USB-C and the BMS

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Hello all, My paranoia may be getting the best of me but I need another pair of eyes on this. The USB-C should be in parallel to the power management board(regulators) and be the output of the 2S-BMS. I feel like something about this is wrong... either it's the output of the BMS for it connects to the 0 and 8.4 V spots respectively (in the smaller picture). Can anyone help me on this matter?
 

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Stitches

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If the BMS doesn't have separate charging and output pads, the charging current should be applied to the P+ and P- pads on the BMS as you have drawn there. Many basic ones use the P pads for output and charging input.
 
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If the BMS doesn't have separate charging and output pads, the charging current should be applied to the P+ and P- pads on the BMS as you have drawn there. Many basic ones use the P pads for output and charging input.
not gonna lie, I didn't know the P pads could be used for both charging and output. I got to see if the current BMS I have now has compatible pads, Thanks!
 

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not gonna lie, I didn't know the P pads could be used for both charging and output. I got to see if the current BMS I have now has compatible pads, Thanks!
What BMS is this btw? Is it the red board?
 

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This is the BMS I drew in the picture. I have to find the datasheet for it since it's been a while. I believe the manufacturer is ACEIRMC
That BMS does not have handling for charge and play, and will require the use of an 8.4v li-ion smart charger. Does the USB-C PD device you plan to use have that capability? A BMS like that will not be able to charge the cells safely with just normal DC current.
 
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That BMS does not have handling for charge and play, and will require the use of an 8.4v li-ion smart charger. Does the USB-C PD device you plan to use have that capability? A BMS like that will not be able to charge the cells safely with just normal DC current.
I was going to be using this. But after checking to see if it is charge&play. I realized it can't even charge li-ion batteries. Do you have any recommendations on a good smart charger?
 

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I was going to be using this. But after checking to see if it is charge&play. I realized it can't even charge li-ion batteries. Do you have any recommendations on a good smart charger?
Any basic wall power 8.4v li-ion smart charger with a barrel jack will do. Otherwise there are USB-C modules like this one that claim to have smart charge capability, but I haven't seen anyone else use one yet and can't comment on reliability
 

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So I can just connect the barrel jack to the P+ and P- pinouts on the BMS and have the on off switch in series for charging?
Yeah just wire the barrel jack +/- to P+ and P- directly, and then use a latching switch on the positive wire between the system and the BMS to turn it on/off. The ground wire should be left connected at all times for safety reasons.
 
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Yeah just wire the barrel jack +/- to P+ and P- directly, and then use a latching switch on the positive wire between the system and the BMS to turn it on/off. The ground wire should be left connected at all times for safety reasons.
Awesome, thank you. I want to use a numeric LED display to show off the battery percentage left but I feel like I'd have to use a microcomputer to control all the LEDs. Maybe just using a 4 pined RGB LED would be easier.
 

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Awesome, thank you. I want to use a numeric LED display to show off the battery percentage left but I feel like I'd have to use a microcomputer to control all the LEDs. Maybe just using a 4 pined RGB LED would be easier.
Most digital li-ion fuel gauges you can buy off ebay/amazon have an integrated microcontroller and will just display information when powered
 

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Just be aware that the gauge will sap some system power as long as it's displaying a reading. It'll probably take off something like 10-20 minutes of playtime if it's always active
 
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