BMS Common port or Seperate port

[The_Geek]

I guess the first question is this. Looking at the common port BMS it looks like the load and the charge source are wired to the same bus.

Does that mean that you can charge the cells at the same time you discharge them?? (best guess is only with a BMS otherwise they need to be seperate)

I can kinda think of reasons to keep them separated. Like maybe you want some other device to be able to cut off the BMS and not have it going through the main power.

But if you wire them like the pic, isn't it the same as a common?

Thank you SO MUCH !

 

[Steve_S]

A Typically, an SCC, Inverter/Charger combo is used on the same common DC Bus (lines) and can both charge the battery as required.
If you do not have an SCC or Inverter/Charger but just a regular Inverter, then an external charger is typically used. Think EV and similar.

An external charger can be used on a common bus but there is potential issues if drawing power to the inverter at the same time, therefore isolating to a separate circuit is reasonable. Every standalone charger is different so this varies somewhat.

Separate Port BMS' also may have a lower Charge Rate Capacity (limited amperage) depending on type & design. Some are more suitable for High Amp Charging while others are suitable for low to mid amp level charging. Again, think of EV and E-bikes... an E-Bike with a 48V/20AH battery does not need as many amps as say a 48V/500AH pack would.

Its's all about the various use cases and applications the BMS has to accommodate, therefore choosing the correct BMS for a specific application is essential.

Simple overview to cover that basics, there is an FAQ on it but finding it is not easy, it isn't in the FAQ sub-forum that details more. If you want to learn & understand more of the technical bits, a goof place is here : http://liionbms.com/php/bms_options.php

Hope it helps.
Steve

 

[grizzzman]

separate port generally (but that is changing) lower charge rate compared to discharge rate. I would NOT recommend that you jump the charge with the discharge on a separate port.

 

[The_Geek]

Thank you both.

I will read the link you provided Steve.

 

[keepsake]

If one has a 48v pv system with Lithium Batteries is there any purpose in having separate ports ? A xw6848 inverter is both the charge source and drain connection.

 

[harbin1234]

Great Thread.
I just cancelled my my 100 AMP 4S Separate Port BMS and I'll order a Common Port. I do only use solar in the day time to charge and a wind turbine at night to help maintain a full charge for the massive AMP Attack with my coffee pot and toaster in the morning. ?