[KiwiEV]

EVAmerica are quite cheap and I've used them for all my major parts in the conversion, however I was stumbling around eBay last night and found a massive supply of different ammeters and voltmeters from a seller in China.
Not only are these cool looking with coloured backgrounds and LCD displays, they're a quarter of the price of the analogue "needle" gauges.

This is the 0-200V DC Voltmeter for sale at $4.99 US.

And that's the 500A DC Ammeter for sale at $25 USD including the Shunt.

Check out this guys eBay Store if you want more details.

Too good to be true or just a good bargain?

 

[Mr. Sharkey]

Too good to be true or just a good bargain?

Neither, just the miracle of modern manufacturing and cheap slave labor.

If the accuracy is good, pick up a few. The price of the ammeter is about what you'd pay for a precision shunt alone.

Be aware, though, that digital meter may look high tech, and give a to-the-tenth reading, but in a moving vehicle, they are much less than desirable than a "needle gauge".

Why?

Because your brain processes the two forms of information in different ways. Looking at a digital display requires you to recognize the numbers, translate them into a meaningful reading, then compare them to a known minimum/maximum/nominal value that you have to remember.

An analog meter can supply the same information by the relative position of the needle, which you can instantly recognize as in-or-out of the proper range without actually knowing the numeric value.

I have both digital and analog meter in my EV, and during on-road in-traffic driving I use the analog metering exclusively. A split-second glance at my volt and amp meters can convey all the information I need without having to even think about what the value is.

Also, digital metering values "jump around" a lot during the varying loads of an EV's operation, making them even harder to get a fast reading from.

For stationary troubleshooting and data logging, digital meters will always be more accurate, and therefore more useful when you don't have to time share with road hazards.

 

[Coley]

I just bought the same 200 volt and 500 amp panel gauges from :
zeva.com.au

I have them mounted and ready to put in the car.
He also sent me a wiring diagram for them.

check with him @ [email protected]
about prices. etc.

Seems to me, that with the colored backlite, it would be no more dificult to glance at them than a digital clock with the unlit gray background.

 

[KiwiEV]

Really? Are they "jumpy" or fairly fluid regarding their readings? I mean, do they update every microsecond or every second for example? I remember some of the old digital dashboards in the 80's updated every second or so. It was no fun to watch when accelerating.
Do you have a picture of how they look installed into your dash?

 

[Mr. Sharkey]

Refresh rate has a lot to do with the amount of "jumpyness", but even fast refresh rates result in a display of numbers that are constantly in flux, making it hard to pin down the reading. Remember that a lot of this has to do with physco-recognition of values, which are more difficult to quatnitfy in a rapidly changing display.

Here's a piccy of my instruments. I usually leave the digital meter set for ampere-hours, which is a fairly slow progression, and is not a reading that can easily be displayed by an analog meter:

The digital display is set to DOD or % remaining remaining in this image.

As you say, digital speedometers are/were a come-down. When driving, you usually don't actually examine the numeric reading on your speedo, but have a built-in sense of about where the pointer should be for a given speed, allowing frequent glances to keep you in the right speed "zone". Doing voltage and current calculations in your head from ever-changing digital readings would away take a lot of the intuitive craft of of driving an EV in my opinion.

 

[moldiebrownie]

I went with analog guages for the reasons Mr Sharkey stated..besides..they came in my kit anyway. This also allowed me to use this cool pillar mounted guage pod....heh heh...keeping it clean for the ladies!

 

[KiwiEV]

I, um, just bought them both.

I couldn't resist it. I looked at all kinds of analogue gauges but these digital display ones just look so cool!
I guess I'm just a sucker for colours and flashing lights.

 

[Coley]

Mine will be in the car after next week. No time right now to install them.
My shop is getting busy again....

 

[KiwiEV]

I went with analog guages for the reasons Mr Sharkey stated..besides..they came in my kit anyway. This also allowed me to use this cool pillar mounted guage pod....heh heh...keeping it clean for the ladies!

I absent mindedly stared at your picture of the pillar-mounted gauges until it clicked. I was wondering why on earth you'd put them there for your passenger to look at. You even mentioned it was fashionably there "for the ladies".

I got it eventually, it's that whole different side of the car/road thing.
I'm a little embarrassed right now...

 

[Coley]

Well, I got mine in the car today and turned on the battery pack expecting to see 75-volts or so.

The gauge read 36 volts and then nothing.

