The battery builders club

How-Tos & Esk8 mechanics
, , , ,
668

Help with charging please :pray:

Problem, newly installed D140 BMS not charging.

Went on ride with a fully charged 42V battery on a 10s4p pack yesterday.

Installed volt meter showed Battery at 35.6V, plugged in my charger and noticed the green light on charger stayed green. Left it on charge for ~ an hour, battery still read 35.6V.

Did some measurements:

  • Charger output is 41.8V (not connected to charger port)
  • Individual 4p pack read 3.4 to 3.6V, 1 pack showed 3.4V with the rest between 3.5 to 3.6V.

Are the voltages between packs too large (0.2V) for the BMS to balance? or my BMS shot?

10S4P%20Unity_D140
10S4P Unity_D140.jpg1280×720 106 KB

669

This sounds suspiciously like it’s the same cause as your other BMS issue. As if the BMS is in protection mode. I still think the most likely issue is some contact problem with the balance leads. Might even be miswired?

Can you measure voltages at the JST-XH connector, with meter positive lead connected to pack (+), check voltage with the meter negative lead at each contact? Looking at your diagram it looks like 10 wirres for 10s, with shared +. so contact #1 should show 0v, contact #2 should show 3.5v, and so on.

If that’s all good, can you check if you have the order correct for the JST-XH pins? Maybe you have them reversed?

Also with charger turned on and connected try reading voltage at pack +,-. Compare to resting voltage. It should go up slightly. If it doesn’t the BMS is probably in some protection mode.

670

Comments concerns on the welds?

I plan to add silicon between the cells. Something with a nice thermal rating? But mostly for mechanical support.

I also am planning.on doubling up the strips.
Dual 6374 in a hilly environment should draw good amps.

IMG_20190803_164311
IMG_20190803_164311.jpg3456×4608 3.52 MB
IMG_20190803_164704
IMG_20190803_164704.jpg3456×4608 4.09 MB

671

Some look a bit overdone; this document has a lot of valuable info.

Screenshot%20from%202019-08-04%2007-28-59
Screenshot from 2019-08-04 07-28-59.png732×368 107 KB

3 Likes
672

double_nickel
double_nickel.png789×378 21.7 KB

Just for lolz, has anyone ever tried this? If your spot welder can’t handle thicker nickel and you don’t want to weld nickel to nickel, maybe this is a viable option? :stuck_out_tongue:

2 Likes
673

Found the problem
apparently, silicone based adhesive that I used to affix BMS to the enclosure caused it to short, went in protection mode.

After cleaning the adhesive, BMS is working fine now.

Thanks for the help :slightly_smiling_face:

5 Likes
674

Silicone is conductive until it cures.
After it cures, conductivity depends on the particular type of silicone used.

1 Like
675

Silicon was not completely cured when I removed it, probably the same thing happened with my previous BMS.

1 Like
676

You shouldn’t have silicone sealant in contact with electronics anyway. Even neutral cure silicone is conductive since it has lots of moisture before it cures.
Not to mention that silicone absorbs moisture.

3 Likes
677

Good to know, what do you use?

678

I usually cover the BMS in heat shrink first then secure on the enclosure.
If I fear there will be any sorts of rubbing, I add fishpaper too.

2 Likes
679

Liked your method with heat shrink and fishpaper :ok_hand:

2 Likes
680

So you would still use silicone but cover first? Honest question from a scared dude who just uses silicone on everything

681

So I got this nickel strip form nlon.nl
https://eu.nkon.nl/accessories/battery-solder-strip/nikkel-batterijpack-verbinding-soldeerstrip-27mm.html
It’s advertised as “CHEMICAL COMPOSITION:NICKEL ≄99.7%”

I still was curious and did a salt water corrosion test. It started to rust after a day. hmm :thinking:

1
1.jpg1927×1295 574 KB
3
3.jpg1336×1999 552 KB

Now the weird thing: I can wipe away the corrosion and rust with a dry paper tissue and the strip looks like new!

2
2.jpg1833×1094 533 KB
4
4.jpg1390×1724 561 KB

(and no, the pics are NOT before I did the test)

So WTF is that “pure nickel” strip made of???
I’m thinking, if it’s nickel plated steel I couldn’t just wipe of all the corrosion?

Oh, and should I use it?

2 Likes
682

How does the voltages look on these pack, do they look to high or low?

Screenshot_20190805-155533_xiaoxiang
Screenshot_20190805-155533_xiaoxiang.jpg720×1480 134 KB

683

The 3.65 one is a little bit low, the rest are all pretty within reason for a balanced pack since they are (±0.01) I think people are fine with ±0.05 but I don’t know for sure

And obviously by the battery indicators they are at like 65% charge

684

#5 is low but not as low as your phone battery :wink:

5 Likes
685

Could be metal dust from manufacturing that’s rusting on the surface.

686

I found the cause for the discharging first P-group in my pack.
The transistor in my BMS that is responsible for that P-group has low resistance.
I basically had around 4,7 kOhm slowly discharging my P-group.

1 Like
687

I need some help guys. I have x4 Li-Po’s that I want to use on an eMTB build. I would like to combine 2 in series, the 2 series in parallel. I have the POS & NEG structure defined, but Im at a loss as to how to connect the balance leads. I haven’t done a lipo build in a couple of years and I don’t wanna make a mistake. Any help would be greatly appreciate.

Each individual pack has the following voltages per lead.
PACK NEG (BLACK)
Cell 1 = 3.7 (YELLOW)
Cell 2 7.4 (YELLOW)
Cell 3 11.1 (YELLOW)
Cell 4 14.8 (YELLOW)
Cell 5 18.5 (YELLOW)
Cell 6(?) 22.2 (YELLOW)
PACK POS (RED)

There are 4 of these packs, given that each one connects to its neighbor in series to make x2 12s1p groups then connects in series to make a single 12s2p group, how do I connect the balance leads to the BMS?

2 Likes