Re: [EVDL] Leaf Busbar Ampacity

[Lee Hart via EV]

Mr. Sharkey via EV wrote:

Beware! Copper water pipe is not pure copper, but is composed of alloy,
you won't be getting the conductivity of 99% copper. Also, crushing and
drilling pipe is time consuming and messy, the drilled holes can't be
properly deburred, and the possibility of corrosion/tarnish in the
sandwiched interior surfaces is real.


Good points. Also, copper work-hardens easily, which makes it stiffer 
but a worse conductor. Coppper water pipe is hardened. As I recall, 
rigid copper water pipe is about 30% less conductive than soft copper 
sheet or wire with the same cross-section.



The only purpose for the stock Leaf busbars was to tie the middle
terminals of the paralleled modules together.



Why would you bother doing that?



These are used modules with a somewhat variable capacity remaining. I
was able to test that capacity and pair weaker modules with stronger
ones, creating a more robust pack assembly. Also, paralleling at the
cell level means half as many BMS channels. You see this as a bug, I see
it as a feature.


I think this is exactly why it is done. Saves money on the BMS, and lets 
the manufacturer use mismatched cells to produce a matched pair.



Maybe tying the center terminals together with a fuse is a more cautious
approach. Using thin-ish wire would be a similar current-limiting
technique.


This has been done. It does reduce the risk of a meltdown or fire in 
case one of the paralleled cells fails shorted. But the BMS needs to 
*know* that it has happened, to prevent overloaded the remaining cell 
and causing further damage.


Lee Hart

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Re: [EVDL] Leaf Busbar Ampacity

[Haudy Kazemi via EV]

I thought the Leaf modules were each 4s, similar to how a 7.2v Prius module
is 6s. I stand corrected. They are 2s2p.

They can be modded to 4s according to
https://www.youtube.com/watch?v=kAznO_p_rEY

So, yes that does mean 228 amps at an 80 kW full throttle at 3.65 volts per
cell with 96 pairs in series.


On Sun, Aug 2, 2020, 02:13 Cor van de Water 
wrote:

> Nonsense, the Leaf modules are internally parallelled, so every Leaf bus
> bar and interconnecting wire alread carries the full ~250 Amps peak current.
>
> Continuous power at highway speed is closer to about 20kW, so just over 50
> Amps.
>
> Internal resistance of the entire pack is about 0.1 Ohms.
> This includes the 96 series cell pairs, the bus bars inside the modules
> that connect the 4 cells together in 2s2p configuration, the 54 bus bars
> that connect the 48 modules, the fused service disconnect and from the
> contactors to the front plug, plus the 3 lengths of high voltage wire.
> Cor.
>
> On Sat, Aug 1, 2020, 8:35 PM Haudy Kazemi via EV 
> wrote:
>
>> I wouldn't recommend using the Nissan Leaf busbars in pack locations that
>> exceed 114 amps. The bars should be fine within the series strings, which
>> is what I meant in my prior reply. The ends of each of the 5 parallel sets
>> should be connected some other way.
>>
>> I have heard of copper pipe being crushed flat, then drilled, to create
>> suitable custom high amp busbars.
>>
>> On Sat, Aug 1, 2020, 21:35 Mr. Sharkey via EV  wrote:
>>
>> >  > stack several of them for the 5p17s pack
>> >
>> > While it looks like you have done the calculations on voltage drop
>> > and heat production, and the values are acceptable, I'd question the
>> > wisdom of trying to build a 5p pack using the Leaf busbars, mostly
>> > because layering up multiple short busbars to parallel the modules
>> > will result in a large number of junctions between the busbars,
>> > resulting in even more resistance and a lot of clutter on the terminals.
>> >
>> > When I built up the 2p5s pack for my Electrak this spring, I went to
>> > fleabay and bought some appropriately-sized copper stock, ran it
>> > through the drill press and made custom-fit busbars that could span
>> > four modules (paralleling two each and making the needed series
>> > connection between the paralleled modules).
>> >
>> > The only purpose for the stock Leaf busbars was to tie the middle
>> > terminals of the paralleled modules together. In my case, that was a
>> > good application, but if you are tying five center terminals
>> > together, I'd even make custom bars for that too, although they won't
>> > need to be very big, as in a perfect world, there isn't going to be
>> > very much current flowing in that part of the circuit.
>> >
>> > Photos of the Et conversion here: http://www.evalbum.com/79
>> >
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Re: [EVDL] Leaf Busbar Ampacity

[Mr. Sharkey via EV]

> I have heard of copper pipe being crushed flat, then drilled, to
> create suitable custom high amp busbars

Beware! Copper water pipe is not pure copper, but is composed of 
alloy, you won't be getting the conductivity of 99% copper. Also, 
crushing and drilling pipe is time consuming and messy, the drilled 
holes can't be properly deburred, and the possibility of 
corrosion/tarnish in the sandwiched interior surfaces is real.


