Use solder paste on terminals-busbar to improve conductivity?

[Frank in Thailand]

So much combined knowledge here I don't want to miss the chance on asking.

For LiFePO4 higher Amperage cells you connect the terminals with bus-bars.
Bus-bars that are bolted onto the terminal.

I personally use headless bolts as they place less stress at he weak shallow aluminium thread (only 6mm deep and max 8Nm torque!!!)

Anyway, to improve connection between bus-bar and terminal they obviously need to be cleaned and flat as possible.

I read that professional installers use silver electricity conductive paste. Expensive stuff!!

Many people use nothing in between.

Would something simple as solder paste improve the connections between the terminal and bus-bars??

Solder paste flux is non-corrosive
Solder paste have about 50% solder.

Naturally, a really thin layer, just to maximize conductivity.

It won't be as good as silver, but I think a lot better then nothing!

Positive is that it's easy to obtain, easy to use and not crazy expensive!

Both terminal and bus-bars (this is not yet bus-bar, now just copper bar) have minimal damages and the terminals have circles.


Flatening by filling the mini gaps should improve total contact surface, yes??

Or is it a dumb idea??
And if it is, why?

I already have 1.4ml silver conductive paste, and use this.
Probably won't be enough....
The order from 3 * 2.5ml turns out to be 3 * 0.2ml....
That will go back to the shop.
Price wasn't like 0.2ml

 

[ianganderton]

Not sure what solder paste is. I've seen mention of tinning busbars to improve connections. It helps in 2 ways

1. prevents corrosion
2. the tin is softer than the copper so helps create a better connection by mounding to the terminal better

I'd like to see a video on how to tin busbars. I think that would be interesting and worthwhile

Would solder paste change over time at all?

 

[upnorthandpersonal]

The flux itself won't help at all; it's non-conductive and the 'micro-beads' of solder paste don't form a smooth surface since you would use only a thin layer of which 50% is just flux. You can tin the bus bars either chemically for a very thin layer, or you can take a blow torch and tin them with some regular solder or tin.

Personally, I have no problems with a copper bus bar and just some anti-corrosion product in between such as Noalox or equivalent.
The datasheet of these cells states that you should polish the pole with some abrasive paper before use, this is to remove the layer of aluminium oxide - this is when you would add the Noalox since otherwise the layer of oxide would just come back in a manner of minutes.

 

[Frank in Thailand]

If solder paste would change over time??
I don't think it will in negative sense.

The flux will vaporise for some part, tin stay the same.
For weight, it's 90%tin, 10% flux.
At start flux volume is like 50% after vaporising, less.

It's like tinning, except no heat
(That is the idea behind it)
Silver conductive paste does the same, prevent corrosion , and also soft to shape to the terminal.

Both also prevent possible galvanic corrosion.

I Like the way copper looks...
And don't want to spoil it with DIY tinning.
If I am going to do it..
It wont look good..
And need hours of time to make flat again

 

[Frank in Thailand]

I never heard of Noalox before
Good tip!!

- after search it seems only available via Amazon or eBay...
Price about 75 USD include shipping and tax :-(

You know home made alternative?
Or just work fast after cleaning

 

[Frank in Thailand]

Few searches later is the cheapest to get in normal time about 50usd.
Or 6,+ free shipment and receive 17 December...

Clean the terminals and bus-bars.
That is most important part as aluminium and copper oxidation are non conductive.

Copper oxidation is slow, I have hours / days time.

Aluminium goes fast, still minutes is more then enough.

My cells first get the parallel bus-bar.

Process:
1. - Clean all copper bus-bar.
2.- Clean 2 aluminium terminals
3. - Apply little bit silver paste, put in headless bolts on both terminals
4. - Place the bus-bar on top,
5. - hand tighten the nut on the headless bolt to press the busbar strong enough on the aluminium terminal to get even layer of conductive silver paste.

Step 3 to 5 should take like 30 seconds, a minute perhaps.

Bus-bars go on top in like 30 seconds after cleaning the terminals.

That is more than enough time

For the copper bars in-between?
I don't have enough silver conductive paste.
Options are :
- nothing
- vaseline or similar
- solder paste
- ?

What would be best?

 

[Zil]

All flux is corrosive. That is how it cleans the surface during soldering. Some more than others. Rosin is least corrosive. Tallow next. Stuff in tinners flux is very corrosive. We used plain old axle grease in the army. As civilian we used Vaseline. Are there not any electricians around with some anti-corrosive paste?

 

[Frank in Thailand]

Electrician implies any level of education or real knowledge on that field???

No. Sorry.
No have.

Flux is corrosive to the oxidation only, or both oxidation and copper??
Most Modern flux now don't need cleaning.(according to the package)
(I Still do, just don't want to take the risk)

I can not buy solder paste locally, that is too advanced.

Soldering iron rare.
Most people, if they need to solder wires, use car battery.

Works perfect for tractor or truck

Most connections are twister bare wires.
Outside? perhaps with plastic bag wrapped around it for rain.
Normal here.
Even in hotels and gouvrement buildings...

