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Dongguan Lighting: Purchase 280AH LiFePo4 cells. Purchase & Review

Finally some progress with my build that's worth writing about :)
All the batteries - 17 cells -were delivered slow but ok. I had 5 boxes, 4 came together and the 5th a week later.
The packaging was done really well, all cells were placed in individual foam casings then placed in carton boxes which had the wall doubled on the inside with more foam sheets. On the outside the corners were reinforced with plastic.
Through transport the cartons incurred some damage but nothing made it all the way through the cells.

The cells measured ok, almost identical to the measurements from the video they sent before shipping. They were quite balanced, still I've put them in parallel and started the top balancing process on the 19/09. After the first 48 hours I started to see an quite obvious difference in the cell voltages: higher at the ends and lower in the middle (3,4x vs 3,3x). I was getting concerned that I would actually imbalance them, so for the following 24 hours I was changing the position of the lead from one end to another and to the middle, every 8 hours.
On the 22/09, after reading some more about the process and it's length especially if done with a low current power supply - 5A - I've decided to build the 48V bank - 16 in series - with the BMS and give it a good full charge with the 48V charger. By this stage, the cells voltage was 3,45 on average.
In 10 minutes the BMS cut off the charger as the battery was fully charged - reached 3,65V.
To my calculations, it should have taken much longer to reach full charge, but then i have no idea what was the actual SOC when delivered - suspect it was quite high... Anyway, I'm not that much concerned as I've tested one random cell for it's capacity, after the top balance, and it was exactly 280A (test conditions: avg temp 12 deg Celsius and current draw 10A - I was aiming for 20A but the cables supplied with the tester were warming up and I wasn't comfortable to let it off my sight like that, so I reduced the load).

Anyway, overall, so far, very happy with my purchase from Dongguan Lightning through Rain Zeng.
One thing I would change in hindsight: order more bus bars and bolts, as I got the exact number for a 17 cell in series bank...I had to be inventive to be able to parallel them for balancing :) which is not a bad thing but just added more variables and potential failing points in the play.
 

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@Johnolar ... Just curious how your Chargery BMS has been performing. More specifically, have you compared cell voltages read on the Chargery to cell voltages read with a multimeter? There have been reports on another thread of bad cell readings with the BMS16T..... going from memory, I think it was in the cell 8, 9, and 10 range. I will try to find that thread and add the link here.

This may be a little off track for this thread, so it might be good to start a new thread and link to it here .... especially if you see any anomalies .... or you could just add your experience to that thread. That thread is here: https://diysolarforum.com/threads/chargery-bms-cell-readings-inaccuracy-should-i-be-concerned.10338/

Jason from Chargery is trying to determine what might have caused the problem and input from others using the BMS16T would be valuable information.
 
The cells measured ok, almost identical to the measurements from the video they sent before shipping. They were quite balanced, still I've put them in parallel and started the top balancing process on the 19/09. After the first 48 hours I started to see an quite obvious difference in the cell voltages: higher at the ends and lower in the middle (3,4x vs 3,3x). I was getting concerned that I would actually imbalance them, so for the following 24 hours I was changing the position of the lead from one end to another and to the middle, every 8 hours.
On the 22/09, after reading some more about the process and it's length especially if done with a low current power supply - 5A - I've decided to build the 48V bank - 16 in series - with the BMS and give it a good full charge with the 48V charger. By this stage, the cells voltage was 3,45 on average.
One way I have read to speed up the process, is build the battery with BMS and charge the whole thing.
Let the BMS cut it off when some cells top out.
Then put them in parallel to finish the top balance process.
Sure it's an extra step, but it may be the quickest method to top balance them all at 3.65V.
A little more work, but shorter overall time.
I only had 4 cells and just waited it out charging at 10A.
 
@Johnolar , thank you for sharing your pictures and story.

I totally agree on the bus-bars, during ordering it's important to ask for plated Bus-bars, preferably double quantity of the cells!!

