On Wed, Feb 15, 2017 at 4:53 PM, Quentin Schulz
[off-list ref] wrote:

Hi,

On 15/02/2017 01:46, Liam Breck wrote:

quoted

On Tue, 14 Feb 2017 10:40:55 +0100 Quentin Schulz wrote:

quoted

This adds the constant-charge-current property to the list of optional
properties of the battery.

The constant charge current is critical for batteries as they can't
handle all charge currents.

Signed-off-by: Quentin Schulz <redacted>
---

added in v3

 Documentation/devicetree/bindings/power/supply/battery.txt | 2 ++

Is constant-charge-current dependent on the battery (e.g. capacity, nominal voltage, etc) or the
system (charger chip, input current/voltage, etc)?

It belongs in Doc.../power/supply/battery.txt if it's a characteristic of the battery.

Note, this page asserts that constant-current charging applies to NiMH batteries:
http://power-topics.blogspot.com/2016/05/constant-voltage-constant-current.html

Related properties to be added to battery.txt near-future in a patchset for the BQ24190
charger are as follows. These are not currently in enum power_supply_property, so the actual names
are still to be decided.

precharge-current-microamp:
   maximum charge current during precharge phase (typically 20% of battery capacity)

termination-current-microamp (or endcharge-current):
   a charge cycle terminates when the battery voltage is above recharge threshold,
   and the current is below this setting (typically 10% of battery capacity)

We have a client with a board whose battery accepts a maximum of 300mA
for charging. So depending on the battery, we cannot have any charging
current we want. The AXP PmMICs set constant charge current in a range
of 300mA-1800mA, so it is enforced by the charger but needs to be
adapted depending on the battery present in the system.

May I ask the capacity of the battery in question?

Typically one charges LiPo batteries at no more than 1C. So if it's
a 1800 mAh battery, the charge current should be no more than 1800 mA.

ChenYu

The AXP PMICs charge battery with constant current (Ichrg) between the
trickle voltage (Vtrkl which is ~3.0V) and the targeted voltage (Vtrgt;
which seems to be the voltage telling the battery is fully charged).

So if I understand correctly, "my" constant-charge-current would be
located in the charging cycle between your precharge-current-microamp
and the termination-current-microamp as it is the current for the
charging process as a whole.

See here[1] for the explanation in the datasheet (page 20).

That would definitely match what is explained in your link for constant
current.

[1] http://dl.linux-sunxi.org/AXP/AXP209_Datasheet_v1.0en.pdf

Let me know if something seems odd,
Thanks,
Quentin

--
Quentin Schulz, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com