Camera Flash Current Draw on 4 NiMH

[gchronis]

Hi,

I just bought a C9000 and I'm trying to determine a battery discharge rate similar to that of my application. Other than my flashlights, which average to about 500 mA, I use Imedions for my camera flashes. Does anyone have any idea of an approximate current draw of a camera flash? I specifically use a Canon 580EX II and a few 430EX's.

I guess I could measure it but I can't figure out an easy way to connect my meter in-line while the camera is charging the flash.

I am just trying to determine an approximate discharge rate, so that I can get an accurate mAh reading from the C9000, when using the discharge function. Also, I would like to charge at the same rate that the flashes discharge.

Thanks!

 

[NiOOH]

AFAIK the C9000 discharges at 1 amp and the average discharge rate is determined by the duty cycle, i.e. 500 mA average rate would be 1000 mA with 1/2 on 1/2 off cycle.

Regarding current draw of you flashguns, I don't know, but can offer you an experiment that can estimate it.

1. Charge your Imedions on the C9000 at 1000 mA (default setting) and let them top-off for two hours after the end of the quick charge. Even better, run a R&A cycle with 1000 mA charge and 800-1000 mA discharge and note the capacity of the cells.
2. Set your flashgun at something like 1/2 power and start firing it manually, counting the recharge time after each burst untill the batteries are fully discharged.
3. At the end of the experiment, add all recharging times, and divide the battery capacity (should be around 1900-2000 mAh) by the time sum expressed in hours. This would give an estimate of your average current draw.

Hope this helps.

 

[Mr Happy]

I am just trying to determine an approximate discharge rate, so that I can get an accurate mAh reading from the C9000

The capacity of NiMH does not vary very much with discharge rate, so almost any rate will do. You might want to do discharge tests at 1 amp and at 200 mA and get a feel for the spread.

 

[gchronis]

AFAIK the C9000 discharges at 1 amp and the average discharge rate is determined by the duty cycle, i.e. 500 mA average rate would be 1000 mA with 1/2 on 1/2 off cycle.

I'm not so sure how exactly it discharges, but it lets you choose what your (average?) discharge rate is from a range of 100mA to 1000mA. According to what I've read, if I set this discharge rate to what my application's discharge rate is, I can see exactly how many mAh the battery will carry for my application, when discharging is complete. This is why I'm trying to determine my application's current draw.

Regarding current draw of you flashguns, I don't know, but can offer you an experiment that can estimate it.

1. Charge your Imedions on the C9000 at 1000 mA (default setting) and let them top-off for two hours after the end of the quick charge. Even better, run a R&A cycle with 1000 mA charge and 800-1000 mA discharge and note the capacity of the cells.
2. Set your flashgun at something like 1/2 power and start firing it manually, counting the recharge time after each burst untill the batteries are fully discharged.
3. At the end of the experiment, add all recharging times, and divide the battery capacity (should be around 1900-2000 mAh) by the time sum expressed in hours. This would give an estimate of your average current draw.

Hope this helps.

That's a good idea. If nothing else comes up, I'll go ahead and try it, though it'll take some time and will heat up/tax the flash a bit. I probably won't be able to see anything afterwards either :sick2:

Thanks!

 

[gchronis]

The capacity of NiMH does not vary very much with discharge rate, so almost any rate will do. You might want to do discharge tests at 1 amp and at 200 mA and get a feel for the spread.

Oh, ok. I'm pretty sure I read somewhere that I should discharge at the same rate as my application. Can't find a quote, though, cause I've been reading up on charging here for a couple of weeks :huh:

I guess a spread would do fine. I'm now starting to become curious as to how much current each flash recharge draws. I'll see if I can track down a guy with a scope to take a look at it over time. It charges some capacitor, so it most probably is not a constant draw.

Thanks!

 

[Mr Happy]

Oh, ok. I'm pretty sure I read somewhere that I should discharge at the same rate as my application. Can't find a quote, though, cause I've been reading up on charging here for a couple of weeks :huh:

That is important with, say, alkaline chemistry since their capacity varies tremendously with load conditions. However, the measured capacity of a good quality NiMH will not likely vary by more than a few percent between 100 mA, 500 mA and 1000 mA discharge rates. 1000 mA is actually quite low for cells which can often perform decently at 5 A or higher discharge rates.

