# EV Display version 2 - feedback wanted



## dimitri (May 16, 2008)

I'm working on a prototype of next version of EV Display. Trying to improve as much as possible to compete with big boys  

Solid zero point across wide temperature range is the most challenging part, since I have no hands on experience with other E-meters I can't compare how well they done it. So, question to those with experience, how well does your E-meter hold the zero point while the car is sleeping in the cold/hot garage, driveway, parking lot, etc? Do you have to recalibrate it when temperature swings a lot?

With my new 16bit AD converter I am able to read currents in the range of +/- 0.1A - 600A using hall effect sensor. The problem is that when I freeze it to 0F or heat to 100F the zero point fluctuates between +/-0.4A. This is within the specs of the parts I am using, so there is no way to improve it. To address this I am thinking to ignore readings less than 0.5A, to stabilize the zero point range. Currently EV Display is ignoring less than 4A current for same reasons, which works OK for larger EVs, but isn't good for smaller packs/chargers. I was limited by 10bit AD converter, hence larger error margin.

I think for lower cost device 0.5A min readout in the +/- 600A range should be acceptable, right?

I am also adding voltage scaling for packs up to 500V, since some people insist on knowing their pack voltage . This will also allow precise Watt and Watt/Hour tracking, if that is something you fancy 

I'm adding PWM output to drive mechanical fuel gauge in addition to low fuel relay I already have.

It will be powered from 12V source, but will be DC-DC isolated from the pack voltage.

Can't think of anything else right now, its been a long week


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## honn1002 (Nov 26, 2008)

I have to recalibrate my EV Display every time the zero point is out of whack like the temperatures change from warm (69F) to cold (42f) or from cold to warm. One day when it was warm outside, the meter showed 3A out so I recalibrated to zero point. When it got cold in the evening, the meter showed 6A in. I recalibrated it again. I messed around with the temperature compensation. I set it at 50%, a few days already and the meter seems to okay. 

I’m using a voltage scaler to power the EV Display and it works great.  

It’s great if you can make the backlight comes on when you press the throttle and certain amount of amps out, so we don’t have to push the bottom for the backlight to see in the dark.  

Another feature if you could integrate an output like a low fuel relay but this one is for a full fuel relay to cut-off the charger when the fuel reaches 100%. Use it to connect to an external relay for the charger cut-off.


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## tomofreno (Mar 3, 2009)

You are talking about the current readout, not Ah, with no load? My TBS Expert Pro always reads 0.0 A with the ignition key off in temperatures from -5 F to 110 F. With key on, no throttle, it displays a small current I assume is due to the DC/DC converter. Haven't paid attention to whether this varies with temperature.

I like this idea:


> Another feature if you could integrate an output like a low fuel relay but this one is for a full fuel relay to cut-off the charger when the fuel reaches 100%. Use it to connect to an external relay for the charger cut-off.


I'm always looking for more redundancy to avoid overcharging.


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## GizmoEV (Nov 28, 2009)

What about a current sensor around the charger lead only and when the current in the main wire drops to below 0.5A or what ever AND the current reading from the charger lead is near zero then ignore the 0.5A otherwise keep it. The current sensor around the charging lead could be of a higher sensitivity and be used to track Ah into the pack if desired.

Another possibility which could be done in addition to the above idea, is to assume 0A if some amount of time has elapsed from when the current was say >1A or something. This way when sitting at a stop light with no accessories draining power the low draw of the other components gets counted.

For your 12V isolated DC-DC: Is it connected across the full pack? I like the CycleAnalyst because it uses full pack voltage so it doesn't rely on another DC-DC and doesn't imbalance the pack.

You could also install a feature that when the pack voltage reaches a set level that the Ah counter resets to zero or 100%SOC. This would need to be user adjustable.


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## honn1002 (Nov 26, 2008)

tomofreno said:


> You are talking about the current readout, not Ah, with no load? My TBS Expert Pro always reads 0.0 A with the ignition key off in temperatures from -5 F to 110 F. With key on, no throttle, it displays a small current I assume is due to the DC/DC converter. Haven't paid attention to whether this varies with temperature.
> 
> It's the current read-out and of course the Ah with no load, the car is parking. For example if the current read-out 3A for one hour it would take 3A from the total AH, from 180Ah to 177Ah. My EV Display doesn't read the current in or out if less than plus or minus 3Ah. I guess your TBS Expert Pro doesn't vary with temperature like the EV Display. I think by increasing the temperature compensation percentage could reduce the effect of varying with temperature.


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## EVfun (Mar 14, 2010)

One possibility is duel current sensors. One for the main traction wire that can read up to 1000 amps. The other one for charging and small HV loads like the DC to DC converter and designed to read +/- 50 amps. The larger one can have a much larger offset to ignore and the one powering smaller loads can be more sensitive.


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## dimitri (May 16, 2008)

Thanks for feedback!

Automatic backlight is easy, will add it to the feature list.

Full charge relay might be doable, but it might interfere with charger in some cases. For example, if you reset the device for whatever reason while the pack is not fully charged, you should then do a full charge to match real SOC with display SOC, but you can't since device inhibited your charger at the reset point. This is catch 22. I'm on the fence about this one, especially since I am very tight on the room inside the device and adding another optocouple is a challenge.

Dual sensors idea is logical, but not practical for low cost universal E-meter. I'd rather give up some sensitivity on the low end, then go with dual sensors.

I will try to programmatically stabilize the zero point at 0.1A across the temp range, but will also add user adjustable zero range setting, to avoid issues in extreme conditions.


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## dimitri (May 16, 2008)

GizmoEV said:


> Another possibility which could be done in addition to the above idea, is to assume 0A if some amount of time has elapsed from when the current was say >1A or something. This way when sitting at a stop light with no accessories draining power the low draw of the other components gets counted.


This is interesting idea, I need to think about it some more to make sure there is no down side.



> For your 12V isolated DC-DC: Is it connected across the full pack? I like the CycleAnalyst because it uses full pack voltage so it doesn't rely on another DC-DC and doesn't imbalance the pack.


Voltage sensing will be across the pack, but device power needs 12V nominal. Internal DC-DC will isolate pack negative from 12V ground, but I can't power device from the pack using internal DC-DC since my planned range is too wide. I will support packs up to 512V, I can't include DC-DC for such wide range. Most EVs have pack voltage DC-DC already, so its not an issue to power display from 12V nominal as long as its isolated from the pack. I think this is most logical and cost effective approach.



