SD Card Size for 24/7 AOV Recording: How Many Days Fit on 64 GB and 128 GB

The short answer: days, not weeks — and bitrate decides it

A microSD card holding 24/7 always-on video gives you retention measured in days. As pure arithmetic, a 64 GB card stores about 6 days of continuous footage at 1 Mbps, about 3 days at 2 Mbps, and about 1.5 days at 4 Mbps. A 128 GB card doubles every one of those figures: roughly 12 days, 6 days and 3 days respectively. Nothing else in the specification — not resolution, not frame rate, not the camera brand — changes that answer directly. They only change it through the bitrate they produce.

SolaGuard ships microSD up to 128 GB as standard across the catalogue, with larger cards available only on custom orders. So the practical planning number for a stock unit is: around one to two weeks of continuous recording before the card starts overwriting itself, then a rolling window that never runs out and never needs a site visit to clear.

That last part is the piece most buyers get wrong. The card is not an archive. It is a rolling window. Below is the arithmetic, what looping actually does to your oldest footage, and how to size retention for a site you cannot visit every week.

The arithmetic, so you can redo it for any camera

Video storage is a single multiplication. One formula covers every recorder ever built:

Hours of footage = (Card capacity in GB × 8,000) ÷ (Bitrate in Mbps × 3,600)

Cards are sold in decimal gigabytes — a "64 GB" card is 64 billion bytes, and after the filesystem takes its share you have a little less than that to write into. Round the results down by roughly five percent and you will not be surprised.

These are generic conversions, not a spec sheet. They apply equally to a wired NVR channel, a dashcam or a solar 4G camera, because the maths does not care what produced the stream. What you need from your supplier is the one missing input: the bitrate the model actually writes at, in the recording profile you intend to deploy. Ask for it in writing on the SKU you are quoting, because it varies by model and by profile, and any retention promise made without it is guesswork.

Why bitrate, not resolution, is the variable that matters

Buyers instinctively assume that a 2K camera eats twice the card of a 1080p one. It often does not. The encoder's job is to throw away redundancy, and how much redundancy exists depends on the scene, not the sensor.

• Codec. H.265 encodes the same picture in materially less data than H.264. If a quote does not say which codec is in use, the retention figure attached to it is unreliable.
• Scene motion. A gate at the end of a still yard compresses down to very little. A field of crops moving in wind, or a tree line behind the frame, generates constant pixel change and pushes the bitrate up all day, every day. Two identical cameras on the same site can differ substantially in days-of-retention purely because of what is behind the subject.
• Rate control. Constant bitrate (CBR) makes retention predictable, which is what you want when planning a fleet. Variable bitrate usually gives more days on a quiet scene and fewer on a busy one — harder to promise a client.
• Night mode. Infrared illumination introduces sensor noise, and noise is, to an encoder, detail that must be preserved. Night hours consume more card than day hours on the same camera.
• Frame rate. Halving the frame rate does not halve the file, but it does reduce it. On a perimeter where you need to identify rather than admire, lower frame rate is the cheapest retention you can buy.

What actually happens when the card loops

Loop recording — sometimes labelled overwrite, cycle recording or FIFO — means the recorder deletes the oldest file to make room for the newest. It is the default on every always-on camera worth deploying, and it should stay on.

Footage is not written as one giant file but as a sequence of short segments. When the card fills, the camera unlinks the oldest segment, reclaims its blocks and writes into them. Three consequences matter commercially:

1. There is no gap and no alarm. The camera does not stop and does not warn you. On the day the card fills you simply stop being able to reach back past your retention window. If nobody knew the window was six days, the first anyone learns of it is the day a client asks for footage from last week.
2. The oldest is always what you lose. Which is exactly backwards from how incidents surface. Theft on a remote site is often discovered days later — a missing spool of cable, a gate found open, stock that does not reconcile at month end. The clip you need is the oldest one on the card, and it is the first casualty.
3. A pulled card is a frozen card. The moment an incident is confirmed, the correct action is to stop the camera overwriting: retrieve the clip over 4G, or physically remove the card and replace it with a spare. Every hour the camera keeps running is an hour eaten off the far end of your evidence.

Cards fail differently under continuous write

A card doing 24/7 always-on video is rewritten end to end every few days, forever — an entirely different duty cycle from a card in a phone, written once and read thereafter. Specify high-endurance or surveillance-rated cards and treat consumer cards as a warranty problem waiting to happen: the failure is silent, and a card that has stopped accepting writes looks exactly like a working one until someone asks for a clip.

Three fleet habits that cost nothing: format the card in the camera rather than in a laptop, so the segment structure matches what the firmware expects; keep two or three spares per site so an incident card can be pulled and bagged without taking a camera offline; and buy one brand and batch across a deployment, so behaviour is uniform when you are diagnosing at distance.

"Can I just fit a 512 GB card?"

It is one of the most common questions we get, and the honest answer has two halves.

Standard SolaGuard units support microSD up to 128 GB. That is the supported, tested ceiling on stock SKUs from the 150-model catalogue. Fitting a larger card than a device supports typically produces one of three outcomes, none of them good: the card is not recognised, it is recognised but only partially addressed, or it appears to work and then corrupts under sustained write. None of these are visible from a photograph of a live view.

Larger capacities are available on custom orders. Shenzhen Leksell — TÜV Rheinland certified, established 2012, also CE, FCC and RoHS — builds to spec, and storage ceiling is one of the things that can be specified alongside battery, panel, resolution and OEM branding. That path runs through MOQ 100 for OEM/ODM work, with quantity, price and lead time coming from a person, not from a web page.

For most sites there is also a better answer than a bigger card. If the requirement is genuinely "we must be able to review any moment from last month", the fix is offload, not capacity: pull the clips that matter over the 4G link and keep them where they can be backed up and handed to an insurer. The card is the buffer that guarantees nothing was missed, not the place a month of evidence should live.

Sizing retention against how the site is actually run

Retention should be set by one question: how long can pass before someone notices something is wrong? Match the window to the visit interval, not to a round number.

That table is the whole argument for continuous recording. A camera that only wakes on motion stretches a card a long way — but it stretches it by not recording, a saving you pay for on the one night that matters. Always-on video buys certainty that the frame exists; the card decides how long that certainty survives.

What to confirm before you place the order

Put these five items in the quote request and the retention argument disappears from your after-sales workload:

1. Configured bitrate and codec on the exact SKU, in the profile that will be deployed.
2. Supported card capacity ceiling and whether the model requires a specific card class.
3. Whether loop recording is on by default and whether it can be locked on.
4. How footage is retrieved remotely over the 4G link, and what that costs in data.
5. Whether recording continues through low-battery states, and what the camera does first when power is short.

Every SolaGuard model runs on solar plus battery plus a 4G SIM — no mains supply, no WiFi — installs in 5–10 minutes per camera and is IP66 sealed on outdoor units, at 1080p–2K standard resolution. Samples ship in 7–10 days by air, bulk orders in 25–40 days by sea, and within Vietnam in 7–10 business days. Dealer margin starts at 20% from around 10 units and reaches 30% from around 50, with MOQ 10 for a trial order.

Browse the range at /en/products/, see volume terms at /en/wholesale/, or read the full technical background in the AOV solar camera guide. For a bitrate figure on a specific model, message us on WhatsApp at +86 188 1869 9870 or email info@solaguard.net — we would rather send you the real number than let you plan a deployment around ours.