Canon LP-E6

Short answer: LP-E6P rarely ages first by “holding less”. It ages by “failing to hold up under heavy load” — daily shooting shows nothing, but as soon as you move to 8K or high frame rates, recording time is noticeably shorter than a new pack. The reason is that it works at high discharge current for long periods, so rising internal resistance becomes the bottleneck before capacity loss does. Swelling risk is genuinely higher than with capacity-oriented packs, but it is manageable, and the key is avoiding a full-charge store immediately after a hot heavy session.

LP-E6P is the model launched in 2024 with the EOS R5 Mark II, and Canon states its selling point plainly: higher continuous discharge capability. In capacity terms it stays in the 2130mAh class, the same tier as LP-E6NH. That means it is not a longer-lasting battery but a battery that handles more current, and judging its health requires a different set of standards.

One: three knock-on effects of high discharge

The first is heat. During high-current output, ohmic losses inside the cells grow with the square of the current, and all of that energy becomes heat. On an R5 Mark II at 8K or high frame rate, the pack’s sustained current is far above what stills demand, and the body’s own heat adds to the pack’s, so temperatures run clearly higher.

The second is rising internal resistance. Heat accelerates the rise in resistance, and higher resistance in turn produces more heat at the same current — a positive feedback loop. That is why packs used under heavy load often degrade faster and faster rather than declining evenly.

The third is voltage sag. The body decides whether there is charge left by reading terminal voltage, which equals open-circuit voltage minus current times internal resistance. Once resistance grows, a large current draw collapses the terminal voltage immediately, and the body concludes the pack is low and ends the take early or asks for a swap. There is still energy inside; it simply cannot be released.

Two: two degradation paths, considered separately

Both paths usually run at once, but at different speeds. In a high-discharge pack, power fade generally leads, which produces an easily misread situation: stills are perfectly normal, then 8K stops early “for no reason”. Users suspect body overheating or a firmware problem, when in fact swapping in a new pack restores normal behavior.

This also explains a common question — why the same pack behaves normally in someone else’s body. Their body may simply never need that much continuous current, so power fade never becomes a bottleneck in their work.

Three: three checks that need no instruments

1. Heavy-load comparison. On the same body, same recording spec, same ambient temperature, record with a new pack and with the pack in question until each stops automatically, and compare the times. A difference within two tenths is normal aging; beyond three tenths, power fade is clearly significant.
2. Voltage sag observation. At low charge (below three tenths), start a heavy recording and see whether the body quickly warns about low battery or stops outright. A new pack still holds for a while; an old one often gives up within seconds to tens of seconds.
3. Charging and heat. Charging from the same level on the same charger, a clearly shorter charge time — or a pack that runs noticeably hotter than a new one during charging — is supporting evidence of raised internal resistance.

Of the three, the first is the most reliable and the most worth doing once when the camera is new, as a baseline record. Without a baseline, every later feeling that “it got shorter” stays unquantified.

Four: swelling risk, when to replace, and spare strategy

Swelling is gas generation inside the cell raising internal pressure. For LP-E6P, three factors stack up: the heat of heavy load, the high potential of a full charge, and electrolyte decomposition after long cycling. All three together is the worst case, and the typical scenario is “half a day of 8K, the pack still hot, straight onto the charger at home until full, then left in a bag overnight”.

The safer routine: after a heavy session, let the pack cool in open air to near room temperature before charging; take it off the charger once full rather than leaving it there; store long-idle packs at four to six tenths of charge. None of this is complicated, but it cuts the risk substantially. The checks match those for capacity packs: lay it flat on a table and see whether it rocks, look along the seam against the light for gaps, and notice whether it slides into the body more tightly. Any clearly abnormal result means retire it.

As for timing, use “heavy-load recording time down to seven tenths of a new pack” as your reference line rather than waiting until it is unusable. Power fade accelerates late in life and tends to surface exactly when you need it most — a sudden stop during an important 8K shoot costs far more than a pack.

On spares, bodies that take LP-E6P generally draw a lot, so two packs is the floor. A sensible arrangement keeps one relatively new pack as the dedicated top-spec pack and demotes older packs to routine 4K or stills. That extracts the remaining value from old packs without putting critical takes at risk. YO’s compatible LP-E6P suits a supplementary role, absorbing cycles. For the generational differences between LP-E6P and LP-E6NH, see the LP-E6P category; if you also shoot bodies like the R5 or R6, the LP-E6NH category covers the capacity-oriented options. Cold further lowers terminal voltage, and the mechanism is described in cold-weather battery behavior.

