# [EVDL] Thanks, Daddy!



## EVDL List (Jul 27, 2007)

Very nice Bill.
What are all the little fans for?
What is the white box front left in pic 3?

Al

----- Original Message ----- 
From: "Bill Dennis" <[email protected]>
To: "'Electric Vehicle Discussion List'" <[email protected]>
Sent: Tuesday, July 26, 2011 10:40 PM
Subject: [EVDL] Thanks, Daddy!


> My father flew out from New Jersey for a 4-day weekend, and with his help 
> I was able to get the rear battery box installed in the MetroLectrical and 
> the car back on the road again. Drove it to the DMV and it passed 
> inspection!
>
> I put together a little slideshow for my father, but thought I'd post it 
> here in case anyone was interested. There are 14 photos. The first six 
> are of the car in general, and the final 8 show the rear battery box.
>
> http://sedwjd.zenfolio.com/p919042231/slideshow
>
> The car now has 33 kWh, and it had no problem climbing the 1700 feet from 
> the inspection station back to my house. On a 90+ degree day, the cells 
> weren't even warm to the touch after I got home. What a difference an 
> additional 21kWh makes. 
>
> One thing I was proud of was meeting my goal of not taking up any trunk 
> space with batteries. The car still has a full trunk, with the rear 
> battery box tucked in under the convertible roof and extending down where 
> the gas tank used to be. I actually even have *more* cargo area than the 
> ICE version, since the rear battery box provides a large flat surface to 
> set things on.
>
> Happy to answer any questions.
>
> Bill
>
>
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## EVDL List (Jul 27, 2007)

Hi Bill,

I could 36 cells in the front box and I think another 30
in the rear battery box.
One cell has a rather black layer on one side of the
center circle - the one in the rear middle.
Was this due to an "oops" event?

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203



-----Original Message-----
From: [email protected] on behalf of Bill Dennis
Sent: Wed 7/27/2011 8:10 AM
To: 'Electric Vehicle Discussion List'
Subject: [EVDL] Thanks, Daddy!

My father flew out from New Jersey for a 4-day weekend, and with his help I was able to get the rear battery box installed in the MetroLectrical and the car back on the road again. Drove it to the DMV and it passed inspection! 

I put together a little slideshow for my father, but thought I'd post it here in case anyone was interested. There are 14 photos. The first six are of the car in general, and the final 8 show the rear battery box.

http://sedwjd.zenfolio.com/p919042231/slideshow

The car now has 33 kWh, and it had no problem climbing the 1700 feet from the inspection station back to my house. On a 90+ degree day, the cells weren't even warm to the touch after I got home. What a difference an additional 21kWh makes. 

One thing I was proud of was meeting my goal of not taking up any trunk space with batteries. The car still has a full trunk, with the rear battery box tucked in under the convertible roof and extending down where the gas tank used to be. I actually even have *more* cargo area than the ICE version, since the rear battery box provides a large flat surface to set things on.

Happy to answer any questions.

Bill


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## EVDL List (Jul 27, 2007)

Nice installation Bill.

DAC



> Cor van de Water <[email protected]> wrote:
> > Hi Bill,
> >
> > I could 36 cells in the front box and I think another 30
> ...


----------



## EVDL List (Jul 27, 2007)

They're cooling fans. There's only about 1/8 inch (3mm) between the top of
the front battery box and the underside of the hood, so I had no room for
bigger fans. These small fans fit up in the recesses of the hood's frame.

The little while box holds the EVision card.

Bill

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Al
Sent: Tuesday, July 26, 2011 9:31 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Thanks, Daddy!

Very nice Bill.
What are all the little fans for?
What is the white box front left in pic 3?

Al

----- Original Message ----- 
From: "Bill Dennis" <[email protected]>
To: "'Electric Vehicle Discussion List'" <[email protected]>
Sent: Tuesday, July 26, 2011 10:40 PM
Subject: [EVDL] Thanks, Daddy!


