Paul C. Buff, Inc. Technical Forum

Apologies if this has already been discussed elsewhere. I was wondering if you would be able to provide any information regarding the self-discharge behaviour of the VML's lithium battery pack. Depending upon how well the battery retains a charge, I'm considering keeping my VML on a timer that would top the battery off once a week. Would that be advisable/excessive/not recommended?

Dave F.

The manual covers 'storing' unit.

http://www.paulcbuff.com/manuals/pdf/vmini_1210w.pdf

Top of page 12

That section of the manual does not address the battery's self-discharge characteristics.

Dave F.

It does seem to very clearly answer your question about setting a timer to do a weekly "top-off"....

Store with charger disconnected, and, interestingly, better to store it with about 50% capacity charge.

You can probably google for self-discharge characteristics of this battery-chemistry type. But since it can apparently be stored for months and months as described, seems like it won't be a factor in practical usage and storage.

I don't think it answers that question at all. I'll simplify: Is it preferable to fully charge the battery immediately after use (as is recommended with SLA batteries) or to fully charge the battery immediately before its next use. In other words, should it be stored partially depleted or fully charged. I read the part about storing it with 50% charge and that seems to suggest the latter but I would like a more precise description of the adverse affects of storing the battery fully charged.

Not having the battery fully charged at all times can, for me, be "a factor in practical usage". We don't always have the required 3 hours available for battery charging before a shoot. I would like to be able to keep the batteries topped off but will only do so if PCB TS says this will not shorten the life of the cells appreciably.

Dave F.

No harm will come from charging to full and letting it sit at room temperature. Charging to 100% and storing in a hot garage/attic/car trunk for long periods of time is not healthy for the battery as extreme temps are the natural enemy of batteries. If you rather charge it after use and let it sit until the next use there will be no problems other than any self discharge all batteries are subject to (5-10% per month for this battery). So if there are long periods between shoots, you may still want to top off. No harm will be done by using the battery then letting it sit until charging before the next shoot. This is unlike the Vagabond 150/300 or Vagabond II, which letting it sit discharged is also not recommended.

Fantastic! Thanks a million for the thorough response.

Not to jump the gun, but the VML could indeed turn out to be a game changer. So far it handily exceeds my expectations.

Dave F.

The stated self discharge rate, according to the manufacturer, is on the order of 6 months from full charge to 70% charge. The big factor is that even if you let it sit until completely discharged (a very long time) no damage will occur and a 3-4 hour recharge will restore the full battery capacity. Don't try this with an SLA battery . . . even storing it at 50-60% charge will cause it to sulfate and become completely worthless.