FAQ

Is LP-E6P longer-lasting than LP-E6NH?

Not in that sense. Both are in the same capacity tier, and LP-E6P’s advantage is continuous discharge capability. On a heavy-load body it keeps top-spec modes running steadily; under light loads its cycle life is not necessarily better than a capacity-oriented pack, because high discharge itself generates more heat.

Does it degrade more slowly in an older body?

Usually yes. Older bodies draw less current, so the pack works in a gentler range, with less heat and slower growth in internal resistance. But that also means the premium you paid for high discharge capability never turns into real benefit.

Is a slightly warm battery normal?

Warmth after heavy recording is normal and subsides as it cools. If it is still clearly warm after resting at room temperature, or becomes unusually hot while charging, stop using it immediately and check the charger.

Can I charge an LP-E6P on a third-party charger?

A reliable dock charger is fine, but confirm that its cut-off voltage and current strategy match a 7.2V two-cell series pack. Chargers of unknown origin at unusually low prices carry higher risk; without complete overcharge protection, they are a common source of swelling and safety incidents.

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

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

1. 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.
2. Use a full pack for the important shot. Changing a battery costs seconds; reshooting may cost an afternoon.
3. 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.
4. 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.
5. 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.

Short answer: yes, it will fill. The LC-E6E is the OEM dock charger for the LP-E6 family, its charging voltage platform matches LP-E6P, and under normal conditions it brings an LP-E6P to full charge, with the body showing 100% as expected. Expect roughly two and a half to three and a half hours, slightly longer than or comparable to an LP-E6NH, depending on starting charge, ambient temperature, and the pack’s current condition.

One common misconception to clear up first: despite the P in the name and the higher positioning, LP-E6P did not change the voltage platform or add a charging port. Like LP-E6NH it is a 7.2V two-cell series pack, and neither has a USB-C charging port. To charge it you either use a dock charger or rely on the body charging the pack while running on USB-C PD power, and the latter depends on whether your specific body supports it.

One: why one charger serves two generations

A dock charger converts mains power into a charging curve of constant current followed by constant voltage, and the cut-off voltage is set by the battery’s chemistry. LP-E6, LP-E6N, LP-E6NH, and LP-E6P all share one voltage platform and the same cut-off voltage, so a charger is electrically interchangeable across them. That is also why Canon used only the LC-E6 / LC-E6E line for years.

The distinction worth making is between “it charges” and “the charging strategy is optimal”. LP-E6P’s selling point is sustained discharge capability, and its internal construction and protection board differ from a capacity-oriented pack, so its current acceptance during charging may differ too. An OEM charger adjusts current according to what the pack reports, which is why an OEM dock is preferable to a universal charger.

Two: estimating charging time

Those are range estimates, not promises. Lithium-ion charging has a constant-current phase and a constant-voltage phase: fast at first, slow at the end, and the last dozen percent often takes a third of the total time. So the difference between “empty to full” and “half to full” is smaller than most people expect.

Three: four factors that change charging speed

Temperature comes first. When the cell is too cold the charger deliberately reduces current or pauses, as a protection measure; when it is too hot, current is limited as well. Charging in an unheated room in winter therefore takes noticeably longer, and that is not a faulty charger.

Starting charge determines how soon the constant-voltage phase begins. The lower the charge, the longer the constant-current phase and the longer the total, but the fastest energy goes in early — twenty minutes of charging in an emergency usually gets you a usable amount.

Charger and cable only matter for in-body USB-C charging. A dock charger is unaffected by the cable. USB-C PD charging requires both the power adapter and the cable to support enough wattage; with too little, charging becomes very slow, or merely holds the charge steady.

Pack condition is the one most easily overlooked. An older pack with higher internal resistance reaches its constant-voltage phase earlier and stays there longer, which shows up as “charges forever but never fills” or “shows full, then drops immediately in use”. In that case the suspect is the pack, not the charger.

