Paul C. Buff, Inc. Technical Forum

Seemingly randomly with any one of my six Einsteins, either of my two fully charged VML's will just power down, usually in the middle of an important corporate shoot! I'm not working them hard, usually with low, sub 200w/s settings. They can be ok for an hour or so, then do the switch-off, even when idle. Or the fault can kick in at the start of a shoot. Very annoying having to watch out for the fault instead of keeping 100% attention on the job. BTW, I'm only connecting one Einstein per VML.

It's not a faulty cable, that's been checked and swapped multiple times with no change to the problem. Is anyone else experiencing this?

-pw

Ok, I have a few questions.

First, how old are the batteries? There is the possibility they batteries are reaching their end of life.

Second, how are you determining the VML's are the ones shutting down and not the E640? Are any lights coming on the VML, like the one next to the USB port? And what color?

Third, are you certain the model lamps are off when in use? Are you certain they are not being switched on by a Cyber Commander in the area, whether it is in active use or not?

I unfortunately have encountered the same problem. The VML would work well for like 10 shots and then stop working. Sometimes it would just stop working after an idle period of like 5 minutes. And even when I put in the backup battery, it still doesn't work, so the charge level doesn't seem to have anything to do with it. It takes a few hours to get back working again. Model lights on the Einstein are off. I still haven't figured out a pattern. It seems to happen more often when the Einstein is turned to full power and there are a few shots in quick sequence.

Thank you for the responses. That's a valid point about identifying whether one of my six Einsteins is "rogue". It's not that. Last time this happened I switched out batteries in the same inverter and was able to keep working which tends to point to the battery pack. I wasn't able to repeat the "fail" back in the studio. Bugs can be like that, showing up only when you're shooting the CEO!

-The batteries themselves are close to two years old.
-The "fuel-gauge" was showing one light. I couldn't tell you if other lights on the battery were on.
-No model light was being used.
-The CC was in my bag, triggers used were the basic CST transmitter & CSXCV transceiver.
-Power setting on the Einstein was under 200 w/s.
-Do the rare VML "fails" generally occur with the battery or the inverter?
-What would occur with the VML battery if one of the 16 cells failed or fell well behind the performance/capacity of the other 15? Is this a possible scenario?

Thanks,
-pw

Sounds like you may be firing 10 shots as rapidly as the light(s) recycle? This is 100% duty cycle, which can overheat the VML and cause temporary thermal shut down.

If this is not your firing pattern, your batteries may be reaching end-of-life).

How old are the batteries and how much use on them?

Follow up to post just received: At two years your batteries are near end-of-life. This is confirmed by the single light on the fuel gauge.

This is a big performance point for the VLX™ . . . battery life is typically over ten years instead of 2-3 years for other lithium batteries. See
http://www.paulcbuff.com/images/ads/vagabond_wysk.jpg

They were getting quite light use at the time...

After a charge you see three lights on the fuel gauge...it was showing one light because I'd been shooting for a few hours.

Wow the VLX sounds like my kind of battery. Thanks for the info!

-pw

That may certainly be possible. Is there any indication on the VML when the thermal shut down has been activated? What is the max. recommended shooting sequence at full power?

Two issues: How many Einsteins were being powered? PWP mentioned in this thread it was a long shoot that started with all three battery lights lit. The lights - particularly Einsteins and more particularly with a 230V VML, draw power from the VML when turned on, but idle. This standby power can deplete the battery in from 2 to 10 hours depending on the the number of lights. So, on a long shoot, the VML should be switched off when idle.

As for the thermal shutoff, you can do several shots in a row as soon as the lights are recycled. But for more than say around 10 shots, thermal shutdown of the VML can occur if the duty cycle exceeds about 50% . . . example: allow about twice the recycle time between shots if you're doing a number of shots.

Normally, if the VML goes into thermal shutdown it will recover after a few minutes of cooling.

As for the shelf life of the batteries themselves, this NMC type (used in cameras, cell phones, Profoto B1, Elinchrom Quadra Ranger Lithium, etc. is typically from 2 to 4 years, and is dependent on storage temperatures, state of discharge during storage, etc.

Also, NMC batteries in high surge current uses like flash inverters can be depleted after 150 to 300 charge/discharge cycles. (I worry about the B1 in this regard because its fast recycle rate vs low battery capacity (a mere 45Wh compared to VML's 130Wh) really reduces the number of charge/discharge cycles.

This stuff is hard to pinpoint because it can take a year or more of lab testing to gather accurate data. Our battery supplier is one of the best - a primary vendor to the Chinese military, but battery makers don't have great data on performance in flash recycling data because it's a specialty market for them.

Finally, don't think our batteries are relatively inexpensive because they come from a "cheap source". They as the highest quality that money can buy. Our cost of goods is about 50%. Compare the $89.95 VML 130Wh NMC battery to the Profoto B1 45Wh NMC battery that they get $250 for. About the same cost/price relationship with Elinchrom Quadra Ranger Lithium.

We would probably sell a comparable battery for about $50 if we made one.

The VLX™ LiFePO4 battery technology seriously improves NMC battery performance limitations (by a factor of about 5:1).

Hi Luap, thank you very much for your replies in this thread. That's all great, basic data. FWIW I only ever power one Einstein at a time off the VML's, and usually remember to power down during longer idle periods. I've had an electronics engineer balance and check the cells and they're at roughly 82-85%, not bad for their age.

Cheers, Paul Wright (pwp)