Canon EOS 1V battery voltage drop

I recently purchased a LN Canon EOS1V with 6 total rolls used on the camera. The first roll was perfect shooting with the EF 85mm 1.2LII, no hiccups. I loaded my second roll and got about 10 exposures in and it started to rewind the roll of 36 exposures. I then noticed on the LCD, that the battery level went from full to 1/3rd with the push of the shutter. I know the EF 85mm has a lot of elements to move, but never expected the 2CR5 that was @5.83v to get only one roll when the camera is rated for at least 50 rolls! I mounted the EF 28mm f/1.8 and had no issues with the battery or rewind. However, whenever I mounted the EF 85mm 1.2LII it drew the battery down each time. My thinking is the camera rewinds automatically when the voltage drops. Has anyone also experienced this on their 1V's? All contacts were cleaned on both the camera and lens, but no joy. Is this a short in the board and can it be fixed to handle an EF 70 200mmf/2.8 for more than a few rolls before changing the 2CR5's?

I had the 1V for a few years as well as the 3 before it with three 2.8L zooms covering 16mm to 200mm + a few other fixed ef lenses. Shot hundreds of rolls and don't recall a battery lasting only 1 or 2 rolls. I do recall I was motivated enough to get the power booster and used lithium batteries in it which seemed to last forever.

johnld said:

the 2CR5 that was @5.83v

Click to expand...

I measured a new 2CR5 just now, which reads 6.4V unloaded.
An old and mostly used up one I took from one of my EOS cameras reads 5.5V. That one is pretty much toast.

Maybe just try a new battery? Also try a different brand. There's considerable variation between batteries. Ask @xkaes!

If new/other batteries don't help, there might be a problem with a leaky electrolytic capacitor in your camera, although the EOS cameras aren't very notorious for it. Still, they're also getting old, and electrolytic capacitors have a limited lifetime. Especially under high load conditions, a weak capacitor will start giving trouble and may 'trick' the camera into thinking there's a low battery condition.

Thanks for the info. I have tried different lithium batteries, but still the EF 85 pulls down the voltage. Can the capacitor be replaced?

koraks said:

I measured a new 2CR5 just now, which reads 6.4V unloaded.
An old and mostly used up one I took from one of my EOS cameras reads 5.5V. That one is pretty much toast.

Maybe just try a new battery? Also try a different brand. There's considerable variation between batteries. Ask @xkaes!

If new/other batteries don't help, there might be a problem with a leaky electrolytic capacitor in your camera, although the EOS cameras aren't very notorious for it. Still, they're also getting old, and electrolytic capacitors have a limited lifetime. Especially under high load conditions, a weak capacitor will start giving trouble and may 'trick' the camera into thinking there's a low battery condition.

Click to expand...

Just curious, but how many rolls does one average on the 1z using just the one 2CR5 and not the battery grip?

I don't know. I don't have a 1z (nor a 1v). And with the EOS 50e that I do use that uses 2CR5's I never kept count.

So far I have about 10 rolls on my 1V and the battery is still going. I use a 70-200 F2.8L IS III, 24-70 2.8L II, and a 100-400L IS II.
I took my power grip off to make the camera less bulky.

Thanks for that info. Good to know it can pulll heavy glass and maintain voltage. I'm curious if it's the EF 85mm 1.2LII. This does not occur when using my only other EF lens; the EF 28mm f/1.8. My choice for this camera would be the 35mm f/1.4 or the 50mm 1.2.. so hopefully these'll work on the 1V.

I prefer the BP-E1 grip on the 1 series cameras, it lets you use rechargeable AAs, but doesn't add the bulk of the power/drive boosters. 40-50 rolls seems to be about normal on a set of AAs, using varied IS and non IS lenses. I've never experienced a premature rewind due to a low battery, however, rarely, a bulk loaded roll of film will rewind early; the camera goes by tension to determine when to rewind and sometimes a 'sticky' roll will trigger the rewind.

The 85mm 1.2 (and 50/1.0, being of a similar design) is notorious for being slow to focus due to moving fairly large elements around, other lenses, the 'big whites' like the 300/2.8, 500/4, etc use internal focusing via smaller elements that shouldn't require a ton of power to run. I found this thread about the 85/1.2 II and battery drain issues, perhaps this is an issue with that lens model specifically?