What brand new 18650 cells should I get for my 3 yr old battery to replace some 0v cells?

[someguy152]

@RagingGrandpa@Chriull@alcatraz@mrelwood@WI_Hedgehog

I think i may have done something potentially stupid hence why im currently leaving my 18S out in the shed.

I attached balance leads and put on a low voltage monitor.

Unfortunately i couldnt think of a way to do so to the actual battery terminals without dissassembling the whole bms hence this ii attached the wires to the BMS.  Even though All these connections are taped down with kapton /PET tape, it is  basically my second time soldering.  I'm not super confident in the connection and im not sure i have enough redundant safety measures.

In addition, the fit was so tight due to that small amount of extra wire on the sides that i had to completely remove the shrink wrap and wont' be able to add on a replacement.  I don't plan on riding it in the rain but not sure what other benefit of shrink wrap there is.

My gut is telling me i should just remove these leads as the BMS still seems to be doing an okay job (and i can reattach balance leads every 2 months if i notice something is imbalanced or just manually charge the lower cells)

https://ibb.co/g3zpQXT

[RagingGrandpa]

The hazard is if your balancing leads have an insulation failure. It would happen from rubbing or chafing, which is simple to address with mechanical means. If you can convince yourself that the leads do not flex, move, or get pressed into sharp surfaces, I think it's fine to leave them in place. Secure them using tape, glue, cable ties, etc.

Shorting between any two leads can cause fire.

Shorting between any lead and other circuits in the pack can cause fire.
 

If you cut the original shrink cleanly, it's not so hard to reuse it by taping over your cut. Leave a gap as needed to account for the extra bulk of your new leads. Shrink is 'extra electrical insulation,' 'chafe protection,' and also provides marginal splash protection. (Your pack was never actually water resistant...)

[.....]

42 minutes ago, RagingGrandpa said:

The hazard is if your balancing leads have an insulation failure. It would happen from rubbing or chafing, which is simple to address with mechanical means. If you can convince yourself that the leads do not flex, move, or get pressed into sharp surfaces, I think it's fine to leave them in place. Secure them using tape, glue, cable ties, etc.

Shorting between any two leads can cause fire.

Shorting between any lead and other circuits in the pack can cause fire.
 

If you cut the original shrink cleanly, it's not so hard to reuse it by taping over your cut. Leave a gap as needed to account for the extra bulk of your new leads. Shrink is 'extra electrical insulation,' 'chafe protection,' and also provides marginal splash protection. (Your pack was never actually water resistant...)

^This!

Invest in a tube of sensor safe RTV from the auto store. I use it all the time, to secure wires and prevent chaffing. Hell, I use rtv on all kinds of crap. It stays flexible and sticks to things pretty well. I wouldnt trust it to secure things under stress, but RTV and Zip-ties makes a good combo.

Edited June 3, 2020 by ShanesPlanet

[WI_Hedgehog]

@someguy152, congratulations on being inventive, it's quite an awesome feeling, isn't it?

I'm guessing you have three sets of 8S balancing leads to connect to 20S, and are checking voltage when at home with an 8S cell monitor.

24AWG Silicone Wire resists fire and melting reasonably well.

 

 

Building Battery Packs (in case you're interested)

Shrink wrap keeps the mechanical connections from vibrating & breaking, so it is important on packs, not as much on a BMS.

Reasonable quality Kapton tape doesn't out-gas or cause chemical reactions, it's what you'd want to use for securing wires in this case. (I'd suggest not using RTV and becoming the Gotway Glue Gun Guy.)

Personally, I re-do a job until it's done extremely well (typically 3 to 4 times on something I'm new at). This way I'm not repairing my own stuff 2 years from now, asking what "genius" (sarcastic) came up with that idea, and what the heck was their goal?

You're probably okay safety-wise, but if you don't feel good about it take it apart and do it again after practicing on something else so you don't lift the pads on the BMS from too much heat.

Congratulations again, I commend your initiative!

Edited June 3, 2020 by WI_Hedgehog

[.....]

But the Gotway glue guy is legendary! I agree with @WI_Hedgehog, IF you are planning to go the distance and try to make this as nice as possible. There's many ways to approach builds. With the resources a builder and manufacturer should have, they should NOT be relying on glues and workarounds. Then there's the times when you want to be OCD and are willing to rebuild something and invest in specific materials and spend a LOT of time and revisions to make it perfect. Then there's times when you realize the rebuild isn't a production idea and you merely want something to work. Then there's the way of doing it in a manner that is unsafe and won't work. How you approach this is entirely up to how much time, money and effort you want to spend, and what you expect it to be in the outcome. I can't recall who did the custom gotway build here, but he obviously went top tier in time, materials, and idea. I'd assume that someone new to soldering, should aim for the middle option, and then perhaps perfection on pieces in the future? How many times are you willing to redo this in order to make it perfect? I'm very OCD, by I'm also impatient... tough mix. Fwiw, good solder and hi-quality wire is kind of required in such a critical  environment. Is a higher temp solder required on this stuff? Im a fan of true lead low temp, but it doesnt mix well with cheap shit, nor high temps.

