Need some advice on setup of battery cells with bms

[alishac]

Hey, So I got my 8x eve 160ah cells and they are great condition.. I checked all the cells with a multimeter and they all on 3.29v.

But I got some newbie questions..

I got a jbd 250a 4s bms from - https://mullerenergy.com.au/product/12v-250a-jbd-smart-bms-with-bluetooth/

So my main question is about the positive.. When wiring up the cells with the bms wires does the positive that you choose on the cells
have no bus bar - I mean the one that goes direct to the bms.. Also like I see a video setup of that bms and he doesn't put a bus bar which
I'm guessing is correct but does any thicker cable go from the positive on cell to bms or is it just a thicker cable from negative to bms..

Also from the bms where the cable from negative to bms do you add another thick cable ffrom the same negative on the bms to case terminal?

I can show you a picture of the bms and the config I'm looking at doing which is 4s2p..

Also Im going to use my 40ah lithium charger to top balance then use the 5a active balancer the bms has to full top balance it so for
that would it be best to do it in 4 cells at a time or can I do it in the 4s2p?

Any help would be sooo helpful.. also here is the video of the bms -

 

[mikefitz]

4S2P needs two BMS, for a 12v system with 8 cells and a single BMS you need a 2P4S setup, see,

Cell Configurations for 12V 24V and 48V LiFePo4 Batteries

This short deck shows 1P and 2P cell configurations for 12V, 24V & 48V LiFePO4 batteries. To get the deck, click on the orange button at the top of this page. Note: Reviews, Comments and corrections are welcome Document Revision History...

diysolarforum.com

 

[alishac]

I'll prob do 2p4s then as I only have 1 bms and costs too much to get another one.. On that pdf in the 2p4s I like B or D but questions is it says to use heavy duty bus bars.. what does heavy duty mean? I got the ones from the factory from docan. Where would I be able to find heavy duty ones?

 

[TomC4306]

I'll prob do 2p4s then as I only have 1 bms and costs too much to get another one.. On that pdf in the 2p4s I like B or D but questions is it says to use heavy duty bus bars.. what does heavy duty mean? I got the ones from the factory from docan. Where would I be able to find heavy duty ones?

Use the ones that came with the cells

 

[alishac]

Use the ones that came with the cells

The ones that came with the cells isnt enough.. If I did the 2p4s (B) it says I need 8 factory and 4 heavy duty.. What came with the cells was 9 busbars.. In total i'd need 11.. And with the 2p4s (D) it says id need 11 heavy duty.. so either way I'm missing 2 bars for (B) and 3 bars for (D)

 

[Steve_S]

You have 160AH cells. They can output 160A (1C) for one hour and take 80A charge 0.5C) max.
IF you build 2x12V/160AH packs and parallel them, you still get the 320AH BUT you are dividing the Load & Charge between two battery packs which is far less stressful on them and allows BOTH to dump up to 160A each or 320A Combined. In those terms that means if your system is pulling 250A that is divided so each battery has to dump 125A to fulfill the demand. This also provides a fallback, if 1 battery cuts off for any reason the other can carry on while you figure things out.

Paralleling cells within a single battery packs works fine with properly Matched & Batched cells but can create a heap of issues IF the cells are not perfectly matched. Unless you paid a premium & purchased Grade-A Certified cells with factory test reports, it is extremely unlikely that you got properly matched cells. Note that Matching & Batching means that all cells will have identical IR (Internal Resistance) across the working/operating voltage ranges from 2.900-3.425V per cell. The vast majority (90%) of vendors DO NOT MATCH & BATCH they only match the IR to the standard storage voltage they are at and do not cycle test as they do in the production factory.

FYI: The busbars shipped with those cells are sufficient for the cells.
Hope it helps, Good Luck

 

[alishac]

You have 160AH cells. They can output 160A (1C) for one hour and take 80A charge 0.5C) max.
IF you build 2x12V/160AH packs and parallel them, you still get the 320AH BUT you are dividing the Load & Charge between two battery packs which is far less stressful on them and allows BOTH to dump up to 160A each or 320A Combined. In those terms that means if your system is pulling 250A that is divided so each battery has to dump 125A to fulfill the demand. This also provides a fallback, if 1 battery cuts off for any reason the other can carry on while you figure things out.

Paralleling cells within a single battery packs works fine with properly Matched & Batched cells but can create a heap of issues IF the cells are not perfectly matched. Unless you paid a premium & purchased Grade-A Certified cells with factory test reports, it is extremely unlikely that you got properly matched cells. Note that Matching & Batching means that all cells will have identical IR (Internal Resistance) across the working/operating voltage ranges from 2.900-3.425V per cell. The vast majority (90%) of vendors DO NOT MATCH & BATCH they only match the IR to the standard storage voltage they are at and do not cycle test as they do in the production factory.

