# Ebike Voltmeter?



## Old & Slow (May 3, 2020)

Anyone have any experience using a voltmeter on an ebike to gauge the remaining battery capacity?

The ones I've found are combined with a thumb throttle and depending on the source are inexpensive: under $10 to under $25. No need to use the throttle part if not needed. Seems just use the correct two wires connected to the battery at the motor and ignore the throttle wires.


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## Old & Slow (May 3, 2020)

So I found one w/o the thumb for under $5 on Aliexpress.








As with anything on Ali 1-2 months delivery. Here's a link:
https://www.aliexpress.com/item/4000274274865.html?spm=a2g0s.9042311.0.0.71564c4dlaY2pD

If it works or not all post back . . . don't hold your breath.


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## PierreR (May 17, 2012)

Why would you monitor your remaining battery with a volt meter when you can use a cheap watt meter and get way more information. You can get them for $15-$30 depending on shunt or no shunt.

Does it void the warranty to hook one up?


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## Old & Slow (May 3, 2020)

PierreR said:


> Why would you monitor your remaining battery with a volt meter when you can use a cheap watt meter and get way more information. You can get them for $15-$30 depending on shunt or no shunt.


Show me what you're referring to. My understanding is a watt meter connects between the battery and the motor, not useful to have a meter down there. No way I'd run those wires to/from the cockpit.

Besides a watt meter tells what I'm drawing, not the energy remaining. Seems a voltage would give me a good idea of what is left in the battery. Better than the four bar display, which is a crude voltmeter.


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## PierreR (May 17, 2012)

Two types of watt meters. You have the watt meter that is connected between the battery and the motor and the watt meter that has a shunt connected between the battery and the motor that takes the bulk of the current and a set of small wires that run up to the meter. 

Watt meters can record all sorts of data and display it. All the way from Watt hours used, voltage remaining, voltage sag, max current draw, instantaneous current draw and instantaneous watts. 
Voltage remaining is not a good indicator of remaining battery power available. At best, its a rough estimate and always favors there being more battery available than their is. There is no sure fire way to tell you exactly how much range you have left. 

With a bit of guessing I come very close to remaining range. Probably the best way to calculate it is to run a test that includes all factors. Charge the battery up fully until it shuts off. Go ride until the battery is low enough that you cannot pull your normal wattage from the battery without the BMS cutting things out. Read your watt hours used. That is your practical pull from the battery, not the mythical Watt hours listed by the manufacturer. Once you have that number, you can subtract the watt hours used from that practical number and have the watt hours remaining. Its rough but a lot closer than anything else. I have enough data to know about how many watt hours per mile that I am using under the conditions that I am riding. I am always within 5% My practical pull from the battery is 980 watt hours under normal riding and 880 at higher power settings or colder temps.


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## Old & Slow (May 3, 2020)

Doing some research I've found all manner of watt meters ranging from $10-$100. At the low end they're inline or require running the power wires to the cockpit or being at the motor.

The most common are solar specific and are panel mount, not bike specific handlebar mount. The shunt type are modestly more expensive but are still panel mount. The only bike specific meter I've found is called the Cycle Analyst and is about $100.

Is this your understanding and assuming you used a panel mount meter, how did you mount it to your cockpit? From your bike photo (#123) you have an amazing cockpit.


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## PierreR (May 17, 2012)

Old & Slow, at the In that photo I have the type that has the power wires all the way to the handlebars. The cycle analyst did not support Bafang but I believe they do now. The cycle analyst replaces your readout. I am considering going to the V2 model. 

I believe there is some blue tooth options now available but I have not done the research for that yet. As new stuff becomes available I have been updating my bike. I would like to build a new bike with updated drive systems as well but will hold off now with the election outcome.


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## Old & Slow (May 3, 2020)

PierreR what is your opinion of Bafang color displays? Specifically as to readability in bright sun? I went with a B/W display because of my negative experience reading various color displays.

Some of the color displays have a voltmeter and also integrated with the +/- control buttons. Because of my terrain I change the PAS frequently.

Thanks


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## PierreR (May 17, 2012)

Old & Slow, the display that I have in the photo is very readable in direct sunlight. Its held up for over 10k miles but its not listed as very water proof. I cover it with a baggy when it rains.
I did not find it to be accurate for 52 volts. Only 48


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## Old & Slow (May 3, 2020)

PierreR said:


> Old & Slow, the display that I have in the photo is very readable in direct sunlight. Its held up for over 10k miles but its not listed as very water proof. I cover it with a baggy when it rains.
> I did not find it to be accurate for 52 volts. Only 48


What is that display? I can't see the model in the pic. I never ride in the rain and my battery is 48V.

Thanks


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## PierreR (May 17, 2012)

Old & Slow, I found a download manual. The model is DCP14

These is nothing on the printed copy to indicate where I downloaded it from.


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## Old & Slow (May 3, 2020)

PierreR said:


> The model is DCP14


Appears the DCP14 is no longer available, replaced by the DCP 18?

Found a Luna YouTube on the DCP 14, much more info than the B&W 961 I have.

Given the way my left hydraulic cylinder is tight to the bar, unlikely I'll be switching because of the large controllers on the color displays.

Thanks for the info.


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## PierreR (May 17, 2012)

Was over at Grin Technologies web site looking for the possible direct connection of BBSHD to the V3 Cycle analyst. I did not find one but I did happen upon this e bike simulator. Justin put a lot of work into this and its way cool.

https://ebikes.ca/tools/simulator.h..._b=13&throt_b=75&tr=14&mass=130&tf=42&grade=0


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