Question - Auto focus speeds & Battery Grips

[Wrathwilde]

Does the added battery in the battery grips help drive the autofocus faster in the 7d & 5d3? Tried searching google but just came up with noise that didn't answer the question, just had all the search words. Anybody know if the grips help drive the lenses any faster?

 

[Drizzt321]

No, they do not. The 1D series has always driven the AF for 'select' lenses faster, but that's due to the higher battery voltage, not the built-in grip.

Now, in theory I suppose the grip might keep the AF running at peak speeds on the 7d/5d3 because it has 2 batteries so it keeps the available power up to spec for longer, but I can't think of any other effect it might have on the AF system.

 

[Loswr]

The 1-series bodies use higher voltage batteries, which drives the lens AF motor faster. The two lower-voltage batteries in a grip are used alternately, not simultaneously, so no boost.

 

[Drizzt321]

The two lower-voltage batteries in a grip are used alternately, not simultaneously, so no boost.

I didn't mean to imply that with a grip it can increase the AF speed. I was referring to the fact that as a battery is almost completely drained it can provide a slightly lower voltage. So a battery grip, since it provides more total energy stored, can keep the rated voltage longer.

 

[Mt Spokane Photography]

The two lower-voltage batteries in a grip are used alternately, not simultaneously, so no boost.

I didn't mean to imply that with a grip it can increase the AF speed. I was referring to the fact that as a battery is almost completely drained it can provide a slightly lower voltage. So a battery grip, since it provides more total energy stored, can keep the rated voltage longer.

The power and voltage of a Li-on battery does not drop off like a regular battery. Circuitry internal to the battery monitors it, and throws a electronic switch when it senses that it is nearly discharged. Any drop in voltage is very small.
This is noticibly apparent in my DeWalt Drill Driver which uses a Li-on battery. It drives screws, even difficult ones with full strength, and suddenly shuts off while driving a screw, it does not fade away like nimh ot nicad batteries.
There is a good reason for this, a Li-on battery cannot stand being fully discharged, if that happens, it cannot be recharged without some special equipment. So the battery may shut down when it gets to 10% or so of capacity.

 

[Drizzt321]

The two lower-voltage batteries in a grip are used alternately, not simultaneously, so no boost.

I didn't mean to imply that with a grip it can increase the AF speed. I was referring to the fact that as a battery is almost completely drained it can provide a slightly lower voltage. So a battery grip, since it provides more total energy stored, can keep the rated voltage longer.

The power and voltage of a Li-on battery does not drop off like a regular battery. Circuitry internal to the battery monitors it, and throws a electronic switch when it senses that it is nearly discharged. Any drop in voltage is very small.
This is noticibly apparent in my DeWalt Drill Driver which uses a Li-on battery. It drives screws, even difficult ones with full strength, and suddenly shuts off while driving a screw, it does not fade away like nimh ot nicad batteries.
There is a good reason for this, a Li-on battery cannot stand being fully discharged, if that happens, it cannot be recharged without some special equipment. So the battery may shut down when it gets to 10% or so of capacity.

Ah, ok. I know Li-ion are a different kind of battery, didn't know that they don't 'wind down', and simply stop discharging when they get to low before any real voltage-dropoff can occur.