Accurate Battery Gauge Project


Well-Known Member
Northeast Pennsylvania
I've searched in vain for some time now for an accurate, programmable, handlebar mounted battery gauge. Some high end bikes come equipped with this type of gauge and the displays on many others are up-gradable. Unfortunately, the controller on my bike isn't one of them.

The battery gauges on most E-bikes, including mine, seem to use a simple bar display. Some also indicate voltage and % charge remaining. The majority of these gauges are voltage based however and are not linear. They work fine for generalizing how much juice you have left but are not reliable enough to tell you when half your power is gone and it's time to turn back.

Out of frustration, I decided to make my own. I found this gauge which is used mostly in campers and RV's

The face of the gauge is weatherproof but the case is not. Since it is a panel mount, I installed it in this waterproof plastic box:

I cut a 2 1/8" hole in the lid which is an exact fit for the gauge body:

The case is an inch deeper than it needs to be but since the cable can't be cut & spliced, it's a good place to coil the slack:
The cable length supplied is 6 1/2 ', which is long enough for most bikes but a 16' extension cable is available.

I mounted the case to the bars with this clamp:

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Although the face of the gauge and the case are weatherproof, I added this vinyl cover to use during transport:

The 3" X 3" size is a good tight fit.


For proper operation, the gauge requires installing a shunt in the negative battery to controller cable:

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In my case, this was easily done inside the bike's controller housing.

The advantage of this gauge is it reads the actual power consumed in tenths of a kilowatt and is truly linear. It is programmable for any battery between 8 and 80V. You set the battery capacity in KWH and the gauge tells you how much actually remains in either KWH or %. The 10 segment bar display is an improvement over the 5 bar on my bike's display. It also reads voltage and the real time current draw. I find this handy to observe how much the current changes as I add pedal effort.

Since you set the battery capacity, it can be adjusted to compensate for loss as the battery ages. This is also helpful for those who only charge to 80% and discharge to 20% since the gauge can be programmed accordingly.

The downside to this project is the gauge case is large and clunky looking. It also takes up a lot of valuable real estate on the bars. I'm a geek though and hardly notice with all the other gadgets on my bars.😁

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Well-Known Member
ya not too many devices (G) the [problem is its not jsut what the battery's voltage is. bosch tells you how many miles you have based on your riding the hills the flats your assist level. it is constantly recalculated. thats really the only accurate way to know what your battery level is going to get you otherwise its all a guessing game. after awhile riding you learn it and don't need t as much.