Bus Bars on LFP

[CaptainRivet]

Originally Posted by s/v Jedi

The cheap EVE cells have had lots of problems, with second hand, rejected etc. cells with a new wrapper being offered as new and orders filled with cells with wildly differing internal resistance. Much of the cautionary comments incl. mine are based on that.

But maybe things have improved and you can now buy really good cells from the same production run and everything is fine. The problem is knowing this for sure.

Had, long long time ago 3 or 4 years ago and if you use reliable resellers like nkon.nl then you don't have this issue. They clearly state grade and you get proper doc with each delivery. Now you partly get even grade A+ as the manufacturer swimming in overproduction.
batteryhockup.com eg buys complete new modules from EV or battery manufacturer overproduction (no rejected moduls or cells) and then dismantle them, these are all grade A+ cells as in one modul parallel, a cheap and very good quality source. Yes they also sell used EV modules and used cells but clearly mark that.

Also get EVE with the 2 pole terminal and you don't have any contact problems at all and if it's a notch from drilling or stamping the hole into the busbar but not the terminal.

[CaptainRivet]

Originally Posted by s/v Jedi

For battery terminals my recommendations:

- use a purple 3M Scotchbrite metal prep pad to polish up the terminals and cable lugs contact surfaces.

- coat the contact surfaces with a good quality dielectric grease, I prefer this one because of its plastic spout: https://www.amazon.com/gp/product/B000CCIDAA

- assemble the terminal connections and use the torque as specified by the cell manufacturer or experts recommend as you research this for your type of cells.

- wipe away excess grease. The exposed metal parts of terminals and cable lugs need protection and I prefer to use the battery terminals protection spray that I apply in multiple thin coats. There’s also other options, like a conformal coating spray but it’s much more expensive and I don’t think it’s much better.
I use this one: https://www.amazon.com/CRC-05046-Bat.../dp/B000CIPUNC

Soft surface of scotchbrite doesn't make the soft alu surface more even.

Aluminum builds up its oxide layer in under a second but that oxide layer is 98% conductive so needs no additional grease. What that grease does is avoiding more layers build up and different oxide layer between eg alu and copper that can buildup over time.

If you do it then do it right:
Use an even piece of alubar. Then use 1200 grid wet and wrap around.
Now apply No-al-ox or similar special electric grease for aluminum to the alu terminal. Then sand with the paste the oxide layer away, the paste will prevent from oxide layer building up again but also works for sanding paper. Now wipe paste away and reapply new paste, wear gloves and lightly scaf over the surface 2 or 3 times with a fresh part of sanding paper over the terminal to get rid of that tiny layer build up inbetween. Now take the rubber glove finger put tiny bit of no-al-ox and wipe over terminal to side to rid of the containment paste and at the same time re-apply a new layer. No oxide layer can form.
Do the same with the contact surface of the busbar. Now put busbar on cells it connects and wiggle it around while applying light pressure, that causes to push to much grease out to the sides of terminal and only have a tiny layer of grease inbetween so your torque down value gets not fooled by too much grease, another error that frequently happens when grease is used.

That's how you do it right but in 98% not needed as the alu oxide level is conductive. Same if you sanding silver or tin plated copper you sand plating away and make it worse.
For 1p series batteries just build as you get, put high load and feel with finger and look at cell values. If different check torque values. If that doesn't fix it, check the busbars are even. Only if that doesn't help do the grease procedure.

No production drop in battery teardown i ever saw uses grease, neither for contact and also corrosion protection.

Over 20 years thats my experience with busbars:
Till 150A and 1p batteries, use what's supplied with cells as thats sufficient and works.
For the rest and especially parallel banks (eg the negative busbar in my 4p4s battery is 62cm long!!! connecting 8 cells)
Best is alu-terminal to silver plated copper(reuse nh blade knife as busbar, works for 2p cells cheap top notch quality), 2nd best is alu to alu busbar that is up in size to be even in resistance as similar copper (also cheaper and the beefier size make it mechanically more stable then copper bar which is soft and bends easily). 3rd best is alu to tin plated copper and only 4th is alu terminal to bare copper as oxide layer can build up over time when contact surface is not 100%=airtight.

[Fuss]

Ok, if thats the way its done, then I would expect that with the care you take with cell selection and installation that you would not need your BMS to be balancing your cells.

Does your installation need cell balancing?

[CaptainRivet]

Originally Posted by Loredo

Then more I use the LFP, then more I read how others assemble and use it, then more I'm led to believe* that at the end of the story the whole LFP thing is much more robust than what we all think it is. With grease; works. No grease; also. Bus bars of all kinds and makes, works. With passive balancer; works. Active balancer; also. And so on... I think* if the cells are a reasonable match in the battery pack, it just works.
Like the lead-acid technology, as long as you don't do anything real stupid, works. As most often, there's more than just one way to skin a cat. Let's start another thread. Who has had a catastrophic failure with LFP? My guess* not too many if any.

*believe, think, guess = worth nothing. Know is the only real thing. How do I know? It has to be observeable, precisely measureable, repeatable.