> My father flew out from New Jersey for a 4-day weekend, and with his help 
> I was able to get the rear battery box installed in the MetroLectrical and

> the car back on the road again. Drove it to the DMV and it passed 
> inspection!
>
> I put together a little slideshow for my father, but thought I'd post it 
> here in case anyone was interested. There are 14 photos. The first six 
> are of the car in general, and the final 8 show the rear battery box.
>
> http://sedwjd.zenfolio.com/p919042231/slideshow
>
> The car now has 33 kWh, and it had no problem climbing the 1700 feet from 
> the inspection station back to my house. On a 90+ degree day, the cells 
> weren't even warm to the touch after I got home. What a difference an 
> additional 21kWh makes. 
>
> One thing I was proud of was meeting my goal of not taking up any trunk 
> space with batteries. The car still has a full trunk, with the rear 
> battery box tucked in under the convertible roof and extending down where 
> the gas tank used to be. I actually even have *more* cargo area than the 
> ICE version, since the rear battery box provides a large flat surface to 
> set things on.
>
> Happy to answer any questions.
>
> Bill
>
>
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere. Thanks.
> |
> | REPLYING: address your message to [email protected] only.
> | Multiple-address or CCed messages may be rejected.
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## EVDL List (Jul 27, 2007)

36 100 Ah LFP cells in the front and 31 200Ah LCP cells in the back. Fully
charged voltages on each work out to about the same (around 130V). I
undercharge to 124.2V, which is 3.45V per LFP cell, right about where they
reach their knee. This works out to 4.0V per LCP cell. The LFP cells
provide the power and the LCP cells provide most of the range.

Yes, it was an "oops" event about a year ago, when I was disassembling the
old pack. I have my tools all wrapped in electrical tape. But the tape had
worn off one end of the ratchet that I hadn't seen. As I was loosening a
bolt, the tip of the ratchet touched another terminal about 60V away and
"boom" the end of the ratchet blew off.

Bill

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Cor van de Water
Sent: Wednesday, July 27, 2011 1:53 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Thanks, Daddy!

Hi Bill,

I could 36 cells in the front box and I think another 30 in the rear battery
box.
One cell has a rather black layer on one side of the center circle - the one
in the rear middle.
Was this due to an "oops" event?

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203



-----Original Message-----
From: [email protected] on behalf of Bill Dennis
Sent: Wed 7/27/2011 8:10 AM
To: 'Electric Vehicle Discussion List'
Subject: [EVDL] Thanks, Daddy!

My father flew out from New Jersey for a 4-day weekend, and with his help I
was able to get the rear battery box installed in the MetroLectrical and the
car back on the road again. Drove it to the DMV and it passed inspection! 

I put together a little slideshow for my father, but thought I'd post it
here in case anyone was interested. There are 14 photos. The first six are
of the car in general, and the final 8 show the rear battery box.

http://sedwjd.zenfolio.com/p919042231/slideshow

The car now has 33 kWh, and it had no problem climbing the 1700 feet from
the inspection station back to my house. On a 90+ degree day, the cells
weren't even warm to the touch after I got home. What a difference an
additional 21kWh makes. 

One thing I was proud of was meeting my goal of not taking up any trunk
space with batteries. The car still has a full trunk, with the rear battery
box tucked in under the convertible roof and extending down where the gas
tank used to be. I actually even have *more* cargo area than the ICE
version, since the rear battery box provides a large flat surface to set
things on.

Happy to answer any questions.

Bill


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## EVDL List (Jul 27, 2007)

So you are running them as two strings in parallel, essentially giving 200Ah
capacity as limited by the string with 100Ah cells? So the charger voltage
limit prevents overcharging as you describe, then I guess you use the Ah
counter on the evision to avoid over-discharge of the 100Ah cells? What
capacity are the LCP cells, 160Ah? If so, you gained about 40Ah capacity in
adding the 100Ah cells? Could you state where you put everything else - the
charger, controller, aux battery, DC/DC, relays/contactor, etc... Nice
work, you really have crammed things in there!

