# LTC 4150 coulomb counter property

I want to monitor the capacity of a 7.4V, 2200mAH Li-ion battery. I have found a that LTC4150 coulomb counter can able to measure the battery capacity. So, suppose I have connected a fully charged battery and monitor the battery capacity. So, after draining the battery to a some amount, what value it will show through a controller, the remaining battery capacity or the amount of AH I have used? I think it will show the amount of battery capacity I have used as per as its calculation of coulomb charge formula given in datasheet. So, if it works like this, then how can I estimate the battery capacity if it is not fully charged? (if 70-90% charged is present and connecting to the load).

1Ah = 3600 • GVF • RSENSE Interrupts (8)

RSENSE= Imax* 50mV

Software can choose value for empty or full.

Using suitable up-down counter. Initialize Count = 100% then count down with ratio to indicate capacity and count up to full .

Calibration check

Reinitialize after CC to CV to 10% CC cutoff = 100%

Cutoff use if capacity is <=10% or Vbat<=3V

But some calibration error checking is needed, something like...

• then if count down = 10% is reached but Vbat > 3.4 add count correction factor

• if Vbat <=3V and count is > 10% reset to 0% and report error difference.

• Ya,this logic is helpful. But if I connect a battery which is not fully charged, it will show 100% fully charged initially in this case and cannot be detect battery capacity accurately. Isn't it?Or Am I wrong? – Aakash Dey Jan 4 at 19:24
• Depends on your initialization battery test and memory. – Sunnyskyguy EE75 Jan 4 at 19:25
• Because my system is battery back up system( not fully battery powered system), so often it is possible that that the culomb counting can start at any level of battery. So, my question is that can the IC automatically detect the initial capacity of the battery? Or it will take any initial level as fully charged battery? – Aakash Dey Jan 4 at 19:33
• It cannot tell the unknown capacity unless you do a load test for 1 sec. and make some historical assumptions based on experience or better a 10 minute test. Based on dV/dt and Vbat – Sunnyskyguy EE75 Jan 4 at 19:35
• Ok, I think after some load current passing through it, it will provide the amount of AH I have used during that time. So, how it will able to provide remaining capacity in the battery because the battery is not fully charged? So, how it will give a correct value of remaining capacity in this case? – Aakash Dey Jan 4 at 19:42