>> The only purpose for the stock Leaf busbars was to tie the middle
>> terminals of the paralleled modules together.

> Why would you bother doing that?

These are used modules with a somewhat variable capacity remaining. I 
was able to test that capacity and pair weaker modules with stronger 
ones, creating a more robust pack assembly. Also, paralleling at the 
cell level means half as many BMS channels. You see this as a bug, I 
see it as a feature. A failing pair of cells in one module will be 
quite apparent in the performance of the tractor, which triggers 
diagnostic actions on the part of the owner/driver (me).


Maybe tying the center terminals together with a fuse is a more 
cautious approach. Using thin-ish wire would be a similar 
current-limiting technique.


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Re: [EVDL] Leaf Busbar Ampacity

[Jay Summet via EV]

On 8/2/20 12:46 AM, John Lussmyer via EV wrote:

This is for a Chevy S10. (converted some years ago using Lead-acid, we are 
updating it)
I THINK we can fit 85 Modules in the battery boxes, which should significantly 
improve range over the old Golf Cart batteries.
This truck has a Z1K controller, and 8" motor (hmm, might be 9" - need to check 
that.)


Is that an 8' bed and including battery boxes under the hood?

My GC6 battery boxes were just a little too short to put the modules 
upright, so I had to lay them down on their sides, and got 48 modules in 
only the under the 6' bed boxes with a small amount of extra space.


If your battery boxes are deeper you can keep them upright (highly 
recommended for access to the terminals!), but 85 is a lot of modules!


Jay
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Re: [EVDL] Leaf Busbar Ampacity

[Jay Summet via EV]

The leaf pack is fused with a 200 (or is it 225?) amp mid-pack fuse, so 
I'd say they are rated at around 200 amps + safety factor...


I used some (totally overkill) 1" wide by 1/4" thick copper bar stock 
when making my interconnects.


I was sizing for a 500 amp max draw using 3 parallel leaf modules.


Bussbar construction starts at around the 3 minute mark at the video here:
https://www.summet.com/blog/2015/10/31/how-to-build-a-16-volt-battery-module-from-six-nissan-leaf-cells/


Jay

On 8/1/20 8:45 PM, John Lussmyer via EV wrote:

I'm trying to figure out what the constant and 30-second Amp ratings are for 
some Leaf Busbars.
The ones I have measure 0.78" wide by 0.08" thick.
That calculates out to 40.25 mm2 (yeah, changing units)
1 awg wire is 42 mm2.
BUT the busbar isn't insulated, and has a much larger surface area, so won't 
heat up as much.
1 awg wire is rated at 0.13 ohms/1000 ft.

It's about 1.25" between modules in a Leaf pack.
That comes out to 0.1354 ohms.
at 200A, there should be a voltage drop of 0.0027V, or 0.542 watts.

What I'm trying to figure out is if I need to stack several of them for the 
5p17s pack we are probably going to do for a friends truck.

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Re: [EVDL] Leaf Busbar Ampacity

[Jay Summet via EV]

On 8/1/20 10:34 PM, Mr. Sharkey via EV wrote:



The only purpose for the stock Leaf busbars was to tie the middle 
terminals of the paralleled modules together. In my case, that was a 
good application, but if you are tying five center terminals together, 
I'd even make custom bars for that too, although they won't need to be 
very big, as in a perfect world, there isn't going to be very much 
current flowing in that part of the circuit.


I considered this when making my busbars, but decided to size the center 
terminal bus bars as large as all the others, just in case a module 
developed an open fault in one half and the other half had to exit out 
the sense terminal. (possibly doesn't matter as internal connections 
inside the module may be smaller as well)   It also made things 
easier to just make everything out of the same bar stock.


Bussbar construction starts at around the 3 minute mark at the video here:
https://www.summet.com/blog/2015/10/31/how-to-build-a-16-volt-battery-module-from-six-nissan-leaf-cells/

Jay

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Re: [EVDL] Leaf Busbar Ampacity

[Cor van de Water via EV]

Nonsense, the Leaf modules are internally parallelled, so every Leaf bus
bar and interconnecting wire alread carries the full ~250 Amps peak current.

