Question about wiring BMS to solar charge controller

rhedbatt

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pardon me buti'm new in building battery packs :huh:
So i ordered a 7SBMS i just wanted to ask if i can wire like this to my charge controller.the C-(yellow wire) and P-(blue wire) seems like they are common(-) but Manual says C- is for charging and P- is for LOAD can i do this? see my diagram. BTW the charge controller will compensate the load if there is enough energyfrom the sun and if the energy fromsun is not enough the load will get energy from the battery.

image_ruzayt.jpg
 

Walde

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test the passage from C- to P- with the multimeter if you have complete passage it could also be the C- and P- the same are only two solder points.
 

DarkRaven

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Most likely, yes. charging negative and load negative (and battery negative for that matter) is usually the same. And the negative ports on the charge controller are usually all commoned as well. Like Walde said, check the traces on the PCB and the continuity between C-, P- and B-. For the controller it should also be stated in the manual.
 

completelycharged

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Check what load you can actually put on the charge controller as they are typically only rated for a light load to be attached, as per the light you have in the diagram. The actual load should be attached to the BMS as this should open circuit the load when the battery voltage drops to the minimum set point on the unit and prevent the battery from being over discharged. Same with over charging.
 

Redpacket

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Given that the Victron unit is much higher quality than the BMS, and that the Victron unit is doing all the main functions like charge control & load disconnect, I'd have the batteries directly connected to it & have the BMS in parallel & across the cells for balancing.
I would not want the BMS to disconnect the Victron if it decided it should for some reason.
You would probably join the C- & P- & B- terminals alll together on the BMS but follow the tracks & test continuity first.
 

daromer

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Victron dont know about individual cell voltage s and thats why you have the bms in between
 

Redpacket

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daromer said:
Victron don't know about individual cell voltages and that's why you have the bms in between

True. Iwas also thinking the Victron might not like it if it wasdisconnected from the battery while charging.
 

rhedbatt

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Redpacket said:
Given that the Victron unit is much higher quality than the BMS, and that the Victron unit is doing all the main functions like charge control & load disconnect, I'd have the batteries directly connected to it & have the BMS in parallel & across the cells for balancing.
I would not want the BMS to disconnect the Victron if it decided it should for some reason.
You would probably join the C- & P- & B- terminals alll together on the BMS but follow the tracks & test continuity first.

I just joined C- P- & B- since they have continuity, i just tried connecting the battery directly to victron and in parallel with BMS so far there is no problem and cells are balancing. thanks for the advice guys speciallyredpacket to the rescueagain :D
 

daromer

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Having the bms in parallel then you just screwed ur self Up... Because you just removed the protection the bms supplies. The balancing is just a minor part among it all.

Please leave the bms in between instead so it can do its job. IF you think it disconnect to Early you have wrong settings.

IF you bypass just to get it charging again im fine with it but monitor it :)
 

DCkiwi

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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..

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.

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 ...

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.

i go by the rough rule that if battery goes out of balance, use more P. my $0.02
 

DCkiwi

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DCkiwi said:
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.
 

rhedbatt

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is the solar charge controller running in common negative (my guess), or common positive?

My Answer: i just switched my controller toEPEVER TRACER-ANController (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..

MyAnswer: 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.

MyAnswer: 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 ...
MyAnswer: 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.

MyAnswer
: 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 afterall. Thank You.
 

rhedbatt

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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, andshort circuit protection)because i am using charging terminal for load.
 

Korishan

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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.
 

rhedbatt

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Korishan said:
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,

image_bjgxqv.jpg


image_bjlgde.jpg
 

rhedbatt

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ok here is an update i just made another 7S6P pack with higher capacity to replace my last 7S6Pand made a big mistake.

FirstB- 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 connectori 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 PCBgot very hot and the copper has fall off(this is totallyshort):

image_xmxemm.jpg


image_ytnjxr.jpg


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 madeand realizei 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:

image_kgreze.jpg
 

Cherry67

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When they are connected you should be able to connect BOTH to minus.
Strange. Must be another Problem.
 

DCkiwi

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rhedbatt said:
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?
 

Cherry67

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I have a 10s BMS with the same issue having -C,-P and -B.
I have checked the circuit arount these and came to:


image_bznmcz.jpg

( 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.
 

DCkiwi

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Cherry67 said:
...
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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