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Connecting P- and C-
#1
I have built a 10S battery back with a BMS that has separate terminals for charging (C-) and discharging (P-). However, since this battery pack will be used to power BLDC motors on a moving object it is important that the battery can charge and discharge through the same wires (when braking, kinetic energy from the motors is turned back into electrical energy to charge the battery).

I'm pretty sure it is safe to just connect C- to P- and treat it as one terminal. After all, it seems BMS boards with just one terminal are made this way. Before blowing up stuff I just wanted to double check with people with more experience, have you done this and/or do you know if it is safe?
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#2
That's not a bet I'd make. BMSs are relatively cheap. Buy one that's right for the project with a combined port.
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#3
Thank you for your advice, it made me do some more research. I found that most MOSFETS have a reverse diode that allows current to flow from source to drain. This is just a diode, when the mosfet is "off" it still conducts so the P- terminal should generally not be used for charging because it cannot disconnect power in case of overcurrent or overvoltage (in case of overcurrent, the mosfets will burn).

For my application, charging briefly through P- will be fine. I will connect my main charger to C- but now I know that the BMS won't block reverse current through P-, which is good because blocking reverse current can cause system voltage to rise dangerously high and kill the ESC.
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#4
Get a proper bms instead.
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#5
I would like to but I couldn't find any. Common terminal BMS boards are very common for lower series configurations like 4S but apparently rare for 10S+

The risk is in my opinion minimal. There should be no need for charging protection from braking, it is impossible to overcharge the battery just by braking. Unless you go down a very long steep hill with a fully charged battery it will always use more energy from the battery than put back
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#6
The risk is that the bms doesnt work as you stated. And the bms is protection. As Said get a proper bms. They exist.

The bms is There for the when not IF. You can overcharge a battery when its fully charged and you break or during normal Charge routine.
Common terminal is the most Common type bms for higher end systems. On ebikes on other hand its more Common with split on cheaper versions.

My first hit googling shows Common port bms for ebikes for 10s. Look at ant bms as example
NOTE! My links supplied in this message may be affiliated with Ebay and by clicking on them you agree on the terms.
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#7
(10-21-2020, 07:05 PM)derkades Wrote: I would like to but I couldn't find any. ....

Aliexpress has a huge selection of BMSs if you have the patience for their delivery.
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