Travelling Westerly
Active member
If it helps any my Daly BMS has a DV disconnect setting at 0.21v from top of my head. It only disconnects the charging side of the BMS and not the discharge side.
270ah DIY LiFePO4 build
- Thread starter Poey50
- Start date
vas
Well-known member
thanks, first need to code that, then the easy bit will be to add the value to lift the flag. Guess I'll experiment and decide on the values for my particular charging/discharging and use patterns. 300mV seems a bit much especially when charging a 304Ah bank at 15-17A (via solar)
vas
Well-known member
good evening all,
since I have a bit more time on my hands, I studied a few more channels and came across this lady who (if I got that right) is building a massive LifePO4 bank for a boat that she's not yet bought
anyway, she's discussing an issue I'm also quite concerned and seems that for some reason hasn't been questioned in here: flexibility of bus bars between cells. Having read quite a bit on compressing/not compressing prismatic cells, I'm unsure if I should be using the copper (hopefully) bars I'm going to get with my 8cells. Has anyone seen this? any comments?
there's another one where she's getting slightly OTT and builts quad 10gauge cable connectors instead of the single 4gauge you see in the video above ?
cheers
V.
since I have a bit more time on my hands, I studied a few more channels and came across this lady who (if I got that right) is building a massive LifePO4 bank for a boat that she's not yet bought
anyway, she's discussing an issue I'm also quite concerned and seems that for some reason hasn't been questioned in here: flexibility of bus bars between cells. Having read quite a bit on compressing/not compressing prismatic cells, I'm unsure if I should be using the copper (hopefully) bars I'm going to get with my 8cells. Has anyone seen this? any comments?
there's another one where she's getting slightly OTT and builts quad 10gauge cable connectors instead of the single 4gauge you see in the video above ?
cheers
V.
gregcope
Well-known member
Ah. Digital mermaid. Yes I too think she does not have the boat yet…
just to confuse have you seen this from lithiumsolar;
just to confuse have you seen this from lithiumsolar;
gregcope
Well-known member
Also here is a good review by ray;
gregcope
Well-known member
Basically Ray says measure the mm2 of each option. 4AWG is 21mm2. The solid bus bars are 20x2=40mm2. The semi-flexible ones that LithiumSolar uses are 3x20mm=60mm2.
He measurements show that a short flexible bus bar from 4/0 AWG cable (55mm2) with lugs is similar resistance to a 2x20mm2 copper bus bar. The delta due to the crimps.
Is your concern resistance or flexibility over time?
He measurements show that a short flexible bus bar from 4/0 AWG cable (55mm2) with lugs is similar resistance to a 2x20mm2 copper bus bar. The delta due to the crimps.
Is your concern resistance or flexibility over time?
vas
Well-known member
thanks, nice try - confuse me even more ?
main concern is that no matter where I get this bank and how I secure it, expanding/shrinking, temps up and down, shaking about and banging when planning (although really rarely do so) terminals will be getting some stress. TBH impressed that none has come up with ripped terminals on prismatic cells still. Amy (and others) approach of soldering SS bolts on ali terminals through a pressed or whatever ali bit on the bolt is not exceptionally sturdy.
The idea of compressing cells then bolting them rigidly with bars at 6 or 8Nm and then all that mess trying to flex is horrible (in my eyes)
Since I will be only sucking 120A max from the setup I don't think I should be concerned about the resistance.
V.
main concern is that no matter where I get this bank and how I secure it, expanding/shrinking, temps up and down, shaking about and banging when planning (although really rarely do so) terminals will be getting some stress. TBH impressed that none has come up with ripped terminals on prismatic cells still. Amy (and others) approach of soldering SS bolts on ali terminals through a pressed or whatever ali bit on the bolt is not exceptionally sturdy.
The idea of compressing cells then bolting them rigidly with bars at 6 or 8Nm and then all that mess trying to flex is horrible (in my eyes)
Since I will be only sucking 120A max from the setup I don't think I should be concerned about the resistance.
V.
Poey50
Well-known member
Yes, an interesting topic especially for mobile applications. I've gone down the compression route - the cells were compressed when about 30% state of charge so they can't expand. I'm not sure why people don't want to do this. I used apparently rigid bus bars supplied by R J Lithium with the batteries. I found that the central section is laminated so they will bend. They have oval holes rather than round ones so there is some possibility of movement of bus bar over the terminals rather than anything bending. The torque is not very high (it can't be on aluminium terminals) and I used Ox-gard between bus bar and terminal which is a graphite grease (itself conductive) and would allow slip if it came to it. I have the pack very firmly attached to the boat using 8 fixing points. The base of the pack is also constrained from movement by epoxied and screwed wooden restraints. I have used studs cemented in place into the terminals rather than bolts so I think these will be unlikely to move although movement against a restraining nut is a possibility. I'm going to do an inspection some time this winter so will know more then if there has been any movement or loosening.
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sailaboutvic
Well-known member
Every time I pop in here there some thing new to think about,
My set up and the other set up belonging to another cruiser have copper pipe bus bars , the 15 mm tubes where flatting and hole drilled just slightly bigger then the stud.
The cells are held in place one end 10 mm ply the other grp molding part of the boat,
Three strap with ratchet keep them all in place,
The bank is just one year old and once month I check all the Connections.
I not found any movement on any of the nuts I should also say I used locking nuts and double the nuts on each stud.
The same applies to my mate cells.
The most at any time drawn as been 120A and while running at that rate there been no heat across any of the bars which I can feel by touch.
Actually the only heat seen to come from the bms modules.
