Short answer: most of the difference is capacity, and the discharge behavior is secondary, though it gets magnified under heavy load and in cold weather. A Canon original LP-E17 is rated about 1040mAh / 7.5Wh, and the 750mAh battery is the smallest of three self-defined tiers, at roughly seven tenths of the original on paper. In other words about seventy percent of the gap comes from holding less charge, and the remaining part comes from the discharge plateau, internal resistance and protection-board behavior.
It is worth separating the two layers, because that is what decides whether the original is worth its higher price. If all you need is more time, an extra battery covers the capacity gap. If what you care about is stability in extreme conditions, that is where the original earns its money.
Layer one: capacity, the bulk of it
Capacity is the most obvious difference. 750 against 1040 is a gap of about 290mAh, close to 28%. That gap is invisible in light use, where a few dozen frames indoors are covered by either battery, but in continuous location work, bursts or video, where total draw is high, 28% translates directly into a swap half an hour earlier.
Note that nominal capacity and usable capacity are not the same thing. Manufacturers quote cell capacity under standard conditions, while how much the body can actually draw also depends on the cut-off voltage and the protection board’s trip point. Precise arithmetic from the nominal figure is unreliable; order-of-magnitude comparison is fine.
One common misunderstanding is worth clearing up here. Canon officially makes a single model, the LP-E17, and there is no official LP-E17H. What you see sold as LP-E17H is mostly a trade name some third parties give their own higher-capacity version, a seller’s label rather than a Canon model. Judge a battery by its rated capacity and the origin of its cells, not by a suffix that implies factory approval.
Layer two: discharge plateau and internal resistance
Two batteries both rated 7.2V do not follow the same voltage curve as they discharge. A higher-capacity cell sags more slowly under the same load current and stays inside the body’s working range for longer; a lower-capacity cell falls away more steeply once it reaches the later stage.
Internal resistance shows up in short bursts of high current. Focus motors starting, the mirror and shutter firing in a burst, and the continuous writes of video recording are all pulsed loads. A battery with high resistance drops more voltage at those moments, and the body’s power management can read that as low battery. This is why some batteries show charge on the gauge and report empty the moment you hold down the burst.
In everyday shooting this layer is usually imperceptible, but it becomes obvious under two conditions: cold, and below about thirty percent remaining. For winter work outdoors, keep the 750mAh in an inside pocket and fit it only when needed, letting body heat preserve its discharge capability.
Layer three: protection board and consistency
| Spec | Original LP-E17 | 750mAh battery |
|---|---|---|
| Nominal capacity | About 1040mAh | 750mAh |
| Nominal energy | About 7.5Wh | About 5.4Wh at 7.2V |
| Discharge plateau | Small sag under heavy load | Slightly steeper at the end |
| Protection | Overcharge, over-discharge, overcurrent | Same functions; thresholds as stated by the maker |
| Cell consistency | Tight batch control, little sample variation | Reputable brands grade cells too, with slightly wider variation |
| Price | Higher | At the budget end of the market, clearly lower |
The protection board is the item most often ignored. It prevents overcharge, over-discharge and short circuits, and a battery with conservative thresholds will cut out earlier and look like a smaller capacity, while an aggressive setting can push the cell deeper, which flatters short-term capacity at the expense of long-term life. There is no common standard here; the maker’s specification is all you have.
Consistency means how closely batteries from the same batch behave alike. Factory batch control is usually tighter, with little variation; good third-party brands also grade their cells, but the spread tends to be wider. For an ordinary user this shows up as the battery in your hand possibly not matching the battery in a review.
So how should you choose
Choosing by use is more practical than choosing by brand. For everyday shooting, spare duty and light travel, the 750mAh is entirely adequate at a clear price advantage, and one extra battery closes the capacity gap. For long continuous sessions, cold conditions, or work that cannot be repeated, the original or a larger tier is worth the money.
The point of this tier is that it is cheap enough to keep several. If your habit is to carry two spares anyway, then trading the price of one original battery for two or three 750mAh batteries leaves you with more total capacity. To open the margin further, look at the 950mAh version; to compare all three side by side, see the capacity and compatibility guide.
FAQ
Is 750mAh mislabeled? Why is it so much lower than the original?
No. 750mAh is one tier in a capacity range, and a Canon original at 1040mAh is a different product to begin with, so there is no premise that the two should match. Whether a battery is honestly rated depends on whether its actual discharge capacity approaches its nominal figure, not on how it compares with another model.
Does mixing batteries affect the camera body?
No. The body identifies a battery by voltage and communication, not by capacity. Alternating between the original and the 750mAh is common practice; just charge each battery on its own and never try to run them in parallel.
Why does an old battery suddenly report low battery during a burst?
That is the classic symptom of rising internal resistance. A burst is a pulsed high-current load, so a high-resistance battery sags sharply, the body judges the voltage insufficient and warns, and the voltage recovers once you release the shutter. Such a battery is unfit for important work but can still serve for static shooting.
Is LP-E17H Canon’s high-capacity version?
No. Canon officially makes only the LP-E17, and there is no LP-E17H. The suffix is what some third parties call their own higher-capacity version, so it is safer to judge by rated capacity and cell origin.