Four: troubleshooting a short fill, and charging habits

1. Try another pack first. Same charger, same outlet, a pack you know is good. If that one fills, the problem is the first pack; if it does not, the problem is the charger or the power supply.
2. Try another outlet and another charger. Rule out the simple causes such as a loose power strip or unstable voltage. Dock chargers tolerate a limited input range, and a poor power strip can genuinely cause trouble.
3. Watch the indicator light. OEM docks signal state with the light: steady usually means charging, slow blinking usually means waiting on temperature or waiting to start, fast blinking generally means a fault. If it blinks fast for a long time, unplug it, remove the pack, let it cool, and retry; if it repeats, stop retrying.

If all three steps fail and the pack is confirmed faulty, stop forcing it. Repeatedly charging a failing pack is one of the main routes to swelling and to genuine safety risk.

On habits: do not charge a pack immediately after a heavy recording session while it is still hot. Let it come down near room temperature first — that does more for longevity than any “care mode”. Do not leave a pack on the charger overnight; take it off when full. Do not charge in a car or in direct sunlight. For packs going into long storage, keep them at four to six tenths of charge rather than full.

Also, when two generations share one charger, label the packs. The habit costs almost nothing and prevents an aged pack from being carried out as the primary one.

For LP-E6P body compatibility and usage boundaries, see the LP-E6P category. The capacity-oriented LP-E6NH follows the same charging logic as described here; see the LP-E6NH category. For how low temperatures affect both charging and discharge, the general conclusions in cold-weather battery behavior apply. YO’s compatible LP-E6P also works with the LC-E6 / LC-E6E dock family.

FAQ

Is there a difference between LC-E6 and LC-E6E?

Both are OEM docks for the LP-E6 family. The main differences are the power plug format and the regional version bundled with the camera; the charging logic is essentially the same. There is no need to distinguish them in daily use, as long as the contacts and plug match.

Can I charge an LP-E6P with a phone charger?

Not directly. LP-E6P has no USB-C port, so it must go into a dock charger or sit in a body that supports USB-C PD input and lets the body charge it. Clamping a so-called universal charger onto the contacts is high risk and not recommended.

Does the indicator go out when charging is complete?

Most OEM docks switch to steady or off when full; check the manual for your unit. The most reliable way to confirm a full charge is to put the pack in the body and read the charge display, not to watch the light.

Does a new battery need a 12-hour first charge?

No. Lithium-ion cells are already formatted at the factory, so charging to full is enough. Extended overcharging brings no benefit and adds heat and aging.

Short answer: the differences between an OEM LP-E6P and a compatible pack such as YO’s come down to three things — whether the decoding protocol is complete, whether sustained discharge has headroom, and how consistent the protection board and cell grading are. In ordinary 4K recording and stills, most of that is imperceptible. Once you move to 8K-class or high-frame-rate sustained loads, the gap shows up as recording that stops early. On price, the OEM pack usually sits well above the budget bracket while compatible packs come in well below it; what you pay for is headroom and consistency.

One premise first: a compatible battery is not a counterfeit. A reputable brand sources its own cells, designs its own protection board, and builds to the electrical spec of the LP-E6 family, with dimensions and contacts that meet the standard, so it fits and powers the body normally. What deserves caution is the unbranded product with no protection board at all.

One: decoding — what the body actually sees

LP-E6 family packs contain a communication chip that exchanges information with the body over the contacts: model, charge level, temperature, cycle status, charging requests. Much of the body’s behavior depends on that data — remaining-shot estimates, when to warn about low battery, whether a heavy mode may start.

OEM packs are developed inside the same system as the body firmware, so data completeness is highest, serial numbers are traceable, and compatibility after firmware updates is assured. Compatible packs reproduce that protocol. A mature brand gets normal recognition, a correctly displayed percentage, and normal charge management, so daily use and judgment are unaffected.

Note that some firmware versions may show a notice for non-OEM packs, or omit secondary data such as per-cycle counts. That does not affect shooting, but it does reduce how precisely you can judge pack health. Also, any claim that “decoding lets you bypass body limits” is not credible — decoding exists so the body can manage the pack correctly, not to circumvent the body’s power protection.

Two: discharge — the part the spec sheet omits

The two rows that open the widest gap are sustained current capability and cell consistency. The first decides whether you can use the body’s top modes; the second decides how much is left after a year. Neither is visible on a spec page — only reputation and hands-on testing will tell you.