Plated, not bare copper.
Your terminals are aluminium, bare copper bars will give galvanic corrosion. It can take a few years before you have a real problem, but why risk it if zinc or tin coated bars will solve the problem before it starts?

Alternatively you can go all aluminium.

I love the transparant sheets to make the compression force between the cells, what is absolutely necessary to prevent delaminating / bloating.

Personally I would use maximal 4 cells between 2 sheets, giving me the idea of being better in control of provide the force even over the cells.

I advise strongly against the screws / bolts provided by any seller.
Best way is headless bolts
The aluminium terminals have 6mm deep hole, 5 mm thread.
That is enough as most M6 nuts are also just 4 mm.
Aluminium isn't strong, and the twisting force while tighting the bolts
Easy can destroy your thread.

Using headless bolts will prevent this.
Like the bars they need to be plated or aluminium.
Or, my choice, 304 stainless steel.
It doesn't have good conductive properties, and that is OK, it could be non conductive at all, as it's not the part that makes the connection.
That is your bus-bar and terminal.
It's just to provide enough force to make optimal strong contact.
304 stainless steel is as much "neutral" for electric charged metal as you can get.

This word electric have nothing to do with working on batteries.
Your metal rain gutter or aluminium roof sheeting have the same issue.
Working with 2 or more different types of metal can easily give galvanic corrosion.

For our battery cells, it slowly eats away the aluminium, being least noble metal.
Probably starting with the thread windings, if the wrong bolt/screw is used.

It will take a few years to do so.
If you battery array starts acting up in a few years, and you find many bus-bar no longer firm contact with the terminals..
Just think back about this advice.

Being the nice guy that I am, here is a possible solution for when this happens:
Drill 7 mm wide holes (still 6 mm deep), and tap new 8 mm thread :cool:

(Also to be used if you choose to ignore the headless bolts tip, and took out the M6 thread...)
If you don't have the tools to do, 2 components epoxy and a headless bolt will work just fine..
(Glue the bolt inside the treadless hole)
The remaining thread is not strong enough for the bolt alone, together with the epoxy it makes a fine grip.

Normally where should not be any need to change the headless bolt, so glue it is not a problem.
 
Finally some progress with my build that's worth writing about :)
All the batteries - 17 cells -were delivered slow but ok. I had 5 boxes, 4 came together and the 5th a week later.

One thing I only now realised ... why 17 cells ?
I was thinking to buy 1 extra if any cell is going wrong, but you say you put them all in serial.
In MPP Solar's manual I see there is the potential (max charge 64V) ... so it can handle 17*3,2 (charge 17*3,65 = 62V)
But is it wise to do so ?

Thx
 
One thing I only now realised ... why 17 cells ?
I was thinking to buy 1 extra if any cell is going wrong, but you say you put them all in serial.
In MPP Solar's manual I see there is the potential (max charge 64V) ... so it can handle 17*3,2 (charge 17*3,65 = 62V)
But is it wise to do so ?

Thx

My initial thoughts were that my electric motor and controller can handle up to 72V, so I thought the bigger the better, but in saying that, the actual reason why I bought 17 was to have a redundancy cell in case something gets damaged in transport or by myself.
Quite everything seems to be designed / built for 4-8-16-24 so being a not so experienced DIYer I decided to stick with the common 16S and have a spare :)
 
My initial thoughts were that my electric motor and controller can handle up to 72V, so I thought the bigger the better, but in saying that, the actual reason why I bought 17 was to have a redundancy cell in case something gets damaged in transport or by myself.
Quite everything seems to be designed / built for 4-8-16-24 so being a not so experienced DIYer I decided to stick with the common 16S and have a spare :)

OK, exactly the same idea :D

Did you think about the last cell? So what to do with it?
Sometime replace one in the 16s with it or just put it in the corner and if something is going wrong then use it ?