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## EVDL List (Jul 27, 2007)

Up to this point, I had just been running on the 100Ah LFP cells in the front, which are about 11 kWh. The LCP cells in the back are 200Ah, so they added around 22 kWh. The two strings in parallel, then, provide 300Ah. I've installed two additional shunts, one on each string, and am awaiting delivery of two the cycle analyst device that Bill Dube mentioned. That will allow me to measure each string separately to make sure that I'm not over-discharging either one.

I'll try to describe where things are. Look at picture no. 3, the closeup of what's under the front hood. Starting on the far left and working toward the right:

1) These are the positive circuit breakers, one for each string. They are mechanically tied together, so that if one trips, they both trip.

2) Next on the right is the little white box, which holds the EVision card

3) Just in front of the white box you see another aluminum box which has some small white cells in it. Those are 90Ah LCP cells that I'm using for the 12V system. Right now, there's lots of extra room in that box. I'll be installing a DC/DC converter there.

4) To the right of the EVision box is a gray electrical box. It contains the two shunts to which I'll be attaching the cycle analyst units.

5) To the right of the gray electrical box is a box with a clear Lexan cover. This contains two contactors. The left contactor (pointing upwards) is the positive contactor. The right contactor (point downwards) is the negative contactor. As soon as I insert the key into the ignition, the negative contactor closes. Then when I turn the key to "Run" the pre-charge circuit engages. A heavy-duty 120V bulb mounted in the dash flashes then dims to let me know that pre-charge has completed. The positive contactor closes when the accelerator is pressed.

6) In front of that clear box, just to the left of the horn, is the hot water heater used to heat the car. 

7) Just behind the water heater is a large black heat sink. You can't see if from this photo, but on the other side of the heat sink, a Curtis 1231C is attached.

8) On the far right of the battery box, just in front of the orange fuse box, you can just make out of strip of gray. This is the top of a water-proof electrical enclosure. It contains the precharge and KSI relays. 

9) Behind the orange fuse box, just to the left of the orange shock absorber strut, you'll see another plastic enclosure. This contains the relay for the heating system (just visible) and below that (not visible in this photo) is the main negative shunt that supplies info the the EVision. This area also contains a metal bus bar where all the two cell strings and the charger negative lead connect.

A) Just behind that plastic box, you'll see the PB-6 potbox, and to the left of that the inertia switch.

B) Moving to the left along the firewall, you see a little piece of gray plastic. This is a cradle that holds a Tweeco connector attached to the negative lead of the front battery box to provide easy disconnect.

C) To the left of that sits a small gray box with a display. This displays the charging amps when I'm charging.

D) And finally, to the left of that (next to the left suspension struct) is the mid-pack fuse for the front battery box. 

E) Inside the car, under the center of the dash, I removed the cup holder and old cassette tape player. This gave me just enough room to slip in a PFC-30 charger. 

F) Under the car, in what I'll call the "transmission tunnel" I've mounted two metal enclosures. Each on contains a circuit breaker attached to the negative lead of each cell string. The switch jut up through the chassis just in front of the emergency break, within easy reach of my right hand. At any time I can flip off one or both of them to cut power to the car in case of an emergency, or to disconnect the two strings from each other if I want to charge separately.

Hope that long-winded explanation gives you a good feel for the component layout. If not, I'd be happy to jabber on some more. 

Bill

----- Original Message -----
From: "tomw" <[email protected]>
To: [email protected]
Sent: Wednesday, July 27, 2011 9:16:42 AM
Subject: Re: [EVDL] Thanks, Daddy!

So you are running them as two strings in parallel, essentially giving 200Ah
capacity as limited by the string with 100Ah cells? So the charger voltage
limit prevents overcharging as you describe, then I guess you use the Ah
counter on the evision to avoid over-discharge of the 100Ah cells? What
capacity are the LCP cells, 160Ah? If so, you gained about 40Ah capacity in
adding the 100Ah cells? Could you state where you put everything else - the
charger, controller, aux battery, DC/DC, relays/contactor, etc... Nice
work, you really have crammed things in there!

