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22/11/2020

Battery Charger Discharger Board - WTF ?

 I am currently building an Amateur Radio project that will run off batteries. In order to stop over-discharging that battery I need a controller to cut the power before damage occurs. I wanted something "off-the-shelf" so I bought a  Battery Charger Discharger Board from Ebay.

The instructions are abysmal so I did some testing and managed to figure out how to operate it.



Connections

The module has different connections to power the module, to measure the voltage from the battery, and for the relay contacts.

To simplify wiring I have added a bodge wire connecting VIN and V+, so the module is powered from the battery it's connected to.

The following images are supplied with the documentation:






Modes

The module supports 6 modes that are documented below:

ON OFF Use Case
U-1 V < Lower Limit V > Upper Limit Controlling a charger
U-2 V < Lower Limit V > Upper Limit or Timer Exceeded Controlling a charger, with timer
U-3 V > Upper Limit V < Lower Limit Preventing the load from over-discharging a battery
U-4 V > Upper Limit V < Lower Limit or Timer Exceeded Preventing the load from over-discharging a battery, with timer
U-5 Lower Limit > V > Upper Limit V < Lower Limit or V > Upper Limit Only supply power when the voltage is within the set range
U-6 V < Lower Limit or V > Upper Limit Lower Limit > V > Upper Limit Only supply power when the voltage is outside of the set range

Serial Control

The module also has a basic TTL Level UART that can be used to receive status updates every second, change the settings, and query the status.

Some sources indicate the baud rate is 115200 however mine was at 9600.

By default the unit will send out the current voltage, time the relay has been enabled and relay status every second. CL means the relay is open. OP means it is closed...  
11.8V,00:01:00,CL
11.8V,00:01:00,CL
11.8V,00:01:00,CL
11.8V,00:01:00,CL
11.8V,00:01:00,CL


Commands

You can send commands to the module to update the settings and query the parameters. If you send an incorrect command the module will reply "fail"

Command Notes Example response
get Gets the current status U-2,11.8,14.0,001 - (Mode, Lower Limit, Upper Limit, Timer)
on Enable logic None
off Disable logic, turn off relay None
start Start sending status updates every 1 second None
stop Stop sending status updates every 1 second None
000 Set the timer period from 0-999 minutes. Only works in timed modes. down
dw11.8 Set the lower limit voltage, must be used in conjunction with up, e.g: dw02.9,up10.1 None
up13.8 Set the upper limit voltage, must be used in conjunction with dw, e.g dw02.9,up10.1 None

Power Consumption

The following values are very approximate as they were managed from my power supply. They were taken with a voltage around 12.5V



State Current Consumption (mA)
Relay closed, Display on 91
Relay open, Display on 10
Relay closed, Display off 87
Relay open, Display off 3

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