FYI: The busbars shipped with those cells are sufficient for the cells.
Hope it helps, Good Luck

not View attachment 145514

Based off the eve LF 160 specs it says max charge and discharge is 1c continuous and 2c pulse. Also the cells are A grade and docan sent me tested reports. I also checked with a multimeter on each cell and they are all the same voltages and there is no bulging.. also the Q code says they are made last year in sept. The design I want to do is (D). I get that the busbas are ok but like I said there isn't enough bus bars to make
what the (D) states which is 11 and I only have 9. Also I know a business in Australia that makes same 2p4s with 250a bms and they do it fine with no issues.. And I see people charge with it over 100ah and discharge at 200ah+ maybe not continuous but for more then 20 minutes. The guy that does it just uses reinforced tape to strap the cells together then puts it into an abs case.. everyone thats bought it hasn't had any issues with it. If I was to make the bus bars out of 99.9% copper flat bar would that be better than the factory ones which look like nickel/copper that have the bend. I plan to put around the cells and between the cells silicone bonded mica 2mm sheets, then maybe put firm eva 3mm foam around it loose and on bottom.. for a bit of compression but ill use the reinforced fibreglass tape around the cells.. Then my dad will make a custom-made 2mm stainless steel case for it. It will be going into my custom made camper trailer which later this year I will be making another 320ah tho the cells based on the report reach 165ah and max 170ah so it be around 330ah x 2 when I make the second one. Also when I connected just 4 cells up and I used the mutli meter on the pos/neg it showed 13.16v or 3.29 on each cell.

 

[HRTKD]

If it was me, I would buy a second BMS and create two batteries. You get twice the amps with two BMS. Yeah, your current BMS is rated to 250 amps and you'll likely never hit that. But with two BMS you could draw more than 250 amps if you needed to.

You're going to have to spend some money one way or the other. Copper flat bar (to make bus bars) isn't cheap.

I'm not a fan of wrapping cells in tape. You're going to be in a mobile environment. You don't want those cells moving one bit. Put them in a proper compression frame so they can't move.

 

[squowse]

To answer your original question

Positive terminal of “top” cell has a thick cable to the battery positive terminal.

Negative terminal of “bottom” cell has a balance cable and connected to the B- of the BMS (thick wire)

The P- of the BMS connects to the battery negative terminal (thick wire). Dont bypass the bms by connecting terminal directly to cells.

 

[alishac]

If it was me, I would buy a second BMS and create two batteries. You get twice the amps with two BMS. Yeah, your current BMS is rated to 250 amps and you'll likely never hit that. But with two BMS you could draw more than 250 amps if you needed to.

You're going to have to spend some money one way or the other. Copper flat bar (to make bus bars) isn't cheap.

I'm not a fan of wrapping cells in tape. You're going to be in a mobile environment. You don't want those cells moving one bit. Put them in a proper compression frame so they can't move.

No point making 2 batteries, plus the bms I got cost me $349 which is allot of money to buy 2.. Also no point making 2 batteries from the 8 cells cause I'm going to get another 8 cells to make another 330ah to have two 330ah which will end up having another bms later so it will end up having more amps draw.

Also taping it will be fine, I know a guy that makes batteries and just wrap then with tape and I know people that has got those batteries and they have no issues with it at the back of there 4wd car and doing 4x4 driving.. Ill have a custom made case that will be tired with the cells so they wont move around with also eva form around it inside the case.. then it will be locked down inside the trailer.. I already have a 140ah lifepo4 battery and its locked down and doesnt move at all...

 

[roly1]

If the bms trips the load charge/bus isnt the battery then offline for both charge and load?
Dunno, thats a Mueller bms; does it have dual buses?
Cant have that for my situation, need a battery online all the time.

 

[alishac]

If the bms trips the load charge/bus isnt the battery then offline for both charge and load?
Dunno, thats a Mueller bms; does it have dual buses?
Cant have that for my situation, need a battery online all the time.

its a jbd custom bms, muller just asked jbd to make him a custom made one. So its the same as the 200a jbd 4s bms and if it keeps it online all the time then the muller one would also its just a better version of the 200a and its 50a more.

Watch this review on them -

 

[roly1]

From a cruisersforum member:
JBD BMS has FETs that can block only ingoing (stop charge) or only outgoing (stop discharge) or both (disconnect bank) current flow, so a common charge and discharge bus is needed for them. Good enough for me. Will test when I top balance to MVd.

 

[Daddy Tanuki]

Also taping it will be fine, I know a guy that makes batteries and just wrap then with tape and I know people that has got those batteries and they have no issues with it at the back of there 4wd car and doing 4x4 driving.. Ill have a custom made case that will be tired with the cells so they wont move around with also eva form around it inside the case.. then it will be locked down inside the trailer.. I already have a 140ah lifepo4 battery and its locked down and doesnt move at all...

so you are building a custom case that hold the cells and clamps them etc. ? if that is so then initially tape should be fine, but if you try to use just tape you will be the next contestant on the up in smoke thread.

 

[alishac]

so you are building a custom case that hold the cells and clamps them etc. ? if that is so then initially tape should be fine, but if you try to use just tape you will be the next contestant on the up in smoke thread.

Yea custom made case out of 2mm stainless steel and will have eva high density 5mm foam around it and on the bottom ill have strip eva foam to hole it in place nice and tight.. and between and around the cells ill have 2mm silicone bonded mica sheets. Also will have custom made copper bus bars

 

[alishac]

From a cruisersforum member:
JBD BMS has FETs that can block only ingoing (stop charge) or only outgoing (stop discharge) or both (disconnect bank) current flow, so a common charge and discharge bus is needed for them. Good enough for me. Will test when I top balance to MVd.

thats a JBD this is a custom JBD.. its not the exact same as the normal jbd bms... there is no such thing as the 250a bms in 4s from jbd.. muller asked them to make a custom made one to his specs.. even the 5a active balancer is custom made by heltic.. So if that member had a issue or not with jbd this muller custom one isnt the same as that jbd that member has.