--
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## EVDL List (Jul 27, 2007)

I've been wondering about this. I also have some of my tools wrapped in
electrical tape, but they are still conductive from one end to the other.
I've been wondering if it's possible to get some tools with steel ends, but
a center handle made of non-conductive material such as nylon or even wood.
When used for electrical purposes, they aren't used to torque down that
much, so they don't need to be that strong. The metal could be inside the
wood or plastic part way as long as there was a sufficient space (1" maybe?)
as a non-conductive gap.

This way, even if the two wrench ends touched hot spots, you wouldn't create
a circuit. Do these tools exist? I've been wondering if I should mock up
my own by cutting up a cheap wrench set and making the centers out of a nice
hardwood such as cherry.

Mike

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Bill Dennis
> Sent: Wednesday, July 27, 2011 5:50 AM
> To: 'Electric Vehicle Discussion List'
> Subject: Re: [EVDL] Thanks, Daddy!
> 
> Yes, it was an "oops" event about a year ago, when I was disassembling the
> old pack. I have my tools all wrapped in electrical tape. But the tape
had
> worn off one end of the ratchet that I hadn't seen. As I was loosening a
bolt,
> the tip of the ratchet touched another terminal about 60V away and "boom"
> the end of the ratchet blew off.
> 
> Bill
> 

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## EVDL List (Jul 27, 2007)

> On 1:59 PM, Mike Nickerson wrote:
> > I've been wondering about this. I also have some of my tools wrapped in
> > electrical tape, but they are still conductive from one end to the other.
> > I've been wondering if it's possible to get some tools with steel ends, but
> ...


----------



## EVDL List (Jul 27, 2007)

Thanks for the details of where things are located. I have a similar car,
and was surprised you could fit a PFC30 behind the center console! You said
"Up to this point, I had just been running on the 100Ah LFP cells in the
front, which are about 11 kWh. The LCP cells in the back are 200Ah, so they
added around 22 kWh. The two strings in parallel, then, provide 300Ah."
That sounds like you are not drawing current from both strings
simultaneously, rather running off one string until it is depleted to some
target SOC, then switching to the other string, so only one string is
connected to the controller at a time, so that total capacity would be 100Ah
+ 200Ah. Is that correct? If they were connected in parallel, and charge
was drawn from both at the same time, you would be limited in capacity by
the 100Ah cells (just as any pack is limited by the capacity of its lowest
capacity cell), so you could draw at most about 80% of 100Ah from both
strings, or about 160Ah, and effective pack capacity would be 200Ah.

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## EVDL List (Jul 27, 2007)

Both strings are connected in parallel and supplying energy at the same time. I haven't run through a complete cycle yet, but I expect it to work something like the following (someone correct me if I'm wrong). I won't know for sure until I get the cycle analyst graphs for each string.

The LFP cells have a flatter discharge curve and a lower internal resistance. So when the pack is near full, the 100Ah cells will be supplying a lot of the energy. As the LFP cells get down toward their lower DOD knee, their internal resistance will increase. The 200Ah cells will start to supply more of the energy and keep the 100Ah cells from dropping too far, until the 200Ah cells internal resistance starts to increase as well. Since they're connect in parallel, the voltage of both strings should be the same, with each string supplying what amperage it can based on its internal resistance.

Unless I'm mistaken (which is always highly likely), I should be able to draw close to the 300Ah, with each string's percentage of the total amperage changing. 

Bill

----- Original Message -----
From: "tomw" <[email protected]>
To: [email protected]
Sent: Thursday, July 28, 2011 8:40:42 AM
Subject: Re: [EVDL] Thanks, Daddy!