As long as you stay 1p batteries all mistakes reveal soon and even a cheap BMS will let you max ruin the cells. How far you can go here showed me Andy from offgrid garage with his Frankenstein battery with different cells even in capacity, different busbars. Basically garbage nailed together an a 180Euro JK inverter BMS has this under control. That's why I recommend buying cells and the EEL kit as building a very good battery that's much better as all these budget chinese surprise boxes and building it is as easy as making bread with your bread maker.

Parallel banks are totally different animal. Why do you think that besides EV and 2p batteries of mostly budget line no one uses anymore multiple parallel cells in commercial use? All went to 1p battery parallel.
And EV must but have highly sophisticated BMS and eg a cell fuse inbetween cells.

Parallel cell banks are experience, experience and again experience that counts and what works over 10 years to have stable and relative dangerous free banks as they are so many dependencies which exponentially grow with each parallel cell more.
And not theories or "experience" from one or 2banks that are 2 or 3 years and you think work flawlessly. Often luck in doing the right thing and/or very low c use prevented catastrophic events.
And that's the reason I stop at 4P batteries with 4S and 8S and for 16s max 2p. And do this less and less as no advantage anymore to 1p batteries parallel.
And from that experience a 6P8S the alarm bells ringing like chingle bells...again I give you my experience for free and have nothing from you changing your battery or do the test I recommend. Take it or not your choice...

And yes I know many catastrophic events of eg burned down houses as I also was head of claims of a big insurer as I mentioned also couple time and in 90% these where multiple parallel cell 8s or 16s banks.

[CaptainRivet]

Originally Posted by Fuss

Ok, if thats the way its done, then I would expect that with the care you take with cell selection and installation that you would not need your BMS to be balancing your cells.

Does your installation need cell balancing?

Parallel cell banks need balancing, always doesn't matter how perfect your cells are and also 13.8V absorption won't do it, 14.4V or 3.55V is needed longtermed as cells can only even themselves perfectly out in the knee as in the flat part they cannot. That's the big difference of lifepo4 to Lio-ion tesla, LTO cells in parallel. Elon also learned that when switching to LFP cells.
But nothing of that doesn't damage or reduce lifespan if you keep it at 13.45V float. And a 15$ cheapo active balancer is a cheap insurance, in worst case it useless but in best case it saves your ass and the bank a long problem free life.

And perfect cells is simply a question of money. Winston are but cost 5x and if used in single cell batteries in 4 and 8S I often skipped a BMS and simply used a BMV712 as BMS plus an active balancer which gave me the cell voltages via BT and well the balancer was for free add on. Better save then sorry for cells with that price.
Winston sells 12V only without BMS but if you look carefully then you see that their specs eg c-rates are reduced and single battery use only. Used them often in cars or as starter and they are awesome.

[s/v Jedi]

Originally Posted by Fuss

I imagine that when you buy A grade from a reputable company, then they are A grade....else all would hear about it right??

Wrong, this is exactly how people were scammed. Surely you remember the fake QR codes etc. ?

No, it was a jungle and I still didn’t hear of a 100% reliable supplier.

[Fuss]

Originally Posted by s/v Jedi

Wrong, this is exactly how people were scammed. Surely you remember the fake QR codes etc. ?

No, it was a jungle and I still didn’t hear of a 100% reliable supplier.

I only have experience with NKON.nl and they are very reliable and would never sell B as A…. call them up, they’re great to deal with… and if you like, they can speak Dutch as well, they’re your compatriots … a dream made in heaven!!!!!
(and 100% reliable too)

[Fuss]

Originally Posted by CaptainRivet

Parallel cell banks need balancing, always doesn't matter how perfect your cells are and also 13.8V absorption won't do it, 14.4V or 3.55V is needed longtermed as cells can only even themselves perfectly out in the knee as in the flat part they cannot. That's the big difference of lifepo4 to Lio-ion tesla, LTO cells in parallel. Elon also learned that when switching to LFP cells.
But nothing of that doesn't damage or reduce lifespan if you keep it at 13.45V float. And a 15$ cheapo active balancer is a cheap insurance, in worst case it useless but in best case it saves your ass and the bank a long problem free life.

And perfect cells is simply a question of money. Winston are but cost 5x and if used in single cell batteries in 4 and 8S I often skipped a BMS and simply used a BMV712 as BMS plus an active balancer which gave me the cell voltages via BT and well the balancer was for free add on. Better save then sorry for cells with that price.
Winston sells 12V only without BMS but if you look carefully then you see that their specs eg c-rates are reduced and single battery use only. Used them often in cars or as starter and they are awesome.

what about your 8s bank… does this need constant balancing?

[newhaul]

Originally Posted by s/v Jedi

Wrong, this is exactly how people were scammed. Surely you remember the fake QR codes etc. ?

No, it was a jungle and I still didn’t hear of a 100% reliable supplier.

My experience with CALB says otherwise .

