# [EVDL] LTC6803 EV Battery monitoring chip



## EVDL List (Jul 27, 2007)

I got excited when I saw this post, but then I read the datasheet and
found out that they are designed to measure individual cells (such as
3.7v LiIon), so the sensing range only goes from 0-5v (and the chip is
rated with an absolute max of 8v between cells, but can't actually
measure 5-8v).

So, unless you can use 2V cells, or drill into your PbA batteries to
connect to each individual cell, this probably won't work with lead acid
batteries. (I have 6v batteries).

Does anybody have a pointer to a similar chip which can do 8v or 14v, so
it can be used with individual PbA battery instead of with individual
cells within the battery?

Jay





> brucedp4 wrote:
> > Measures up to 12 individual battery cells in series
> > =
> 
> ...


----------



## EVDL List (Jul 27, 2007)

OK, so I did some web research and got:

http://google.com/#sclient=psy&hl=en&q=chip+ic+battery+monitor
gives

http://www.analog.com/en/press-release/Oct_16_2006_ADI_Adv_Auto_Battery_Monitoring/press.html
ANALOG DEVICES ADVANCES AUTOMOTIVE BATTERY MONITORING WITH HIGHLY 
INTEGRATED MIXED-SIGNAL IC



http://google.com/#sclient=psy&hl=en&q=chip+ic+battery+monitor+6v
gives

http://homepages.which.net/~paul.hills/Circuits/BatteryMonitor/BatteryMonitor.html
Battery Monitoring [several chips listed]

http://www.myra-simon.com/bike/charger.html
Sealed Lead-Acid Battery Charger Circuit [L200 chip]


Lastly, try
http://google.com/#sclient=psy&hl=en&q=chip+ic+battery+monitor+pbso4


I hope this helps.
{brucedp.150m.com}

--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/LTC6803-EV-Battery-monitoring-chip-tp3329682p3332766.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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## EVDL List (Jul 27, 2007)

Granted, it would up the cost of the project, but could you use some sort of
scaler chip that takes 0-15V, cuts it by 3, and outputs 0-5V? That'd work as
an input range for the LTC6803.



> brucedp5 <[email protected]> wrote:
> 
> > OK, so I did some web research and got:
> >
> ...


----------



## EVDL List (Jul 27, 2007)

I actually was thinking about that, but the complication is that the
chip uses each wire in two different directions (+ from lower battery,
and - from upper battery). Most voltage scaling chips would have
problems being chained and expected to work with both batteries, etc..

But I am now thinking that perhaps a half-rectifier type arrangement
(two diodes back to back) on each sensing wire would act to reduce the
voltage by the diodes voltage drop, not exactly a scale just a straight
subtraction, but since our batteries should never need to be measured in
the 0-3v range, it should work....somebody with an EE degree can tell me
if I'm totally off base here...

The only way to tell for sure if this would actually work with the chips
internal circuits is to buy one and try it out...

Jay

Jeff Haskell wrote:
> Granted, it would up the cost of the project, but could you use some sort of
> scaler chip that takes 0-15V, cuts it by 3, and outputs 0-5V? That'd work as
> an input range for the LTC6803.
> 
>


> brucedp5 <[email protected]> wrote:
> >
> >> OK, so I did some web research and got:
> >>
> ...


----------



## EVDL List (Jul 27, 2007)

Hi all,

What about the low tech solution - simple resistor voltage divider.

eg for a 6v lead acid battery.
put two high ohm resistors in series from batt- to batt+
connect sensor pin 1 to batt-
connect sensor pin 2 to connection between resistors
connect sensor pin 3 to batt+
(and so on for all your batts in series)

On the software side, take the voltage reading between 1&2 and between
2&3 and simply add them together to give the voltage of the 6v batt.
It doesn't matter about the exact values of the resistors or their
precision, since you simply want the sum of the two voltages - as long
as each individual voltage stays within 0-5v.

Similarly, you could do a 12v battery by dividing it with three
resistors instead of two, though you'd want to be a bit more accurate
matching the resistors, since at full charge the voltage will approach
15v (which divided into 3 is 5v - the limit of the sensors)

Granted, this uses more sensor pins per battery, but it will probably
turn out cheaper to use multiple sensor chips than fancy scaling
circuits on each sensor pin.

Mark

On 4 March 2011 01:53, Jay Summet <[email protected]> wrote:
> I actually was thinking about that, but the complication is that the
> chip uses each wire in two different directions (+ from lower battery,
> and - from upper battery). Most voltage scaling chips would have
> problems being chained and expected to work with both batteries, etc..
>
> But I am now thinking that perhaps a half-rectifier type arrangement
> (two diodes back to back) on each sensing wire would act to reduce the
> voltage by the diodes voltage drop, not exactly a scale just a straight
> subtraction, but since our batteries should never need to be measured in
> the 0-3v range, it should work....somebody with an EE degree can tell me
> if I'm totally off base here...
>
> The only way to tell for sure if this would actually work with the chips
> internal circuits is to buy one and try it out...
>
> Jay
>
> Jeff Haskell wrote:
>> Granted, it would up the cost of the project, but could you use some sor=
t of
>> scaler chip that takes 0-15V, cuts it by 3, and outputs 0-5V? That'd wor=
k as
>> an input range for the LTC6803.
>>
>>


> brucedp5 <[email protected]> wrote:
> >>
> >>> OK, so I did some web research and got:
> >>>
> ...