Three: price — what the gap buys

The OEM price covers cells and manufacturing, but also certification, quality control, distribution, and after-sales support, which is why it sits well above the budget bracket. Compatible packs drop part of that, so they cost clearly less — often the difference is enough for another pack or two.

Translate that gap into value and it becomes clear. If your body is an R5 Mark II or an R1 and you shoot 8K and high frame rates regularly, the OEM pack buys “it will not fail at the worst moment”, and the premium is worth it. If your work is routine 4K, interviews, and stills, a compatible pack handles it completely, and spending the saved budget on extra packs delivers more real benefit.

YO’s LP-E6P is positioned for the second case: it covers normal loads and pushes the price bracket down so the number of spare packs is no longer limited by budget. For video work that approach is often the more practical one — two cheaper packs in rotation are more reliable than one expensive pack stretched to its limit.

Four: a five-step check and a pairing suggestion

1. Check recognition. Does the body identify the model correctly, and does the percentage move continuously rather than jumping? Jumping usually points to a sampling or communication problem.
2. Check charging. Charge it in an OEM LC-E6E. Does it reach full, does the indicator behave normally, and does the body show 100% afterwards?
3. Check heavy load. Record on the same body at the same spec alongside a pack known to be good, and compare when each stops. A large gap means insufficient discharge capability.
4. Check heat. Under identical routine recording, a compatible pack that runs noticeably hotter has higher internal resistance, and its long-term life will suffer.
5. Check the build. Are the case seams even, the contacts evenly plated, and does it slide in smoothly? Fit and finish usually reflect what is inside.

Step three is the one most often skipped, and it is exactly what separates “it works” from “it holds up”. Run the whole check within a week of delivery so problems surface while returns are still easy.

A sound pairing is one OEM pack dedicated to top-spec modes plus one or two compatible packs for routine recording and backup. Heavy-load work is covered, everyday costs stay controlled, and the compatible packs absorb cycles, which actually extends the OEM pack’s life.

One more thing when buying: naming such as LP-E6+ exists in the market but is not an official Canon model — it is third-party labeling with inconsistent specs. Judge by the description of cells and protection board rather than by the name. For how the four generations interchange, see the LP-E6 category; for compatible naming, see the LP-E6+ page; capacity-led needs belong in the LP-E6NH category, and high-discharge needs back in the LP-E6P category.

FAQ

Can a compatible battery damage the camera?

Not in normal use, provided it is a reputable brand with a complete protection board. The risk comes from unbranded products without one, which may have no ability to cut off under over-current or over-temperature. Choosing a brand with clear after-sales support and published specs is the most effective way to avoid that risk.

What if the body says “not a Canon original battery”?

It is a firmware notice and does not affect operation. If restricted features appear alongside it — for example an unavailable top-spec mode — the pack’s communication or discharge capability does not meet the body’s requirement, and you should use a different pack. Whether the notice appears at all depends on both body model and firmware version.

Can I trust a compatible pack’s rated capacity?

Discount it. Some products quote the cell’s theoretical capacity rather than what can actually be delivered, and overstatement is possible. For real performance, how long it lasts in the same situation is far more reliable than the label.

Why is the OEM pack so much more expensive, and is it worth it?

It depends on how hard you work the gear. For heavy users of high-load bodies, a single early stop can cost far more than the price difference. Light users can cover their needs with compatible packs and turn budget into quantity. There is no universal answer — do the math for your own situations.

Short answer: LP-E6P is the fourth official battery in Canon’s LP-E6 family, introduced in 2024 alongside the EOS R5 Mark II. Its core change is not capacity but continuous discharge current — it is built for heavy loads such as high-bitrate video and fast bursts. It needs both body and firmware support to deliver its full capability; fitted to older bodies such as the 5D Mark III, 6D, 7D Mark II, or 5D Mark IV, it typically behaves as an ordinary LP-E6-class pack, and in some cases may not even be recognized. Calling it an upgraded LP-E6NH misses the point: the two solve different problems.

This article moves through three layers: what actually changed, who can use it fully, and what older bodies will run into.

LP-E6P changes discharge, not capacity

From LP-E6 to LP-E6NH, Canon’s upgrade path was all about capacity: 1800 → 1865 → 2130mAh. With LP-E6P, the thinking changed.