> You could also install a feature that when the pack voltage reaches a set level that the Ah counter resets to zero or 100%SOC. This would need to be user adjustable.


I already have this feature in current version, but its useless unless you power device from the pack, which needs external voltage scaler. New version will have everything integrated, no need for external scalers, just feed 12V for power and attach voltage sensing wires to a pack from 12V to 512V. Jumpers on the sending board will provide selection of popular voltage ranges for best accuracy.


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## honn1002 (Nov 26, 2008)

dimitri said:


> Thanks for feedback!
> 
> Automatic backlight is easy, will add it to the feature list.
> 
> ...


It's true about the full charge relay might interfere with the charger if you reset or recalibrate the EV Display when your pack is not fully charged. Well if you can manage to add another optocouple in the meter, put a user setting ON/OFF option for the full charge relay. So you can turn off the full charge function and allow the charger to fully charge your pack. After the pack is fully charged, set the full charge function back on. 

Adding user adjustable zero range setting is a lot better than a temperature compensation setting. Over all the next EV Display gen will be much better. Great job Dimitri...now you can compete with big boys.


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## GizmoEV (Nov 28, 2009)

Another idea would be to add a half pack voltage comparison feature with a center zero adjustment so that it can work with an odd number of cells. It would be nice to have a 2-3V swing each side, maybe with a more sensitive center region. This would be useful whether you have a cell level BMS or not since you could see if you have a low cell or a high resistance connection in one side of the pack.


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## MN Driver (Sep 29, 2009)

I agree that if it is possible to build in a system for half-pack voltage differential comparison to see if something is out of whack if it isn't too difficult or expensive to integrate.


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## DIYguy (Sep 18, 2008)

dimitri said:


> I think for lower cost device 0.5A min readout in the +/- 600A range should be acceptable, right?


Hi Dimitri
I think you were referring to resolution here... but thought I would jump in on the max amp range issue. I think you should make it to 1000 amps. I accelerate using over 600 amps often, granted not for all that long..but 
I wouldn't want it not measuring the energy above 600 amps. Thanks.


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## dimitri (May 16, 2008)

DIYguy said:


> Hi Dimitri
> I think you were referring to resolution here... but thought I would jump in on the max amp range issue. I think you should make it to 1000 amps. I accelerate using over 600 amps often, granted not for all that long..but
> I wouldn't want it not measuring the energy above 600 amps. Thanks.


Are you sure you are measuring on the battery side of the controller? For how many seconds at a time do you go over 600Amp? How much over 600Amp? I'm pretty sure that AH accuracy will remain acceptable even if we dismiss some short spikes over the 600Amp limit. I am using largest sensor available.


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## Yabert (Feb 7, 2010)

+1 here!

1000A readout will be very usefull for me to. The conversions than use 1000A (controller, batterie, motor) are really available these days.

Is it that much complex to find a 1000A rated ampermeter instead a 600A to do the same work?


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## DIYguy (Sep 18, 2008)

dimitri said:


> Are you sure you are measuring on the battery side of the controller? For how many seconds at a time do you go over 600Amp? How much over 600Amp? I'm pretty sure that AH accuracy will remain acceptable even if we dismiss some short spikes over the 600Amp limit. I am using largest sensor available.


Yes, I'm sure. Not only do I pull more that 600 amps, I have pulled 1000 amps on many occasions. Again, it's not for long periods of time however, if I am going to capture consumption, I want to capture it all.  The CA I have does capture this now.


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## dimitri (May 16, 2008)

DIYguy said:


> The CA I have does capture this now.


Looking at CA site I don't see any reference to 1000A measuring capability. I suppose if you selected your own shunt, not the ones CA sells, then it might scale to 1000A, but then you will also lose fine resolution at low end, which is advertised as 0.1A for their shunts.

Accoding to datasheet of hall effect sensor I use it will generate data past 600A, up to 1000A, but it won't be as accurate. It looks like my device would work past 600A, if only I had a way to test this. I don't have any way to generate 1000A current.


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## DIYguy (Sep 18, 2008)

dimitri said:


> Looking at CA site I don't see any reference to 1000A measuring capability. I suppose if you selected your own shunt, not the ones CA sells, then it might scale to 1000A, but then you will also lose fine resolution at low end, which is advertised as 0.1A for their shunts.


Yes, I used a shunt out of an industrial DC welder.



dimitri said:


> Accoding to datasheet of hall effect sensor I use it will generate data past 600A, up to 1000A, but it won't be as accurate. It looks like my device would work past 600A, if only I had a way to test this. I don't have any way to generate 1000A current.


I could test it for you... except I just started pulling things apart for my winter upgrades. . unless u want to wait for a bit. What about Tesseract? U tested his beta Soliton....seems fair to me. He has a dyno and batts set up to draw 1000 amps... at least he use to.


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## Yabert (Feb 7, 2010)

dimitri said:


> I am using largest sensor available.


What about LEM HTFS 800-P? It can read to 1200A.
The accuracy of 1% is it the problem?


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## EVfun (Mar 14, 2010)

dimitri said:


> Looking at CA site I don't see any reference to 1000A measuring capability. I suppose if you selected your own shunt, not the ones CA sells, then it might scale to 1000A, but then you will also lose fine resolution at low end, which is advertised as 0.1A for their shunts.
> 
> Accoding to datasheet of hall effect sensor I use it will generate data past 600A, up to 1000A, but it won't be as accurate. It looks like my device would work past 600A, if only I had a way to test this. I don't have any way to generate 1000A current.


For temporary testing you should be able to get away with a smaller gauge wire passing through the sensor. You could run 2 passes through the sensor by passing through then looping around to pass through again. The hall effect sensor should "see" twice the actual amps for testing purposes. Two pieces of bus bar with heat shrink passing through the sensor may work out easier. Either way, the goal is to read twice actual amps for setup purposes above 600 amps.


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## dimitri (May 16, 2008)

Update point. Major milestones reached with V2 prototype.

Able to read current with 0.1A resolution and hold zero point across wide temp range.

Able to read pack voltages up to 512V, pack voltage isolated from 12V power.

Have 3 output pins , isolated open collector type, one for Full gauge, one for Empty gauge ( selectable level ) and one PWM to drive mechanical fuel gauge.

Full relay circuit only trips when climbing from under 100% to 100%, so no false tripping upon initial power up.

Auto backlight upon non-zero current or button press.