I was thinking of stripping the cells before the season start and rebalanced them, but it's quite a big job and fiddling with the type of BMS I'm using plus at 14.2v with is the maximum I charge at time (normally 13.8V ) the cells are within 0.05 @14.2v and 0.01@13.8v so probably not worth the risk of breaking some thing.
It seen these YouTube stuff are people who just like to play, I'm not sure it help anyone improving their batteries bank more likely cause confusion.
My set up and the other set up belonging to another cruiser have copper pipe bus bars , the 15 mm tubes where flatting and hole drilled just slightly bigger then the stud.
The cells are held in place one end 10 mm ply the other grp molding part of the boat,
Three strap with ratchet keep them all in place,
The bank is just one year old and once month I check all the Connections.
I not found any movement on any of the nuts I should also say I used locking nuts and double the nuts on each stud.
The same applies to my mate cells.
The most at any time drawn as been 120A and while running at that rate there been no heat across any of the bars which I can feel by touch.
Actually the only heat seen to come from the bms modules.
I was thinking of stripping the cells before the season start and rebalanced them, but it's quite a big job and fiddling with the type of BMS I'm using plus at 14.2v with is the maximum I charge at time (normally 13.8V ) the cells are within 0.05 @14.2v and 0.01@13.8v so probably not worth the risk of breaking some thing.
It seen these YouTube stuff are people who just like to play, I'm not sure it help anyone improving their batteries bank more likely cause confusion.
Poey50
Well-known member
I agree Vic. They sound well enough balanced to me.
gregcope
Well-known member
@vas
Ordered some flexible bus bars as per the lithiumsolar youtube above. Arrived in less than a week from CN. Look nice. Thicker than the other bus bars (3mm vs 2mm) and oddly flexible. I write oddly, as the ends are solid and the middle (under pink heatshrink) is flexible. Feels odd being able to bend metal!
Could this help your vibration/terminals concern?
Ordered some flexible bus bars as per the lithiumsolar youtube above. Arrived in less than a week from CN. Look nice. Thicker than the other bus bars (3mm vs 2mm) and oddly flexible. I write oddly, as the ends are solid and the middle (under pink heatshrink) is flexible. Feels odd being able to bend metal!
Could this help your vibration/terminals concern?
Poey50
Well-known member
They sound promising. Do you have a link?
gregcope
Well-known member
@Poey50
Link here; 2.87￡ 5% OFF|LiFePO4 Lithium Battery Flexible Busbar Posts Straps Clips Contacts Tabs Connecting Bars For 280AH 320Ah 271Ah Battery Cell Bus|Battery Accessories| - AliExpress
Need to order/select the size you need. I understand they can do custom sizes.
In the package was a business card as they are made/sent by Weber Power Tech; www.weberpowertech.com which redirects to; https://weberpowertech.aliexpress.com/store/911833500
Link here; 2.87￡ 5% OFF|LiFePO4 Lithium Battery Flexible Busbar Posts Straps Clips Contacts Tabs Connecting Bars For 280AH 320Ah 271Ah Battery Cell Bus|Battery Accessories| - AliExpress
Need to order/select the size you need. I understand they can do custom sizes.
In the package was a business card as they are made/sent by Weber Power Tech; www.weberpowertech.com which redirects to; https://weberpowertech.aliexpress.com/store/911833500
vas
Well-known member
could of course, issue is that I have to somehow organise them with the cell controller/balancer which looks like this:
OK, ignore the temp sensor protruding, that's going to be cut off and stuck to the side of the cell. the rest is not that wide, so worried how they'd both fit on the terminals.
Mind this controller/balancer PCB should be ON TOP of the connectors so that the current is not flowing through the PCB side terminals to "catch" the thick bus bar.
So bus bar first, this on top and screw it down.
Greg, can you also give us exact dims of the thing?
I may be able to fit the flex bus bars, screw them down to 6Nm or whatever with a thin nut, then fit this PCB on top and finish it off with a self locking nut. PCB is 1.6mm
cheers
V.
OK, ignore the temp sensor protruding, that's going to be cut off and stuck to the side of the cell. the rest is not that wide, so worried how they'd both fit on the terminals.
Mind this controller/balancer PCB should be ON TOP of the connectors so that the current is not flowing through the PCB side terminals to "catch" the thick bus bar.
So bus bar first, this on top and screw it down.
Greg, can you also give us exact dims of the thing?
I may be able to fit the flex bus bars, screw them down to 6Nm or whatever with a thin nut, then fit this PCB on top and finish it off with a self locking nut. PCB is 1.6mm
cheers
V.
gregcope
Well-known member
Measuring the resistance of these;
Copper 2mmx20mm bus bars 10mOhm
These 3mmx20mm bus bars 8mOhm
Copper 2mmx20mm bus bars 10mOhm
These 3mmx20mm bus bars 8mOhm
gregcope
Well-known member
The ones I ordered are;
90mm long
20mm wide
3mm thick
They are the L71.5mm + 300A version. The 71.5mm is the centres on the holes.
90mm long
20mm wide
3mm thick
They are the L71.5mm + 300A version. The 71.5mm is the centres on the holes.
vas
Well-known member
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
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
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Poey50
Well-known member
They look great, Greg but when I click on the link I'm redirected to a dutch? site. I'd like to order the same as you - any tips?
gregcope
Well-known member
Aliexpress can be a right language pain. It sometimes sets itself to Italian or Spanish for me..
Try; www.weberpowertech.com
Or change the language in the top menu bar under the banner...
Poey50
Well-known member
Excellent thanks. Easy when you know how!
This is a good find. These deserve to be the standard for the aluminium cells.