Thanks for the details of where things are located. I have a similar car,
and was surprised you could fit a PFC30 behind the center console! You said
"Up to this point, I had just been running on the 100Ah LFP cells in the
front, which are about 11 kWh. The LCP cells in the back are 200Ah, so they
added around 22 kWh. The two strings in parallel, then, provide 300Ah."
That sounds like you are not drawing current from both strings
simultaneously, rather running off one string until it is depleted to some
target SOC, then switching to the other string, so only one string is
connected to the controller at a time, so that total capacity would be 100Ah
+ 200Ah. Is that correct? If they were connected in parallel, and charge
was drawn from both at the same time, you would be limited in capacity by
the 100Ah cells (just as any pack is limited by the capacity of its lowest
capacity cell), so you could draw at most about 80% of 100Ah from both
strings, or about 160Ah, and effective pack capacity would be 200Ah.

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## EVDL List (Jul 27, 2007)

Tom,
I just re-read your post. I think I understand now. You're envisioning that amperage will be divided evenly across the two parallel strings. So if the car is drawing 150A, then each string will supply 75A. But I think what happens instead is that each string supplies an amount of the amperage according to its internal resistance. So if the 200Ah string, for example, had 1/2 the internal resistance of the 100Ah string, then the 200Ah string would be supplying 100A and the 200Ah string would be supplying 50A, roughly.

Bill

----- Original Message -----
From: "tomw" <[email protected]>
To: [email protected]
Sent: Thursday, July 28, 2011 8:40:42 AM
Subject: Re: [EVDL] Thanks, Daddy!

Thanks for the details of where things are located. I have a similar car,
and was surprised you could fit a PFC30 behind the center console! You said
"Up to this point, I had just been running on the 100Ah LFP cells in the
front, which are about 11 kWh. The LCP cells in the back are 200Ah, so they
added around 22 kWh. The two strings in parallel, then, provide 300Ah."
That sounds like you are not drawing current from both strings
simultaneously, rather running off one string until it is depleted to some
target SOC, then switching to the other string, so only one string is
connected to the controller at a time, so that total capacity would be 100Ah
+ 200Ah. Is that correct? If they were connected in parallel, and charge
was drawn from both at the same time, you would be limited in capacity by
the 100Ah cells (just as any pack is limited by the capacity of its lowest
capacity cell), so you could draw at most about 80% of 100Ah from both
strings, or about 160Ah, and effective pack capacity would be 200Ah.

--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Thanks-Daddy-tp3697491p3701515.html
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----------



## EVDL List (Jul 27, 2007)

When I work on my batteries I throw rubber mats on top of the batteries, an=
d leave a little gap for what I am working on.


________________________________
From: Bill Dennis <[email protected]>
To: 'Electric Vehicle Discussion List' <[email protected]>
Sent: Wednesday, July 27, 2011 5:49 AM
Subject: Re: [EVDL] Thanks, Daddy!

36 100 Ah LFP cells in the front and 31 200Ah LCP cells in the back. Ful=
ly
charged voltages on each work out to about the same (around 130V). I
undercharge to 124.2V, which is 3.45V per LFP cell, right about where they
reach their knee. This works out to 4.0V per LCP cell. The LFP cells
provide the power and the LCP cells provide most of the range.

Yes, it was an "oops" event about a year ago, when I was disassembling the
old pack. I have my tools all wrapped in electrical tape. But the tap=
e had
worn off one end of the ratchet that I hadn't seen. As I was loosening a
bolt, the tip of the ratchet touched another terminal about 60V away and
"boom" the end of the ratchet blew off.
-------------- next part --------------
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----------



## EVDL List (Jul 27, 2007)

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c2pzdS5lZHUvbWFpbG1hbi9saXN0aW5mby9ldgo=


----------



## EVDL List (Jul 27, 2007)

My two volts worth,
First point to make is that when two banks are in parallel, the negative
cable needs to come from one bank and the positive cable needs to come from
the other bank. The second point I would like to make is that it would be an
extremely short period of time, 30 seconds under load? Until the load from
both banks would be within amps of each other. 

Sincerely,
Mark Grasser


-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of WILLIAM DENNIS Owner
Sent: Thursday, July 28, 2011 3:12 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Thanks, Daddy!