Hardware is all done, remaining stuff is all software:

1. Charge efficiency. 100% for LiFePO4, but less for Lead Acid etc. Same as Puekert setting. Do we really need it? If so, how to best implement it? I'm thinking scale down AH count during charge, so partial charges will have meaningful impact on Fuel Gauge value? Feedback from lead acid users wanted...

2. How to reference WattHours? AmpHours are referenced against pack size AH setting to know when pack is "full". Current is integrated over time to count AH. Not sure how to reference WH data? Introduce nominal pack voltage in setup menu? What would be the reference point? Nominal WH? Not sure how to make this feature useful. Feedback from users of other meters wanted...

3. Current is tracked with 0.1A resolution, but display size is limited, so need to scale data output based on some ranges, so data can make sense at a quick glance while driving. For example, only show decimals when value is less than 10. Only show kW and kWh when value is over 10000. Any ideas in this regard?


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## GizmoEV (Nov 28, 2009)

dimitri said:


> Able to read pack voltages up to 512V, pack voltage isolated from 12V power.
> 
> 2. How to reference WattHours? AmpHours are referenced against pack size AH setting to know when pack is "full". Current is integrated over time to count AH. Not sure how to reference WH data? Introduce nominal pack voltage in setup menu? What would be the reference point? Nominal WH? Not sure how to make this feature useful. Feedback from users of other meters wanted...


If you can read pack voltages up to 512V I don't understand the question about Wh. Merely integrate W along with the A. Isn't the voltage read at the same time as the A? Use actual voltage, not nominal. I do not have to enter any voltage anything in my CycleAnalyst. The only thing I did was adjust the Voltage Sense number so the CA reading matched my DVM reading.



> 3. Current is tracked with 0.1A resolution, but display size is limited, so need to scale data output based on some ranges, so data can make sense at a quick glance while driving. For example, only show decimals when value is less than 10. Only show kW and kWh when value is over 10000. Any ideas in this regard?


I would let the display limits tell you when to eliminate the decimal value. I don't know what your character limitations are but it would be fine to leave the power and energy in kW and kWh and not display W and Wh unless you are talking about Wh/mi or something. On my CA I have pack V (0.1 resolution), A (to 0.1 resolution), kW (to 0.01 displayed) and Ah (to 0.01 resolution up to 99.99Ah then to 0.1Ah until I believe 999.9Ah then to 1Ah), all visible at the same time. I have to go to other screens for other values.



> Auto backlight upon non-zero current or button press.


This is nice. How long is the back light lit after returning to zero current? I would think a minute or so would be sufficient.


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## GizmoEV (Nov 28, 2009)

dimitri said:


> Looking at CA site I don't see any reference to 1000A measuring capability. I suppose if you selected your own shunt, not the ones CA sells, then it might scale to 1000A, but then you will also lose fine resolution at low end, which is advertised as 0.1A for their shunts.


For shunts, the CA uses:

```
·0.763 to 9.999 mOhm in Low Range Mode
·0.0763 to 0.9999 mOhm in High Range Mode
```
They advertise 0.01A resolution in low range and 0.1A in high range.


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## tomofreno (Mar 3, 2009)

> 2. How to reference WattHours? AmpHours are referenced against pack size AH setting to know when pack is "full". Current is integrated over time to count AH. Not sure how to reference WH data? Introduce nominal pack voltage in setup menu? What would be the reference point? Nominal WH? Not sure how to make this feature useful. Feedback from users of other meters wanted...


 Do you mean no reference to how many Wh constitutes a "full" pack, so no way to report how full a cell is in terms of Wh? That's a problem. How many Wh you put into a pack during charging will depend on the voltage drop across each cell, which depends on the charge current and temperature. How much you pull out during discharge will have similar dependence on voltage sag which varies with discharge current and temperature. If you just integrate the product of voltage, current, and time that tells how much total energy went into the cell, but some was dissipated and is not available for useful work by discharging, so you don't have as much stored energy available as that indicates. You also won't get all the stored energy out, dissipating more internally in the cells the higher the discharge current. If you use nominal cell voltage to estimate a nominal pack voltage to in turn estimate a nominal pack Wh, then you will calculate more Wh going into the cell during charging than the nominal pack Wh (due to higher voltage), and less going out during discharge (lower voltage), and the values will depend on the current level and cell temperature. Maybe you have to tweek the Puekert exponent for your cells to get Wh in equal Wh out, each as calculated by the integral of the product of the current, voltage, and time, since this accounts both for stored and dissipated energy? Ah is a lot easier. The charge goes in, the charge goes out...
Edit: Maybe others just calculate Wh, report percent of full based on Ah, and report the corresponding Wh as the same percent of full Wh. So "full Wh" would vary run to run with voltage variation run to run during charge and discharge, but would be scaled to Ah so it gave an accurate percent of full for that particular run. (by "run" I mean one charge/discharge cycle)



> 3. Current is tracked with 0.1A resolution, but display size is limited, so need to scale data output based on some ranges, so data can make sense at a quick glance while driving. For example, only show decimals when value is less than 10. Only show kW and kWh when value is over 10000. Any ideas in this regard?


 Only covering two orders of magnitude would be fine with me, i.e. for currents of 10A and below report to 0.1A, for greater than 10A to 100A report to 1A...


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## honn1002 (Nov 26, 2008)

That’s great news. 

Able to read current with 0.1A resolution and hold zero point across wide temp range, this is mainly what I want on my EV Display. But between what temperatures? Is it between 0F to 100F. It would be nice if it goes up to 120F because in the summer here (central Cali), it could go up to 115F plus inside the car parking outside between 8am to 5pm. 

To reference WattHours, introduce adjustable full charged cell voltage between 3.4 to 3.8V times the total cells in the pack. I think this is the most accurate way for the reference point. So the users can set to fully charge the pack for example 3.45V per cell. The total WH would be 3.45V times the total cells.


To reference WH data, use the active pack voltage under load as the current EV Display. I’m using a voltage scaler and the WH reading is pretty close on par with the AH. The WH should calculate the pack voltage and currents under load. And stop calculating when less than 0.1A. I notice my EV Display slightly still calculating when the load is removed (no current flow present). Or may be it's just rounding off.


One feature I think it’s not necessary and confusing is the fuel percentage. S.O.C percentage is I always use. Keep the fuel bars and counts it against S.O.C. the same to the 3 outputs for the full gauge, empty gauge and mechanical fuel gauge.


