BQ2060 Remaining Capacity

Vikas Saraswat

Other Parts Discussed in Thread: BQ2060A, BQ2060

Hi all,

I am working on a project where i need to monitor the battery strength of Li-ION having the capacity of 7200 mv with 6600 mAh. I have used bq2060A and configured the external EERPOM with the required data.

In the EERPOM i have written my Full Charge Capacity with the value of 0x1c20 = 7200mv. When i kept the battery for charging, simultaneoulsy i read register which give the battery information through UART, I found the Remaining Capacity increases at a regular interval.

But once it reached the value of 0x1c20 (after about 2 hours), I again rolls over to 0 and again start to increase ??!!!. I think, that this should not happend since the Full capacity which i have stored in the EERPOM is 0x1c20 and the battery Capacity is 7200 mv. Pleae let me know why it has rolled over and where is my error.

Also every time when i read the bq2060 internal register the MAX ERROR was comming 0x0064, How to decrease this??

I am using an external charger to charge the battery which will be kept continously ON.

Regards

Vikas

over 15 years ago

0 Doug Williams4811 over 15 years ago

TI__Expert 6470 points

Not sure whats going on here, but there seems to be a misunderstanding. Full Charge Capacity is given in units of mAh, not mV. If your battery is 6600 mAh, then that would be a good starting place for FCC and Design Capacity. Remaining capacity should not roll over, so I suspect some kind of communication issue with the gauge.

Reducing the initial MAX ERROR requires a valid learning cycle.

0 Vikas Saraswat over 15 years ago in reply to Doug Williams4811

Prodigy 110 points

Dear Sir,

Sorry, its my mistake in the previous thread. I have already mentioned FCC in the mah factor.

Also i would like to ask that, what would happend if it write the FCC to the value less than the actual capacity of the Battery Pack?? Whether the RC will roll over in this case or will stay at the max value of the FCC??

Here is the table of the EEPROM data which i have written.

Address	Function	Value in decimal	Value in hex
00	Check Byte	15487	3C 7F
02	Remaining Time alarm	10 min	00 0a
04	Remaining Capacity Alarm	660 mah = 0x294	02 94
08	Misc	0	00
0a	Charging Voltage	7200 mv = 1C20	1C 20
12	Design Voltage	7200 = 1c20	1c20
14	Specification Information	0x0021	00 21
1a	Fast Charging Current	1000 ma	03 E8
1C	Maintenance Charging Current	0	00 00
1E	Pre Charge Current	100 ma	00 64
2e	Max Overcharge	6600 mah	19C8
38	Last Measured Discharge	6600 mah	19 C6
3a	Pack Capacity	6600 mah	19 C8
3c	Cycle Count threshold	65535 - 5280 mah =60255	EB 5F
3e	Reserved	0	00
3f	Pack Configuration	180	b4
40	Device Chemistry	4	04
41	Character 1	L	4C
42	Character 2	I	49
43	Character 3	0	4f
44	Character 4	N	4e
46	Overload Current	6000 ma	17 70
48	Over voltage Margin	400 mv	19
49	Over current Margin	300 ma	12
4a	Cell Under / Over Voltage	118	76
4b	Fast charging Termination	100 %	9C
4c	Fully Charged clear %	95 %	A1
4d	Charge Efficiency	100 %	Ff
4e	Current Tapper Threshold	200 ma	12
4f	Current Taper Qual Voltage	128 mv	40
51	Control Mode	5	05
52	Digital Filter	50 uV	2d
53	Self Discharge Rate	0.21 %	05
54	Battery Low %	7 %	12
55	Near Full	200 mAh	64
5e- 5f	VFC Offset	0	0
60	VFC Offset	0	0
66	ADC Voltage Gain	16:1	4e 20
68	ADC Sense Resistor Gain	0.05 ohm	30 d4
6a	VFC Sense Resistor Gain	0.05 ohm	20 00
6C	VOC 25%	10550	D6 ca
6e	VOC 50%	10750	D6 02
70	VOC 75 %	11200	D4 40
72	EDVF/EDV0	10265 mv	28 19
74	EDVF/EDV1	11550	2d 1e
76	EDV T0 Factor	4475	11 7b
78	EDV C1/C0 Factor / EDV2	C1 = 0 C0 = 235	00 eb

0 Bill J10799 over 15 years ago in reply to Vikas Saraswat

TI__Intellectual 940 points

Hello Vikas,

I have several comments about these parameters.

1. Charging Voltage for a 2S lithium pack is typically 8400mV, though some would charge it with as low as 8200mV for longer battery life.

2. Max overcharge is typically 10% of full capacity, not 100%.

3. Setting VFC offset to a typical 0xA03800 value is much better. I understand that if initially set to 0, the VFC offset calibration command doesn't work.

4. For a 2-cell application, you could get better ADC resolution by using a voltage divider of 7:1 and setting the ADC gain to 8:1 (half the value in EEPROM)

5. The VOC values are somewhat typical for a 3S pack and this is a 2S pack. However, the VOC function is not enable, so no problem.

6. The EDV coefficients are set for Compensated EDV (CEDV) values that would be more appropriate for a 3S pack. You need to determine appropriate fixed thresholds for EDV0, EDV1, and EDV2 and clear the CEDV bit in Pack Configuration (change to 0xA4). You will need to do some characterization discharges on your pack to choose appropriate values. The CEDV coefficients are much more difficult to determine. There is a MathCad tool that you can download from the website along with instructions on what characterization data needs to be taken if you have either a very dynamic load or very wide temperature operation. Fixed EDVs is fine for narrower load and temperature performance windows.

Bill

0 Vikas Saraswat over 15 years ago in reply to Bill J10799

Prodigy 110 points

Ok i will change the data as per you have commented. For your information, i have only 1 cell pack which i have connected to Vcell 4 point of the IC through voltage divider of 1.25 V at FC.

Also, the charging current always give me value = 0 while reading from the BQ2060??!!!

Regards

Vikas

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BQ2060 Remaining Capacity