A battery can say 100% with half of it dead.
Mine did, for two years. The figure that can’t hide it is the kWh that go in each day. Paste a month of them from your battery app and see what they say. Free, in your browser, and if it looks fine the page says so.
- what the screen showed
- up to 100%
- what went in a day, measured
- 4.7 of 9.2 kWh
About half, every day, for two years. Neither the app nor the company that sold it noticed. A set of clamps found it in a week.
the check
a month of days, then your priceshow full it gets
Paste a month of daily figures, or read the app’s export, and add the battery’s size to see how full it gets and the shape of the month.
what those days were worth
Add the month above and your evening price and your feed-in to see what it saved.
where to find the numbers
your app and your billThe month view
Most battery and inverter apps have a daily energy chart with a figure called charged, to battery or battery in. Switch it to the month and type each day's figure, or copy the table and paste it.
The CSV export
The portal's web version usually exports daily energy as a CSV. Read it here: the file opens in your browser and is never uploaded. If the page guesses the wrong column, pick the charged one.
Battery size
The usable capacity in kWh, from the spec sheet, the quote or the installer's paperwork. Use the usable figure, not the total.
Your prices
Optional. The evening rate on your power bill, and the feed-in or off-peak rate the battery fills from. A free window costs nothing.
low, but not a fault
rule these out firstOne low day means little, and a month shows which days were low and why. A battery that never gets close to its usable size in a month, after you’ve ruled these out, is the one to ask about.
A backup reserve
If it keeps a share back for blackouts, it never empties below that, so it never takes in more than the rest. A 20% reserve caps every day at about 80%.
It didn't start empty
A cool evening or a quiet night leaves charge in it, and a battery that starts half full can only take the other half. That shows as some low days, not a month of them.
Not enough spare solar
Cloud, or a house using the solar as it's made, leaves less to put away. A month shows those days beside the sunny ones.
Its charge rate and window
A battery allowed to charge at 3 kW fills about 12 kWh in four hours at most. A short window or a low rate set by the installer can cap every day at the same figure, which looks like a fault and isn't one.
A virtual power plant
If you've signed up to one, it charges and discharges the battery on its own schedule, so the month follows theirs, not yours.
not sure what you’re looking at?
Send me the screenshot.
If the numbers don’t make sense, or the app has no month view, email me a screenshot of the battery’s daily or monthly chart and the battery’s size. I’ll tell you what I see, in a sentence or two, usually within a day. Free, and if it looks fine I’ll say so.
Your screenshot stays in my inbox. Nothing about it goes on this site, and I don’t keep a list.
free
One email, with the screenshot attached and the size in the body. No form, no sign-up.
Email a screenshotif you want it read properly
one hour, or half a daythe read · one hour
$90
You send the app’s history, an export or screenshots, and a recent bill. I read how the battery, solar and plan work together, remotely, and write back: what the battery saves now, what its settings cost you, and the changes worth making.
If it needs more than the hour, I say so before, not after. The first 20 minutes on the phone are free.
the set-up · half a day
$350
Home Assistant on a small box in your house: solar, battery, grid and the car on one screen, and the battery, hot water or air-con run in the cheap hours. 4 hours, prepaid, remote where it can be.
Before changing how a battery charges, I check its warranty and any virtual power plant contract. Anything on the switchboard is a licensed electrician’s job.
How my own house runs its battery in a free window is on the household stack page.
questions
10 answeredIs anything I type or upload sent anywhere?
No. The sums run in your browser, and a CSV you choose is read by the page in your browser and never uploaded. Like every page on this site, it counts that it was viewed, and nothing else: no cookies, no trackers. If you email me a screenshot, that is the one thing that reaches me.
Which figure do I paste?
The energy that went into the battery each day, in kWh. Apps call it charged, charged energy, to battery or battery in. Not the percentage, and not discharged, which is what came out. Seven days is enough to start; a month shows the pattern.
Why does a healthy battery read over 100%?
The charged figure counts the energy going in, before the losses inside the battery, and a battery that tops up twice in a day (a free window, then solar) takes in more than its size. Mine reads 9.1 to 10.5 kWh a day against 9.2 usable. Over 100% is fine; about half, every day, is not.
What does the page count as a fault?
Nothing on its own. It shows how close the battery gets to its usable size over the month and the shape of the days. A best day under 70%, with most days sitting at the same figure, is the pattern mine had with a dead module. Rule out the reasons above, then ask the installer or the maker why, in writing, with the dates and figures.
Why does it take off 10%?
Some energy is lost going into a battery and coming back out. Spec sheets call it round-trip efficiency and usually quote 90 to 95%. The check uses 90%, which keeps the saving on the low side.
How is the yearly figure worked out?
It is those days' saving scaled to a year, so it assumes every month is like the one you pasted. A sunny month overstates it and a winter month understates it. The payback uses the same figure, so it moves the same way.
What happens in the one-hour read?
It's one hour at my small-jobs rate, $90, done remotely. You send the app's history (the export or screenshots) and a recent bill. I read how the battery, solar and plan work together and write back: what the battery saves now, what its settings cost you, and the changes worth making. If it needs more than the hour, I say so before, not after.
Do I need to be in Adelaide?
No. I'm in Adelaide and the read is remote, so it works anywhere in Australia with the app and a bill. Anything on the switchboard is a job for a licensed electrician near you.
Can you make it run better?
Yes. That's the half-day block, $350 for 4 hours: Home Assistant on a small box in your house to put solar, battery, grid and the car on one screen, and to run the battery, hot water or air-con in the cheap hours. Before changing how a battery charges, I check its warranty and any virtual power plant contract.
Do the prices include GST?
The price shown is the total you pay. Nothing is added on top, and your invoice spells out the GST position.
Prices in AUD, last set October 2026. The hour and the half day are my small-jobs rates. What happened to my own battery, and how it runs locally now, is in the battery post.