But that's OK.
I don't need anti-oxidation.

Acid like lemon juice or vinaigrette with some baking soda makes perfect oxidation remover for aluminium and copper.

For the terminals I'm good, I have silver paste.
For bus-bar to bus-bar, (copper on copper) I don't have enough.
Vaseline, that I have loads

Voltage difference between cells of 0.02 is already significant for LiFePO4. (Due to not excellent conductive connection)

My current setup using just vaseline works mostly good.
2 parallel strings act little funny and hard to reconnect quickly.

Little funny, not bad enough to take immediate action.
During high loads they "walk away".

Just want to be sure not to have it in my permanent setup.
Situation of better safe then sorry.

I now use stock bus-bar, they will be replaced by bus-bar that cover the whole terminal surface.
That already will make difference.

Once all is connected it won't be easy to access all cells.
For some I need to disassemble a lot of I need to do maintenance.

You need to be here to realise how back to basics life here is.
Fancy stuff is not available, or perhaps via mail order.

Even a pair of pointy tweezers can't be bought at farmecy or drugstore.
Surprised as I was, I was sure our local town must have...
8 stores later I decided to order online.
(All stores do have the wide ones to remove eyebrow hairs... They won't work for splinter)

In Bangkok or Phuket, loads of stuff and specialist.

I'm 20km from Laos border..

Google Maps

Find local businesses, view maps and get driving directions in Google Maps.

maps.app.goo.gl

Just getting groceries takes 45-60 minutes to get to the store.
(By car)

 

[ianganderton]

I’m feel like I need to chime in here

the question was asked “what’s best?”

best is what’s right for the job. The right thing will be that which is designed for the job.

you have an incredibly expensive and powerful battery pack there that should provide excellent value for many many years if put together and looked after correctly.

put together incorrectly with the poor quality parts and you’ll have poor connections and they will at best damage the expensive cells, at worst cause a fire.

while lifepo4 won’t in itself cause a fire by chemical reaction it can very easily because of the huge amount of power stored, lifepo4 can release that power quite quickly too

that’s my 2 cents worth. Best product is the right product is the one designed for the job

 

[Frank in Thailand]

And that is??

"Best product is the right product is the one designed for the job"

What I could find is silver conductive paste to be used by professional installers in telecom.

That I have

For in between bus-bars, I don't know.
Possible also silver conductive paste.
Problem is that it will take weeks to get enough.

For this I like to know what is best out of the available options:
- nothing
- vaseline or similar
- solder paste
- ? Local available other solution

Your input is highly appreciated ??

 

[ianganderton]

anti-corrosion product in between such as Noalox or equivalent.

 

[ianganderton]

Vaseline dries out. Not good

 

[ToadHarbor]

So much combined knowledge here I don't want to miss the chance on asking.

For LiFePO4 higher Amperage cells you connect the terminals with bus-bars.
Bus-bars that are bolted onto the terminal.

I personally use headless bolts as they place less stress at he weak shallow aluminium thread (only 6mm deep and max 8Nm torque!!!)

Anyway, to improve connection between bus-bar and terminal they obviously need to be cleaned and flat as possible.

I read that professional installers use silver electricity conductive paste. Expensive stuff!!

Many people use nothing in between.

Would something simple as solder paste improve the connections between the terminal and bus-bars??

Solder paste flux is non-corrosive
Solder paste have about 50% solder.

Naturally, a really thin layer, just to maximize conductivity.

It won't be as good as silver, but I think a lot better then nothing!

Positive is that it's easy to obtain, easy to use and not crazy expensive!

Both terminal and bus-bars (this is not yet bus-bar, now just copper bar) have minimal damages and the terminals have circles.


Flatening by filling the mini gaps should improve total contact surface, yes??

Or is it a dumb idea??
And if it is, why?

I already have 1.4ml silver conductive paste, and use this.
Probably won't be enough....
The order from 3 * 2.5ml turns out to be 3 * 0.2ml....
That will go back to the shop.
Price wasn't like 0.2ml

I saw David Poz use this stuff for his huge DIY BYD battery packs. I got it myself. it's very messy.

MG Chemicals Carbon Conductive Grease, 80g Tube: Automotive Anti Seize Lubricants: Amazon.com: Industrial & Scientific

MG Chemicals Carbon Conductive Grease, 80g Tube: Automotive Anti Seize Lubricants: Amazon.com: Industrial & Scientific

www.amazon.com

 

[Frank in Thailand]

Silicone dry out?? That's new for me.

Noalox can not be obtained here.
Ox-guard have the same problems.
If someone know their chemical active component, I might be able to get.

I have silicone based grease.



About 8 USD for 14.2gr.

Silicone based grease or petroleum based grease have virtually the same use as this di electric grease.

silicone based is not agressieve for rubber petroleum based is.
I'm not sealing O rings

Not doing lubrication -> increase conductivity!
"Nothing" will dry out between 2 layers of copper compressed.
(Or be a problem with being dry)

What I like to establish is to increase conductivity.