 

[Mike Painter]

Hi,

I guess I could measure it but I can't figure out an easy way to connect my meter in-line while the camera is charging the flash.

I am just trying to determine an approximate discharge rate, so that I can get an accurate mAh reading from the C9000, when using the discharge function. Also, I would like to charge at the same rate that the flashes discharge.

Thanks!

A camera flash works on very high voltage. Current draw will be a trade off between maximizing battery life and minimizing time between flashes. I'd bet a nickel that almost any charger will charge at a higher rate and I'd bet a dime that the "15 minute" chargers do.

 

[gchronis]

That is important with, say, alkaline chemistry since their capacity varies tremendously with load conditions. However, the measured capacity of a good quality NiMH will not likely vary by more than a few percent between 100 mA, 500 mA and 1000 mA discharge rates. 1000 mA is actually quite low for cells which can often perform decently at 5 A or higher discharge rates.

Aha! Great piece of info, there. I hadn't realized that. This will save me some time.

Thanks!

 

[qwertyydude]

My Olympus flash uses 2 AA batteries and a multi-step capacitor charging system. It peaks at 3 amps but averages about 2 amps. So your flash is probably similar. Seeing as the big 4 AA flashes tend to be more powerful.

 

[UnknownVT]

I use Imedions for my camera flashes. Does anyone have any idea of an approximate current draw of a camera flash? I specifically use a Canon 580EX II and a few 430EX's.
I guess I could measure it but I can't figure out an easy way to connect my meter in-line while the camera is charging the flash.

Measuring it yourself probably is the best way to determine the current draw.

If it's of any help - there is a measurement of the built-in flash on a Pentax K200D dSLR which uses 4x AA (and various other draws) in Post #23 (link) in the thread - K200D Battery Meter Problem over at the Pentax dSLR forum.

The reading obtained was 1.480 Amps when charging the flash on the Pentax K200D dSLR -
this may help as a ballpark level for your own measurement.

EDIT to ADD - just read qwertydude's response above where on 2x AA his camera's flash was drawing 3 Amps peak -
this would be in line with the Pentax K200D's flash with 4x AA drawing 1.48Amps -
as the total peak power (watts) drawn are both about 7.2 watts.

 

[gchronis]

Ok, great responses. I'll measure it myself, but this helps a lot. It does give me a pretty good idea and that's what I was asking.

Thanks, all!

 

[TakeTheActive]

...I'm pretty sure I read somewhere that I should discharge at the same rate as my application. Can't find a quote, though, cause I've been reading up on charging here for a couple of weeks :huh:

This rings a bell with me as something from SilverFox, but, as you say, finding it again will take time. IIRC, it related to crystal size:

• FAST discharge requires small crystals so that they can release their energy quickly.
  .
• SLOW discharge can tolerate larger crystals because it can 'wait' for them to break apart into smaller crystals and release their energy.

Try looking at the SilverFox LINKs related to 'Charging' and 'Crystals' in my Sig Line LINK.

 

[bhvm]

http://www.candlepowerforums.com/vb/showthread.php?t=237641

camera Phone LEDs?
lets discuss.

 

[txg]

In my opinion, the numbers over here are way too low. The 580ex II is a very bright and very fast flash, and although i haven't measured this one myself, i would rather estimate the current in the beginning of recharging the capacitors in the range of 8 Amps.

 

[Chodes]

In my opinion, the numbers over here are way too low. The 580ex II is a very bright and very fast flash, and although i haven't measured this one myself, i would rather estimate the current in the beginning of recharging the capacitors in the range of 8 Amps.

You get the prize!
I just tested my 430EX. Just used a piece of foil across 2 cells , meter on the other two cells. Used full power flash in manual mode - over 8 amps with eneloops. About 9point something to start , but probably 6A within 1 second, about 3A in around 2 seconds.

I've got a 580EX , I think it will be similar. Th 580EXII recharges much faster , suspect it sustains a higher current.

FYI , standby current for the 430EX is 60ma

 

[koala]

Please have a look at this, see second page too. Might help you with your numbers.

Sanyo Eneloop vs PowerEx Imedion. in a Nikon SB800.