Thanks
 
I've kind of voltage matched the lot and the one with the lowest voltage after the top balancing was set aside. It's the cell I did the capacity test on, while assembling the main 16s bank. After that I've charged it back to 3,25v and put it in a foam box. It will stay there until needed :) but I won't rotate it with random ones from the main bank.
Cheers
 
One thing I only now realised ... why 17 cells ?
I was thinking to buy 1 extra if any cell is going wrong, but you say you put them all in serial.
In MPP Solar's manual I see there is the potential (max charge 64V) ... so it can handle 17*3,2 (charge 17*3,65 = 62V)
But is it wise to do so ?
Thx
I would not recommend you try to balance charge via PV solar.
A lab bench charger like this works well
 
Stainless is not "neutral" when in contact with aluminium... Google galvanic scale.
Correct. Not neural.
Henceforth the quote " "
More neutral then iron/ steel, carbon steel, copper or brass.
(The normal available options world wide)

Less neutral then aluminium, or tinned headless bolts.

Problem is to find aluminium or tinned headless bolts or even threaded rods!

USA seems to have everything. Thailand and probably the rest of the globe is highly limited with access to aluminium treaded M6 rods.
Aluminium headless bolts a total no-go.

In the list of bad options 304 headless bolts are the least bad choice that is widely available.

Not to forget about the washers and the nuts.

I can find aluminium washer, tonnes.
Aluminium nuts are already getting a challenge.

Most people probably will use standard iron/ steel bolts/screws or headless, as they already have them, or easy to get.

For those people the warning about galvanic corrosion and the best available options to prevent or greatly reduce this.

304 stainless steel headless bolts in threaded aluminium terminal will continue to work a lot longer then standard iron would.

Standard iron will give a problem within 5 years.
 
Incorrect, Steel is less reactive than stainless with aluminum. Especially when it's zinc plated, which is 95% of common steel hardware.

Galvanic-series-of-some-metals-in-ambient-seawater-23.jpg
 
Incorrect, Steel is less reactive than stainless with aluminum. Especially when it's zinc plated, which is 95% of common steel hardware.
Incorrect.

You are forgetting an important part: Mass.
Cathodic or Anodic
Making the difference if it is the one getting desolved. :)

Next step, when/as it does, how good can it handle it, and how long before it becomes a problem.

One thing I do stand corrected, it is not the terminal but the headless bolt that is getting desolved.

unnamed.png

There is a headless bolts or a normal bolt/screw for a reason: connect the bus-bar.

In most cases a copper bus-bar.

We have at least 3 different metals, 2 with a large mass, one with a small mass (headless bolt/ bolt screw)
This is when using the same material for washer and nut.
Otherwise more different metals, more parts that play a role.

The item that is used to make contact isn't the biggest issue, it's the copper of the bus-bar and the aluminium of the terminals.

I'm sure we can agree that those 2 don't like eachother then talking about galvanic corrosion.
 
Just throwing a question in: As I read the above, if one uses zinc plated bolts and washers, into aluminium cell terminals, would be a better solution then using stainless steel 304 /316? Still with copper bus bars...
 
Just throwing a question in: As I read the above, if one uses zinc plated bolts and washers, into aluminium cell terminals, would be a better solution then using stainless steel 304 /316? Still with copper bus bars...
Correct.

The 300 range of stainless steel, 304 being most adviced, is good.
I read that "ferritic stainless steel" (410 / 400 series) that is not advisable to use.

I am no specialist in metals at all, nor in galvanic corrosion.

I did spend a few weeks reading numerous articles about galvanic corrosion, figuring out what metal is best to be used in our situation, to get the least change on galvanic corrosion that will give bad contact with the cell.

Zinc plated doesn't work.
Don't believe me for it, just check the car batteries that have often brass clamps on a lead terminal and sometimes zinc plated bolts/nuts.
Well... What's left of it.
You won't be unscrewing, just snap it off.
Those that have brass bolts and nuts can be cleaned and reused.

Looking at the way I have my setup, it is not an easy operation to clean the lower level back side located connections!

That would require disassemble almost all.

Probably more easy, go to your local car cemetery and check out the battery clamps :)

You get a fine idea what does work and what not.

