I have a tutorial on it: https://www.youtube.com/watch?v=jxHQjlHv1y4
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What brand of bms is that? There are some bms that use a ground wire on the balance port but battery supports or Supower, do not. In the diagram for battery supports, it shows only 6 pins for 6s battery a wire goes from the positive side of each cell to one of the 6 pins on the balance port. That is what the diagram shows.
Though all the cells and in both packs are connected in series through the main power leads. The balance wires isolate each cell so that the bms can monitor each cell separately.
It’s a Chinese brand, but my BMS is also a 6S, and it does not use a ground wire on the balance port.
@mmaner 's BMS also balances each cell, just like mine does. I don’t think you are correct in any of your claims. The plus and minus of the two batteries are supposed to be connected together, and to the balance port; the negative lead of the entire pack from the balance port is NOT connected; this system should work.
@mmaner The main power leads are connected in series but the balance wires are not suppose to be connected in series. They are suppose to be isolated. That is why there are 6 pins on the bms balance port. One pin for eace positive side of each cell. In a Lipo pack, that means the colored balance wires only. The black balance wire is connected to the main ground lead of each pack. and has to be omitted when connecting to a Bms balance port.
Here is my Lipo with bms build
Ok, after reconsidering this I realize that connecting the ground wire from the 2nd pack as shown in the diagram should not cause any problem. However, it is unnecessary.
Thank God. I was running out of popcorn!
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Wow. Thoroughly entertaining! And informative. Tune in next week!
Oh yeah…Think this was entertaining? Try wrapping your head around this discussion! You’re going to need a lot of popcorn!
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I corrected the balance wires in the drawing, they now appear in the correct order.
The BMS I bought is a 60 AMP, I guess I posted the wrong link earlier in the thread. The BMS I am using is here.
Using the interface definition on the product page I used the following instructions, defined as (bms1) through (bms5), to make the POSITIVE & NEGATIVE connections as I understood them.
- (bms1) The Positive output on Battery Pack (22V + ) could connecting to charger positive pole (charger +)
- (bms2) Battery Pack (22V -) connecting with B- on board
- (bms3) Chip board P- connecting to Charger Negative Pole (charger -)
- (bms4) Chip board P- could be Negative output for charger, motor, controller
- (bms5) Battery B+ could be Positive output for charger, motor, controller
I used a mulimeter to check the cells of a Zippy 5000mAh 3s 30c LIPO Pack. With the negative probe on the BLACK wire and the positive probe on the WHITE wire I got 4.03v. Leaving the negative probe on the BLACK wire I then used the positive probe on the YELLOW wire and got 8.09v. Lastly Leaving the negative probe on the BLACK wire and moving the positive probe to the RED wire I got 12.13v. If I understand correctly, the results mean that WHITE is Cell 1, YELLOW is Cell 2 & RED is Cell 3.
I am not clear which is battery 1 (Cells 1, 2 & 3) and which is battery 2 (Cells 4, 5 & 6). Assuming the battery order is unimportant, though I dont see how it can be, I made the battery closest to the charging port Battery 1. I then made the balance connections Using the Balance Connector illustration on the linked product page.
I would assume if pin 4 on battery 1 and pin 1 on battery 2 were bridged, that would define the cell order. As there are only 6 balance connections on the BMS I am pretty much out of ideas. I hope someone can help me understand this.
Otherwise I think the diagram is accurate. Let me know if I missed something. Thanks again for all the help.
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Your getting close, you have the balance wires correct but the main supply wires are not. The negative supply wire should come from pack 1 The positive supply wire should come from pack 2
Like this? I have no idea why, can you explain? I am really trying to understand this, but the idea of multi cell power source has me pretty confused when it comes to the charging requirements :). Also, since it s a 60A BMS, do we need to bypass it while running? Is there a benefit to including the BMS while running assuming the ESC does its job and cuts off at 3.2V?
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All the wiring looks good now, assuming that the white balance wire is the first cell in each pack and the yellow wire is the second cell in each pack. As a precaution, you should check the voltage of each. The wire with the lowest voltage is cell one of each pack. The red balance wire is usually the last cell in the pack but it wouldn’t hurt to check that one as well.
Since you have a 60a Bms, You could discharge through it. Just set the Vesc max batt amps at 60 or less. I have measured current from the battery feeding dual motors going uphill and at 6s full throttle I was pulling less than 40a
I checked the cells with a multi-meter… With the negative probe on the BLACK wire and the positive probe on the WHITE wire I got 4.03v. Leaving the negative probe on the BLACK wire I then used the positive probe on the YELLOW wire and got 8.09v. Lastly Leaving the negative probe on the BLACK wire and moving the positive probe to the RED wire I got 12.13v. If I understand correctly, the results mean that WHITE is Cell 1, YELLOW is Cell 2 & RED is Cell 3.
Which of the POS/NEG wires do I move to discharge through the BMS?
You are correct with the balance wires Wht 1 Yel 2 Red 3 Your most recent diagram is also wired correctly to discharge through the BMS. Another advantage of not bypassing the BMS is that when you have regen braking the charge back to the batteries goes through the BMS. So you shouldn’t have to worry about over voltage when using brakes on a full battery.
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awesome, I really appreciate all the help on this.
Your very welcome
Im still a couple of weeks away from my BMS card getting here, but as soon as it does I am going to build this and post the results, with build pics and diagram, in a tutorial format. Thanks rpn314, Namasaki & VladPomogaev for educationg a n00b :).
For reference this is how I wired my 3x 4S Zippys up to my BMS (With help from @mccloed) and it’s been working perfectly.