Transportable mini-studio and power management

Question

Wanting to improve my portraits, I invested a few months back in 2 off-camera flashes, 2 radio receivers and 1 radio transmitter. For all of that, I need 2*4 + 2*2 + 2 = 14 batteries (eneloop) for the setup to work and 10 more to replace failing batteries during the shooting session (about 2-3 hours long). So after the shooting, I need to recharge 24 batteries, which is beginning to be boring, but still manageable.

Now, I would like to add a third flash (and its radio reciever) to have more options regarding lighting setup. It will add 10 more batteries into the equation.

I also have the project to add small led panels close to the flashes, in order to provide a constant source of light. That will help me to better visualize the effect that each flash will produce. With 2 to 4 batteries per led panel, it will add between 12 to 24 more batteries to my collection (taking into account back-up batteries).

As you can imagine, managing about 50 batteries is going to be time-consuming and probably quite maddening.

I am wondering if I could use regular power bank to replace the flashes batteries and the led panel batteries (so I will be left with the 8 batteries required by my 1 radio transmitter and 3 radio receivers).

My analysis of the situation : each flash requires 4 AA batteries. 1 AA battery is 2500mah/1.2V, so in total about 5V and 10000 mah. Many power banks could deliver 5V with capacity over 10000mah. The main issue is probably amps and cycle time : the flash require about 5-6 amps to have a correct recycling time (about 3 sec), so the power bank will need to have an output of about 25W. After a brief market review, most cheap power bank have only an output of 5 to 10W, but some are promoting 45 to 60W (5V). For example, Xiaomi says that one of its 20000mah power bank model can provide 5V/5.4A (using its 3 outputs), so a little more than 25W (about $50).

Can I use regular (and cheap) USB power bank to optimize power management? Are there other (cheap) alternatives? How do you manage it?

I have looked at "serious" power bank (Godox propac for example), but they are a little expensive and heavy.

Regarding possible DIY solution and my experience with electronics, it has been a few years since I have soldered something on a pcb, but I could probably still manage it.

An important constraint is to have a "transportable" mini-studio. I would like to still be able to carry it around in two (big) bags.

Thanks in advance.

Answer 1

I'm going to propose an alternate solution: consider switching to the Godox flash system, which uses big lithium rechargeable batteries. The battery is proprietary, so that's not so handy, but they're also not that expensive and easily available from major retailers.

These will generally give you more shots than a set of Eneloop batteries in a flash, but perhaps more importantly, if you need to swap, it's really easy and fast: none of this " managing about 50 batteries" — if you have three flashes and three backup batteries, that's just six, and each swap is just one out, one in. As you note, the transmitter battery isn't really a big issue and should last several sessions — and in the Godox case, you don't need a separate radio receiver as it's built in.

If you're going all-manual, the flash units with one battery cost around $140 plus $40 for spare batteries — so, $540 for three flashes and three spares, plus $46 more for the transmitter.

That's an almost-$600 outlay, which I know isn't trivial, but if you were already planning to add a ~$100 flash, $20 worth of new eneloops, and a $50 USB bank, plus whatever else needed to make that work, the real difference in price decreases. And having three back-up batteries may be overkill — especially if you're not always shooting at full power. All in all, it seems like it might be worthwhile for your sanity.

(For what it's worth, I've got exactly this setup, albeit with the older generation of Godox li-ion flashes and the 433mhz trigger system. In combination with a portable lightbox kit and some foldable lightstands, the whole thing definitely easily fits in two big bags.)