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Author Topic: how to use 4.36V battery  (Read 155 times)

PaddleStroke

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how to use 4.36V battery
« on: July 14, 2019, 03:31:28 PM »
Using a lime2 on armbian mainline how can I set the battery voltage as 4.36V instead of 4.2V?

I tried to modify the register of AXP209 directly with I2Cset, but after reboot the setting is reset...

LubOlimex

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Re: how to use 4.36V battery
« Reply #1 on: July 15, 2019, 10:01:20 AM »
Make sure to look trough the sources, for example in mainline it seems 4.36 is disabled in the drivers

https://github.com/torvalds/linux/blob/master/drivers/power/supply/axp20x_battery.c

Around line 362 you can see the switch case has only 4100000, 4150000, and 4200000, nothing higher:

"AXP20x max voltage can be set to 4.36V and AXP22X max voltage can be set to 4.22V and 4.24V, but these voltages are too high for Lithium based batteries (AXP PMICs are supposed to be used with these kinds of battery)."
« Last Edit: July 15, 2019, 10:12:09 AM by LubOlimex »
Technical support and documentation manager at Olimex

PaddleStroke

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Re: how to use 4.36V battery
« Reply #2 on: July 15, 2019, 04:23:31 PM »
Thanks for your reply!

Actually I finally could edit this parameter. I think first it was not registering because I was using the command emulator from desktop. When doing the i2cset from console directly the change registered.

This comment about max voltage for lithium bat is deprecated. Now manfuacturers make 4.35V and even 4.4V batteries.

However I noticed the battery charged only to 4.17V not up to 4.35V... So the driver may be having an effect, however the board was turned OFF so I don't understand how it could prevent correct charging up to 4.35V.

PaddleStroke

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Re: how to use 4.36V battery
« Reply #3 on: July 16, 2019, 12:51:17 PM »
Afterall the parameter got back to 4.2V/0xc9 after few reboots!
This is probably why it was charging only up to 4.17V.

Something must be changing it automatically...