Tom,
I just re-read your post. I think I understand now. You're envisioning
that amperage will be divided evenly across the two parallel strings. So if
the car is drawing 150A, then each string will supply 75A. But I think what
happens instead is that each string supplies an amount of the amperage
according to its internal resistance. So if the 200Ah string, for example,
had 1/2 the internal resistance of the 100Ah string, then the 200Ah string
would be supplying 100A and the 200Ah string would be supplying 50A,
roughly.

Bill

----- Original Message -----
From: "tomw" <[email protected]>
To: [email protected]
Sent: Thursday, July 28, 2011 8:40:42 AM
Subject: Re: [EVDL] Thanks, Daddy!

Thanks for the details of where things are located. I have a similar car,
and was surprised you could fit a PFC30 behind the center console! You said
"Up to this point, I had just been running on the 100Ah LFP cells in the
front, which are about 11 kWh. The LCP cells in the back are 200Ah, so they
added around 22 kWh. The two strings in parallel, then, provide 300Ah."
That sounds like you are not drawing current from both strings
simultaneously, rather running off one string until it is depleted to some
target SOC, then switching to the other string, so only one string is
connected to the controller at a time, so that total capacity would be 100Ah
+ 200Ah. Is that correct? If they were connected in parallel, and charge
was drawn from both at the same time, you would be limited in capacity by
the 100Ah cells (just as any pack is limited by the capacity of its lowest
capacity cell), so you could draw at most about 80% of 100Ah from both
strings, or about 160Ah, and effective pack capacity would be 200Ah.

--
View this message in context:
http://electric-vehicle-discussion-list.413529.n4.nabble.com/Thanks-Daddy-tp
3697491p3701515.html
Sent from the Electric Vehicle Discussion List mailing list archive at
Nabble.com.

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
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----------



## EVDL List (Jul 27, 2007)

Hi Mark,

You are talking about creating a perfect matched pair
of battery packs, such as two strings of identical
lead-acid batteries and avoiding uneven charge-discharge.

The pack for this vehicle actually consists of two uneven
strings, different chemistry and capacity so it is
essentially impossible to keep them perfect in balance
and Bill is not even trying to achieve that.
The current supplied by each string is depending on their
instantaneous impedance, which will vary over the range
of discharge so I agree to Bill's original assesment that
initial current could mainly come from the stiffer batteries
and when they drop in SoC, it would shift more towards the
higher capacity batteries, but it will also be a dynamic,
with that I mean that if the car is stopped for a while then
the high capacity string might charge up the stiffer string
a bit and when you start driving again, initially that
stiffer string might again deliver a large portion of the
current.
Due to the higher capacity of the "softer" cells it is
unavoidable that at lower SoC levels of the stiffer string,
the majority of the current is supplied by the softer string
which leads to deeper sag and possibly very low SoC of the
stiff string, maybe even alarm from its BMS that the minimum
voltage is reached on some of its cells long before the
other string is empty. Still you better stop driving at
that point and wait for the soft string to recharge the
stiff string a bit again...
Only testing will show if you are able to pull the 300Ah
capacity or that soon after drawing the 100Ah down you will
run into under-discharge alarms of this string...

Hope this clarifies,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Mark Grasser
Sent: Thursday, July 28, 2011 12:52 PM
To: 'Electric Vehicle Discussion List'
Subject: Re: [EVDL] Thanks, Daddy!

My two volts worth,
First point to make is that when two banks are in parallel, the negative
cable needs to come from one bank and the positive cable needs to come
from the other bank. The second point I would like to make is that it
would be an extremely short period of time, 30 seconds under load? Until
the load from both banks would be within amps of each other. 

Sincerely,
Mark Grasser


-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of WILLIAM DENNIS Owner
Sent: Thursday, July 28, 2011 3:12 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Thanks, Daddy!

Tom,
I just re-read your post. I think I understand now. You're
envisioning that amperage will be divided evenly across the two parallel
strings. So if the car is drawing 150A, then each string will supply
75A. But I think what happens instead is that each string supplies an
amount of the amperage according to its internal resistance. So if the
200Ah string, for example, had 1/2 the internal resistance of the 100Ah
string, then the 200Ah string would be supplying 100A and the 200Ah
string would be supplying 50A, roughly.