Continuous power at highway speed is closer to about 20kW, so just over 50
Amps.

Internal resistance of the entire pack is about 0.1 Ohms.
This includes the 96 series cell pairs, the bus bars inside the modules
that connect the 4 cells together in 2s2p configuration, the 54 bus bars
that connect the 48 modules, the fused service disconnect and from the
contactors to the front plug, plus the 3 lengths of high voltage wire.
Cor.

On Sat, Aug 1, 2020, 8:35 PM Haudy Kazemi via EV  wrote:

> I wouldn't recommend using the Nissan Leaf busbars in pack locations that
> exceed 114 amps. The bars should be fine within the series strings, which
> is what I meant in my prior reply. The ends of each of the 5 parallel sets
> should be connected some other way.
>
> I have heard of copper pipe being crushed flat, then drilled, to create
> suitable custom high amp busbars.
>
> On Sat, Aug 1, 2020, 21:35 Mr. Sharkey via EV  wrote:
>
> >  > stack several of them for the 5p17s pack
> >
> > While it looks like you have done the calculations on voltage drop
> > and heat production, and the values are acceptable, I'd question the
> > wisdom of trying to build a 5p pack using the Leaf busbars, mostly
> > because layering up multiple short busbars to parallel the modules
> > will result in a large number of junctions between the busbars,
> > resulting in even more resistance and a lot of clutter on the terminals.
> >
> > When I built up the 2p5s pack for my Electrak this spring, I went to
> > fleabay and bought some appropriately-sized copper stock, ran it
> > through the drill press and made custom-fit busbars that could span
> > four modules (paralleling two each and making the needed series
> > connection between the paralleled modules).
> >
> > The only purpose for the stock Leaf busbars was to tie the middle
> > terminals of the paralleled modules together. In my case, that was a
> > good application, but if you are tying five center terminals
> > together, I'd even make custom bars for that too, although they won't
> > need to be very big, as in a perfect world, there isn't going to be
> > very much current flowing in that part of the circuit.
> >
> > Photos of the Et conversion here: http://www.evalbum.com/79
> >
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Re: [EVDL] Leaf Busbar Ampacity

[Haudy Kazemi via EV]

On Sat, Aug 1, 2020, 23:46 John Lussmyer via EV  wrote:

> Comments on multiple postings...
>
> On Sat Aug 01 20:34:51 PDT 2020 ev@lists.evdl.org said:
> >I wouldn't recommend using the Nissan Leaf busbars in pack locations that
> >exceed 114 amps. The bars should be fine within the series strings, which
> >is what I meant in my prior reply. The ends of each of the 5 parallel sets
> >should be connected some other way.
>
> Note that with 5 modules in parallel - it's not JUST the between-groups
> busbar that gets hi-current.  The next busbar down will have 4/5 of the
> current, etc..
>

Maybe we are using different terminology? I am calling the Leaf's module to
module jumpers busbars. I am recommending that within a single series
string of 17 modules per your plan that you can use Nissan busbars and
limit things to 114 amps per string. I am not recommending using the same
Nissan busbars to parallel one string to the next.

Leaf has 2 parallel strings. I have not looked to see how those strings are
paralleled.


> On Sat Aug 01 19:34:12 PDT 2020 ev@lists.evdl.org said:
> >> stack several of them for the 5p17s pack
> >
> >because layering up multiple short busbars to parallel the modules
> >will result in a large number of junctions between the busbars,
> >resulting in even more resistance and a lot of clutter on the terminals.
>
> True, that is a problem.
>
> >The only purpose for the stock Leaf busbars was to tie the middle
> >terminals of the paralleled modules together.
>
> Why would you bother doing that?  All the center terminals are good for is
> voltage monitoring to detect a module that is half-failing.  Tieing modules
> together there will just make it impossible to detect a problem - and
> provide X times more power to dump through a failing cell.
>
> On Sat Aug 01 20:23:44 PDT 2020 ev@lists.evdl.org said:
> >Gen 1 Leaf is rated at 80 kW. Pack is 96s2p. Leaf modules have 4 cells in
> >each (48 modules x 4 cells each=192).
> >
> >Voltage is 96x 3.65 V=350.4 V
> >80 kW / 350.4 V = 228.3 amps
> >228.3 amps / 2 parallel strings = 114 amps per string
>
> Note that I am talking purely about Modules, not the cells they are made
> of.
> So, the 228.3 Amp number is the only one that is relevant.
> So the Leaf can PEAK at 228A or so, good to know.
> Likely cruises at more like 15KW, so about 43A.
>

The 114 A value is relevant as a per string limit. You probably do not want
to exceed that. If you do, you will be drawing more current from each
module than the Leaf did. Leaf used parallel strings to get up to ~228 A
per PACK.