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## DIYguy (Sep 18, 2008)

GizmoEV said:


> Another idea would be to add a half pack voltage comparison feature with a center zero adjustment so that it can work with an odd number of cells. It would be nice to have a 2-3V swing each side, maybe with a more sensitive center region. This would be useful whether you have a cell level BMS or not since you could see if you have a low cell or a high resistance connection in one side of the pack.


Did this not make it in?

Also, wondering about the current range. Did I miss it? To what upper range did you go?

... and the relay for charge control??

Thanks.


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## dimitri (May 16, 2008)

honn1002 said:


> That’s great news.
> 
> Able to read current with 0.1A resolution and hold zero point across wide temp range, this is mainly what I want on my EV Display. But between what temperatures? Is it between 0F to 100F. It would be nice if it goes up to 120F because in the summer here (central Cali), it could go up to 115F plus inside the car parking outside between 8am to 5pm.


I tested from 0F to 130F and it held zero point well. I also added adjustable dead zone, up to 0.9A. In dead zone current going from 0 to dead zone limit is ignored, but current sliding back into dead zone ( i.e. CV charge current is counted with a 60 minute timeout ). I believe this will make very accurate count, while maintaining solid zero point.


> To reference WattHours, introduce adjustable full charged cell voltage between 3.4 to 3.8V times the total cells in the pack. I think this is the most accurate way for the reference point. So the users can set to fully charge the pack for example 3.45V per cell. The total WH would be 3.45V times the total cells.


I already have this, its called full pack voltage. AH is set to full when this voltage is reached. The problem is that full voltage is much higher than nominal and WH count based on full voltage will be grossly overestimated.



> To reference WH data, use the active pack voltage under load as the current EV Display. I’m using a voltage scaler and the WH reading is pretty close on par with the AH. The WH should calculate the pack voltage and currents under load.


You confuse W with WH. I have very accurate W reading now and I can integrate it to very accurate WH count, but it needs a reset/reference point, otherwise it will be all over the map in a few days. AH count is primary function of the E-meter, WH count is just a bonus, but I want it to be meaningful to people. To be meaningful it needs a reset/reference point at the end of full charge cycle, but ideally based on nominal voltage, rather than full voltage. Maybe I am overthinking it and should just use full voltage as reference.


> One feature I think it’s not necessary and confusing is the fuel percentage. S.O.C percentage is I always use. Keep the fuel bars and counts it against S.O.C. the same to the 3 outputs for the full gauge, empty gauge and mechanical fuel gauge.


This is surprising. I thought fuel gauge with custom set low limit was a very good feature. I use it exclusively, so I don't run my pack below preset limit. Its meant for non technical drivers, so they don't have to learn not to drive the pack to zero. Its purposely protecting the battery, by hiding its real limits from the driver.


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## dimitri (May 16, 2008)

DIYguy said:


> Did this not make it in?
> 
> Also, wondering about the current range. Did I miss it? To what upper range did you go?
> 
> ...


I was never interested in adding half pack comparison thingy into EV Display, I personally don't find it useful, and I don't want to engage in its discussion in this thread. There is a another thread for it and looks like some good progress is being made there.

I stated that full charge output has been implemented, you can use it for charger cutoff if you wish.

Current range shoul be up to 1000Amp according to datasheet of the sensor I use, but testing will have to confirm this.


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## dimitri (May 16, 2008)

tomofreno said:


> Do you mean no reference to how many Wh constitutes a "full" pack, so no way to report how full a cell is in terms of Wh? That's a problem.


Its not really a "problem". SoC and fuel gauge are always based on AH count, which is rock solid. WH count is a bonus, IMHO its quite useless, but people keep asking for it, so I want to implement it, but I want it to be as useful/meaningful as possible.

"WH in" is always more than "WH out", so without tying it to some reference point on the regular basis it will lose its meaning after few charge/discharge cycles.

I have a couple ideas I need to think thru, I will post them later today.


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## DIYguy (Sep 18, 2008)

dimitri said:


> I was never interested in adding half pack comparison thingy into EV Display, I personally don't find it useful, and I don't want to engage in its discussion in this thread. There is a another thread for it and looks like some good progress is being made there.


Oh, I thought you were interested in what other ppl wanted in an EV display.  Or is it because it conflicts with the BMS thing? (just askin)


dimitri said:


> I stated that full charge output has been implemented, you can use it for charger cutoff if you wish.


 Oh, ok. Yup I see that.



dimitri said:


> Current range shoul be up to 1000Amp according to datasheet of the sensor I use, but testing will have to confirm this.


 Okeedoke thanks.


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## dimitri (May 16, 2008)

DIYguy said:


> Oh, I thought you were interested in what other ppl wanted in an EV display.  Or is it because it conflicts with the BMS thing? (just askin)


It doesn't conflict with BMS, since BMS is much more useful than a half pack bridge.

I am interested in what people want, but I have to make my compromises in what makes it and what doesn't make it into the final product.


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## DIYguy (Sep 18, 2008)

dimitri said:


> It doesn't conflict with BMS, since BMS is much more useful than a half pack bridge.


It does if you plan to not use a BMS.....



dimitri said:


> I am interested in what people want, but I have to make my compromises in what makes it and what doesn't make it into the final product.


OK,.,,, but u never answered the guy who suggested it...and how do you know who wants it? Maybe u'll sell 5 times more units with it... I dunno.... It's ur gizmo I guess.


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## dimitri (May 16, 2008)

DIYguy said:


> Maybe u'll sell 5 times more units with it...


If I sell 5 times more E-meters with half-bridge monitor than E-meters without it, than it must be a really crappy E-meter 

You can always buy Evision, its got tons of bells and whistles....


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## tomofreno (Mar 3, 2009)

> Its not really a "problem". SoC and fuel gauge are always based on AH count, which is rock solid. WH count is a bonus, IMHO its quite useless, but people keep asking for it, so I want to implement it, but I want it to be as useful/meaningful as possible.


 I don't see how you can implement it using direct integration of the product of V, I, and t, because as I said Wh in during charge will always exceed Wh out during discharge due to the voltage difference, so Wh will just keep increasing over multiple charges. I would guess the other meters just multiple the Ah by nominal pack voltage and report that as Wh. It is the only way I see you can get a repeatable number.


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## dimitri (May 16, 2008)

tomofreno said:


> I don't see how you can implement it using direct integration of the product of V, I, and t, because as I said Wh in during charge will always exceed Wh out during discharge due to the voltage difference, so Wh will just keep increasing over multiple charges. I would guess the other meters just multiple the Ah by nominal pack voltage and report that as Wh. It is the only way I see you can get a repeatable number.


