Balance Wire placenment

Am dim nooby. But understand me stuff, like balancing cells is a call made when a BMS detects an average P cell group is at too low a level and shoots current to the group out of whack, to equalize or balance the group needing it.

How it does this is accepted, but does it make a difference how BMS finds out?

Or, does it make a difference where the balance wires are placed, as long is all are the same and can detect parallel group's averages?

IOW can poor balance detectecd on the Serial circuits?

Think of it as a direct connection to each cell. It's main job is to monitor cell voltages. If it goes out of spec, it responds.
The leads are at high potentials, so make sure they can't touch anything.

Jones, Thanks.

bobbill said:

when a BMS detects an average P cell group is at too low a level and shoots current to the group out of whack, to equalize or balance the group needing it.

Click to expand...

You're not alone as that's a common newbie misconception. There was a time when all of us were newbies ... so you're initial BMS understanding is by no means unexpected.

BMSs don't supply more current, but rather use resistance discharge to lower the voltage of a p-group that is higher than the other p-groups. As an example in a 10S3P pack three cells in one of the p-groups are: 4.19v, 4.17v, 4.17v = 4.177v. The next highest p-group is 4.137v. Because there is more than 0.025v to 0.030v difference the majority of BMSs should start discharging the higher p-group (4.177v) as it's more than 0.030v (30 millivots) higher than the next highest p-group at 4.137v (a difference of 0.040v) until it's within 0.025v to 0.030v of the next highest p-group (assuming all the other p-groups are within 0.025v to 0.030v of each other.

All BMSs use resistance discharge balancing and it's a very slow process. With a new pack of "good" brand name cells (that aren't abused) BMS discharge balancing in most cases isn't necessary. This in part is because the interconnecting of series and parallel bus bars serves to balance the p-groups. The major purpose of a BMS is for protection (BPS) in case there is an internal short in one of the cells.

Thanks, Mark. I sort of guessed, "Restance" was a word I had not in brain or vocab...

Does it matter where the wire is placed--near the group or plus area of the group? I understand the "resistance" to bring the group into phase, but have yet to figure out how the BMS segmeant filters the information.

Recall, I had 30 new, carefully checked cells, (Sams 30Qs or IMRs) and ended up with voltages from 2.4 to 4.2 when check later...
all save cells from Vruzend...I was unlucky twice with two packs, same result.

Has to be way to note if BMSs are bummed.

Am learning thanks to you, Ron, Angry Bob and a few others...

I figure this is mechanical/physics thing and will beat it.

bobbill said:

Recall, I had 30 new, carefully checked cells, (Sams 30Qs or IMRs) and ended up with voltages from 2.4 to 4.2 when check later...
all save cells from Vruzend...I was unlucky twice with two packs, same result.

Has to be way to note if BMSs are bummed.

Click to expand...

Very doubtful the voltage variances was caused by the BMS from Vruzend. That earlier Vruzend V1.5 kit and V2.0 kit (without barrel bolts) were meant to be secured tightly together with zip ties. Without tight zip ties some of the cell to cap contacts may have never made contact (e.g. 4.2V); while others maintained contact (e.g. 2.4V), and other voltages in between depending on when contact was broken. 2.4V is toooo low and has probably shortened its cycle life. Also, those as low as 2.4V could also be due in part to a "high rate" of self-discharge (a 30Q downside apparently unique to both 30Q 136 and 141 cells.

The first thing your need to do is establish a common voltage with all 30 cells. If I were you i'd invest in the MiBoxer ... https://www.amazon.com/Battery-Smart-Universal-Intelligent-Batteries/dp/B07JB3RZLS ... (or more expensive Opus) ... https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313&_nkw=MiBOXER+C4&_sacat=0 ... and discharge the cells above 4.2V to say 3.96V (as discharge rate is only 0.40 amps). Then charge the lower cells at 1.50 amps to 3.96V. After resting for 3 days check all 30 cell voltages with your DMM to see how many cells may suffer from self-discharge. Then check again after 10 days to see how many are still at 3.96-3.95V. That will give you an idea of how many 30Q cells you may need to replace for those that have a high rate of self-discharge (e.g. 3.80V and lower) after ten days.

The MiBoxer C4 insructions are not the easiest to understand, but i've found it to be a handy tool to have around. If you should purchase it give me a PM and i'll explain how to set it for a charging amperage from 0.10 amps up to 1.50 amps and discharging the C4 cell slot at 0.40 amps.

Could not get either...but have some decent ones...last one can discharge cells also...

Yes, postential of two bummed BMS boards is nill, and figured Vruzend might be decent...but does "Murphy" know?

As it is am planning to make all cells same at 3.5/3.6 and use N.E.S.E modules...stable and rather ingenious designs...will make one 10S3P and one 10S4P, and have the Wallen pack to fall back on.

Just have to know what I am doing. Will agin, double check continuity of all connections, and all currents with my trusty meter.

Thanks, Mark...still have not cashed it...sorry.

jonescg said:

Think of it as a direct connection to each cell. It's main job is to monitor cell voltages. If it goes out of spec, it responds.
The leads are at high potentials, so make sure they can't touch anything.

Click to expand...

What if 4P in 10S4P pack? How does a single wee wire at + area know which P-cell is amok?

I figure volt of group drops etc, and BMS feeds group, as Mark noted.

Because all 4 cells will be at roughly the same voltage. Measure one you measure them all.

@Jones...downunder,

So, not disagreeing, one can place wires from BMS "near" or on balance connections...someone says near group...another says, close by...I am only trying to trace reason for problem I had...and moved to Agnius wondrous modules from Vruzends...me no welder dude. Just want to place BMS wires in right place within these clever modules Agnius made...

And, mate I Thank-you)...

BMS attachment points in orange.

I highly recommend the second option for any battery pack.

Dig and thanks.

I can visualize reason to segregate, but if non-discriminatory,

Why not attached to same bus as serials? Am planning to form pack using NESE AG mods...?

In the second diagram, the BMS attachment point can be anywhere on that link, even on the end of one of the cells. The voltage difference will be negligible.

Much thanks....So, for example, I have a NESE module, preset for P with exterior serial buses. I can just hook wires from BMS to the P bus, and should be OK? Not a weld pack dodger (me) just want ebike to run using pack...and learning more than I should.
Thanks, from Perth...dig...around the globe patter.

Bobbill, i have emailed you a rendering how to wire NESE modules. I dont know how you still have same question? I mean it shows you modules, balance wires and where it is attached. Just repeating:

I know. But, I have this gnawing idea, from reading stuff, that the connection of BMS wires to pack should be between or on the balance bus. Recall, my orig pac just quit and later check of voltages showed some at 2.2v and some at 4.2. I just do not want to do lots of work and have another failure. Just want to ride the wee bike.

Thanks, will go down and grab the envelope you send with the caps and screws...am certain all fine...

Ag, I did as you advised and now bike quit, just being sure of it...have not checked indiv cells, to diagnose problem...just being careful and learning.

agniusm said:

Bobbill, i have emailed you a rendering how to wire NESE modules. I dont know how you still have same question? I mean it shows you modules, balance wires and where it is attached. Just repeating:

Click to expand...

:lol:

i Forgot investigation of cell. takes time, for me, and must report one cell, in mid pack was too low, but NESE packs made change easy.

I gave bike to former neighbor, (before I found problem, so must wait on current status reporting0...but must say the NESE packs made the investigation process much easier...simple is usually best and is proven again.

Too bad others cannot see simple in American politics...Truth is so simple. I know I should include pics, but camera was inside house and was too busy to stop and get it...sorry.