Leaf highway cruising takes 15-20 kW depending on specific condtions.


This is for a Chevy S10. (converted some years ago using Lead-acid, we are
> updating it)
> I THINK we can fit 85 Modules in the battery boxes, which should
> significantly improve range over the old Golf Cart batteries.
>

Don't forget to account for the degradation many Leaf batteries have
experienced. You might prefer used Tesla modulea.

>
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Re: [EVDL] Leaf Busbar Ampacity

[John Lussmyer via EV]

Comments on multiple postings...

On Sat Aug 01 20:34:51 PDT 2020 ev@lists.evdl.org said:
>I wouldn't recommend using the Nissan Leaf busbars in pack locations that
>exceed 114 amps. The bars should be fine within the series strings, which
>is what I meant in my prior reply. The ends of each of the 5 parallel sets
>should be connected some other way.

Note that with 5 modules in parallel - it's not JUST the between-groups busbar 
that gets hi-current.  The next busbar down will have 4/5 of the current, etc..

On Sat Aug 01 19:34:12 PDT 2020 ev@lists.evdl.org said:
>> stack several of them for the 5p17s pack
>
>because layering up multiple short busbars to parallel the modules
>will result in a large number of junctions between the busbars,
>resulting in even more resistance and a lot of clutter on the terminals.

True, that is a problem.

>The only purpose for the stock Leaf busbars was to tie the middle
>terminals of the paralleled modules together. 

Why would you bother doing that?  All the center terminals are good for is 
voltage monitoring to detect a module that is half-failing.  Tieing modules 
together there will just make it impossible to detect a problem - and provide X 
times more power to dump through a failing cell.

On Sat Aug 01 20:23:44 PDT 2020 ev@lists.evdl.org said:
>Gen 1 Leaf is rated at 80 kW. Pack is 96s2p. Leaf modules have 4 cells in
>each (48 modules x 4 cells each=192).
>
>Voltage is 96x 3.65 V=350.4 V
>80 kW / 350.4 V = 228.3 amps
>228.3 amps / 2 parallel strings = 114 amps per string

Note that I am talking purely about Modules, not the cells they are made of.
So, the 228.3 Amp number is the only one that is relevant.
So the Leaf can PEAK at 228A or so, good to know.
Likely cruises at more like 15KW, so about 43A.

This is for a Chevy S10. (converted some years ago using Lead-acid, we are 
updating it)
I THINK we can fit 85 Modules in the battery boxes, which should significantly 
improve range over the old Golf Cart batteries.
This truck has a Z1K controller, and 8" motor (hmm, might be 9" - need to check 
that.)

I'll probably look into copper stock to make bus bars.
Hard part is going to be finding an affordable charger to use.  It used to have 
a pair of 72V chargers - one of which is dead.
(and yes, there will be a BMS installed as well.)



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Re: [EVDL] Leaf Busbar Ampacity

[Haudy Kazemi via EV]

I wouldn't recommend using the Nissan Leaf busbars in pack locations that
exceed 114 amps. The bars should be fine within the series strings, which
is what I meant in my prior reply. The ends of each of the 5 parallel sets
should be connected some other way.

I have heard of copper pipe being crushed flat, then drilled, to create
suitable custom high amp busbars.

On Sat, Aug 1, 2020, 21:35 Mr. Sharkey via EV  wrote:

>  > stack several of them for the 5p17s pack
>
> While it looks like you have done the calculations on voltage drop
> and heat production, and the values are acceptable, I'd question the
> wisdom of trying to build a 5p pack using the Leaf busbars, mostly
> because layering up multiple short busbars to parallel the modules
> will result in a large number of junctions between the busbars,
> resulting in even more resistance and a lot of clutter on the terminals.
>
> When I built up the 2p5s pack for my Electrak this spring, I went to
> fleabay and bought some appropriately-sized copper stock, ran it
> through the drill press and made custom-fit busbars that could span
> four modules (paralleling two each and making the needed series
> connection between the paralleled modules).
>
> The only purpose for the stock Leaf busbars was to tie the middle
> terminals of the paralleled modules together. In my case, that was a
> good application, but if you are tying five center terminals
> together, I'd even make custom bars for that too, although they won't
> need to be very big, as in a perfect world, there isn't going to be
> very much current flowing in that part of the circuit.
>
> Photos of the Et conversion here: http://www.evalbum.com/79
>
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Re: [EVDL] Leaf Busbar Ampacity

[Haudy Kazemi via EV]

Gen 1 Leaf is rated at 80 kW. Pack is 96s2p. Leaf modules have 4 cells in
each (48 modules x 4 cells each=192).