High-bitrate video (8K, or high-frame-rate 4K) and fast bursts share a trait: both instantaneous and continuous current demand are high, and the demand lasts. If the pack cannot discharge fast enough, voltage gets pulled down, and the body either throttles, limits recording time, or reports low battery and stops. That bottleneck is exactly what LP-E6P targets.

So when reading LP-E6P specs, the number to focus on is not mAh but “how much current it can deliver steadily, and for how long”. This is also why so many older bodies feel “about the same as LP-E6NH” with it fitted — those bodies never needed that much current, so the extra capability goes unused.

Four official generations compared

All four share the same shape and will fit any body that accepts the LP-E6 family. The row most often misread is the last one: the body column says “new bodies that support high discharge”, not “all bodies”. Fitting is not the same as using the capability.

Compatibility in three tiers

Tier one: full capability

The EOS R5 Mark II is currently the main target for LP-E6P, with both power circuitry and firmware adapted for high discharge. Only on this body does LP-E6P deliver its value in high-bitrate recording and fast bursts.

Tier two: works, but not fully used

The EOS R5, R6, R6 Mark II, and R7 can all shoot on LP-E6P. But they were designed around LP-E6NH and do not need higher continuous current. There is no problem fitting it, and no obvious benefit either — a case of “it works, but there is no reason to buy it deliberately”.

Tier three: degraded operation or recognition errors

Older bodies such as the 5D Mark III, 6D, 7D Mark II, and 5D Mark IV were never adapted for LP-E6P in either circuitry or firmware. The usual outcome: it powers on and shoots, but is treated as an ordinary LP-E6-class pack. Some bodies fail to recognize it, show odd charge readings, or even report a communication error. The pack is not broken; the body simply does not know it.

If you own one of those older bodies, there is no reason to buy LP-E6P as an “upgrade”. Their bottleneck is the body, not the battery. For context, compare the LP-E6 base model and the LP-E6NH category.

Charging: still no built-in port

Like LP-E6NH, the LP-E6P pack itself has no USB-C charging port. No battery in this generation of the LP-E6 line offers in-pack charging, so you charge in the LC-E6 / LC-E6E dock, or charge the pack inside the body over USB-C.

• OEM dock. LC-E6 and LC-E6E belong to this family and will charge LP-E6P; charging time varies with capacity, temperature, and dock model.
• Third-party dock. Confirm the label lists LP-E6P. Older docks marked only for LP-E6 / LP-E6N may take longer or fail to reach full charge because the charging curve differs.
• In-body charging. Suitable for emergencies; charging while shooting a long heavy session adds extra heat.

A practical rule for a shoot day: plan on one pack per hour of intensive recording, and make the dock charger, rather than in-body charging, your main way of topping up.

Who should buy LP-E6P

1. EOS R5 Mark II owners. Buy it — this battery was designed for that body.
2. Anyone shooting high-bitrate video with long continuous takes. Even if your body is not an R5 Mark II, confirm the body supports it before deciding.
3. Teams sharing packs with an R5 Mark II. Standardizing on LP-E6P simplifies gear management, and older bodies can still use it as an ordinary pack.
4. Everyone else. LP-E6NH is better value: same capacity class, lower cost, wider compatibility.

Third-party products at this spec level are still catching up, with uneven recognition and discharge behavior. YO offers alternatives across the LP-E6 line, but for a model as dependent on body adaptation as LP-E6P, OEM should come first. Details are in the LP-E6P category.

FAQ

Does LP-E6P have more capacity than LP-E6NH?

They are in the same capacity class. LP-E6P’s upgrade is continuous discharge capability, not capacity. On a lower-draw body, switching to LP-E6P will not produce a noticeable runtime gain.

Can LP-E6P be used in a 5D Mark IV?

Physically it fits, but the 5D Mark IV firmware was not designed for it, so it typically runs as an ordinary LP-E6-class pack, and some bodies show recognition or charge-display errors. It is worth trying as an emergency supply; it is not recommended as your daily pack.

Does LP-E6P have a USB-C charging port?

No. No battery in this generation of the LP-E6 line has one, so you must use a dock charger or charge in the body over USB-C.

Why does an older body report low battery with LP-E6P fitted?

Older bodies estimate charge from a voltage curve, and LP-E6P’s discharge characteristics differ from the profile those bodies expect, so the estimate drifts. It does not mean the pack is empty, but it does affect your judgment, which is why this combination should stay an emergency option.