Bill

----- Original Message -----
From: "tomw" <[email protected]>
To: [email protected]
Sent: Thursday, July 28, 2011 8:40:42 AM
Subject: Re: [EVDL] Thanks, Daddy!

Thanks for the details of where things are located. I have a similar
car, and was surprised you could fit a PFC30 behind the center console!
You said "Up to this point, I had just been running on the 100Ah LFP
cells in the front, which are about 11 kWh. The LCP cells in the back
are 200Ah, so they added around 22 kWh. The two strings in parallel,
then, provide 300Ah."
That sounds like you are not drawing current from both strings
simultaneously, rather running off one string until it is depleted to
some target SOC, then switching to the other string, so only one string
is connected to the controller at a time, so that total capacity would
be 100Ah
+ 200Ah. Is that correct? If they were connected in parallel, and 
+ charge
was drawn from both at the same time, you would be limited in capacity
by the 100Ah cells (just as any pack is limited by the capacity of its
lowest capacity cell), so you could draw at most about 80% of 100Ah from
both strings, or about 160Ah, and effective pack capacity would be
200Ah.

--
View this message in context:
http://electric-vehicle-discussion-list.413529.n4.nabble.com/Thanks-Dadd
y-tp
3697491p3701515.html
Sent from the Electric Vehicle Discussion List mailing list archive at
Nabble.com.

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
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_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
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|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
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----------



## EVDL List (Jul 27, 2007)

Well-stated, Cor. It's the low end of DOD that'll be interesting to watch. By putting a separate cycle analyst on each string, I'm hoping I can effectively monitor how many amp-hours have been drawn out of each one. If the softer string is recharging the stiffer one, I'm assuming that the analyst's AH counter will take that into account. If not, I'll have to look for some other form of monitoring.

Bill 

----- Original Message -----
From: "Cor van de Water" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Thursday, July 28, 2011 2:55:49 PM
Subject: Re: [EVDL] Thanks, Daddy!

Hi Mark,

You are talking about creating a perfect matched pair
of battery packs, such as two strings of identical
lead-acid batteries and avoiding uneven charge-discharge.

The pack for this vehicle actually consists of two uneven
strings, different chemistry and capacity so it is
essentially impossible to keep them perfect in balance
and Bill is not even trying to achieve that.
The current supplied by each string is depending on their
instantaneous impedance, which will vary over the range
of discharge so I agree to Bill's original assesment that
initial current could mainly come from the stiffer batteries
and when they drop in SoC, it would shift more towards the
higher capacity batteries, but it will also be a dynamic,
with that I mean that if the car is stopped for a while then
the high capacity string might charge up the stiffer string
a bit and when you start driving again, initially that
stiffer string might again deliver a large portion of the
current.
Due to the higher capacity of the "softer" cells it is
unavoidable that at lower SoC levels of the stiffer string,
the majority of the current is supplied by the softer string
which leads to deeper sag and possibly very low SoC of the
stiff string, maybe even alarm from its BMS that the minimum
voltage is reached on some of its cells long before the
other string is empty. Still you better stop driving at
that point and wait for the soft string to recharge the
stiff string a bit again...
Only testing will show if you are able to pull the 300Ah
capacity or that soon after drawing the 100Ah down you will
run into under-discharge alarms of this string...

Hope this clarifies,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Mark Grasser
Sent: Thursday, July 28, 2011 12:52 PM
To: 'Electric Vehicle Discussion List'
Subject: Re: [EVDL] Thanks, Daddy!

My two volts worth,
First point to make is that when two banks are in parallel, the negative
cable needs to come from one bank and the positive cable needs to come
from the other bank. The second point I would like to make is that it
would be an extremely short period of time, 30 seconds under load? Until
the load from both banks would be within amps of each other. 

