DSLRUsers.com

A mate was shooting a school graduation and was taking 2 shots of each person as they got their certificate. His SB-900 shutdown due to overheating. He took it outside and removed the batteries, which were very hot and it cooled down. Is the overheating normal? I have looked through the forum but I haven’t found anything.

He did go back after and put the ISO to 800, moved closer and only took one shot of each person and didn’t have any more problems. Do you think that this is an issue with the flash or has this happened to others? I have never has this issue with my SB-900.

Depends on his settings at the time. If he was shooting at F11 @100 ISO and was standing well back....using a bit of focal length to bring his subject closer...then yes....the gun would overheat if he was using it fairly consistently. Consider...if he was using F8 instead, then the gun would only have to put out half the amount of light. If he then changed to F5.6 then half the amount again and so on. If heavy flash use is anticipated then F4 at ISO 200 or 400 would be a lot easier on the gun. So too, getting a little closer to the subject would also ease the burden on the gun.

Matt. Yes you are correct. It sounded like the flash was on or close to full power. I couldn't tell you the distance, but he made it sould like it was further back than he should have been. I assume that he was on ISO 200 (Nikon D700) before changing it to 800. He changed it to F4 where I think it may have been F5.6.
So changing the above would have lowered the power quite a bit. Maybe from 1:1 to 1/8 or less.

Yes it is normal. I did a test firing whenI got mine & this happened to me. You can disable the temperature sening, but would you eally want to? I suspect it has to do with the "high effficiency recharge circuit" in them. It must draw a higher current from the batteries (TAANSTAFL for ATJ ). If you really need rapid cycle & lots of photos, an external battery pack (or two!) would be the way to go.

the sb900 overheating issues are pretty well documented. while this is not a "fault" per se. its an issue that most of us have to deal with. i only find it an issue when i shoot in daylight and try to overpower the sun @ 1/1.

Sounds like that flash got tortured. I am not suprised that it overheated, but was 800ISO really needed afterwards?

Cameron, I suspect that the ISO of 800 was just to make sure that it didn't happen again.

Mr Darcy, does the external battery pack help? Is it the batteries overheating that triggers the shutdown, the internal circuits or both?

I would think that if the flash was truly overheating, an external battery pack would make it worse, not better. The overheating would either be caused by the rapid flashes of the tube or by the frequent recycling of the capacitor (or both). An external battery pack would just make it easier and quicker to do both.

ATJ wrote:I would think that if the flash was truly overheating, an external battery pack would make it worse, not better. The overheating would either be caused by the rapid flashes of the tube or by the frequent recycling of the capacitor (or both). An external battery pack would just make it easier and quicker to do both.

That is my worry. Does anyone know if the external battery pack would make it better or worse?

I don't think the issue is so much with the SB-900 itself, but rather the usage of the batteries.

If you rapidly discharge batteries (as flashes are very capable of doing) .. the battery heats up. Also, different batteries handle this rapid discharge better than others, so maybe he could try a different type next time.

The SB-900 has as sensor that picks up this heat and stops working. Usually a quick replacement for cold batteries will fix the issue.

Cheers

Hi,

We have 4 x SB800's and 1 x SB900. The SB800's have the 5th battery fitted and we have used an external battery pack on them. never had an isue with a SB800. Our SB600 died but he SB800's have been a good reliable work horse. So we purchased a SB900 for more power and ease of use and it's been good on both those accounts. However while shooting a wedding or event I have to swap to the SB800 as the SB900 overheats after firing rapid (many) shots.

This can be a real issue while the bride is halfway down the church or a moutain bike rider is in mid flight for example. So we stick with the SB800 when we know we'll have lots of shots to take with flash in a short period of time.

Hudo

Looking at the manual for the SB-900, it appears the overheating and thermal cut-off are more a function of the number of times the flash is fired in quick succession rather than heat being generated by the batteries.

It even provides a table of the maximum number of continuous firings (a 6 frames/sec.).

It does warn about the batteries getting hot but doesn't relate that to overheating or thermal cut-out.

Hudo wrote:Hi,

We have 4 x SB800's and 1 x SB900. The SB800's have the 5th battery fitted and we have used an external battery pack on them. never had an isue with a SB800. Our SB600 died but he SB800's have been a good reliable work horse. So we purchased a SB900 for more power and ease of use and it's been good on both those accounts. However while shooting a wedding or event I have to swap to the SB800 as the SB900 overheats after firing rapid (many) shots.

This can be a real issue while the bride is halfway down the church or a moutain bike rider is in mid flight for example. So we stick with the SB800 when we know we'll have lots of shots to take with flash in a short period of time.

