Short answer: on these two bodies, the “power floor” for LP-E6P is not “will it still turn on” but “will it hold a heavy load without stopping when the charge is low”. The practical floor: do not start a top-spec recording below two to three tenths of charge, rotate two packs rather than stretching one, and the moment the body warns about low battery, stop the demanding take instead of gambling on another few dozen seconds.
The EOS R5 Mark II and the EOS R1 are both 2024 high-end models paired with LP-E6P. Their heavy-load profiles are not identical: the R5 Mark II has 8K-class recording needs, while the R1’s sensor resolution means 8K is not its selling point and the pressure comes more from 6K RAW and high-frame-rate 4K. What they share is that both demand more continuous discharge current than the R5 and R6 generation.
One: the floor is a voltage question, not a capacity one
The body judges pack condition from terminal voltage. Terminal voltage equals the cell’s open-circuit voltage minus internal resistance times current. At high charge the open-circuit voltage is high and resistance is low, so a big current draw barely dents it. At low charge the open-circuit voltage is already low, and resistance has grown with cycling and temperature, so the same current pushes terminal voltage below the protection threshold.
Once the threshold trips, the body typically warns about low battery, stops recording, or simply shuts down to protect itself. There is still energy in the pack; it just cannot be released under heavy load. That is why “one bar left” and “can record 8K” are two entirely different statements.
Temperature magnifies the problem. In the cold, electrolyte viscosity rises and internal resistance climbs, so terminal voltage collapses sooner. After long heavy recording the pack heats up, and higher temperature raises resistance as well. The same pack can therefore behave very differently outdoors in winter and in an air-conditioned room.
Two: how three load types compare
| Load type | Current profile | Main source of strain | Relative strain |
|---|---|---|---|
| 8K-class recording | Sustained high current | Sensor readout, encoding, cooling, card writing | Highest |
| 6K RAW / high frame rate | Sustained high current, sharper peaks | Data volume, processor load, storage writes | High |
| Routine 4K recording | Moderate sustained current | Encoding and screen | Medium |
| Continuous stills | Short pulses | Autofocus and shutter | Low |
The way to use that table is to allocate packs: give the healthiest one to the highest-strain tier and leave older packs for routine recording. Not the other way round — do not send a degraded pack into 8K and then suspect the body is overheating.
Three: five rules you can act on
- Two to three tenths of charge is the red line. Below that, do not start a top-spec recording. Not because it cannot record, but because it may stop at any moment, and it usually stops at the worst moment of the take.
- Use a full pack for the important shot. Changing a battery costs seconds; reshooting may cost an afternoon.
- Do not relay between hot packs. Swapping one pack for another after a pack has run hot does nothing for the body’s internal temperature, and the second pack then works in worse conditions. Giving the body a few minutes to cool is more effective than swapping.
- Warm packs up in the cold. For winter outdoor work, carrying packs in an inside pocket rather than the outer compartment of a bag buys noticeably more time.
- Prefer external power for fixed positions. Some bodies support USB-C PD input, so for long interviews or livestreams you can run on mains and save packs for handheld work. Whether yours supports it depends on the body manual.
Four: variables beyond the battery, and a pre-shoot checklist
Memory cards. High-bitrate recording demands high write speeds, and an inadequate or overheated card will also stop the recording. That kind of stop looks very much like a power problem and is easily misdiagnosed as a battery fault. When troubleshooting, swap in a known-good card first, then a battery — it saves a lot of wasted effort.
Cooling. An overheated body will drop specs or stop recording on its own, independent of the battery. During long top-spec takes, open the side covers, keep direct sun off the camera, and avoid running it inside a closed bag. Good cooling also extends how long a given pack lasts.
A pre-shoot checklist follows the same logic. On the battery side: are there at least two fully charged primary packs, is one of them fairly new, do you have insulation for cold weather, are the charger and cables packed. On the body side: is the firmware reasonably current (some high-spec features depend on it), is there enough free space on the card, and does the recording spec match the card’s speed.
The list looks fussy, but it prevents the overwhelming majority of “it stopped halfway” incidents. Worrying about exactly how many minutes a particular pack will record is far less useful — that number changes with bitrate, temperature, cooling, and card speed, and only your own baseline data means anything. For how LP-E6P differs in intent from capacity-oriented packs, see the LP-E6P category; if you work on bodies like the R5 or R6, the LP-E6NH category is the better fit. For the physical shape of the four generations and how they interchange, see the LP-E6 category. YO’s compatible LP-E6P works well as a second or third pack covering routine recording blocks.
FAQ
Can I still record 8K at 15% charge?
Technically it may start, but it is not advisable. At low charge the terminal voltage is already low, and the current surge of a heavy load can easily trip protection within tens of seconds. A take that starts but cannot finish is worse than a clean low-battery warning.
If I rotate two packs, is runtime simply the sum of both?
Close, but not a simple sum. The body does not cool down during the swap, so the second pack works in worse conditions, and the real total is usually slightly below the sum of the two measured separately. Do not plan your day on 1+1.
Why is one pack fine on an R5 but strained on an R5 Mark II?
Because the two bodies draw different currents. The R5 Mark II needs higher sustained discharge in top-spec modes, and a degraded pack with raised internal resistance sags more easily in that situation. The pack is not broken; it simply no longer meets this body’s peak demand.
What does a “battery communication error” mean?
Usually oxidized or dirty contacts, or a fault in the pack’s protection board communication. Clean the contacts and retry first. If several packs fail in the same body, check the body’s contacts; if the same pack fails in several bodies, the pack needs replacing.