You are probably right, I have been overthinking it too much 
I checked user manuals of other E-meters and I don't see any of them separately tracking WH data, most likely for same reasons. What I will do is just show W and WH based on current voltage and current A and AH, so W will always be accurate and WH will be a very good approximation. Afterall, if someone really wants accurate WH data, it should be measured at the wall via AC based E-meter, to account for charger's efficiency.


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## honn1002 (Nov 26, 2008)

The temp range from 0F to 130F is nice.

For the full gauge, have a compensation like from 0 to 10% adjustable by the users. Most of the time when my EV Display S.O.C. reaches 100%, my charger still puts out 19A about half an hour or so. I charge my battery pack average 3.45V per cell. 

I think the full gauge is a great add-on feature. It protects the battery pack from overcharging simply by disconnecting the charger through an aux relay that controlled by a full gauge driver in the EV Display. Most people are going to find this feature very useful.


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## DIYguy (Sep 18, 2008)

dimitri said:


> If I sell 5 times more E-meters with half-bridge monitor than E-meters without it, than it must be a really crappy E-meter
> 
> You can always buy Evision, its got tons of bells and whistles....


The thing is, there are quite a few meters that count energy usage. The CA already does this and a whole bunch of other things that yours doesn't at a low price. What will make ppl want to buy yours more? The feature of driving contacts for charger control is one such feature. Half pack monitoring would be another such feature. Your title says "feedback wanted".


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## tomofreno (Mar 3, 2009)

> Your title says "feedback wanted".


 That's correct. It doesn't say feedback will be implemented.


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## DIYguy (Sep 18, 2008)

tomofreno said:


> That's correct. It doesn't say feedback will be implemented.


lol, that's very true... lol. Just sayin as there seemed to be a lot of interest in it. What the heck....


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## GizmoEV (Nov 28, 2009)

dimitri said:


> I checked user manuals of other E-meters and I don't see any of them separately tracking WH data, most likely for same reasons. What I will do is just show W and WH based on current voltage and current A and AH, so W will always be accurate and WH will be a very good approximation. Afterall, if someone really wants accurate WH data, it should be measured at the wall via AC based E-meter, to account for charger's efficiency.


When you want to compare one vehicle's efficiency to another with different pack voltages it doesn't make sense to compare Ah, it is Wh which have to be compared. I thought this is what you were talking about and now all of a sudden AC Wh are being introduced. The CA counts Ah and Wh but they are only as they relate to the pack not the charger efficiency. While it would be nice to have an AC meter in the car to see line voltage, current, Watts and kWh, it wasn't clear that this is the type of meter you were wanting feedback on.


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## dimitri (May 16, 2008)

GizmoEV said:


> When you want to compare one vehicle's efficiency to another with different pack voltages it doesn't make sense to compare Ah, it is Wh which have to be compared. I thought this is what you were talking about and now all of a sudden AC Wh are being introduced. The CA counts Ah and Wh but they are only as they relate to the pack not the charger efficiency. While it would be nice to have an AC meter in the car to see line voltage, current, Watts and kWh, it wasn't clear that this is the type of meter you were wanting feedback on.


You missed my point. I'm not talking about AC meter in the car at all.
I think my questions about Wh counting went over the head of most posters here, probably my fault for not explaining the issue in more detail. Anyway, its no longer an issue, I decided to do what is most logical and what most other E-meters out there do in regards to Wh count.


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## dimitri (May 16, 2008)

honn1002 said:


> For the full gauge, have a compensation like from 0 to 10% adjustable by the users. Most of the time when my EV Display S.O.C. reaches 100%, my charger still puts out 19A about half an hour or so.


Already done. I added charge efficiency to the code. Default is 100%. If you see your meter reaching 100% too soon, adjust this setting to lower number. Full will also be reached based on preset pack voltage, this will guarantee correct sync every time on either AH or voltage or both.

Charge efficiency will also make it useful for Lead Acid users, partial charges will have more accurate fuel gauge presentation, etc.


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## dimitri (May 16, 2008)

DIYguy said:


> Half pack monitoring would be another such feature. Your title says "feedback wanted".


I try not to get sucked into this, but its not working 

Here are some reasons I am not touching "half pack bridge":

- its not related to E-meter functions, its more of a "poor man's BMS" solution. I consider BMS and E-meter to be separate tools, both designed for overall battery management, but with enough functional differences to be separate tools. That is just my personal opinion, of course.

- people can't even agree what half pack bridge should do, how to use it, how to implement it, etc. See related thread, which is now on page 3, or what I call "no man's land" 

- E-meter is a user/driver facing tool, while BMS ( I put half pack bridge in BMS category, reluctantly  ) is a technical/maintenance tool. Trying to combine the 2 in one device could be a mistake. Remember, most users/drivers aren't technical enough to even grasp the concept of battery management issues, adding BMS functions to E-meter can backfire.

- I don't see many reports of experienced EV'ers using half pack bridge on LiFePO4 packs and reporting any useful results. All I see is empty talk from armchair designers and wannabes. My personal LiFePO4 experience tells me that half bridge tool is useless "bell and whistle". If it wasn't, there would be offerings of such tool at every EV site.

Feel free to throw stones at me, but please stop spamming *this thread* with "half pack bridge" remarks, I think my position on it has been made as clear as it can be.


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## DIYguy (Sep 18, 2008)

dimitri said:


> I try not to get sucked into this, but its not working
> 
> Here are some reasons I am not touching "half pack bridge":
> 
> - its not related to E-meter functions, its more of a "poor man's BMS" solution. I consider BMS and E-meter to be separate tools, both designed for overall battery management, but with enough functional differences to be separate tools. That is just my personal opinion, of course.


I guess it's no less a part of an e-meter function than a "full output" to drive charger off... 


dimitri said:


> - people can't even agree what half pack bridge should do, how to use it, how to implement it, etc. See related thread, which is now on page 3, or what I call "no man's land"
> 
> - E-meter is a user/driver facing tool, while BMS ( I put half pack bridge in BMS category, reluctantly  ) is a technical/maintenance tool. Trying to combine the 2 in one device could be a mistake. Remember, most users/drivers aren't technical enough to even grasp the concept of battery management issues, adding BMS functions to E-meter can backfire.
> 
> - I don't see many reports of experienced EV'ers using half pack bridge on LiFePO4 packs and reporting any useful results. All I see is empty talk from armchair designers and wannabes. My personal LiFePO4 experience tells me that half bridge tool is useless "bell and whistle". If it wasn't, there would be offerings of such tool at every EV site.


