Bypass Bms

Hey just a quick question about bypassing bms discharge and only using it for charge. This was talked about on a different thread but i just had one question. The diagram below for bypassing the bms shows that you connect the charge positive and negative directly to the battery pack and the only thing you connect from the bms is the sense wires (or w.e they're called thats equal to your series number.) My question should i connect the P- to the charge negative? Or like the diagram shows connect charge wires directly to battery pack? With the charge negative not connected to P- will it still be able to balance the pack?

Thank you




http://www.vanderworp.org/Battery%20Management%20System%20BMS

To bypass the bms you must ignore -p. Both discharge wires are soldered to the pack main -&+
-b and-c must be soldered
You keep the balancing feature but you lose the lvc. You must program your controller to cut discharge. Keep that in mind or you will kill your pack.

rojitor said:

To bypass the bms you must ignore -p. Both discharge wires are soldered to the pack main -&+
-b and-c must be soldered
You keep the balancing feature but you lose the lvc. You must program your controller to cut discharge. Keep that in mind or you will kill your pack.

Click to expand...

Thanks for the reply, yes im going to carefully monitor battery voltage and set the controller to proper LVC. However can you clarify what you meant by -b and -c must be soldered? On the common port bms i have theres only B- and P-. As you mentioned, i should ignore the p-, and if so then that means both my charge and discharge wires will get directly soldered to main battery + and -. And the only thing connected from my bms is the "sense" wires, w.e there called. Which would be exactly like the diagram shows.

If you have only -b and -p then you have a "shared port" bms -p is charge and discharge wire.
You must connect -b to main negative.
Then you solder the balance wires in order. Double check the voltage pin by pin with a multimeter(do you know how to?) If they are ok you can plug the jst to the bms
Solder -p to charge negative
Solder charge positive to main positive.
Solder the discharge wires +&- : black on main negative and red on main positive.
The process as you can see is the same as usual but you connect -discharge on main negative instead, ignoring the bms port. By doing that the amps limit of the bms is removed but you lose the lvc protection along with It.

rojitor said:

If you have only -b and -p then you have a "shared port" bms -p is charge and discharge wire.
You must connect -b to main negative.
Then you solder the balance wires in order. Double check the voltage pin by pin with a multimeter(do you know how to?) If they are ok you can plug the jst to the bms
Solder -p to charge negative
Solder charge positive to main positive.
Solder the discharge wires +&- : black on main negative and red on main positive.
The process as you can see is the same as usual but you connect -discharge on main negative instead, ignoring the bms port. By doing that the amps limit of the bms is removed but you lose the lvc protection along with It.

Click to expand...

Ok now you cleared up which wires get soldered where, all understood. Then you said just double check to make sure everything is wired correctly, by checking voltage of balance wires. To do so just put the postive of the multimeter to the positive of the cell group and negative to the pin correct?

No. You put the negative probe of the multimeter on the main negative or the negative pin of the jst. It will be the first or the last depending on the bms model. Then you place the positive probe on each pin of the jst in order. The first time you should read around 3.4v the second pin should show 6.8v and so on... Each pin should show an increase of the storage voltage of the cells. If any pin fails don't plug the jst.
[youtube]yOnGAHu_odw[/youtube]

This pack has a bypass. Watch from 5:15
That part can't be skipped. Double check It before you plug the jst to the bms.

rojitor said:

No. You put the negative probe of the multimeter on the main negative or the negative pin of the jst. It will be the first or the last depending on the bms model. Then you place the positive probe on each pin of the jst in order. The first time you should read around 3.4v the second pin should show 6.8v and so on... Each pin should show an increase of the storage voltage of the cells. If any pin fails don't plug the jst.
[youtube]yOnGAHu_odw[/youtube]

This pack has a bypass. Watch from 5:15
That part can't be skipped. Double check It before you plug the jst to the bms.

Click to expand...

Ok understood. Thanks for clearing it up.