discharges to the point where there is no longer
sufficient voltage for the bq78412 to operate, it shuts down. Under such conditions, when the device powers up,
these variables are restored and battery is assumed to be at 50% relative SoC. If a charge current is present, the
device begins to measure the accumulated charge and time. Charging proceeds as normal with the appropriate
end-of-charge detection criteria. If the bq78412 powers up and there is no current, the device goes into idle state
followed by sleep state until a current is detected.
Battery Capacity Update
The bq78412 has two mechanisms for updating the battery capacity as the battery ages. (Note that the initial
capacity programmed into the bq78412 could be in error due to manufacturing tolerances or formation
procedures. This translates to a gas gauging error until the battery capacity is accurately learned.)
Both the Learned Capacity method and Age-Based Capacity method operate independently and both may be
enabled or disabled separately in order to maintain the correct measure of capacity of the battery over a variety
of operating conditions, but it is suggested that both be enabled for optimal performance.
Learned Capacity Method
When DevConfig1[14] is set to "1", the bq78412 opportunistically learns the full charge capacity (FCC) of the
battery based on a qualified discharge. A complete discharge from fully charged to fully discharged with no
charging events raising the remaining state of charge (SoC) above 80% is considered qualified. An internal state
variable qualified discharge (QD) is used for maintaining the status of discharge qualification. QD is initially
disabled. When the battery has reached the fully charged state, QD is set to enabled and discharge learn
accumulator is cleared to zero. When a discharge begins, QD is set to active. While QD is active, all passed
charge (positive or negative) is accumulated in the discharge learn accumulator. If at any time (while QD is in an
active state) a charging event raises SoC above 80%, QD is set to disabled and the discharge learn accumulator
is ignored. If the battery reaches the fully discharged state and QD is still active, the algorithm learns FCC based
on the discharge learn accumulator and the current load de-rating using Equation 1.
where
Derating is the capacity derating fraction as a function of load current
(1)
Age-Based Capacity Method
The counter for the elapsed time starts when the device is activated.
When DevConfig1[15] is set to "1" (non-default), the bq78412 updates the FCC based on elapsed time and an
aging algorithm with manufacturer defined parameters. The bq78412 decrements the FCC by 0.100 Ah every
CapDerateL days until DerateChange days have elapsed, after which the FCC decrements by the same amount
every CapDerateH days.
In this way the FCC is regularly de-rated (decremented) at regular intervals independently of the learned capacity
method.
The values for CapDerateL, DerateChange, and CapDerateH must be carefully chosen to implement an
appropriate age-based capacity decrease formula.
For example: Assuming a 100Ah battery (when new) and a 3%/year capacity fade for the first 3 years and a
4%/year fade afterwards, the parameters might be set as follows:
3% of 100Ah = 3Ah decrease in one year
3Ah decrease in 0.1 Ah steps = 30 separate steps over 365 days
365 days / 30 decrement steps = one decrement step every 12.1 days
So CapDerateL = 12
4% of 100Ah = 4Ah decrease in one year
Copyright © 2010, Texas Instruments Incorporated
Submit Documentation Feedback
7
Product Folder Link(s): bq78412


Html Pages

1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36 


Fiches technique Télécharger

Go To PDF Page


Lien URL




Politique de confidentialité
ALLDATASHEET.FR
ALLDATASHEET vous a-t-il été utile ?  [ DONATE ] 

À propos de Alldatasheet   |   Publicité   |   Contactez-nous   |   Politique de confidentialité   |   Echange de liens   |   Fabricants
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn