Hi,
Bit of a wordy problem here.
I am looking to install a charging station that will recharge these batteries (via the onboard usb port) that do not have the circuit protectors.
https://hobbyking.com/en_us/turnigy-nan ... tore=en_us
Is this a sensible way of doing this? the batteries will be cycled through at most 40 times. Should I perhaps use a dedicated charger instead?https://hobbyking.com/en_us/turnigy-up- ... s_products
The other question is about discharging. I have been told that the real danger with these batteries is not to deplete them too far. I am planning to write some code or firmware change that will prevent the drone from taking off if under a certain voltage. if the drone lands as soon as the red light is displayed (whatever that voltage is, I cant remember the value) is this a sensible value? or should it be higher?
Thanks for your help!
[Solved] Charging and Discharging unprotected batteries.
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[Solved] Charging and Discharging unprotected batteries.
Last edited by cafeciaojoe on Mon Feb 01, 2021 6:48 am, edited 3 times in total.
Re: Charging unprotected batteries via USB.
The charger will work fine and is designed for LiPo and will cut off at 4.2V. The depletion though should perhaps be handled a bit better and is the most common risk I see. Something as simple as shutting off the system if the voltage has been lower then 2.9V for e.g. 3 seconds. This should preferably be handled in the nRF51 but could be handled in the STM32 as well.
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Re: Charging unprotected batteries via USB.
Thanks very much for the info, I think I will start with the STM32, as it is vaguely familiar to me.
in pm_stm32f4.c line 149 there seems to be the beginnings of a ACTIVATE_AUTO_SHUTDOWN condition, Is this the reason why the CF just tries to restart itself indefinately when the batt is critically low?
Any tips on how to finish this feature off?
I assume some sort of message needs to be passed to the nRF51 in a special format. I see that '0x11' is the 'on/off' switch between the two. and that in syslink.h there is some sort of function (struct? sorry not familiar with C) that seems to be able to send packets,
in pm_stm32f4.c line 149 there seems to be the beginnings of a ACTIVATE_AUTO_SHUTDOWN condition, Is this the reason why the CF just tries to restart itself indefinately when the batt is critically low?
Any tips on how to finish this feature off?
I assume some sort of message needs to be passed to the nRF51 in a special format. I see that '0x11' is the 'on/off' switch between the two. and that in syslink.h there is some sort of function (struct? sorry not familiar with C) that seems to be able to send packets,
Code: Select all
typedef struct _SyslinkPacket
{
uint8_t type;
uint8_t length;
char data[SYSLINK_MTU];
} __attribute__((packed)) SyslinkPacket;
Re: Charging unprotected batteries via USB.
This is fully untested but might work
You might also want to change the auto off timeout if it works, PM_SYSTEM_SHUTDOWN_TIMEOUT which is now set to ~5min.
The critical low behavior is caused by the voltage being so low that the MCUs can't run reliably. Hitting what is normally called brown-out reset.
Code: Select all
/**
* Shutdown system
*/
static void pmSystemShutdown(void)
{
#ifdef ACTIVATE_AUTO_SHUTDOWN
SyslinkPacket slp;
slp.type = SYSLINK_PM_ONOFF_SWITCHOFF;
slp.length = 0;
syslinkSendPacket(&slp);
#endif
}
The critical low behavior is caused by the voltage being so low that the MCUs can't run reliably. Hitting what is normally called brown-out reset.
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Re: Charging unprotected batteries via USB.
Hi Tobias,
Thanks for the suggestion. I implemented the code, the 'pmSystemShutdown' function did not seem to be able to be called unless I uncommented the line below from the config.h file.
Thanks for the suggestion. I implemented the code, the 'pmSystemShutdown' function did not seem to be able to be called unless I uncommented the line below from the config.h file.
Code: Select all
#define ACTIVATE_AUTO_SHUTDOWN
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Re: Charging unprotected batteries via USB.
Is it possible to change this maximum value of 4.2v in the firmware?tobias wrote: ↑Wed Jan 27, 2021 1:14 pm The charger will work fine and is designed for LiPo and will cut off at 4.2V. The depletion though should perhaps be handled a bit better and is the most common risk I see. Something as simple as shutting off the system if the voltage has been lower then 2.9V for e.g. 3 seconds. This should preferably be handled in the nRF51 but could be handled in the STM32 as well.
Re: [Solved] Charging and Discharging unprotected batteries.
The 4.2v is controlled by the BQ24075 charger and looking in the datasheet the charging voltage can't be changed.