# [EVDL] SOC gauge



## EVDL List (Jul 27, 2007)

I use a CycleAnalyst from ebikes.ca. It doesn't give SOC directly but
it does give a count of Ah used. For my 200Ah pack I know that 160Ah
is 20%SOC so I stay above that. The CA does not have any peukert
adjustment so if you aren't using it on a Li pack you may want
something else.

Another option is the ZEVA-2 which runs the origional gas gauge.



> Alan Shaw <[email protected]> wrote:
> > Can anyone recommend a reliable and accurate "state of charge" gauge?
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
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## EVDL List (Jul 27, 2007)

At evparts.com, you can look at Item #IN2541. It is a Westach meter custom
made for the EV industry. You will also find a wide variety of other gauges
and meter in the same section. Please contact me off list if you need help
with these or any other items of this sort.
Regards,
Tom True



> Alan Shaw <[email protected]> wrote:
> 
> > Can anyone recommend a reliable and accurate "state of charge" gauge?
> > -------------- next part --------------
> ...


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## EVDL List (Jul 27, 2007)

> Alan Shaw wrote:
> > Can anyone recommend a reliable and accurate "state of charge" gauge?
> 
> I like the Cruising Equipment E-meter, later renamed the Heart Interface
> ...


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## EVDL List (Jul 27, 2007)

Hi Alan,
It depends on some various factors, such as cost, and battery pack. If you have an Elithion BMS (and if you don't, they do work great for Li-ion conversions), then you can get one of their SOC displays:

http://elithion.com/lithiumate-pro-displays.php

Granted, the BMS + SOC will run you at least $1k.

--corbin



> Alan Shaw wrote:
> 
> > Can anyone recommend a reliable and accurate "state of charge" gauge?
> > -------------- next part --------------
> ...


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## EVDL List (Jul 27, 2007)

Like Lee, I enjoyed my Cruising Equipment E-meter. It told me 
everything I needed or wanted to know, for EV driving, EV Charging, 
and general status of my pack health. I mainly used the accuracy of 
the pack (surface) voltage, AHrs in or out, and while the terse energy
gauge led bar (like a fuel gauge) was OK, but it was not that accurate.
Looking at how many amp-hours I had used, and at the pack voltage to 
know how hard I had hit-on / pulled-from the pack told me how full
or empty I was. 

My S-10 Blazer with the 132V T145 configuration would start out on a
trip fully charged at about 152V (no load). After drawing a few amps 
off the pack to drive the 5 miles to get on the highway and driving at
55mph, the e-meter would display 133V at 75amps (this is at near full
charge). 

When I was nearing the end of my easy highway speed 50 mile range, my
pack voltage would be 108V at a 150amp draw at 55mph.

When recharging at a public EV Charging site using my pfc charger, the
e-meter would show the surface voltage rising, the amps into the pack,
and the amp hours decrementing. With all my chargers on, it 
decremented very-fast.

For those that did not know, I had various charger configurations,
with all their outputs tied to the pack. With enough outlets, I could
pump almost 200 amps into my pack from an AC grid source.

Usually, public EV Charging sites only had one 6kW AVCON to pull 
from. But sometimes, I would find a way to power on all the 
chargers.

At the 2002 Las Vegas NEDRA EVent, a local EAA Chapter member 
brought a huge generator which I promptly plugged all my 
chargers into 
http://brucedp02.0catch.com/lvnedra02/f_lvnedra020323-003.jpg

With so much power, the surface voltage would rise quickly, and thus
the amps going into the pack would correspondingly go down. So, if I
had someone else turn on my chargers while I sat in the driver's seat
when charging a fully depleted PbSO4 wet-cell pack, would have seen 
the most current my chargers could put out. As it was, by the time I 
got around to taking this next pic the current had dropped to 172 amps
http://brucedp02.0catch.com/lvnedra02/f_lvnedra020323-015.jpg

Still, that is pretty fast-charging wouldn't you say? At a surface 
voltage of 168V and 172amps going in, that is 28896W or 28.9kW of 
serious EV Charging power. At that rate, the pack reached 60% SOC in 
less than 30 minutes, and I started unplugging chargers. By the time 
45 minutes came around, I had reached 80% SOC and was down to one 
on-board charger on (of course my sweet pfc), and the rest of charge 
took its usual slow-time. Normally, I would unplug at the 80% SOC 
point and get back on the highway heading to the next charging site. 
But this was an EVent, so I just let the pfc do its magic.

