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Question about wiring BMS to solar charge controller
#11
(02-05-2019, 10:59 AM)DCkiwi Wrote: is the solar charge controller running in common negative (my guess), or common positive?

it appears this BMS is in common positive mode.  which is fine.  but ... to be aware of if you are mixing with a common neg controller..

[...]

im just not convinced you are going to be able to use these two things together and keep functionality from both. (refer first my two paragraphs)


so ... I'd quite like to know if this (ref OP) is in fact possible.  can someone please chime in to confirm/deny validity of my concern here?  cheers.
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#12
is the solar charge controller running in common negative (my guess), or common positive?

My Answer: i just switched my controller to EPEVER TRACER-AN Controller (feb 7) and yes it is common negative charge controller), also as Daromer said to leave bms in between the charge controller and battery(i also did that when swapping my charge controller)

it appears this BMS is in common positive mode.  which is fine.  but ... to be aware of if you are mixing with a common neg controller..

My Answer: thanks for reminding i will need to confirm this to the seller if it is common positive or neg. BMS.

NB do NOT EVER short B- with either P- or C-.  this will bypass all shunts which provide over current protection. shunts will show as 'shorts' on multimeters but they are NOT just commoned.  the B- is for the battery only.  ever.

My Answer: Actually i always put external fuse and mostly underrated (just to make sure, what is the protection fails?) to all my projects even it says it has shortcircuit protection,overload protection, etc.

the big/real load -ve SHOULD be connected to P- (blue wire), as completelycharged noted.  also, my gut feeling says the blue wire should be connected to nothing else.  as daromer says, you need the BMS protection inline. but then ...
My Answer: i will need to try and disconnect P-(blue wire) tommorow and see if something happens. as of now P-,C- is connected.

redpacket brings up a good point about disconnecting a battery from a charge controller while charging.  that is a bad thing for sure.  im just not convinced you are going to be able to use these two things together and keep functionality from both. (refer first my two paragraphs)

FYI if the battery does not get to 4.25V / cell it is unlikely that the 'BMS' will do any balancing at all. that is, if you have the charge limit set on the controller too low ... might never get balanced by this method. 

My Answer
: this is why i swapped my EPEVER TRACER-AN Solar controller it has an Equalization Charge every 28th of the month which will balance all cells.


any corrections to what i am doing wrong is highly appreciated, it is for my safety after all. Thank You.
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#13
sorry guys i forgot to post an update about this, just an update for others who are also finding answers. I disconnected the P- (blue wire) so the correct connection is this : DCkiwi's advice is correct that P- is connected to nothing.

i also want to ask since the P- Load terminal is not connected. do i still have the bms protection?(overcurrent,overvoltage,overdischarge, and short circuit protection) because i am using charging terminal for load.
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#14
rhedbatt: Can you give us a really good picture of "your" bms top/bottom so we can see the circuitry layout? I say yours, because there are several variants out there and the stock photos may not look like yours on the pcb level.
This can help us to see the traces where they go.
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#15
(02-28-2019, 12:54 PM)Korishan Wrote: rhedbatt: Can you give us a really good picture of "your" bms top/bottom so we can see the circuitry layout? I say yours, because there are several variants out there and the stock photos may not look like yours on the pcb level.
This can help us to see the traces where they go.
here it is,
 
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#16
ok here is an update i just made another 7S6P pack with higher capacity to replace my last 7S6P and made a big mistake. 

First B- on PCB(The one that need to be soldered on PCB) must not be connected to the battery if you connected the B- in the 8pin connector i just tried connecting the B- in the PCB and B- in the 8pin Connector to negative terminal on battery(just like my first diagram) but the copper in the back side of PCB got very hot and the copper has fall off(this is totally short):



I want to ask the experts here why did the B- on PCB and B- on 8pin connector shorted? as i can see in the PCB they are in the same parallel side of circuit?

i just went and see the last 7S6P Pack i made and realize i did not connect the B- on PCB  to the negative battery terminal because i already connected the B- on the 8pin connector,thats why it's working perfectly, F*ck me.

Also the C- can be use for light loads(Led lights) only. i tried connecting my 500w inverter(without load i just turn it on) and bms shutsoff instantly so instead i used the P-(load terminal) and the BMS did not shut off.

So this is my final diagram:
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#17
When they are connected you should be able to connect BOTH to minus.
Strange. Must be another Problem.
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#18
(02-28-2019, 12:41 PM)rhedbatt Wrote: DCkiwi's advice is correct that P- is connected to nothing.

ummmmmmmm ... dont think i ever said this /that ...

????

shunts are not to be avoided ... what just happened?
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In The Morning !
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#19
I have a 10s BMS with the same issue having -C,-P and -B.
I have checked the circuit arount these and came to:


( sorry i did not properly draw the fets, Sources are backtoback at -P)
(sorry i forgot the 2 sensing lines at -B and -B)
(and it is obvious i simplified to 5s)

which means, from battery -B to Power -P is the current measurement resistor, then the FET.

From there another FET goes to -C.

Means the charging current can be switched off from the PMS without disconnecting the load.

When i look at the pictures of the OP then i see the same.

means at least (!), B- must be connected (due to the current path), the identical potential at the connector could perhaps be left off, not the other way round.

If you dont want to use -C then just leave it off and load over -P.

Thats my conclusions.
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#20
(03-04-2019, 06:25 PM)Cherry67 Wrote: ...
the current measurement resistor
...


A.K.A the 'shunt'. (something that looks like a short on a multimeter, but is NOT a short...)


anyone else?

I have so much to say ... this is a great thread ... please jump in ... anyone?
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