tomcat

I was taking pictures at an event yesterday, using my SB-900 flash with a Quantum battery pack for the supply. This is a rig that I have used for several years for indoor events, so it is battle tested and has worked great in the past. After a flash mis-fire, I noticed the low AA battery warning in the SB-900 display. This is totally unexpected because the AA batteries were not that old. I checked ahead of time and they ranged from 1.2-1.4 volts for all 4 of them. Plus with the Quantum battery pack feeding juice to the flash, the AA batteries merely act as a conduit, so there is almost 0 drain on them and I have been using them for some time, checking the current each time out. So this is the setup scenario.

Now, when this occurred, I changed to a new Quantum battery pack and also a new flash connection cord and still got the AA low battery warning. I've never had this happen to me before, so I though maybe my Quantum rig was at fault, since I "knew" the AA were ok. I switched to one of my SB-800 units with a different set of AA batteries and finished the job, with no more mis-fires.

When I got home, I rechecked the batteries in the SB-900 and got the same previous voltages, ranging from 1.2-1.4 V. Then I put those "used SB-900 AA batteries" into the SB-800 flash and they worked perfectly with no mis-fires! I fired off about 50 shots with no mis-fires. I then put those same AA back into the SB-900 and got the same AA low battery warning again.

Thinking that there was a problem with those batteries, I put in 4 brand new ones in the SB-900 and then took about 100 shots with no misfires.

So:
1) Why would a set of AA batteries with voltages from 1.2-1.4 not work in the SB-900, but worked perfectly in the SB-800?
2) What would cause a set of AA batteries that worked in the SB-800 to fail to work in the SB-900?

I hate electrical problems and this is a weird one to me

IDguy Loc: Idaho

Partial coating on contacts?

I just had a wierd one on my SB700. Doubt it is related. Went to use it and batteries were dead (it seemed). Thought they should have been good. Tested them and two were like new and two totally dead. Have yet to put in replacements for dead ones.

TBerwick Loc: Houston, Texas

IDGuy!

I hope you're not leaving the AAs in the flash for extended periods. I lost an Nikon flash because I forgot to remove the AAs and the next time I grabbed the flash, it was a paperweight.

TBerwick Loc: Houston, Texas

Tomcat: have you checked your batteries in the Quantum? One of my units quit holding much of a charge & I had to have the battery pack replaced.

larryepage Loc: North Texas area

.2 volts is a significant difference. Replace the cells that measured low and see what happens. And the SB-800 may have a completely different threshold for flagging a low battery than the SB-900.

DICK32

My suggestion is to clean the contacts on the battery contact terminals of the flash unit--they corrode--and the batteries as well. I've had this problem and used a metal cleaner on a cloth to take the corrosion off the contacts and the SB-900 and 800 worked fine. The cause may be that batteries leak and the flash unit may be stored in a damp location.

IDguy Loc: Idaho

Good advice I will take to heart.

tomcat

Yes and it's not the Quantum because it worked perfectly with the SB 800. thanks

tomcat

How do you get deep into the contacts on the flash unit itself? I can clean the upper contacts on the lid, but down deep, only a Q-tip can get in there.

tomcat

Is it possible that the 900 could have a higher energy draw than the 800 and that the 0.2 volts is not enough? Just seems strange because I used to use rechargeable batteries in the flashes and as you know, they will only charge up to 1.2 volts and never get to 1.5. So it seems to me that 1.2v Duracell batteries should have been plenty enough power.

larryepage Loc: North Texas area

The difference is that 1.2 volts from a 1.5 volt alkaline cell (which I am supposing is what you are referencing) represents a fairly depleted cell, especially if it is a no-load open circuit voltage. Once you put that cell under load, the voltage is going to drop quite a bit further, I'd expect. And even if it is not supplying any power to the flash, its increased internal resistance (one characteristic of a depleted cell) could be causing further problems.

I have and use two SB-800 Speedlights, but do not have experience with the SB-900. It would not surprise me if its newer, presumably more sophisticated design and circuitry just behaves differently from the SB-800.

BebuLamar

While NiMH at 1.2 is OK. Alkaline at 1.2 is considered dead. Now the 1.2V is sufficient but when the flash started to draw current it would be less than 1V with alkaline.

tomcat

Well, then that's what caused the problem with the 900. But they worked in the 800, so it's bound to be a design issue. So I will recycle those batteries and start using only new each time. thanks.

tomcat

Then that's probably what the problem was and from now on, I will use brand new ones before each job. thanks

Largobob

I agree with larryepage. It is the CURRENT, not the voltage that does the work. The working voltage of a battery under load, can be significantly lower than the voltage measured without the load....which you did. I'm guessing the SB-900 draws/requires more current (amps, milliamps) than the other speed light. Those batteries could not deliver the required current to power the flash tube.