Not sure why you ask for feedback if you just want to ignore/criticize it. 


dimitri said:


> Feel free to throw stones at me, but please stop spamming *this thread* with "half pack bridge" remarks, I think my position on it has been made as clear as it can be.


The stones seem to be coming from your direction lol . There is no spam, Dimitri. You don't get to decide what is spam, when you ask for input. The chap who raised the point, never got a response. If you're going to ask, at least have the courtesy to answer, without criticism. 
Perhaps the idea conflicts with the BMS stance you have. Perhaps your not sleeping well worrying about fires and liability.... (good reason to add that output for charge control)  
Now get this thing done so I can try it out!


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## dimitri (May 16, 2008)

"Full" output was a simple addition without additional complexity/cost, so it was a no brainer. It doesn't have to drive the charger, it can drive a light, buzzer, door bell, whatever you want.

I took action on every feedback point except "half pack bridge", for reasons I clearly stated above, so good feedback was not ignored.

Thanks everyone for feedback!!! GizmoEV, thanks for "half pack bridge" idea, sorry I did not take it on, see above posts for explanation


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## dimitri (May 16, 2008)

At this point hardware and software is all done, all features bench tested, just put prototype unit in my own EV for road testing. Here are some pics, without face plate, so I can update software during testing phase if bugs are found.

This is just before end of charge, few seconds before my NG3 goes from yellow to green.








This is after keyswitch is turned on, after vacuum pump is done running and controller precharged, so basically just accessories load.








This is after I start the motor and its idling at 700RPM ( I have auto transmission ).


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## GizmoEV (Nov 28, 2009)

dimitri said:


> You missed my point. I'm not talking about AC meter in the car at all.


Then what are you talking about in the following quote?



> Afterall, if someone really wants accurate WH data, it should be measured at the wall via AC based E-meter, to account for charger's efficiency.


It looks like you are the one which brought up the AC meter.

Also, I see you are using a + sign in front of your current reading. What about using no sign for regular operating current and a - sign for charging current so that you have one more digit to display while driving?

As for displaying a half-pack voltage read out, regardless of whether it should be part of an e-meter, it looks like your display wouldn't really have room for it any way.


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## JRP3 (Mar 7, 2008)

How did I miss out on all the fun? Sounds as if you've addressed the changes I'd want, better temp change stability and the backlight that comes on without having to press buttons, and then scroll through to get back to the display parameter you already had. (I know you don't want to hear it but I would have been one of those who wanted the half pack bridge, and since you would have been the only unit other than the insanely expensive Evision to offer it I think you could have gotten some sales from that feature.)


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## honn1002 (Nov 26, 2008)

Looking good. The Wh read out makes a lot of sense now.


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## vmrod (Jul 2, 2010)

One feature I think it’s not necessary and confusing is the fuel percentage. S.O.C percentage is I always use. Keep the fuel bars and counts it against S.O.C. the same to the 3 outputs for the full gauge, empty gauge and mechanical fuel gauge. This is surprising. I thought fuel gauge with custom set low limit was a very good feature. I use it exclusively, so I don't run my pack below preset limit. Its meant for non technical drivers, so they don't have to learn not to drive the pack to zero. Its purposely protecting the battery, by hiding its real limits from the driver. 


I like continuing the use of the 'custom' fuel gauge. When others drive the EV, they will see a gauge and know when the are out of fuel. They will not want to stop when it still has an itty bitty left on the gauge. (Suddenly you just got your lifepo4 pack trashed)

An extra relay contact for "ultra low" amps used is great. That way the pack can just be shutoff to prevent damage.

The contact for high pack voltage is great too, for those that do not have a charger that will shutoff automatically.


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## dimitri (May 16, 2008)

vmrod said:


> I like continuing the use of the 'custom' fuel gauge. When others drive the EV, they will see a gauge and know when the are out of fuel. They will not want to stop when it still has an itty bitty left on the gauge.


Don't worry, fuel gauge feature is not going anywhere. Afterall, if someone wants Fuel_Gauge=SOC then simply set Min_SOC=0 in the setup menu. Problem solved 

BTW, when you quote someone's post, use quote tags, so it shows correctly. Its hard to tell in above post that you quoted someone else and then responded with your feedback.


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## jackbauer (Jan 12, 2008)

Any ideas yet on pricing and availability? Sorry if its been asked already.


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## dimitri (May 16, 2008)

jackbauer said:


> Any ideas yet on pricing and availability? Sorry if its been asked already.


Unfortunately availability hinders by factory shortages of hall effect sensors. I have a long standing bulk order, which is currently showing mid March shipping, but it can't be 100% trusted. I will be ready to ship as soon as I get those sensors.

Pricing will be adjusted somewhat due to many new additions, increasing my costs. But it will definitely be competitive with similar products.


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## azdeltawye (Dec 30, 2008)

dimitri said:


> At this point hardware and software is all done, all features bench tested, just put prototype unit in my own EV for road testing. Here are some pics, without face plate, so I can update software during testing phase if bugs are found.
> 
> This is just before end of charge, few seconds before my NG3 goes from yellow to green.
> View attachment 9181
> ...


Great job Dimitri!

One comment: you need to flip the sign. Standard convention for power measurement is positive for power leaving the system that is instrumented (battery) and negative for power entering the system. So motoring current should be positive and charging current negative.


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## dimitri (May 16, 2008)

azdeltawye said:


> Great job Dimitri!
> 
> One comment: you need to flip the sign. Standard convention for power measurement is positive for power leaving the system that is instrumented (battery) and negative for power entering the system. So motoring current should be positive and charging current negative.


Thanks, I have been wondering about that. It just seems so unnatural to me, though. When I drive I spend energy, when I charge I gain it, it seems more logical to me to use signs the way I have them. Maybe its just me


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## azdeltawye (Dec 30, 2008)

dimitri said:


> Thanks, I have been wondering about that. It just seems so unnatural to me, though. When I drive I spend energy, when I charge I gain it, it seems more logical to me to use signs the way I have them. Maybe its just me


I’m not sure but I think the convention originated from a power producing revenue perspective. Energy delivered to customers yields positive income and energy purchased costs money (negative income).


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## dimitri (May 16, 2008)

GizmoEV said:


> Then what are you talking about in the following quote?
> 
> It looks like you are the one which brought up the AC meter.
> 
> ...


Sorry, I don't have time to go into WH metering again, Tomofreno has covered it pretty well in his post #23 in this thread. I am past this subject now.

