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BMS voltages on C- & P-
#1
I installed a 36v BMS, all seemed fine, when I tested the voltage I noticed

B- Battery is at 36.6v
P- Load is at 18v (approx)
C- Charger is at 18v (approx)

The device drawing the load would not work at 18v

Has anyone come across this ?
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#2
(05-08-2020, 01:33 PM)18650 Wrote: I installed a 36v BMS, all seemed fine, when I tested the voltage I noticed

B- Battery is at 36.6v
P- Load is at 18v (approx)
C- Charger is at 18v (approx)

The device drawing the load would not work at 18v

Has anyone come across this ?
Maybe the individual cell (voltage) balance leads were not hooked up properly  - interesting that you only have 1/2 of 36v.
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#3
(05-08-2020, 02:35 PM)OffGridInTheCity Wrote: Maybe the individual cell (voltage) balance leads were not hooked up properly  - interesting that you only have 1/2 of 36v.

I was extremely careful to check all the balance leads.  The battery was recycled so it has solder in place for all the balance leads.

I was really hoping for a response from someone who has a battery BMS and can measure it or who has actual relevant experience of the issue I have raised.
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#4
Are you sure the Positive connection is common terminal? Which bms are you using? pictures of the unit wired up would be helpful
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#5
If this is the Bluetooth boards, make sure it is switch on in software...

This is why I made something like this to test these boards. If you send me a photo ill see if I have the same and will try and test it or see if I can replicate it with mine.

https://youtu.be/rgj_GXzNYTQ
OffGridInTheCity likes this post
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#6
(05-08-2020, 09:24 PM)Korishan Wrote: Are you sure the Positive connection is common terminal? Which bms are you using? pictures of the unit wired up would be helpful

Sorry for delay in reply, I must have missed the email notification

[Image: a2GA3mr.jpg]

I have since found that this BMS unit was 16amp, I originally planned a single 10s setup but ended up witing two together, which are 20A, so I have now ordered a 35v
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#7
This is new one I bought

[Image: mZKnVYP.png]
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#8
(05-10-2020, 01:18 PM)18650 Wrote: This is new one I bought

[Image: mZKnVYP.png]
It looks like the illustration shows where you could connect.  But not all at once.
The pictures below illustrate the 2 ways to connect a typical  BMS

The BMS most likely has 2 sets of Mosfets. You can control the charge and load separately.
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#9
Your balance leads in the photo are not plugged in... were they connected when you took your measurement?

Make sure its connected correctly with all cells in balance otherwise the board may have went into protection mode.
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#10
(05-10-2020, 10:03 PM)Crimp Daddy Wrote: Your balance leads in the photo are not plugged in... were they connected when you took your measurement?

Make sure its connected correctly with all cells in balance otherwise the board may have went into protection mode.

Yes all wires go to right cells

I unplugged it as I am replacing it.

(05-10-2020, 02:42 PM)Bubba Wrote: It looks like the illustration shows where you could connect.  But not all at once.
The pictures below illustrate the 2 ways to connect a typical  BMS

The BMS most likely has 2 sets of Mosfets.  You can control the charge and load separately.

It is the type with different port.
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