Edited June 4, 2020 by ShanesPlanet

[someguy152]

21 hours ago, ShanesPlanet said:

^This!

Invest in a tube of sensor safe RTV from the auto store. I use it all the time, to secure wires and prevent chaffing. Hell, I use rtv on all kinds of crap. It stays flexible and sticks to things pretty well. I wouldnt trust it to secure things under stress, but RTV and Zip-ties makes a good combo.

I'll have to look into RTV. never heard of it.

Unless i rewire the balance leads so its coming from the front or back of the battery, I have no width clearance to add anything else to the pack (unless i sand/file down the plastic in the unit itself.   It was a real struggle to get the existing pack in. Honestly the fact that my voltage alarm was showing that nothing got disconnected after that endeavor gave me a bit more confidence.  But not sure how that will compare to the stresses of riding and taking bumps and eventual but rare falls.

I've done one 20mile ride so far.

[.....]

https://www.permatex.com/products/gasketing/gasket-makers/permatex-sensor-safe-blue-rtv-silicone-gasket-maker/

Admitting to not knowing what room temp vulcanizing compound is, speaks volumes in itself   Its just a type of adhesive, there are MANY kinds, but some off gas and arent suitable for electronics. RTV in an auto shop is about as common as elmers glue at a school.

[someguy152]

21 hours ago, WI_Hedgehog said:

@someguy152, congratulations on being inventive, it's quite an awesome feeling, isn't it?

I'm guessing you have three sets of 8S balancing

Congratulations again, I commend your initiative!

im pretty proud of this method of balancing i came up with using stuff i had around the house. i ppwer it woth a  battery bank i have. its silow at 1amp, and could be annoying if i didnt guess right that my weak cells dont continue to be  the first and fifth ones, but i can easilymake some more.

Edited June 4, 2020 by someguy152
too much info

[someguy152]

4 minutes ago, ShanesPlanet said:

https://www.permatex.com/products/gasketing/gasket-makers/permatex-sensor-safe-blue-rtv-silicone-gasket-maker/

Admitting to not knowing what room temp vulcanizing compound is, speaks volumes in itself   Its just a type of adhesive, there are MANY kinds, but some off gas and arent suitable for electronics. RTV in an auto shop is about as common as elmers glue at a school.

me and cars dont get along. in my 15 to 20ish years of having the ability to drive , ive driven what a normal suburban person does in probaly two or three (i had a commuting job finally lol).  EUCs have been one of the only things to get me out of the house on my own volition lol

[someguy152]

21 hours ago, WI_Hedgehog said:

I'm guessing you have three sets of 8S balancing leads to connect to 20S, and are checking voltage when at home with an 8S cell monitor

it's a 16series battery so 2 of these 8s leads works so darn well.

[.....]

Time to get out and play! To be fair, when i had the misfortune of living in a city, I didnt get out much either. Sounds like the euc is going to help save you from an otherwise sheltered life. Buy two of those things, get a camera and get on out from between  those four walls!

[someguy152]

i have the whole kingsong S series! never a dull ride...pretty much perfect speeds

[someguy152]

Instead of tape is there some sort of non conductive compound that i can put over the soldered connections that is EASILY removable if i do need to access the connections?

i think having that would make me way more comfortable than tape as adhesive probably degrades over time

[someguy152]

hello again,

@RagingGrandpa@Chriull@alcatraz@mrelwood@WI_Hedgehog

So my pack is a bit more out of balance than first thought and my concocted method is a bit slow and intrusive to normal life.  I'd like to change one of those things and was thinking about getting one of these BattGo BG-8s units(amazonlink) or maybe two of them to balance.  They're slow but at least i won't have to attend to them.

Just double checking that I'm okay to hook up two of these 8s units to my 16s battery at the same time without shorting something (does that only apply to single units with balance boards?). I'm afraid my understanding of batteries stops when it comes to grounding and all these different connections unless there are clear pictures.

 

I can't get myself to give kingsong another $500-600 for a new 840wh battery when i think inmotion is close with much improved smart battery monitoriing

Edited June 15, 2020 by someguy152
added deets

[alcatraz]

If the battgo isn't connected to a power supply it can't top balance. You might end up with two sets of 8s cells at different levels.

Also I think it will take an eternity. Check the balancing current it can supply. How much is it?

I know attending it is annoying but you already have to take the euc cover off etc. Better to turn the juice up on those unbalanced cells and save you some time.

If you are using a balancer with a power supply. Make sure they each have a separate supply and that they run off the mains. Any DC-DC power supply can't be used as it will short the pack.

If I were you I'd buy one of those 8s balancers and 2-3 (how many you need?) single cell high amp chargers. 

The really useful thing about balancing without top balancing (power supplied balancer) is that you can balance at any charge level which is good. Otherwise you might only be able to balance at 100% which takes an eternity.