As you can see, I would have been lost without that e-meter. What
ever e-meter you choose to use, make it a good one that tells you
the same information as I stated above. It costs more, but like a 
pfc charger, it is really-really worth it.

I am rather disappointed to read Lee's statement that these e-meters
are no longer available. I would hope that for my above stated 
purposes, a Xantrex LinkLITE would would work if I were lucky enough
to own an EV again.

If that is true, and I found them available 
http://google.com/search?q="Xantrex+LinkLITE"&tbs=shop%3A1&hl=en&aq=f

Besides buying the e-meter, didn't you also have to buy a proper
shunt, and a small 12V DC to DC to provide isolated power?




{brucedp.150m.com}




On Sat, 28 May 2011 11:55 -0500, "Lee Hart" <[email protected]>


> wrote:
> > Alan Shaw
> 
> 
> ...


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## EVDL List (Jul 27, 2007)

A great recap of your innovative charging history, Bruce. On the Xantrex 
LinkLite and LinkPro:



> bruce parmenter wrote:
> > I would hope that for my above stated
> > purposes, a Xantrex LinkLITE would would work if I were lucky enough
> > to own an EV again.
> ...


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## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> 
> > The LinkLite and LinkPro are built for the marine and RV markets. They
> > only support 12v or 24v battery packs (35vdc absolute max), and don't
> ...


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## EVDL List (Jul 27, 2007)

> Roger Stockton wrote:
> > Lee Hart wrote:
> >
> > > The LinkLite and LinkPro are built for the marine and RV markets. They
> ...


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## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> 
> > The LinkLite is missing many features. It only displays 3 digits (12.3v)
> > compared to the E-meter's 4 digits (12.35v). Even TSB's version does not
> ...


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## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> 
> > Which TBS meter do you have? The one that corresponds to the LinkLite,
> > or LinkPro? Does it have the setup option to display the correct voltage
> ...


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## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> > Thank you very much indeed, Willie! Sounds like I'll have to buy one for
> > my next EV project, instead of finding another used E-meter.
> 
> ...


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## EVDL List (Jul 27, 2007)

Willie, we once owned a Xebra and found that the CycleAnalyst, combined wit=
h some PowerCheq equalizers was probably the single most important factor i=
n long healthy battery life. Having the speedometer sensor running off the =
half-shaft from the differential also gave us direct consumption figures, m=
aking it easy to calculate "miles to empty". Even my non-techie wife was=
able to easily understand the display information as it applied to her com=
mutes.

We did not use the CA during recharge, so holding the reset button to clear=
figures resulted in fairly accurate cycle indications. Using established f=
igures for the Deka batteries, we figured that the 98 ah pack (c/20) was re=
ally only good for 49 ah (1c) and by extension, 24.5 of them would mean fif=
ty percent depth of discharge. Watching the ah display on the CA, with 25 a=
s "empty, with reserve" made it simple for my wife to get to her destinatio=
n and return.

If you have LiFePO4, those numbers only get better!

fred



________________________________
------------------------------

Beginning of Original Message: 21
From: Willie McKemie <[email protected]>
Subject: Re: [EVDL] SOC gauge

I believe the Cycle Analyst:
http://www.ebikes.ca/drainbrain.shtml
offers about the same capabilities as the TBS and is a bit cheaper. =

Several, including David Nelson, report satisfaction with the CA. I =

am about to try one on a Xebra.