The amp gauge showed 1 amp and nothing more as I drove around town.

Tried to fire them up with the car battery first.

Changed to a seperate 9 volt battery, same results.

Not too happy at this time.

Voltmeter (handheld) shows 75 volts, right at the dash gauge so wiring should be OK.

9/16/07 Update

Today as I was driving back to town, the amp gauge reads "1000". No"dc a", just 1000.

9/20/07
Both meters are now blank, (with the nice blue background).

I have a new 12/12 converter coming from ZEVA and we will see if that makes a difference.

If not, I was told new meters would be sent.

 

[KiwiEV]

Hmmm. That's bad.

Did they definitely give you the 12v input version or maybe they cocked up and sent you the 5 volt input version?

That's got me worried now. If mine do the same then I'll have to drop that idea and go with the needle gauges that others use. Would be a terrible waste of money if they don't work.
Not sure about the voltmeter but you could try wiring from the shunt to your handheld ammeter, going for a drive and seeing if it's the cheap chinese shunt or the actual gauge that's faulty.
I hope you figure a way to let you use them ok. Let us all know if they work ok (especially me!)

 

[Coley]

I didn't see a 5volt set, but these can either be a 9volt or the car 12volt for feed.

I should be getting the new 12/12 converter soon.

Both meters were blank today, except for the nice blue background.....

just plugged it in, for the trip to work tomorrow.

 

[KiwiEV]

Hey Coley, my meters arrived today and they have some odd warnings which I didn't expect.
Out of interest, did your meter come with this note:
WARNING:
The voltage meter and the current meter can not jointly use one DC power supply.
If you are unable to supply the single working power, please buy our DC-DC converter Isolated Power Supply.

Well. That's just what I need. After buying something being told that I need something else to make it work.
Is that the reason yours failed?

"There you are sir, enjoy your new Audi"
"Thanks! Ummm... Where are the keys?"
"Oh, you want to USE your car? I'm very sorry sir, keys cost extra"

 

[Coley]

Mine didn't state that, but it may be why they failed.

I am getting a new 12/12 converter (free), because the original one was marked with reverse polarity.

THAT may have been the thing that did my meters in.

I am going to hook them up to a 9volt battery and check them, to see if they will work that way.

If that 12/12 thing is true, then you would need 2 of them, (one for each meter).

Not fun....

 

[KiwiEV]

I've just bought one 12v/12v isolator off that same guy in China that I bought the meters from.

Surely I'd only have to use one isolator for one meter, as the other meter would be effectively on a "different" feed. Anyone?

I hope so as I don't really want to spend another $20 getting another isolator sent down here.

 

[Greenflight]

IDK, sounds like the Chinese may have lost it... This makes no sense. Why would they require two separate supplies? I mean, the 12v should just power the display and such- not take the actual reading, right? Or is there something I don't understand (please no remarks about the meaning of life )?

 

[Mike D EV]

Many cheap digital panel meters do not have isolated inputs, and internally reference the signals to the supply ground.
Depending on where in the circuit you place the amp shunt, that could blow one or both meters.

KiwiEV's included warning note would be appropriate for that type of meter.

Coley's idea of testing them with 9V battery would be a good way to test them .
I have also seen DPM's that are rated for 12V, that would be damaged at 13.6V, so check the max volts spec.
From the description, only the ammeter should need an isolated dc/dc.
Good luck.

 

[KiwiEV]

Thanks mate, I'll give it a shot with the 12v/12v isolator on the ammeter.
You mentioned that the location of the shunt within the circuit could cause the ammeter to get a little upset... Or die.
Or both.
Presuming my ammeter is a die-before-you-buy model, where would you recommend placing the shunt?

 

[Mike D EV]

If your complete 12V system is powered from an isolated dc/dc converter, that is not common with your HV battery supply, and your volt meter is powered with that supply, and your ammeter is powered with the other isolated dc/dc, the placement of the shunt in the circuit should not matter.
My reference to the shunt location was without isolation.
A simple ohmmeter test or visual circuit trace of the meter circuit should tell us if the measuring input terminals are common with the power inputs.
Need the specs or better yet a schematic of the meter to make an assumption free determination.

 

[KiwiEV]

I'm not going to use a DC to DC converter in my EV. Too hard, expensive etc.
The car's 12v electrics are powered off an AGM battery tucked away in the engine bay. Not sure if that affects the shunt location.