----------



## EVDL List (Jul 27, 2007)

Dear Sir/ Maa'm
Please don't send anymore email regarding any kinds of battery or whatever =

product you have. It has been years that I am receiving these emails for yo=
u. I =

put them in spam and I still recieve them. I am not interesed.
Thank you



________________________________
From: Jay Summet <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Thu, March 3, 2011 6:53:02 AM
Subject: Re: [EVDL] LTC6803 EV Battery monitoring chip

I actually was thinking about that, but the complication is that the
chip uses each wire in two different directions (+ from lower battery,
and - from upper battery). Most voltage scaling chips would have
problems being chained and expected to work with both batteries, etc..

But I am now thinking that perhaps a half-rectifier type arrangement
(two diodes back to back) on each sensing wire would act to reduce the
voltage by the diodes voltage drop, not exactly a scale just a straight
subtraction, but since our batteries should never need to be measured in
the 0-3v range, it should work....somebody with an EE degree can tell me
if I'm totally off base here...

The only way to tell for sure if this would actually work with the chips
internal circuits is to buy one and try it out...

Jay

Jeff Haskell wrote:
> Granted, it would up the cost of the project, but could you use some sort=
of
> scaler chip that takes 0-15V, cuts it by 3, and outputs 0-5V? That'd work=
as
> an input range for the LTC6803.
> =

>


> brucedp5 <[email protected]> wrote:
> > =
> 
> >> OK, so I did some web research and got:
> ...


----------



## EVDL List (Jul 27, 2007)

Dear Sir/ Maa'm
Please don't send anymore email regarding any kinds of battery or whatever =

product you have. It has been years that I am receiving these emails for yo=
u. I =

put them in spam and I still recieve them. I am not interesed.
Thank you





________________________________
From: Jay Summet <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Thu, March 3, 2011 6:53:02 AM
Subject: Re: [EVDL] LTC6803 EV Battery monitoring chip

I actually was thinking about that, but the complication is that the
chip uses each wire in two different directions (+ from lower battery,
and - from upper battery). Most voltage scaling chips would have
problems being chained and expected to work with both batteries, etc..

But I am now thinking that perhaps a half-rectifier type arrangement
(two diodes back to back) on each sensing wire would act to reduce the
voltage by the diodes voltage drop, not exactly a scale just a straight
subtraction, but since our batteries should never need to be measured in
the 0-3v range, it should work....somebody with an EE degree can tell me
if I'm totally off base here...

The only way to tell for sure if this would actually work with the chips
internal circuits is to buy one and try it out...

Jay

Jeff Haskell wrote:
> Granted, it would up the cost of the project, but could you use some sort=
of
> scaler chip that takes 0-15V, cuts it by 3, and outputs 0-5V? That'd work=
as
> an input range for the LTC6803.
> =

>


> brucedp5 <[email protected]> wrote:
> > =
> 
> >> OK, so I did some web research and got:
> ...


----------



## EVDL List (Jul 27, 2007)

Ahh the irony....this guy complains about EVDL spamming him, then he spams
the EVDL with 9 or 10 duplicate, dumb messages in 5 minutes.

To quote ventriloquist Jeff Dunham's "Walter": "Dumbass!"

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Aazam Fakharian
Sent: Thursday, March 03, 2011 3:26 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] LTC6803 EV Battery monitoring chip

Dear Sir/ Maa'm
Please don't send anymore email regarding any kinds of battery or whatever =

product you have. It has been years that I am receiving these emails for
you. I =

put them in spam and I still recieve them. I am not interesed.
Thank you





________________________________
From: Jay Summet <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Thu, March 3, 2011 6:53:02 AM
Subject: Re: [EVDL] LTC6803 EV Battery monitoring chip

I actually was thinking about that, but the complication is that the
chip uses each wire in two different directions (+ from lower battery,
and - from upper battery). Most voltage scaling chips would have
problems being chained and expected to work with both batteries, etc..

But I am now thinking that perhaps a half-rectifier type arrangement
(two diodes back to back) on each sensing wire would act to reduce the
voltage by the diodes voltage drop, not exactly a scale just a straight
subtraction, but since our batteries should never need to be measured in
the 0-3v range, it should work....somebody with an EE degree can tell me
if I'm totally off base here...

The only way to tell for sure if this would actually work with the chips
internal circuits is to buy one and try it out...

Jay

Jeff Haskell wrote:
> Granted, it would up the cost of the project, but could you use some sort
of
> scaler chip that takes 0-15V, cuts it by 3, and outputs 0-5V? That'd work
as
> an input range for the LTC6803.
> =

>


> brucedp5 <[email protected]> wrote:
> > =
> 
> >> OK, so I did some web research and got:
> ...


