Watt Meter and Battery Gauge

[LunaKB]

Watt Meter and Battery Gauge


Product Link: Watt Meter and Battery Gauge

This device is an inline measurement tool for use with battery packs 48 volts or less,(optional 60 volt max available).
The unit comes with XT-90 connectors pre-installed to match Luna battery packs. It is lightweight and more accurate than most of the dashboard displays that come with conversion kits.
Note that the device has no memory features, it works when connected and resets to zero upon disconnection.
The device is NOT bi-directional, or auto sensing. It must be connected with the correct current flow direction.

• The "in" side of the unit has a male XT-90 connector and is attached to the device supplying power.
• The "out" side of the unit has a female XT-90 connector and is attached to load.

The front of the device has a large LCD display with a back light. The display range is 0 to 150 amps.
When used between your battery and controller it will give you:

• The voltage of the battery pack , the State of Charge (SoC)
• An accurate reading of the current flow to the controller in amps
• A reading of Ah used, "fuel gauge"
• The real time current in watts

When used between your charger and your pack (remember the direction of flow) the display will give you:

• The output voltage of your charger in real time
• The charging rate, used to calculate the C-rate
• A reading of Ah put into the pack , fuel gauge
• Wattage, calculated from the voltage and the charging rate.

Note: Some users have had difficulty mounting this meter. Zip ties have been effective if not pretty. Some users have fabricated their own mounts for a more OEM look.

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​This article originally authored by Bicycle365
with additional contributions from @LouisLuna

[jrstewart3]

Is this display "always on" ? When bike is parkked.

[JPLabs]

It is always on when connected to power, as sold, yes. So if plugged into bike, yes. Mine is on all the time. Like, 3 years so far, except for rare repair or battery swaps when it needs to be unplugged.

On my wife's bike I found the switched power lead on the Bafang harness, and used that to power the meter. That one only turns meter on when bike is powered on. nicer, but a hassle to set up.

I just found a schematic here someplace, and cut open the harness to pull controller power. Don't remember exact details. But as I recall, there is a separate, thin wire to power the meter. It is connected to the battery positive wire, as shipped. I moved it to bike switched power lead on the controller harness.

So, you can do it either way.

[Panter]

I have owned three of these from different sellers and all of them died within the first hour of use with 48V batteries, so cannot recommend them.

[JPLabs]

I've bought 2, one failed right away. Was replaced by seller. So, sure, a bit of a gamble. But the ones which worked, continue to work and ones been on for YEARS

[AZguy]

I was trying to use these as charge meters between charger and battery and the first one lasted a week or two and died.... second one lasted two or three weeks then died and I gave up on them... They don't cost much OTOH...