About OneWatt

Why

Most home batteries tell you a single number: how full they are. That is the least interesting thing about them. What actually matters is whether the cells inside are staying together, how much you really got in and out last month, and what the battery was doing at the moment something went wrong — and almost none of it is visible unless you happen to be stood in front of an inverter at the time.

OneWatt puts that on a web page. Every cell, every probe, every amp in and out, kept for a year, from wherever you are.

How it works

A small logger sits by your battery and reads it — over a cable for Sunsynk and other PACE batteries, over the CAN bus for the Sunsynk L5.3, over Bluetooth for JBD and Xiaoxiang. It sends what it reads to us over an encrypted connection, and we show it to you at an address of your own.

The logger only ever calls out. Nothing on your home network is exposed, there are no ports to open, and there is no app to install.

What we think matters

Say what is actually true. If a figure cannot be relied on, the page says so rather than showing a confident number. If a battery has stopped reporting, it says that too, instead of quietly displaying the last thing it heard.

Your data is yours. Download the lot as a spreadsheet whenever you want. If you would rather not use our service at all, point the logger at your own MQTT broker and it will publish straight into Home Assistant. The hardware is yours either way.

Nothing is tracking you. No analytics, no advertising, no third-party scripts. One cookie, and it is the one that keeps you signed in.

Getting hold of us

ukonewatt@gmail.com. If it is about a logger already installed, send the serial number from its label — it starts with OWB- — and roughly when the trouble started. We can see the same readings you can, which usually settles it without a visit.