----------



## EVDL List (Jul 27, 2007)

Yes, a voltage divider on each battery would work, but it would half the
number of six volt batteries you could measure (to six). And be even
worse for the 12 volt batteries (4 batteries). (The main problem is that
the chip multiplexes input lines, which is normally good, but in high
voltage cases, you can't construct independent voltage dividers.)


Also: I realize that with the correct high ohm resistors the current
draw from the batteries would be so small as to not matter for EV
applications, but I really like the idea of near 0 draw when the chip is
in standby mode, which you would lose with a voltage divider array.

Jay

Mark Fowler wrote:
> Hi all,
> 
> What about the low tech solution - simple resistor voltage divider.
> 
> eg for a 6v lead acid battery.
> put two high ohm resistors in series from batt- to batt+
> connect sensor pin 1 to batt-
> connect sensor pin 2 to connection between resistors
> connect sensor pin 3 to batt+
> (and so on for all your batts in series)
> 
> On the software side, take the voltage reading between 1&2 and between
> 2&3 and simply add them together to give the voltage of the 6v batt.
> It doesn't matter about the exact values of the resistors or their
> precision, since you simply want the sum of the two voltages - as long
> as each individual voltage stays within 0-5v.
> 
> Similarly, you could do a 12v battery by dividing it with three
> resistors instead of two, though you'd want to be a bit more accurate
> matching the resistors, since at full charge the voltage will approach
> 15v (which divided into 3 is 5v - the limit of the sensors)
> 
> Granted, this uses more sensor pins per battery, but it will probably
> turn out cheaper to use multiple sensor chips than fancy scaling
> circuits on each sensor pin.
> 
> Mark
> 
> On 4 March 2011 01:53, Jay Summet <[email protected]> wrote:
>> I actually was thinking about that, but the complication is that the
>> chip uses each wire in two different directions (+ from lower battery,
>> and - from upper battery). Most voltage scaling chips would have
>> problems being chained and expected to work with both batteries, etc..
>>
>> But I am now thinking that perhaps a half-rectifier type arrangement
>> (two diodes back to back) on each sensing wire would act to reduce the
>> voltage by the diodes voltage drop, not exactly a scale just a straight
>> subtraction, but since our batteries should never need to be measured in
>> the 0-3v range, it should work....somebody with an EE degree can tell me
>> if I'm totally off base here...
>>
>> The only way to tell for sure if this would actually work with the chips
>> internal circuits is to buy one and try it out...
>>
>> Jay
>>
>> Jeff Haskell wrote:
>>> Granted, it would up the cost of the project, but could you use some sort of
>>> scaler chip that takes 0-15V, cuts it by 3, and outputs 0-5V? That'd work as
>>> an input range for the LTC6803.
>>>
>>>


> brucedp5 <[email protected]> wrote:
> >>>
> >>>> OK, so I did some web research and got:
> >>>>
> ...


----------



## EVDL List (Jul 27, 2007)

> Jay Summet wrote:
> > Yes, a voltage divider on each battery would work, but it would halve
> > the number of six volt batteries you could measure (to six). And be
> > even worse for the 12 volt batteries (4 batteries). (The main problem
> ...


----------



## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

> Evan Tuer wrote:
> > I use the predecessor, LTC6802, for car BMSs.=C2 The fundamental
> > capability of measuring voltages is the same no matter how large the
> > cells are, and these ICs have a communication option which allows them
> ...


----------



## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

First line on the spec sheet " Measures up to 12 Li-Ion Cells in Series (60V
Max)"

Sincerely,
Mark Grasser
=



-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Jay Summet
Sent: Monday, March 07, 2011 9:41 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] LTC6803 EV Battery monitoring chip





> Evan Tuer wrote:
> > I use the predecessor, LTC6802, for car BMSs.=C2 The fundamental
> > capability of measuring voltages is the same no matter how large the
> > cells are, and these ICs have a communication option which allows them
> ...


----------



## EVDL List (Jul 27, 2007)

That's for one chip; they're designed to be connected in a daisy chain
for large packs.

Second line on the spec sheet "Stackable architecture enables >1000V systems"

That said, I think they're more appropriate for an OEM battery
solution than a BMS for homebrew EVs. I'm skeptical about how
well/reliably it would work with the amount of noise present in many
homebrew EVs.

In an OEM EV, there will be extensive EMC testing to make sure the
controller doesn't interfere with the BMS and so on, but in a homebrew
EV, no thought is given to such matters.

Highly integrated chips like the LTC6802 can simplify a system and
reduce cost, but they can also be brought down by noise that wouldn't
be a problem in a system with a discrete analog front-end with plenty
of filtering.

-Morgan LaMoore



> Mark Grasser <[email protected]> wrote:
> >
> > First line on the spec sheet " Measures up to 12 Li-Ion Cells in Series (60V
> > Max)"
> ...


----------

