Higher capacity batteries in strobe

[Interceptor121]

The reason why manufacturers put warning on eneloop is because they run hotter
Assuming voltage stays constant the 20% resistance reduction turns into 25% more power
P=V^2/R as R=0.8*(standard resistance of NiMH) P=1.25P of a normal battery to the point that in a closed compartment it may vent
Obviously it takes time to build heat so only if you take repeated full power shots you have a real chance of overheating as E=P*t
In practical terms if you shoot macro nothing will happen if you are shooting full power wide angle lots of repeated shots it may overheat

 

[Chris Ross]

If the power goes up we should see eneloops having faster recycle times, as the current is higher - is this the case? The behavior of the circuit depends on limiting/overall resistance. The power from the battery goes through a coil which is switched rapidly to run a transformer to increase the voltage to charge the capacitor, the inductance of the coil will limit the current flow.

 

[Interceptor121]

If the power goes up we should see eneloops having faster recycle times, as the current is higher - is this the case? The behavior of the circuit depends on limiting/overall resistance. The power from the battery goes through a coil which is switched rapidly to run a transformer to increase the voltage to charge the capacitor, the inductance of the coil will limit the current flow.

Yes that's the case eneloop have the fastest recycle time among all batteries

 

[Schwob]

There are several ways to vent without water transport. Think GoreTex. Teflon film has really good gas transport properties and it (or some other PTFE, sorry Mr. DuPont) is used in the Sea and Sea Cap. Inon has a similar construct (I haven't torn one apart). that I suspect uses PTFE or similar (silicone might work as well).

Bill

I highly doubt GoreTex could be used. What is it rated for? At or a tad above 20,000mm H2O column? Thats just about 2 bar.

 

[Chris Ross]

there is no way you would use any sort of membrane to release pressure, the transport rates are too slow, S&S and INON both use one way valves to vent pressure.

 

[bvanant]

In my battery tests, eneloops did not show any appreciable recycle time advantage but did show more strobe flashes than higher capacity traditional NiMH batteries. But that is time to the charging light going on and that might not be the best metric since it seems to go on at about 80% full charge.
Bill

 

[Interceptor121]

In my battery tests, eneloops did not show any appreciable recycle time advantage but did show more strobe flashes than higher capacity traditional NiMH batteries. But that is time to the charging light going on and that might not be the best metric since it seems to go on at about 80% full charge.
Bill

Based on the fact that the resistance is 20% lower on average it should charge 20% faster now on 3 seconds this is around half second at best. In order to test this you need to load two strobes with different batteries fire them at full power and check the eneloop comes ready faster however reaction time is not as fast to detect half second ...I will shoot a video when am back home
I don't get instead the more flashes that you do anyway this is semantics as you would not use other NiMh regardless

 

[Chris Ross]

20% lower internal resistance will result in 20% more current only if that is the only resistance in the circuit. I found some forums where people were measuring speedlite current draws from Ni MH batteries and the answer for something like a Canon 430 or 580 flash is around 8 amps, I would expect the UW flashes to be in same ball park. If this number is correct then the battery resistance is only 10-15% of the total resistance. This makes sense as you would be drawing near 50 amps (100 mOhm resistance) from the batteries at peak charge rate which seems a bit excessive if the battery was the only resistance in the circuit.

 

[bvanant]

Back when I was doing the computer battery testing, my EE wizard friends at Medtronic measured the charging currents for a Z240 (they could take it apart but not put it back together) and they suggested that Chris is right, they said that 10A was about the highest current that I should test the batteries at.
Bill

 

[Interceptor121]

No AA battery can deliver more than 10A anyway and I think you guys are making some confusion here
The heat generated in the battery is only to do with the battery resistance the rest of the circuit does not matter
Furthermore eneloop will also hold voltage better than normal batteries developing even more heat
Different to other batteries however they will be less affected long term by the hear itself