Hudo

i found exactly the same thing. my sb800 and sb28 has never had the same issue.
it is absolutely not a battery issue. i have heard this theory before and used all sorts of batteries to try and test the differences to no avail. this included lithium ones and eneloops/powerex using a proper maha charger.

Hi Rooz,

Glad I'm not the only one with what I have experienced. We too use the Powerex batteries now exclusivly. However before post the SB900 in the SB800's we used batteries that where far far less impressive to those we use today and never had apart from less number of shots we could take any issues in the SB800's.

Long live the SB800!!!!!

Hudo

It is worth noting that the SB-900 has Thermal Cut-out and the SB-800 doesn't. i.e. the former has circuitry to prevent the unit from overheating whereas the latter does not. If the SB-900 is overheating due to a large number of continuous firing (and Thermal Cutout is turned on), it will shutdown to prevent damage to the unit. If the SB-800 is overheating due to a large number of continuous firing, it will not shutdown and it is possible that damage could occur.

I have to wonder if Nikon added Thermal Cut-out to the SB-900 because they saw a lot of SB-800 units damaged due to overheating.

Thanks all. I will this info back to my friend.

ATJ wrote:It is worth noting that the SB-900 has Thermal Cut-out and the SB-800 doesn't. i.e. the former has circuitry to prevent the unit from overheating whereas the latter does not. If the SB-900 is overheating due to a large number of continuous firing (and Thermal Cutout is turned on), it will shutdown to prevent damage to the unit. If the SB-800 is overheating due to a large number of continuous firing, it will not shutdown and it is possible that damage could occur.

I have to wonder if Nikon added Thermal Cut-out to the SB-900 because they saw a lot of SB-800 units damaged due to overheating.

andrew, i have heard this discussed aswell and to me, it just doesnt sit right. the sb800's have a reputation for reliabiltiy and being bulletproof. while i agree that the lack of a thermal cutoff is the reason they dont cutoff and stop firing, i think nikon are a little too conservative on the 900. perhaps that massive head and the zoom mechanism accumulates too much heat and they couldnt figure out how to control it ? i dunno.

not a big deal, cos it only happens in certain unique situations...but annoying none the less.

Gadgit wrote:Mr Darcy, does the external battery pack help? Is it the batteries overheating that triggers the shutdown, the internal circuits or both?

I don't know. It is my guess.

Like others who have responded, I also have a couple of SB800s, so if I am expecting heavy use, I use one (or both!) of them. When I did the test, the heat seemed to be in the batteries rather than the head which is why I think that it is the current draw in the batteries, rather than the discharge in the flash/capacitor heating the unit, Though I am sure the latter contributes as well. By separating the batteries from the unit, I would expect the heat rise to be significantly less in the unit itself. The battery pack will get hot though, hence my suggestion for a couple of them. I repeat though that this is an educated guess, not experience.

Nikon state that they are using a new rapid recharge circuit. If you increase the speed of recharge, you MUST increase the current draw from the batteries. This, in turn, must heat them faster, and this is what I, and others , are seeing.

rooz wrote:i found exactly the same thing. my sb800 and sb28 has never had the same issue.
it is absolutely not a battery issue. i have heard this theory before and used all sorts of batteries to try and test the differences to no avail. this included lithium ones and eneloops/powerex using a proper maha charger.

This is not a valid conclusion. If you discharge a battery through a 1Meg Ohm resistor, it won't get hot in use. If you discharge the same battery through a paperclip it WILL get hot, and very quickly (I've done both!) It doesn't really matter what battery you use, though some, e.g. NiCads are more susceptible than others, but if you increase the current, you will increase the temperature generation. Nikon have stated that they are closer to the paperclip than the resistor in the SB900, so it is no surprise to me that the batteries get hot.

Andrew,
The head in the SB900 is actually lower power than the one in the SB800 (look at the GNs at the same ISO & zoom), so I would expect the heat generation in the head itself to be lower with the SB900 than the SB800. THe difference is in the recharge circuit. That is pulling power more quickly from the batteries. My guess is that the thermal cutout in the SB900 is to protect the batteries as much as to protect the head. It is a small space though, and the heat will transfer everywhere fairly quickly.

Mr Darcy wrote:If you discharge a battery through a 1Meg Ohm resistor, it won't get hot in use.

How can you be sure? Nobody has ever tried that. That's of course because it takes about 150 years to discharge a 2000mAh 1.5V cell through a 1MOhm resistor Not to mention that even low-discharge Powerex or Eneloop cells would spoil that experiment by self-discharging much sooner.

This does not detract from the point you were making, of course

Cheers
Steffen.

Mr Darcy wrote:My guess is that the thermal cutout in the SB900 is to protect the batteries as much as to protect the head. It is a small space though, and the heat will transfer everywhere fairly quickly.

The manual strongly implies otherwise.