Sincerely,
Mark Grasser


-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of WILLIAM DENNIS Owner
Sent: Thursday, July 28, 2011 3:12 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Thanks, Daddy!

Tom,
I just re-read your post. I think I understand now. You're
envisioning that amperage will be divided evenly across the two parallel
strings. So if the car is drawing 150A, then each string will supply
75A. But I think what happens instead is that each string supplies an
amount of the amperage according to its internal resistance. So if the
200Ah string, for example, had 1/2 the internal resistance of the 100Ah
string, then the 200Ah string would be supplying 100A and the 200Ah
string would be supplying 50A, roughly.

Bill

----- Original Message -----
From: "tomw" <[email protected]>
To: [email protected]
Sent: Thursday, July 28, 2011 8:40:42 AM
Subject: Re: [EVDL] Thanks, Daddy!

Thanks for the details of where things are located. I have a similar
car, and was surprised you could fit a PFC30 behind the center console!
You said "Up to this point, I had just been running on the 100Ah LFP
cells in the front, which are about 11 kWh. The LCP cells in the back
are 200Ah, so they added around 22 kWh. The two strings in parallel,
then, provide 300Ah."
That sounds like you are not drawing current from both strings
simultaneously, rather running off one string until it is depleted to
some target SOC, then switching to the other string, so only one string
is connected to the controller at a time, so that total capacity would
be 100Ah
+ 200Ah. Is that correct? If they were connected in parallel, and 
+ charge
was drawn from both at the same time, you would be limited in capacity
by the 100Ah cells (just as any pack is limited by the capacity of its
lowest capacity cell), so you could draw at most about 80% of 100Ah from
both strings, or about 160Ah, and effective pack capacity would be
200Ah.

--
View this message in context:
http://electric-vehicle-discussion-list.413529.n4.nabble.com/Thanks-Dadd
y-tp
3697491p3701515.html
Sent from the Electric Vehicle Discussion List mailing list archive at
Nabble.com.

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
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_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
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## EVDL List (Jul 27, 2007)

Bill, make sure to get at least the data loving USB cords (or make your own)
and log the discharge data from both CA's. It would be interesting to see
the discharge data over time for both strings on the same graph.

If you have the shunts in the right place the CA will properly count Ah both
ways if one string charges the other. Note that the CA records Ah consumed
not Ah left in the pack so a positive current is discharge and a negative
current is charge. I use the Ah to track my partial charges but it does mess
up the Wh/mi and % regen values.



> WILLIAM DENNIS Owner <[email protected]> wrote:
> > Well-stated, Cor. It's the low end of DOD that'll be interesting to
> watch. By putting a separate cycle analyst on each string, I'm hoping I can
> effectively monitor how many amp-hours have been drawn out of each one. If
> ...


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## EVDL List (Jul 27, 2007)

"By putting a separate cycle analyst on each string, I'm hoping I can
effectively monitor how many amp-hours have been drawn out of each one. If
the softer string is recharging the stiffer one, I'm assuming that the
analyst's AH counter will take that into account. If not, I'll have to look
for some other form of monitoring." 

I think that should work well. My charge counter (TBS) typically tracks to
within a few Ah accuracy, for example showing a couple Ah short of full
charge when the cells are actually full after charge. I usually reset it to
"full" once every 10 charges or so when the pack is full. 

I understand your thinking on behavior of the two parallel strings. Usually
voltage sag becomes larger at lower SOC of a pack due to the greater work
required to move charge out of the pack and greater internal energy
dissipation as a result. But in this case voltage must be the same across
both strings as you say so more of the charge will be supplied by the other
larger Ah string at higher SOC. The operation seems risky to me, if the
100Ah string must be down close to the low voltage "knee" before the 200Ah
string starts supplying most of the current. It is a quick drop down below
the knee - not many Ah there. But maybe the pack will just hold in a narrow
voltage range near the "knee" of the 100Ah string as you say as the 200Ah
string supplies most of the current. The 100Ah string will be supplying
some charge though and there are not many Ah left in it at that point. Will
be interesting to see how it behaves.

--
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