The voltage of my batteries is not enough to move the focus motor of my telephoto lens?

[Fer.Saravia]

I came across this publication (https://josebruiz.com/blog/lo-que-los-fabricantes-no-dicen-mi-teleobjetivo-no-enfoca-bien/) where a photographer states that poor focusing results and high rates of out-of-focus photos could be due to the fact that the 7 Volt batteries are not strong enough to move the focusing motor of some "heavy" telephoto lenses fast enough.

There, they say things like:

-It is very logical to think that if a focusing motor turns (for example) at 15.000RPM with a voltage of 7.2V and at 21.000 RPM with a voltage of 11.1V, then with the 11.1V it will manage to acquire a better (faster or more accurate) focus.

-Of course the focusing systems are different in higher end models, but that is not as influential as the battery voltage in getting results.

-Of course if the focusing system works by contrast, we will get better results with good light and bright lenses, but these lenses are the ones with very heavy lens groups that need that extra voltage that "low end" cameras do not have (7 volts).

I have never heard or read anything similar.... What do you think?

 

[John Navitsky]

it’s hard to say. there are dc to dc step up circuits so voltage mismatches between batteries and workloads need not be a problem

however, i suspect there may be situations where certain cameras were not optimized to drive certain lenses

and there is a lot of opportunity for nuance. for example the camera mfg could choose not to drive some big lens at full speed because they want to conserve the battery budget with that specific body

so, there could be battery considerations, but i doubt it’s a literal voltage issue

 

[Mal Paso]

DC motors run faster with higher voltage, they also burn up faster to say nothing of the control circuits.

This sounds like speculation based on a very small amount of information.

Tossing old batteries as capacity declines is as far as I would go.

 

[NorthernFocus]

In my experience Nikon "flagship" DSLRs with big prime lenses certainly seem to focus faster than the same lens on bodies with smaller batteries. But honestly I've never tried to quantify the difference. Without further information it's hard to say whether battery voltage(or capacity) is the reason vs something else in the AF system. The statement quoted in the OP about DC motors turning faster at higher voltage is accurate. However we don't know if a lens actually sees the different voltage or if the camera normalizes voltage/wattage to the lens. I know @Steve has done a good bit of testing of AF speed between lenses. Can't recall if he's compared a given lens on different bodies.

 

[Calson]

I have never seen this in all my years. Lithium ion batteries are designed to provide maximum voltage until they die. Some cameras have stronger motors and can focus a lens faster but that is different than not focusing properly. My D5 was noticeably fast to focus with any telephoto lens than the D850 with it powered by the EN-EL18 battery in the accessory grip.

I have had two Nikon E lenses experience autofocus module failures in less than 2 years of use and this was a complete failure with no warning. It is conceivable that the electronics can be failing and not functioning properly but this is a lens and not a camera issue.

 

[Vincent_VdB]

I read the article and I was hoping to read proof to the claim but none was given. Second, it is comparing older gear with a flagship body vs prosumer.
Per today do we have with Nikon 2 very comparable bodies but one has a low(er) voltage battery (Z8) and the other a high(er) voltage battery (Z9).
Many here, including myself, have a Z8 & Z9 side by side and _for me_ do I not see a difference in both AF accuracy and keepers rate.
Equally shot my D5 and D850 side by side and found no difference in the same 2 fields being AF accuracy and general keepers rate.

This is for me an article that makes unfounded claims and for sure not relevant in the Nikon realm when comparing the the said DSLR and ML models.

 

[Fer.Saravia]

Thank you for your answers. I also believe that there is no evidence for what the article claims. And I think it would be foolish to hinder the performance of 10k lenses by not being able to use $125 batteries.