Since my most recent controller redo, my TBS has been reading low only =

while charging with a Zivan. Symptoms:
1) While using Zivan alone, charging reading is around 12 amps while =

charging at 16-17 amps
2) While using ANY other combination of chargers, reading is correct. =

A single 1500 watt charger, two 1500 watt chargers, a 1500 watt =

charger plus the Zivan are all read correctly by the TBS.

This is the ONLY issue I've ever had with the TBS and I suspect the =

root cause is not with the TBS.

BTW, TBS reports total ah used over the life of the pack. Mine =

currently shows something like 42,000 ah.

The TBS will also report number of charge-discharge cycles. It it =

inaccurate on mine because a "cycle" is counted only when the cycle ah =

count goes back to zero while charging. Mine rarely reaches zero =

because balancer modules draw a bit of current that the TBS shunt =

doesn't see. I typically have 1-2 ah on the meter when charging is =

complete. That's with trips that use between about 120 ah and about =

200 ah. Based on average trip lengths, I have about 350 cycles on the =

pack and the TBS says it is about 150. I believe the cycle count =

would be correct if I did a manual reset after each charge, but I =

haven't.

-- =

Willie, ONWARD! Through the fog!
http://counter.li.org Linux registered user #228836 since 1995
Debian3.1/GNU/Linux system uptime 261 days 3 hours 50 minutes


End of Original Message
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## EVDL List (Jul 27, 2007)

With the E-Meter or Link10 or pro line , I would rather see the pack
voltage show up like it was one 12v battery . If I'm in a car with 24
12 v batteries and then get into a 13 battery car I don't want to
have to learn new numbers for each car . I set up all the cars to
read like they are one 12v battery . I do this by adjusting the
resistor that I put in series on the v sense input . I don't do a
voltage divider with one end to the traction neg as this can blow the
meter if the neg wire come off of the divider . The links has a
different input resistance than the e-meter but as I end up add or
subtraction resistors to make the meter read true it doesn't really
mater. Yes it dose take some time and fooling around to get it to read
right . You also so have to be careful to use a high enough value
resistor as not to blow out the meter when you start . For 120v I
start with a 300,000 ohm resistor . With the li-ion batteries I have
the meter read 33.5 to =3D a cell voltage of 3.35v .
Steve Clunn
Tomorrows Ride TODAY !
Visit our shop web page at: www.Greenshedconversions.com

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## EVDL List (Jul 27, 2007)

the "Watts Up" meter u say is cheap how much & were can u buy one at lee? 
that sounds like what I need on my 24 volt mini bike!

-----Original Message----- 
From: Lee Hart
Sent: Saturday, May 28, 2011 12:55 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] SOC gauge



> Alan Shaw wrote:
> > Can anyone recommend a reliable and accurate "state of charge" gauge?
> 
> I like the Cruising Equipment E-meter, later renamed the Heart Interface
> ...


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## EVDL List (Jul 27, 2007)

> Jack <[email protected]> wrote:
> >Lee how many watts in 1 volt?
> 
> Well since Watts = Volts x Amps, there are Amp Volts in a Watt.
> ...


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## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> > On 5/31/2011 8:23 AM, Willie McKemie wrote:
> > > I believe the Cycle Analyst:
> > > http://www.ebikes.ca/drainbrain.shtml
> ...


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## EVDL List (Jul 27, 2007)

>> Good luck with the Xebra. :-/



> Willie McKemie wrote:
> > Yeah, I know. :-( It's a personality flaw.
> >
> > I believe your pizza delivery guy recently posted on the yahoo xebra
> ...


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## EVDL List (Jul 27, 2007)

> Alan Shaw wrote:
> > Can anyone recommend a reliable and accurate "state of charge" gauge?
> 
> I just noticed that the miniBMS guy is now offering an amp-hour
> ...


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## EVDL List (Jul 27, 2007)

The problem with most hall affect sensors is that they have a shift at zero
that occurs when you go from charge current to discharge current. When used
in a situation where the counter is on all the time you will get counting
even though there is no current and since it is never the same it is
impossible to zero it. In the situation where it is used in an EV where
there at hundreds of amps being counted and it is probably switched off with
the key switch it probably won't matter so much. There will be need for
occasional zeroing of the instrument but that would be true for an amp hour
counter using a shunt also.

