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DIY Mini 12v Router UPS malfunction


Mobeen
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Hi, I created a couple of router UPS (2s and 3s) according to the attached circuit diagram, minus the voltage display. They work fine except that when batteries are completely depleted and output is turned off, it doesn't give the necessary output after the power restores until I turn the circuit off and on again manually through the on/off button. My router's light blinks in a cycle for a brief moment and turns off as if it is not getting the necessary voltage/current. Can someone help me resolve this problem, please?

I used this YouTube video as a reference to build these circuits: 

 

PgwSa2K.jpeg

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If you do not see the 8.4 volts at the 5v to 12v converter it suggest that the power supply has gone into  a thermal overload state. Perhaps due to the drain from the charger. Switching it off resets it perhaps.

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16 minutes ago, HarryA said:

If you do not see the 8.4 volts at the 5v to 12v converter it suggest that the power supply has gone into  a thermal overload state. Perhaps due to the drain from the charger. Switching it off resets it perhaps.

@HarryA For 2s setup, I am using 8.4v 1A charger and for 3s, 12v 1.5A adapter. Do you think that using 12v 2.5A or 3A can fix this issue, at least for 3s circuit?

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If you use a 12v and 3 ampere charger that would require a little over 36 watts. A 12v and 1 ampere charger would be about 12+ watts. That would be less load on the power supply. Assuming the power supply is the limiting factor here. The slower charge rate would not be a problem if you do not have power outages more than once a day?

 

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On 5/17/2022 at 6:06 PM, HarryA said:

If you use a 12v and 3 ampere charger that would require a little over 36 watts. A 12v and 1 ampere charger would be about 12+ watts. That would be less load on the power supply. Assuming the power supply is the limiting factor here. The slower charge rate would not be a problem if you do not have power outages more than once a day?

 

@HarryA What do you mean by charger here? I am not using any charger but instead a power supply of 12v 1.5A connected directly to the circuit. Are you suggesting me to use a 12v 1A power supply instead?

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Your BMS (HW-391):

Product Model: HW-391
Charging Voltage: DC 8.4-9V
Version: Balance
Constant Discharge Current: Max 20A (If the heat dissipation environment is not good, please reduce the use of load current)
Constant charging current: Max 10A)

https://makerselectronics.com/product/lithium-battery-charger-protection-module-bms-2s-20a-7-4v-balanced-version

Some say a BMS (battery management system) is not a charger but there seems to be come confusion here.

One thing that is not clear is what is the nature of your 8.4 volt power supply.

Also is the BMS preventing the battieries from discharging below the allowable voltage level for a li-ion battery.

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