270ah DIY LiFePO4 build

[gregcope]

not bad I guess, don't remember what the other guy doing tests found on his bus bars...
Greg, putting 4 and another 4 on their side, does the connector from one bank to the other needs to be longer on Ami's cells? wondering what lengths I should be ordering, 7 identical, or 6 + 1 longer?

I'm talking about fitting them as in this pic:
https://ae01.alicdn.com/kf/H18a2a70...les-Clips-de-Contacts-barres-de-connexion.jpg

For the ones that are "long side to long side" the 71.5+/-4mm ones fit. The71.5mm refers to the centre of the the bolt holes/studs. You will need six of these.

I cannot split my pack presently as its taped up doing a charge/discharge test.

However measuring from "short end to short end" is 25+/-1mm from centre of stud to side. So assume that two cells side by side the studs centres would be 50+/-2mm apart. The 71.5 ones will not fit.

For the "end to end" ones I would get the 50.5+/-4mm ones. You would need one of these. The pricing includes shipping to UK or Greece and it only took a week so bar the cost of one bus bar the risk is low if I have that wrong. Will buy you a beer if we meet to compensate if so!

Their cells look different in that the terminals are nearer the middle and have a larger gap to the shorter edge, hence why they spec 84mm ones for the cross over bar.

If you mean Ray as "the other guy" he found similar to the 2mm ones. We both have the same Internal Resistance tester (YR1035+). These ones should give an even better IR / connection compared to his.

 

[vas]

thanks Greg, found the guys list v.clearly all the options of bars they have on sale. Will measure and decide.
Only catch is that delivery for GR is estimated for 11of March :-(
BTW, did it arrive with RM, or some other courier service?

V.

 

[gregcope]

Arrived via Royal Mail. Mine says 12-Mar too. I ordered (UK) morning of 24-Dec. Arrived morning of today (4-Dec).

There are also comments on Aliexpress about their fast shipping to other European areas. Hopefully, if you order, @vas yours arrive as quickly.

 

[vas]

For the ones that are "long side to long side" the 71.5+/-4mm ones fit. The71.5mm refers to the centre of the the bolt holes/studs. You will need six of these.

OK that matches the specs on Amy's PDF (72+-1mm width of cell)

I cannot split my pack presently as its taped up doing a charge/discharge test.

However measuring from "short end to short end" is 25+/-1mm from centre of stud to side. So assume that two cells side by side the studs centres would be 50+/-2mm apart. The 71.5 ones will not fit.

For the "end to end" ones I would get the 50.5+/-4mm ones. You would need one of these. The pricing includes shipping to UK or Greece and it only took a week so bar the cost of one bus bar the risk is low if I have that wrong. Will buy you a beer if we meet to compensate if so!

Their cells look different in that the terminals are nearer the middle and have a larger gap to the shorter edge, hence why they spec 84mm ones for the cross over bar.

lost you here though!
width of cell is 173.5mm+-1
post spacing is 90mm+-0.3
so (173.5-90)/2 = 41.75mm which means I'd need the 84mm ones.
Am I missing something? I thought we have the same cells!

V.

 

[gregcope]

OK that matches the specs on Amy's PDF (72+-1mm width of cell)



lost you here though!
width of cell is 173.5mm+-1
post spacing is 90mm+-0.3
so (173.5-90)/2 = 41.75mm which means I'd need the 84mm ones.
Am I missing something? I thought we have the same cells!

V.

Using your maths, but different figures..
Post spacing is 72+-1mm not 90mm
so (173.5-71.5)/2 = 51mm

Which is pretty close to my guesstimate of 50mm by measuring from post to thin side edge.

 

[vas]

Using your maths, but different figures..
Post spacing is 72+-1mm not 90mm
so (173.5-71.5)/2 = 51mm

Which is pretty close to my guesstimate of 50mm by measuring from post to thin side edge.