Sincerely,
Mark Grasser


-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Willie McKemie
Sent: Friday, June 17, 2011 1:52 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] SOC gauge



> Alan Shaw wrote:
> > Can anyone recommend a reliable and accurate "state of charge" gauge?
> 
> I just noticed that the miniBMS guy is now offering an amp-hour
> ...


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## EVDL List (Jul 27, 2007)

IIRC, the the EV Display compensates for small currents.

I just looked through the manual and here is a section about the
display setup parameters.

"DeadZone =96 Dead Zone. In some cases when temperature fluctuations are
wide and fast, EV
Display might show non-zero current reading when not expected. This is
due to imperfect
temperature stability of Hall Effect sensors. EV Display software
compensates for this, but in
some extreme situations it might not work 100%, resulting in small
current reading when not
expected. Dead Zone allows ignoring small current readings when they
are likely false (when
small reading starts after zero reading). During charge, when current
is dropping during CV
phase, EV Display will count it even in the Dead Zone. If small
reading persists for over 60
minutes, it will be considered as false reading and will be ignored.
You can turn off this feature
by setting this value to zero. Default 0.3A is recommended for best
zero reading stability."

http://minibms.mybigcommerce.com/template/files/EV%20Display%20V2%20User%20=
Guide.pdf

On Fri, Jun 17, 2011 at 11:50 AM, Mark Grasser <[email protected]> wr=
ote:
> The problem with most hall affect sensors is that they have a shift at ze=
ro
> that occurs when you go from charge current to discharge current. When us=
ed
> in a situation where the counter is on all the time you will get counting
> even though there is no current and since it is never the same it is
> impossible to zero it. In the situation where it is used in an EV where
> there at hundreds of amps being counted and it is probably switched off w=
ith
> the key switch it probably won't matter so much. There will be need for
> occasional zeroing of the instrument but that would be true for an amp ho=
ur
> counter using a shunt also.
>
> Sincerely,
> Mark Grasser
>
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Beh=
alf
> Of Willie McKemie
> Sent: Friday, June 17, 2011 1:52 PM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] SOC gauge
>
>


> Alan Shaw wrote:
> >> Can anyone recommend a reliable and accurate "state of charge" gauge?
> >
> > I just noticed that the miniBMS guy is now offering an amp-hour
> ...


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## EVDL List (Jul 27, 2007)

I have been very impressed with the EV Works fuel gauge sender in my
conversion. Every morning when I get in the car, it shows a full gauge. If
I only get a chance for a partial charge, it seems to represent that
accurately also. I haven't done anything to zero it out or account for
drift. 

The gauge is wired in the middle of the pack with the wire going from the
rear battery back going through the current loop sensor. Because of that,
it sees all current usage. However, my conversion has a period after each
charge where current is at zero. (I don't have any parasitic loads on the
battery pack that go through the pack wiring when the key is off.) Each
cell does have a miniBMS module on it, but that won't be seen by the EV
Works fuel gauge sender.

By design the EV Works module is powered on (12V) all the time. It requires
that to be able to watch the charge current when the key is off.

Mike

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Mark Grasser
> Sent: Friday, June 17, 2011 12:51 PM
> To: 'Electric Vehicle Discussion List'
> Subject: Re: [EVDL] SOC gauge
> 
> The problem with most hall affect sensors is that they have a shift at
zero
> that occurs when you go from charge current to discharge current. When
> used in a situation where the counter is on all the time you will get
counting
> even though there is no current and since it is never the same it is
impossible
> to zero it. In the situation where it is used in an EV where there at
hundreds
> of amps being counted and it is probably switched off with the key switch
it
> probably won't matter so much. There will be need for occasional zeroing
of
> the instrument but that would be true for an amp hour counter using a
shunt
> also.
> 
> Sincerely,
> Mark Grasser
> 
> 
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Willie McKemie
> Sent: Friday, June 17, 2011 1:52 PM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] SOC gauge
> 
>


> Alan Shaw wrote:
> > > Can anyone recommend a reliable and accurate "state of charge" gauge?
> >
> > I just noticed that the miniBMS guy is now offering an amp-hour
> ...