Voltage is 96x 3.65 V=350.4 V
80 kW / 350.4 V = 228.3 amps
228.3 amps / 2 parallel strings = 114 amps per string

NEC ampacity (conservative) rating for 1 gauge wire is 110 amps with wire
rated for 60 degree C, 130 amps with 75 C rated wire, 150 amps with 90 C
rated wire. Insulation type determines the temp ratings.

The real answer depends on how much power you need. In your 5p
configuration, with uninsulated busbars of the dimensions you report, you
could assume 5x 114 amps = 570 amps at the pack output to match how Nissan
used the bus bars between modules.

You might possibly even go up to 5x 150 amps = 750 amps by using the NEC
ampacity at an assumed temp of 90 C, but this risks exposing the battery
terminals to too much heat, and would put higher discharge C rates on the
battery.

17s modules x 4 cells/module x 3.65 V per cell = 248.2 V pack.

248.2 V x 456 amps = 141 kW available

5p17s modules = 85 modules
85 modules x 0.5 kWh/module (when new) = 42.5 kWh

I think you have enough energy for a useful short range truck, and enough
power to meet light duty truck needs.


On Sat, Aug 1, 2020, 19:45 John Lussmyer via EV  wrote:

> I'm trying to figure out what the constant and 30-second Amp ratings are
> for some Leaf Busbars.
> The ones I have measure 0.78" wide by 0.08" thick.
> That calculates out to 40.25 mm2 (yeah, changing units)
> 1 awg wire is 42 mm2.
> BUT the busbar isn't insulated, and has a much larger surface area, so
> won't heat up as much.
> 1 awg wire is rated at 0.13 ohms/1000 ft.
>
> It's about 1.25" between modules in a Leaf pack.
> That comes out to 0.1354 ohms.
> at 200A, there should be a voltage drop of 0.0027V, or 0.542 watts.
>
> What I'm trying to figure out is if I need to stack several of them for
> the 5p17s pack we are probably going to do for a friends truck.
>
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Re: [EVDL] Leaf Busbar Ampacity

[Mr. Sharkey via EV]

> stack several of them for the 5p17s pack

While it looks like you have done the calculations on voltage drop 
and heat production, and the values are acceptable, I'd question the 
wisdom of trying to build a 5p pack using the Leaf busbars, mostly 
because layering up multiple short busbars to parallel the modules 
will result in a large number of junctions between the busbars, 
resulting in even more resistance and a lot of clutter on the terminals.


When I built up the 2p5s pack for my Electrak this spring, I went to 
fleabay and bought some appropriately-sized copper stock, ran it 
through the drill press and made custom-fit busbars that could span 
four modules (paralleling two each and making the needed series 
connection between the paralleled modules).


The only purpose for the stock Leaf busbars was to tie the middle 
terminals of the paralleled modules together. In my case, that was a 
good application, but if you are tying five center terminals 
together, I'd even make custom bars for that too, although they won't 
need to be very big, as in a perfect world, there isn't going to be 
very much current flowing in that part of the circuit.


Photos of the Et conversion here: http://www.evalbum.com/79

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[EVDL] Leaf Busbar Ampacity

[John Lussmyer via EV]

I'm trying to figure out what the constant and 30-second Amp ratings are for 
some Leaf Busbars.
The ones I have measure 0.78" wide by 0.08" thick.
That calculates out to 40.25 mm2 (yeah, changing units)
1 awg wire is 42 mm2.
BUT the busbar isn't insulated, and has a much larger surface area, so won't 
heat up as much.
1 awg wire is rated at 0.13 ohms/1000 ft.

It's about 1.25" between modules in a Leaf pack.
That comes out to 0.1354 ohms.
at 200A, there should be a voltage drop of 0.0027V, or 0.542 watts.

What I'm trying to figure out is if I need to stack several of them for the 
5p17s pack we are probably going to do for a friends truck.

--
Bobcats and Cougars, oh my!  http://john.casadelgato.com/Pets
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