View Full Version : Analog gauges

08 April 2013, 2017
Anyone have any luck repurposing old school ammeters or voltmeters for gauges?

Reading this thread
and plotting simple two gauge analog cluster.

Speedo and ammeter ?
Speedo and volts?

Not cranking on it often so leaning to volts not amps.

Anybody working on this and if so, how would you wire?

08 April 2013, 2320
Westach makes nice analog volt and amp meters for EVs. They come in different ranges so you can match your system voltage or max current.


If you're going to choose one, probably voltage. That's what tells you if you're pushing your cells too hard, and if you're getting low on charge.

09 April 2013, 0149
I love these meters: http://metersandinstruments.yokogawa-usa.com/category/toughmeter-panel-meters? I found a vintage VM at the MIT Flea Market, but it's only a matter of time before it rattles apart.

I use a volt meter, a low-voltage warning light, and a speedo. Works great. Analog VMs are much easier to read since the numbers aren't bouncing around.


09 April 2013, 1912
As per that original thread, I went with an analog speedometer. Happens to be high tech GPS type inside, but the display is pure old school analog. Now the second display is where you will get some discussion from people here I think. I believe you need SOC information. I think you look only at the speedo for most of your riding time, but need to glance at the "gas gauge" once in a great while to keep you informed of your energy status. Since I use Li based batteries, the voltmeter is not a good inidicator of remaining charge. I use a Cycle Analyst and really only look at one number: Ah used. Lots of other info like pack voltage and current if you are troubleshooting, but not normally used durring riding. (By the way that slick analog speedo has a miniature lcd display that you can check while not moving for all kinds of data including your 0-60 and 1/4 mile times!)

10 April 2013, 1506
Must be an electronic genius out there somewhere that could build a circuit to convert the AH used from something like a cycle analyst into a signal to drive a resistance based analog fuel gauge. I have no idea, but what I do know about electronics makes me think that it would not be too difficult for someone who knows what they are doing.

From my experience with Lipo's in RC helis and quadcopters, I think AH used is the most valuable info you can have for knowing the state of charge of your battery pack.

I'm not even close to there yet, but I would like to have an analog speedo, and AH used fuel gauge. I think that's all the info I would care to know for actually riding.

BTW, Ted your gauge bezel is beautiful!

10 April 2013, 1715
You can get away with using voltage, but you have to know how to read the voltmeter. SOC based on Ah is much more straight forward.

I don't think the CA has any outputs for SOC.

Some BMSs have an analog output that can run to an analog SOC meter. Elithion has a 0-5V output that will work with any SOC meter that uses 0-5V full-scale. I think Westach makes one.

The miniBMS EV display has an output to drive an analog fuel gauge. So does the ZEVA fuel guage. The ZEVA also has an output to drive a tach to act as an ammeter. They're both kind of pricey.



You could also program a microcontroller (like an Arduino) to take readings from a Hall effect or shunt current sensor, count Ah and output a signal to drive a meter. Would be a fun project.

10 April 2013, 1950
i am actually thinking of running an arduino or raspberry pi on the bike and might look into that idea. could be kinda cool to have it driving ah and volt dials, right?

11 April 2013, 0728
Ted, what's the name of that vintage voltmeter you have? Cool.

11 April 2013, 0900
Ted, what's the name of that vintage voltmeter you have? Cool.

Thanks! Itís a 0-150v Simpson bakelite panel meter, probably around 1960 vintage.

11 April 2013, 1650
Westach doesn't make SOC meters that work off a seperate 0-5V drive as far as I can tell. They make multiple versions that are designed to work with various voltage lead acid batteries. Works reasonably well for LA because of the direct relationship between voltage and SOC. (Solectria cars use all Westach gauges except for SOC for instance)

Great idea for a little microcontroller job though. Pretty simple in concept. Current shunt input plus positive pack voltage properly scaled can easily be read and calculated every second by a micro. Pack voltage to 5V very low power converter needed to operate it along with a reset button to let it know its full again. Two wires to a 0-5V Westach analog fuel gauge meter like the 2C7V found on their website and you are in bussiness. Could easily drive a scaled voltage meter from the same micro if you decied not to feed the high voltage up to the display area like some people are loath to do.

An isolated version that ran off the bikes 12V system would also be possible but would be a bit more complicated.....


11 April 2013, 1758
Elithion's site lists 0-5Vfs SOC meters, but Westach's site doesn't have them. Weird. Maybe Westach used to make them?


11 April 2013, 1827
Westach does do custom meters for customers. Maybe this is a case of Elithion ordering something specifically for them. I know a vendor in California that had a whole series of Westach gauges made especially for them that were upside down. (So you could read them well when they were hung under the dash of an EV.) Maybe Westach would make you one since they are a simple deriviative of what they list in their catalog...

11 April 2013, 1838
That could be - Elithion say to get a part number and then contact Westach. None of the part nos from Elithion match anything on Westach's site, so you're probably right that they're special order.

Would be simple enough to email them.

11 April 2013, 2108

EV Parts has carried these custom Westach guages for a long time.
(disclaimer: I'm a sucker for anything with a lightning bolt)

11 April 2013, 2216
Arduino Analog Gauge

Who wants to take it on?!!


I have an arduino Pro Mini around here somewhere, built into a old quadcopter controller . I know how to flash it with existing code, but I haven't the foggiest on coding. Willing to collaborate with someone who knows a bit about writing code.

ARC EV Racing
12 April 2013, 1712
We designed an interface box that turns a standard Aprilia rs125 dash into an elmoto dash. It drives the digital Speedo and analogue rev counter in place of the original ecu, the fuel gauge becomes state of charge (based on ah used measured via an inductive sensor) and the temp gauge reads motor temp. It's based on an 8-bit avr micro so it's pretty cheap and simple.

We just built it for one customer and never really developed it as a product but if there's any interest we could put some kits together and send out the micros pre-programmed.

12 April 2013, 1859
Been looking at the arduino coding a bit today, it doesn't look like it would be too difficult to put something together. I just ordered a cheapo 5v panel meter and a Arduino Pro Mini clone to play around with. total $8.73 a worthwhile investment!


It's only been about 30 years since I wrote anything in a programming language.

12 April 2013, 2037

i am game to try this with you. i have arduino and pi ready to try it with.

14 April 2013, 1354
Is there someone who understands electronic components a bit better than me who can point me in the right direction for a hall effect current sensor for a 72V pack running the Mars 1003/Alltrax 7245 combo?

I was looking at these: http://www.lem.com/docs/products/hais_e_rev11.pdf

Would the 150 do it? 150A Nominal, but reads up to 450A

Arduino code looks to be quite simple for reading a sensor, and driving a gauge. Just need to manage input and output voltages to keep them in the range that the arduino can handle. I bought a bunch of bulk components and a breadboard. So I will dig into it when everything arrives.

14 April 2013, 1646
I'd recommend a Honeywell CSLA2EL. +/-550A. They seem more robust than the LEM one you found, mounting points built in, hole is big enough you can run cable through without a separate bus bar.

I have one. Seems really well made, I just never got around to using it.