(Something I didn't do for gaining this knowledge, but have been there quite a lot when I was younger, building my own car from trash)
0_fiat 003 (Small).jpg3_IMAG0225.jpg1_IMAG0229.jpg
(Most proud of the engine. A 903cc from different model (850) that turned the wrong way around, modified to work on this fiat 600 Abarth, like they did for the races in 1965-70)
In the Dyson roller tester it could do 160km/h 100 miles :) (yes!!)
Driving faster then 130 made you feel like meeting death real soon)

Feel free to use standard zinc coated iron.
Just don't blame me when it rusts quickly, and is getting eaten away by the aluminium and copper.

Did you know that in the old days (1970 and earlier) they put a iron nail in the water cooling of the car?

Aluminium motor, copper radiator.
That wasn't a happy ending for the aluminium.
They used a sacrifice metal, a nail or iron rod to fix the galvanic corrosion problems.

Nowadays, most radiators are aluminium also.
And, the coolant liquid (chemical mix) stops this process.

Just a side step.

Feel free to use whatever you feel comfortable with.

And when ( or if) you replace them, you know why.
10 years is a long, long time.

Even without our "almost optimal for galvanic corrosion" setup.
(Almost optimal, we heat up the contact during higher charge and discharge, add electricity, all we are missing is some salt or acid in the mix.
Unless you use your fingers who probably are nice salty....and the rest.
Ever wondered why computer builders who like their computers to last long time not only wear anti static, but also gloves??)

10 years is a long, long time.
Once the corrosion process gets grip it goes a lot faster.

I did electroplated all my Bus-bars with tin.
JPEG_20200928_090848_9042044081056338124.jpgIMG_20200928_154256.jpg

That took a few weeks.

Better spend +10 weeks now, and be sure that it can last the time the cells will, and not shorter due assambling errors.
With1016Ah, 50 kWh and our power consumption the cells should be able to last +10 years.
 
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Thinking about it, in my choice of words, the "neutral" is not a good one.

Neutral would be metals that are close in electric difference.

Lead (-0.27) and brass (-0.29) are just 0.02 apart (if copper (-0.36) is used more, -0.11) and that already gives spectacular results.

Aluminium (-0.79) and galvanised (zink coated) steel (-0.98) are considered to be neutral..
Yet also 0.11 difference.

One important part is how good it can withstand the electric difference.

Stainless steel can do it exceptionally well.
Copper and aluminium both reasonable.

Iron is really weak with resisting the corrosion.
The zink coating usually isn't made to prevent galvanic corrosion, but standard corrosion aka rust.
Even during normal transport is likely to damage the zink coating, for rust not a big issue.
Tighting a bolt will slightly damage the coating on the threads of bolt and nut.
Again, for normal weather conditions, not a big probem.

For us, out setup, frequent temperature changes, electricity, and moisture (unless you live really dry climate) will increase the galvanic corrosion.

Or normal corrosion, what is a bad thing for our electric conductivity, our main reason to use Bus-bars in the first place, connect the cells in series or parallel!!

Reduction is a good thing.
I'm reluctant to write prevention.

Maximal reduction will prevent problems in the next few decades, it doesn't stop the fact that the different metals have different values.

I'm reducing by tin plating my coper Bus-bars.

Other step in reducing is the use of electrical conductive paste, silver based.
It will be an extra layer of prevention, and increase overall performance.

Surface area:
A small bus-bar on a large aluminium terminal will give soon problems, spreading out, contact maximal surface area is an other way to reduce galvanic corrosion.

It's all reduction.
Not total prevention.
As there will be corrosion, it's good to use metals that can withstand this the best.
304 (or 316) stainless steel headless bolts will not be your problem in the chain of different used metals.

Zink coated or bare and carbon steel will be a problem, where carbon steel is a lot more resilient, if you can't get stainless steel, carbon would be the next choice.

If you can't get stainless or carbon, zink coated steel is an option.
Please do keep an eye on the headless bolts. At the first sight of rust, replace them with new or different headless bolt.
That probably will be within a year...

