Qsn: How does a battery grip manage power from 2 Li-ion rechargeable batteries?

I am referring to a 5D and BG-E4. I only have an original BP-511 (relatively newer and better in terms of capacity) and 2 other 3rd-party batteries. My concern is that the batteries were purchased at different time and there may be a gap in condition (voltage, capacity). I usually used them individually in the camera. But now i would like to add the battery grip to improve handling when using a heavier lens

May I know how a battery grip (BG) manage power from 2 Li-ion rechargeable batteries?

Normally, a BG takes an array of 6 AAs in a tray which gives a typical 7.2V that is equivalent to 1 Li-ion. So I assume all 6 works at the same time.

I'm interested to know what goes on inside when the BG is loaded with 2 standard Li-ion rechargeable batteries. Does it switch from one to another, or work in parallel?

If it switches, would there be an indication or marking on which chamber is 1st priority? This method (if so) is of lesser concern in that I would incline to put the better battery in there, and a backup battery in the other chamber, while have a 3rd battery in the pocket.

On the other hand, if 2 chambers work in parallel, I would have to consider changing all my batteries to the same brand and capacity because I am quite sure the batteries I have varies in voltage and may not be efficient when used in parallel.

Good question and I'll relate my experience with a 5D3 and genuine Canon grip.

Not had the 5D3 for many months and recently did a wedding gig with it. A 14 hour day didn't hardly touch the power level with two genuine Canon batteries but when I checked the battery condition the next day the batteries each showed a different shutter count ...

My conclusion from this (as it's not the first time I've noticed this, just the first wedding I did with it) is that the 5D3 'manages' it's batteries and draws from which ever it needs to. My 10D and 40D don't have a shutter count for the batteries so I don't know when this system of managing the batteries came in. Most probably is on the 5D.

Thinking about it, I suppose this is how it should be as otherwise the battery indicator would be lying if it said half full for instance as you would not know in the field which battery needs to be swapped out.

Assuming Canon have maintained the same system since 20D, 1 batt at a time.
I can't remember which one is used first. Easy to check, charge 2 batts, use camera and see which one has depleted.

Choderboy wrote in post #18113456
Assuming Canon have maintained the same system since 20D, 1 batt at a time.
I can't remember which one is used first. Easy to check, charge 2 batts, use camera and see which one has depleted.

Not according to Canon they don't it seems:

"Rudy Winston Wrote

Yes, Canon's battery packs for EOS cameras which accept two battery packs have always worked this way. If the unit senses different power in the two batteries, the one with the higher power is used first, and once their voltage becomes equal, power is drawn simultaneously from both batteries."

I have had battery grips on several bodies (20D, 40D, 7D mk1, 5D mk1 and mk3) and every time I took the batteries out to charge them that I remember one was much closer to dead than the other which leads me to believe what Choderboy stated is indeed correct.

This is of course just my extremely unscientific experience. lol

Travis Ingle wrote in post #18114754
I have had battery grips on several bodies (20D, 40D, 7D mk1, 5D mk1 and mk3) and every time I took the batteries out to charge them that I remember one was much closer to dead than the other which leads me to believe what Choderboy stated is indeed correct.

This is of course just my extremely unscientific experience. lol

Page 20 of the .pdf here:

http://www.robgalbrait​h.com …/rebel_xt_white​_paper.pdf

This forum also confirms the info:

https://photography-on-the.net …/showthread.php​?p=2625908

LincsRP wrote in post #18113554
Not according to Canon they don't it seems:

"Rudy Winston Wrote

Yes, Canon's battery packs for EOS cameras which accept two battery packs have always worked this way. If the unit senses different power in the two batteries, the one with the higher power is used first, and once their voltage becomes equal, power is drawn simultaneously from both batteries."

Yes, this is true.

When the levels of the two batteries have equalized (or when two good freshly charged batteries are inserted), the camera alternates between the two batteries shot for shot (which can be seen by the shutter count).