PDF states terminal spacing is 90mm, if it's 72 I'm shafted as I've ordered already balancing modules that have 90mm spacing!
Oh well, i'll wait for them to arrive and see what I get!

 

[gregcope]

Hang on you are right on terminal spacing. Let me go measure mine.

 

[gregcope]

Measuring mine terminals are 125mm centre to center on a cell.

 

[gregcope]

Best effort of measuring and photo

 

[gregcope]

@vas, I think the data sheet is an older version or for different cells ...

 

[vas]

@vas, I think the data sheet is an older version or for different cells ...

Greg, thanks, tbh I'll just wait for them to arrive and just measure, longer I don't mind I can connect my balancing boards with a short stub of a bus bar. Shorter will be a problem.
Will ask Amy just in case. I consider this task done, next one is latching battery disconnect which doesn't cost an arm and a leg! Will post my options over the w/e

cheers

V.

 

[gregcope]

@vas

I have a new / Scanned data sheet from Amy as she tells me this is a data sheet issue.

Some good/less good news;

Less good; the new data sheet does not appear to have the terminal spacing dimension that I can see (its quite long and a scanned image so not searchable). Have asked Amy for a PDF version that is searchable.

Good news; These cells are rated to 4000 Cycles (to 80% capacity, if compressed) which is more than the previous data sheet. More good news is that they give examples of cell compression - which is a 6mm Ali/Steel plate with three M6 bars along each side - so very similar to what lots of people are doing. Also they give suggested temp sensor locations, either on the side just below the terminal or near the Black (+?) terminal. Finally its 35 pages long so very detailed.

 

[Stingo]

From GHA, who is no longer on the forums:

Hi guys, I'm not on these forums anymore but... doing some more work on new voltage etc monitoring PCB's so would welcome any input about what you'd like to have for lifepo4 monitoring from greg/vas/poey/ , well anyone really.. created a discord so come say hello & share your experience, ta. -- Join the Rasp Pi boat monitoring Discord Server!

 

[vas]

Say hi to GHA from me hope he's doing good!

re monitoring lifepo4, after spending the last couple of months on diyBMS, which is an opensource project, I'd urge him to have a look (either for ideas or to join in!)
1+A passive balancers per cell (attiny controller on each)
esp32 main board
attiny powered current shunt
testing main board and balancers now for 2months, brilliant integration to my victron only setup onboard (working a bit on editing the rules passed on via canbus to victron atm)

cheers

V.

 

[Kelpie]

What's everybody doing for protection of terminals? In the states something called Ox-Gard seems to be favoured, but it's not so easy to come by over here.
Any other brands I should look out for?

 

[vas]

aren't you meant to use some sort of vaseline like petrol jelly?
on my Trojans I'm using a spray on thing I bought locally, creates a foam thing that lasts reasonably well

 

[Kelpie]

aren't you meant to use some sort of vaseline like petrol jelly?
on my Trojans I'm using a spray on thing I bought locally, creates a foam thing that lasts reasonably well

There seems to be two schools of thought.
One is that almost any corrosion inhibiting paste will do.
The other is that you should use something which will conduct electricity, so that you can be as liberal as you like and it won't risk creating a barrier anywhere.

 

[vas]

There seems to be two schools of thought.
One is that almost any corrosion inhibiting paste will do.
The other is that you should use something which will conduct electricity, so that you can be as liberal as you like and it won't risk creating a barrier anywhere.

two clean surfaces (pole and busbar) bolted down to 6Nm or so. sorry but imho it's not reasonable to expect that any corrosion inhibiting paste/jelly will create a barrier. So I'm in #1 school of thought and find #2 OTT.
I'd count non flex busbars as more of an issue re conductivity!

V.

 

[pcatterall]

Best effort of measuring and photoView attachment 128189View attachment 128190

Steel tape and battery terminals gives me a bit of a shiver! ( dont ask!)

 

[gregcope]

Steel tape and battery terminals gives me a bit of a shiver! ( dont ask!)

I was very careful! I will not ask, but can imagine.