The word: Di-electric = non conductive
(I looked it up in the dictionary.
As non native English, that helps)

Both silicone and petroleum based grease are non conductive.

I am missing the part where using di-electric grease helps with conductivity!!

I am going to spend time to get rid of the non conductive oxidation layer to do next: add non conductive grease layer??
That doesn't sound right...

What am I missing here??

Apparently silicone / petroleum based grease is not helping, making conductivity worse.

It might help for a light bulb to be able to screw lose again, but that is not what I'm doing here.

Probably best is the first option:
- nothing

Just cleaning by removing oxidation and use rubbing alcohol to remove possible finger prints.

For the terminals and copper bus-bar adding a layer of silver conductive paste is good to prevent galvanic corrosion without decrease the conductivity.
Probably increase as it flattering the surface filling the little gaps in the terminal


Besides this, just copper on copper with nothing in between will give the best conductivity.

For the copper, material as flat as possible gives the best connection.

I'm lucky to get good quality bars!
They are so flat that it almost sticks to eachother by vacuum.
(Like 2 clean piece of glass stick together with nothing in between)

Thanks for thinking with me!

 

[BiduleOhm]

I am missing the part where using di-electric grease helps with conductivity!!

It doesn't increase conductivity but prevents oxydation.

I am going to spend time to get rid of the non conductive oxidation layer to do next: add non conductive grease layer??
That doesn't sound right...

What am I missing here??

Dielectric grease is displaced when you clamp the busbar and only fills the gaps not making a metal/metal contact.

Probably best is the first option:
- nothing

My best option given what you have would be the dielectric grease for where you can't use the silver paste

 

[Zil]

You have to clean the contact area. Then use something that prevents fresh corrosion from forming. Tin plated copper is protected. Aluminum needs no-ox or grease. Bare copper needs protection.

 

[Frank in Thailand]

You all know I'm full of crazy ideas.

In the past, one trick of keeping copper nice shiny was/is spray with varnish.

I never used it in electronics setup.
Spray can naturally is flammable.
If all is correct there will be nothing to ignite.

Possible good test to see nothing sparking there (just joking)

After all bars are fitted I can use the rest of the grease to prevent oxidation on the visible surface.
When I run out, vaseline is a good option also.
It's only purpose will be it prevent oxidation in not critical way.
Just good looks

Thanks all for thinking with me.

 

[Pierre]

The aluminum busbars I made I just lightly sanded and sprayed with WD40 and lightly wiped. No 1 go-to when I was in the Navy .

 

[Zil]

Aluminum corrodes pretty rapidly with out some kind of no-ox grease. WD-40 may not work long term.

 

[Hedges]

Flux is corrosive to the oxidation only, or both oxidation and copper??
Most Modern flux now don't need cleaning.(according to the package)
(I Still do, just don't want to take the risk)

That is called RoHS. By not washing off residue at the factory and adding a label telling consumers to recycle and not trash the item, manufacturer reduces its waste stream to nearly nothing.

What I specified for a product supposed to achieve 0.1% stability of megohm circuits was to use "no clean" flux and then wash the boards thoroughly with alcohol-based cleaner. There were specific products recommended by solder paste vendor, with measured results for a variety of cleaners.

What the PhD in charge of production orders said was "<contract manufacturer> are the experts. We should listen to them."

What <contract manufacturer> said was, "We have a PCB washing machine (dishwasher with resistance measurement of discharge water) and we're not afraid to use it."

So they wash the boards with water and "saponification agents", i.e. something similar to DrainO. Flux residue remained. So they extended washing cycle to several times recommendations on the cleaning product, resulting in metal surfaces of components being discolored, and proclaimed success.

I wasn't able to demonstrate problems from contamination, so I didn't win that one.

Previously, a "power good" circuit that had worked one day failed to enable the board after a warm spell. It was measuring than 24V input voltage was in the range 18 to 28V or something like that. A 6 meg ohm circuit had several volts deviation, indicating 30 meg ohm leakage, which I cured simply by washing with IPA. That indicated 30 meg ohm leakage due to flux. And my analog circuits required 1 to 10 gig-ohm accuracy. My circuits, which passed testing under ambient conditions, had failed to meet spec at elevated temperature. Washed with IPA, they passed.

The flux will be somewhat corrosive, might cause bad contact in a high-current circuit. No-clean flux is supposed to be heated driving off solvents, and what remains forms a somewhat protective encapsulation. It is high enough resistance to be OK for battery circuits. I would only use it for soldered joints, not as an anti-corrosion compound without heating it to reflow the solder. In soldering, it is supposed to follow a time/temperature profile, and for lead-free solders and environmentally friendly fluxes, the operating window isn't as wide.

Planarity of your busbars is a separate issue, ought to be dealt with in some mechanical manner. It might be that annealing to remove stress and filing to flatten the surface would help. I would imagine that a different construction, e.g. many thin sheets of metal, would make it more limber so it could be clamped flat with less pressure. Or a stud with large nut between battery and busbar, so more torque could be applied to busbar connection without over-torquing the weaker thread in the battery.