Bare steel / iron, sure, temporary solution, better than nothing :)

Again, rust is here the first signal that there will be (serious) problems soon.

Personally I have a hard time understanding how a tin layer prevent galvanic corrosion when it comes in contact with aluminium, or why tin and copper being contacted together via electroplating aren't going to be galvanic coroded, as they have electric difference between them, it should bladder the tin almost instantly from the copper, right??

A really patient teacher explained to me that this is the surface area that makes all the difference.

Complex material if you really dive into it.
What's important is what works, and what does not.

Best scenario I've wrote down, and what possible can / will happen with other scenarios.

Take from it what you can use, discard what you think is nonsense.

Perhaps @Will Prowse can make section for long time installations with and without issues.
Time will tell if my information is correct, or that I'm freaking out over "nothing".

Having fixed many " unsolvable" electronic car problems from people just by cleaning the lead acid battery terminal connections, I know first hand how galvanic corrosion can give all sorts of crazy problems.
LPG not working, car computer, air-conditioning, stereo system, etc. etc.

All 12v systems, and not inverters to AC.
Still, I'm careful.
 
Lead (-0.27) and brass (-0.29) are just 0.02 apart (if copper (-0.36) is used more, -0.11) and that already gives spectacular results.

You forgot the acid vapors with the LA batteries, big factor.

The zink coating usually isn't made to prevent galvanic corrosion, but standard corrosion aka rust.

Zinc isn't to avoid corrosion, it acts like a sacrificial anode so the other metals are safe but doing so it corrodes itself.

Even during normal transport is likely to damage the zink coating, for rust not a big issue.
Tighting a bolt will slightly damage the coating on the threads of bolt and nut.

That's not a problem, see just above ;)

A small bus-bar on a large aluminium terminal will give soon problems, spreading out, contact maximal surface area is an other way to reduce galvanic corrosion.

Nope, you'll not reduce galvanic corrosion that way. As soon as the metals are in contact they create a voltage which is the cause of the galvanic corrosion, the surface area doesn't matter. You'll reduce contact resistance however, always a good thing ;)

why tin and copper being contacted together via electroplating aren't going to be galvanic coroded, as they have electric difference between them, it should bladder the tin almost instantly from the copper, right??

You need water for the corrosion to happen, Plating is so well attached water can't get under, hence no corrosion.

A really patient teacher explained to me that this is the surface area that makes all the difference.

Please explain more, I'm curious to know why it would make a difference.


NB: my 0.02$ on this problem: I'll use aluminium for the busbars, studs, washers and nuts so that way I completely avoid galvanic corrosion on the cells (the expensive non-repairable part of the battery) and then the only place it can happen will be between the last busbars and the battery cables (but easily replacable, not expensive) ;) if you can't avoid a problem then move it where it'll be minimal and make the least amount of damage.
 
As BiduleOhm explained, you have some significant misunderstanding of how galvanic corrosion works. To further complicate things, you seem to be confusing regular corrosion resistance with galvanic corrosion potential.

Your absolute faith in your own knowledge never seems to wane though.

Maybe you should listen to actual experts, instead of saying we are wrong. Which is silly given your self admitted "read a few articles" education on the subject.
 
Well...I got confused, so went with my original plan of copper 101 connectors (1x1/4).
Final assembly done, the whole pack weights 100kg! I've enlisted a few mates to transport the box in the boat.
One thing that happened because of bolting and unbolting the things so many times, I've stripped the main positive terminal thread.
Now I'm looking into tapping the cell terminal with an M8 x 1.25 bottom tap, and upgrade the bolt from M6 to M8...
Any tips on how to tap the alu cell terminal?
Besides that, everything went quite smooth and uneventful.
Cheers
 

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Use Helicoil to repair and stick with M6 but use a stud (which you can even loctite) and nut instead of bolts. That's what I'm doing for all my cells. Because I, too, stripped things by using bolts. The studs are a far superior solution IMHO.
 
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