I have plenty of room for digits, now that I dropped "in" and "out" tags and replaced them with signs. I actually chose not to display decimal Amp points over 10A because its difficult to grasp fast changing values on digital displays while driving. Afterall, do you really care about fractions of an Amp when you pull way over 10A most of the time? The device still counts all data with 0.1A resolution, its just rounding up display values to make it "easy on the eye" so to speak.

As for signs, I find it easier to grasp when there is a sign showing current direction relative to the battery. I don't have to show it, but I like it personally. It seems my preference is also opposite to a standard, according to above post 

Not sure what to do with signs, obviously its all software, so I can do anything I want, but WHAT WORKS BEST FOR EVERYONE????


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## dimitri (May 16, 2008)

After thinking about it for a while......what about this approach:

Show no sign when driving ( discharge ), show + sign when charging?

Sorry Darren, I just can't wrap my brain around negative current sign when I am charging my battery


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## Ziggythewiz (May 16, 2010)

dimitri said:


> As for signs, I find it easier to grasp when there is a sign showing current direction relative to the battery. I don't have to show it, but I like it personally. It seems my preference is also opposite to a standard, according to above post
> 
> Not sure what to do with signs, obviously its all software, so I can do anything I want, but WHAT WORKS BEST FOR EVERYONE????


Maybe use in and out arrows instead of +/-.

-> = Charging <-= draining, or just >/<


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## JRP3 (Mar 7, 2008)

I liked the old In and Out since it tells you exactly what is happening. I do agree with Dimitri that + for current out and - for current in is the opposite of what you'd expect but that does seem to be how it's done. My Curtis 840 meter uses no sign for discharge current and - for regen, probably to designate that regen is the opposite current flow to normal operation. I think doing it the opposite would put it at odds with other displays that may be in the vehicle so you should probably stick to the standard.


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## GizmoEV (Nov 28, 2009)

I think it may have to do with how much has been used out of the pack. With + current draining the pack it counts up how much has been taken out and the - current undoes the amount you took out. Maybe it is + means you are using energy and - is you are un-using it.

Any way the CA has - for regen and charging current but it doesn't have an SOC display so the user has to know what the end should be.

As I think about it more, my analog gauge doesn't have any negative value only positive so maybe the sign is based on that.

If you have room in software maybe make the sign choice a menu setting or just make a down arrow for discharging the battery and an up arrow for charging.


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## EVfun (Mar 14, 2010)

dimitri said:


> After thinking about it for a while......what about this approach:
> 
> Show no sign when driving ( discharge ), show + sign when charging?
> 
> Sorry Darren, I just can't wrap my brain around negative current sign when I am charging my battery


I like that idea Dimitri. I always thought showing the sign when driving was redundant, as if I couldn't tell what my right foot was doing.


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## bart_dood (Sep 2, 2010)

dimitri said:


> I'm working on a prototype of next version of EV Display. Trying to improve as much as possible to compete with big boys
> 
> Solid zero point across wide temperature range is the most challenging part, since I have no hands on experience with other E-meters I can't compare how well they done it. So, question to those with experience, how well does your E-meter hold the zero point while the car is sleeping in the cold/hot garage, driveway, parking lot, etc? Do you have to recalibrate it when temperature swings a lot?
> 
> ...


 
Maybe this got covered in the thread somewhere but I don't have time to read it all now.
The obvious solution to thermal drift is to add a temp sensor in thermal contact with your drifting device, you can then add a simple compensation algorithm in your microcontroller to stabilize the offset.

Hope this helps.


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## dimitri (May 16, 2008)

bart_dood said:


> Maybe this got covered in the thread somewhere but I don't have time to read it all now.
> The obvious solution to thermal drift is to add a temp sensor in thermal contact with your drifting device, you can then add a simple compensation algorithm in your microcontroller to stabilize the offset.
> 
> Hope this helps.


Yes, that is exactly how I handled it. Worked out pretty well.


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## dimitri (May 16, 2008)

Status update. Here is the pic of finished product. It will come in 2 options, 2" round automotive gauge or square board for mounting behind dash panels.

Also attached is wiring diagram. I am still working on updated user guide.

Missing parts are coming in finally, so I should be able to start production soon. Software has been stable and tested OK in my own EV for a couple of weeks now.


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## DIYguy (Sep 18, 2008)

Nice job Dimitri. (Now all u have to do is add the half pack bridge. lol I'm just teasing... couldn't resist... )


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## dimitri (May 16, 2008)

Here is the latest user guide. Hope it makes sense.
Let me know if any parts need more details ( or less details  ).

View attachment EV Display V2 User Guide.pdf


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## jackbauer (Jan 12, 2008)

Like it a lot. I'll take one in the pod as soon as they are available.


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## Yabert (Feb 7, 2010)

It's a really interesting product! Especially with the square board option!
What will be the price?


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## dimitri (May 16, 2008)

Yabert said:


> It's a really interesting product! Especially with the square board option!
> What will be the price?


I am still working out final production details with my manufacturing partners, so I can't finalize the price just yet, but I am shooting to stay right under $200 or slightly above it.

Will likely be another week or two before I am ready to take orders. I have a strict policy of not taking people's money until I can deliver the product


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## bart_dood (Sep 2, 2010)

I have a quick general question about measuring current, I am working on my own EV display (just for my car, not trying to compete with anyone).

My system has current transformers on each phase leg of the 3 phase controller, they sit at 2.5volts and swing between 0-5 volts.

My question is how do I get the total current (so I can calculate total power etc?)

At the moment I remove the 2.5 volt offset, then remove the - sign if the value is negative, then I add up the 3 phases to get a total current. I then multiply this by the voltage to get the power.

Is this correct?


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## dimitri (May 16, 2008)

bart_dood said:


> My question is how do I get the total current (so I can calculate total power etc?)


Why would you measure on the motor side? Measuring should be done on the battery side of the controller, where DC current flows, making measurements much more easier and effective.


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## dtbaker (Jan 5, 2008)

dimitri said:


> Status update. Here is the pic of finished product. It will come in 2 options, 2" round automotive gauge or square board for mounting behind dash panels.



This looks really great... and at $200 will be an attractive alternative. I will read thru your user guide to make sure it does everything I would really want, but it looks great so far.


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## dtbaker (Jan 5, 2008)

Dimitri, or some other EE type, can you give a quick education on why a Hall Effect sensor based system is better than a shunt based system?