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## EVDL List (Jul 27, 2007)

>> Would I be right in assuming that a shunt (as on TBS meter) would be
>> more accurate and precise than a hall effect sensor?

Hall effect sensors are inexpensive, small, and efficient. They are best 
employed when you have a limited current range (say, 10:1) and don't 
need high accuracy (like 50-500 +/-1 amp).

Common problems are readings that change with temperature, large errors 
for currents less than a few percent of full-scale, and offset errors 
following momentary high currents. You can compensate for these effects 
in software, but with only limited success (you have to somehow know 
what the correct current is to correct for the Hall sensor's errors).

A shunt is a precision power resistor. It is bigger, more expensive, and 
produces heat. It has a voltage drop precisely related to current, and 
(if it's a good one) not affected by time, temperature, or momentary 
overloads. There is no zero offset, and accuracy is a percent of the 
actual current (like 0-500 amps +/-1%).



> David Nelson wrote:
> > IIRC, the the EV Display compensates for small currents.
> 
> They can make some guesses, and correct based on them. This will work in
> ...


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## EVDL List (Jul 27, 2007)

From: Lee Hart/ David Nelson
>

> Would I be right in assuming that a shunt (as on TBS meter) would be
>> more accurate and precise than a hall effect sensor?

My current job Has both , On a few conversions I have had both . The
BMS that my battery guy gives me uses the hall effect sensor but some
of my wiser customers have also let me install one of the many forms
of e meter. like the TBS or pro linkx ,(seems this meter changes its
name every few years) . The stuff with hall effect sensors to me are
just fluff. I would not count on them for hi accuracy just nice to
look at and if you have a e meter, tbs pro links ,links , links 10 (
wish we just had one name for this meter as to me they all seem ABOUT
the same all good , except they need different resistors for the
voltage scale which keeps me busy).. c

>Hall effect sensors are inexpensive, small, and efficient. They are best
employed when you have a limited current range (say, 10:1) and don't
need high accuracy (like 50-500 +/-1 amp).<

and if you have a TBS ( what I will now call all e meters and there
children unless somebody has a better name) why have anything else .
Man with two meters never knows what the voltage is for sure , 8-<

>Common problems are readings.......

well when you get right down to it I don't trust any of them , If they
say what I think they should I'll give them 95%. maybe back to the
idie light at least you know that's off %-(

>that change with temperature, large errors for currents less than a few percent of full-scale, and offset errors

all just make new comers think " what the F" us old timers know that
when the weather man say rain it just might .

> You can compensate for these effects in software, but with only limited success (you have to somehow know
what the correct current is to correct for the Hall sensor's errors).<

I feel for you engineers Its got to hurt when the boss says "give me
give me give me ,, hay this ain't very accurate here." But what do we
installers say to the poor customers who can't under sand why his
watch keeps time all year and his ah counter can't make it through the
week. Must be the installer didn't hook it up right , maybe he's from
Flora-a- da ( can't believe Bob Rice isn't with us , now that was an
old time , he could do tell a week battery in the pack by the funny
sag in the total volts ,kids today got it so easy B-) .


>A shunt is a precision power resistor. It is bigger, more expensive, and
produces heat. It has a voltage drop precisely related to current, and
(if it's a good one) not affected by time, temperature, or momentary
overloads. There is no zero offset, and accuracy is a percent of the
actual current (like 0-500 amps +/-1%).<

And as you have said even 1% adds up , still much better than a hall effect
The problem is , If the bms comes with the hall effect and does
everything the TBS ( I kind of like e meter , first time I saw the
TBS ,I though it was a pro link )



> David Nelson wrote:
> > IIRC, the the EV Display compensates for small currents.
> 
> >They can make some guesses, and correct based on them. This will work in
> ...


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