[alcatraz]

Remember that you don't have to balance often. As long as you don't go under 2.8V or over 4.2V you're fine. You will get a hang of how long you can go between.

If one group is 4.0v and the others 4.2v it's no big deal. Even if you deplete the pack to 3.4v that low group won't go under 2.8v.

When the low groups start to get to 0.3-0.4v below the median then you should balance I think.

[Chriull]

15 minutes ago, someguy152 said:

Just double checking that I'm okay to hook up two of these 8s units to my 16s battery at the same time without shorting something

Yes, no problem.

15 minutes ago, someguy152 said:

(does that only apply to single units with balance boards?).

Sorry, i don't understand this.

As 

4 minutes ago, alcatraz said:

If the battgo isn't connected to a power supply it can't top balance. You might end up with two sets of 8s cells at different levels.

means you will end up with 8 cells getting balanced to the average of this 8 cells, and the other 8 to the their average.

As @alcatraz was again faster with typing  "major" balancing is to happen seldomly. One can do this cell by cell with a single cell li ion charger. Important is to measure regularly the voltage so one knows if they are balanced!

21 minutes ago, someguy152 said:

So my pack is a bit more out of balance than first thought

Maybe you should check first if it is still working out after a manual balance. If it gets out of balance about every (few) ride(s) you'll have to replace some cells anyhow.

If so, changing to a smart bms will be the better option...

[someguy152]

22 minutes ago, alcatraz said:

Make sure they each have a separate supply and that they run off the mains. Any DC-DC power supply can't be used as it will short the pack.

@alcatraz  so the way im doing it now, i power this with a battery bank. are you saying i could have an identical setup with another power bank and i wont be shorting because it's two separate power supplies?

 

 

24 minutes ago, alcatraz said:

If I were you I'd buy one of those 8s balancers and 2-3 (how many you need?) single cell high amp chargers. 

that seems like a smart compromise

 

22 minutes ago, alcatraz said:

Remember that you don't have to balance often. As long as you don't go under 2.8V or over 4.2V you're fine

thank you, that makes sense. i have my low voltage alarms too. I think i'll set them to 3.2 to eak out as much capacity as i can

[someguy152]

15 minutes ago, Chriull said:

Maybe you should check first if it is still working out after a manual balance. If it gets out of balance about every (few) ride(s) you'll have to replace some cells anyhow.

yea i haven't unwrapped my other 420wh battery but on my latest charge, the bms for the one i have opened up didn't seem to be balancing.  the charger seemed to stop when one of my cells hit 4.25v (according to the low voltage alarm, which is cheap and probably inaccurate.)  I left the charger on and while that cell went down to 4.2v, the other cells also dropped by the same amount

 

17 minutes ago, Chriull said:

If so, changing to a smart bms will be the better option...

i agree, but i'd need to figure out how i can create more space

i really appreciate all the feedback!

[Chriull]

15 minutes ago, someguy152 said:

yea i haven't unwrapped my other 420wh battery but on my latest charge, the bms for the one i have opened up didn't seem to be balancing.  the charger seemed to stop when one of my cells hit 4.25v (according to the low voltage alarm, which is cheap and probably inaccurate.)

Yes - at ~4.25V the BMS shuts off the charger (cell overvoltage protection)

15 minutes ago, someguy152 said:

  I left the charger on and while that cell went down to 4.2v, the other cells also dropped by the same amount

Every cell above 4.2V will have the balancing resistor in parallel until discharged to 4.2V again.

You can repeat this until the cells are equal or single charge with an extra li ion charger individual paralleled cell groups with an external charger.

[someguy152]

17 minutes ago, Chriull said:

Every cell above 4.2V will have the balancing resistor in parallel until discharged to 4.2V again.

but the issue it seemed was that all the other cells seemed to drop by the same amount of voltage, whereas in proper balancing, i should have seen the smallest voltage cell increase.

[Rafal]

16 minutes ago, someguy152 said:

should have seen the smallest voltage cell increase.

This is active balancing what you talking about.

99.9% of BMS uses passive balancing.

[Chriull]

24 minutes ago, someguy152 said:

but the issue it seemed was that all the other cells seemed to drop by the same amount of voltage, whereas in proper balancing, i should have seen the smallest voltage cell increase.

About which voltage do they have?

Every li ion cell drops voltage after charging if no full charge cycle was done.

If some cells are already too full you need to discharge them (or all) or just charge the empty ones.

[someguy152]

38 minutes ago, Rafal said:

This is active balancing what you talking about.

99.9% of BMS uses passive balancing.

sorry i guess what i meant is i shouldn't have seen the other cell voltages drop too, only the ones that were above 4.2, right?

[Rafal]

1 hour ago, someguy152 said:

sorry i guess what i meant is i shouldn't have seen the other cell voltages drop too, only the ones that were above 4.2, right?

Yes if BMS balance cells above 4.2 voltage. But others cell voltage can drop a bit as well. That is normal. But lets say about an hour after disconnecting the charger only cells above 4.2V  should drop due to balancing.