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## dimitri (May 16, 2008)

dtbaker said:


> Dimitri, or some other EE type, can you give a quick education on why a Hall Effect sensor based system is better than a shunt based system?


I don't know if its better, but I like the fact that its electrically isolated from power circuits and you can put the sensor in any location in the battery loop, while shunt location must be very specific and if mistake is made you would blow the sensing circuit. I guess each one has its pros and cons. I personally like hall effect sensors, so I used them in my design.


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## JRP3 (Mar 7, 2008)

Hall effect also eliminates two high power connections points.


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## bart_dood (Sep 2, 2010)

dimitri said:


> Why would you measure on the motor side? Measuring should be done on the battery side of the controller, where DC current flows, making measurements much more easier and effective.


I have to have the three phase current sensors for my FOV control (AC motor) and the sensors are already in place, so am I correct? I just add them up?


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## dimitri (May 16, 2008)

bart_dood said:


> I have to have the three phase current sensors for my FOV control (AC motor) and the sensors are already in place, so am I correct? I just add them up?


Not 100% sure, but my guess is to add them up. However, I am still confused what you going to get out of motor current. Is your goal to have an SOC meter? You can't easily translate motor current into battery current and you can't easily get motor voltage, so I think motor current alone is pretty useless data. Without battery current you can't have SOC or any other useful battery data.


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## dimitri (May 16, 2008)

Status update. I added one more function to the device, ability to select PWM frequency and phase of fuel gauge output, and added an optional wiring diagram with MOSFET amplifying PWM output for mechanical gauges which may need more than 50mA to run. This should provide better flexibility for various mechanical gauges for those who convert old classic cars, and want original fuel gauge to work. I played with a couple of gauges myself and found that some respond better to different PWM frequencies than others, so I think having selection of frequencies could be beneficial.

Another thing that bugged me for a while was crappy quality of the screen overlay, which was made from vinyl by a local print shop. It would often peel off inside the case and make the faceplate look like crap. I finally found a local metal stamping shop with reasonable prices, they will stamp out screen overlay from black anodized aluminum, they specialize exactly on this type of work for custom instuments and various electronics panels, etc. Can't wait to see the results. I will be getting new overlays by end of next week, which was the last piece of the puzzle. Final production boards arrive on Monday, so if all goes as planned, I will start selling on March 21st or so.

Meanwhile I have been updating my Web store to get ready for new display. Product page has been updated, price finalized at $209, most updated user guide published, etc. Here is direct link

http://minibms.mybigcommerce.com/products/EV-Display.html

I will also offer optional copper bars, for those who are lazy to make their own  , for simple installation.


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## EV-propulsion.com (Jun 1, 2009)

Good idea about the fuel gauge output, the more gauges it will work with the better, that's about the number one wish (to use the stock fuel gauge) of our customers....
Thanks!
Mike
www.EV-propulsion.com


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## dimitri (May 16, 2008)

EV Display v2 is available now at my Web store.


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## EVfun (Mar 14, 2010)

While using the stock gas gauge as an amp hour counter is desirable it is not without potential problems. I don't want to discourage the use of this feature but you really should do more than just hook it up and set empty. I see 2 problems, the 50 milliamp current limit of the fuel gauge function on the EV display and the way many car fuel gauges actually read. 

Many vehicles use a voltage regulator for the gas gauge. Many, if not most, of these are slow switching thermal relays. The draw of my VW Beetle fuel gauge with regulator is about 200 milliamps. It switches between that and zero current a couple times a second. It is on about 30 to 40 percent of the time. Even if this is replaced with a LM317 type voltage regulator it will still likely be to much current for the built in output.

The other issue with fuel gauges is how non-linear they can be. Looking at my gas gauge:

0 ohms is pegged full hard
5 ohms is pegged full softly
10 ohms is full line
20 ohms is 1/2 line
40 ohms is top of "reserve" (about the last 1/8 tank is reserve)
50 ohms is the center "of reserve"
60 ohms is the empty line. 

If I use 0 ohms as full the top 1/6 of the range is pegged full and not readable. If I use the 60 ohm full range then half charge reads as 30 ohms, about 1/4 tank. 

Since this is my gauge, and since I took the time to play with resistors to figure out how it reads, I can learn to work with it. I will likely use a 5 ohm offset with a 40 ohm full to empty range (just inside the reserve range at 45 ohms is empty.) That will put 25 ohms as half range used and just below half tank.


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## dimitri (May 16, 2008)

EVfun said:


> While using the stock gas gauge as an amp hour counter is desirable it is not without potential problems. I don't want to discourage the use of this feature but you really should do more than just hook it up and set empty. I see 2 problems, the 50 milliamp current limit of the fuel gauge function on the EV display and the way many car fuel gauges actually read.


Thanks for detailed feedback. I pretty much discovered the same things during my testing. This is why I added another wiring diagram to the user guide and some more details on using fuel gauge output and a PWM selection feature.

See the latest version of the user guide at the product page at my Web store.


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## EVfun (Mar 14, 2010)

Ooh, an amplifier based on an IRF510 MOSFET to drive the fuel gauge. That ought to be enough overkill to drive any thermal fuel gauge out there.  Overkill is good in this case, that part is easy to get and hard to kill.

Perhaps software Rev 3.0 will include a 1/2 full reading point to allow bending the PWM to help make the reading more accurate.  For example, in my case I could set 55 ohms as empty and bend up the curve so 15 ohms is half (then add 5 ohms to pull all readings down so full isn't pegged so hard.)


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## MalcolmB (Jun 10, 2008)

Hi Dimitri

Sorry to dredge this old thread up, but I've just got around to tidying up my dashboard and would like to use the PWM output from your Android dashboard to drive my fuel gauge.

The tablet display works very well, but I also want to have a minimalist set of analogue gauges for use as backup.

There's a reference in the user guide to an additional amplifier circuit based on a FET to interface with a fuel gauge (which you also mentioned above), but that diagram is missing from my user guide. Do you still have the diagram available? I know you can't guarantee it will work with every gauge, but I'd still like to try it out.

Malcolm


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## dimitri (May 16, 2008)

Here it is, although it shows 4 pin connector at the back of the LCD display, which you don't have if you use EMW Dashboard unit. That unit has 4 pin connector on the Bluetooth box with pin 4 near the RJ45 plug. Look at connector on the attach diagram and turn the connector 90 degrees counterclockwise, that would be its position on the BT unit.


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## MalcolmB (Jun 10, 2008)

Many thanks for your quick response. I'll give that a try.


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