[Loredo]

In two years, I've "tried" to top balance twice. I say tried because both times the cells were (still) in perfect balance. No need for balancing.
But wait a moment, let me explain, as per my my BMS (it's there only to gain easy access to the cell voltages) I should've balanced. Off of my memory, it said something in the 40mV difference @3.6ish V. I turned the active balancer on and it started to do it's thing. Yuhu, my stuff works! NOT!!! I pulled out the trusty Fluke and checked the cells directly on the bus bars. YIKES, there was no 40mV difference, they were in balance down to 0.001V. Then I checked the voltages directly on the BMS connector, they were right on the dime, no voltage loss in the wires. Gives? So, in two years no balancing needed.


Cell quality certainly is the most-most-most important part in the whole build. Another vote here for Nkon.nl. Good to talk with, easy to deal with, honest people, delivery when promised. My vote for them is a AAA+. Usual disclaimer, not affiliated, just a happy customer.
I got scammed three times too with junk cells before I found Nkon. I was lucky and got them to take the cells back all three times.

Another reliable source for LTO cells: Lto-store.de same vote as for Nkon.



Wait a moment, something's just wrong here! All of a sudden we all agree upon something? Nah, can't be!
Should we start a thread for the DIY folks? Pointing out where to find quality cells, BMS's... ?

[CaptainRivet]

Originally Posted by Fuss

I only have experience with NKON.nl and they are very reliable and would never sell B as A…. call them up, they’re great to deal with… and if you like, they can speak Dutch as well, they’re your compatriots … a dream made in heaven!!!!!
(and 100% reliable too)

Fully agree, never had an issue with nkon.nl with them.
And in US batteryhockup.com as well absolutely clear what they sell.
And Andy from offgrid has some good recommendations as well.
And do you know what quality you have in Li-time, powerqueen....? You don't have even cell voltages.
A JK BMS with active balancing makes it also absolet to have grade A if you build single cell battery and 50 or 60 Euro for 300AH, even if they are only 270AH is still an absolute great deal. But at nkon.nl or hookup you get what you order.

[CaptainRivet]

Originally Posted by Fuss

what about your 8s bank… does this need constant balancing?

It's a a parallel lifepo4 cell bank, so it's needs balancing and the 150mA passive balancing of the ElectrodacusBMS was not enough in iteration 2. Maybe now in iteration 3 where I really made everything perfect but I didn't try, why should I?

I have 4p4s and that's in the 4 till 8mV at 3.55V incl. an 5A active balancer but eg my bank was now for 53 days not in the balancing range and is still showing in the 4 till 8mV range even when i pull 350A. The BMS always balances passive above 11mV deviation but till now balancer didn't kick in. but I expect if I now get into the knee that I would end up in around 15-20mV deviation at 3.55V without active balancing but why should I?? The 15$ heltec does a perfect job to keep the bank always perfectly balanced and only works above 8mV and from 3.4V charge till 3.35V discharge.

[s/v Jedi]

Originally Posted by newhaul

My experience with CALB says otherwise .

Huh? Calb isn’t Eve afaik. I never heard of fake new Calb cells being sold with scratched-out qr codes etc.

On reliable sellers: maybe there are, but there are thousands and you need one local to you. Americans aren’t buying cells from Europe etc.

for cells inside LiTime you can simply watch what Will Prowse finds when he cut them open and tests them. His tests quickly reveal some that have less capacity than usual and that’s immediate suspects of course.

[CaptainRivet]

Originally Posted by s/v Jedi

Huh? Calb isn’t Eve afaik. I never heard of fake new Calb cells being sold with scratched-out qr codes etc.

On reliable sellers: maybe there are, but there are thousands and you need one local to you. Americans aren’t buying cells from Europe etc.

for cells inside LiTime you can simply watch what Will Prowse finds when he cut them open and tests them. His tests quickly reveal some that have less capacity than usual and that’s immediate suspects of course.

You find dozen US based sellers in Will Prowse forum.
For US incl. Caribbean you can order from batteryhockup.com
There are also some relaible Chinese sellers eg through offgrid garage.
Winston doesn't have a local us seller and you need shipping from China. For Europe winston finally seem to have at least some stock but for 5x they can be up my doorstep and I wouldn't buy except the 12V sealed ones and maybe small cells.

LI time what will does is one battery of millions. General build quality and new cells with some capacity but how do they actually look after 3 years when you have no cell voltages...every cheap BMS has BT so that's getting red flag...
Better have grade B and a good BMS with active balancer....

[newhaul]

Originally Posted by s/v Jedi

Huh? Calb isn’t Eve afaik. I never heard of fake new Calb cells being sold with scratched-out qr codes etc.

On reliable sellers: maybe there are, but there are thousands and you need one local to you. Americans aren’t buying cells from Europe etc.

for cells inside LiTime you can simply watch what Will Prowse finds when he cut them open and tests them. His tests quickly reveal some that have less capacity than usual and that’s immediate suspects of course.

Mine came direct from the factory remember I used to own a marine repair business.
I still have a few Comercial contacts .
They even supplied busbars that met the specs they wanted at the time ..
Follows my quoted links back it did not specify any manufacturer, suppliers , or local to anyone vendors.