DIY: Build Your Own Flash Battery Pack: PART 1

[Vermin87]

PART 1: Adding a coaxial power jack to your flash

Okay! I finally got around to adding the jack to my Sigma EF-500 DG Super flash. I totally voided my warranty, but all in the name of DIY! Here is part one of my DIY guide to building your own external battery pack. The pack will consist of 8 AA's that can be used with the 4 inside, or without, much like the CP-E3, I believe.

NOTE: I am just a poor college student with limited knowledge of electrical engineering, but I like to try and apply concepts I'm learning in my classes. I'm actually studying mechanical engineering, so bear that in mind as you read my DIY guide. There are probably better ways of doing this or improving on the method I will demonstrate below. Feel free to give me input and suggestions for improving should I ever try to do it again on another flash, or fix this one up more. Also, the pictures are taken using my 30D's on camera flash, so excuse the harsh flash in some of the photos or generally bad lighting.

The Ingredients: (1) Flash, (1) Size N coaxial Jack needed for PART 1


Looking inside, this seems like the best place to put the jack.


Here are the leads from the internal battery compartment.


The proposed spot for drilling


Used a drill with an 8mm counterbore bit.


After drilling, it looks like this with the jack installed. I was a little concerned that it was too close to the edge, but it turned out to be okay. If it wasn't that close to the edge, the jack might not have cleared the other parts inside the flash.


Soldered 22 Gauge wire onto the circuit board where the battery leads come through, and then onto the jack. The (+) lead goes to the outer shell of the jack and the (-) lead goes to the center pin of the jack.


Here it is put back together


The flash still works after installing the jack. I haven't built the battery pack yet, so PART 2 is coming once I gather more parts.

[Lotto]

Nice and clean mod, vermin87. If anything, I would reverse the +/- lead at the jact. It's safter not to expose the hot lead to the outside, I think.

Good luck with the rest of the mod.

[Vermin87]

Hmm, I was thinking that Lotto, but then I saw it done the other way on a website for RC planes, so I guess I was swayed into thinking that was the better choice. I'll probably switch it up when i finish the rest of the mod.

[Goonish]

Great idea. I've actually thought about doing this with some AC adapters so I can make a portable studio setup with a couple of cheaper flashes and have multiple slave flashes mounted semi-permanently on stands. The AC adapter of course will provide a permanent power source.

[DocFrankenstein]

Just keep in mind that I fried two vivitars that way.

If I were to do it again, I'd feed it off FOUR D batteries.

[olly_k]

Nice mod, but thinking on would it not be better to have a switching jack so that should a power supply be plugged in, any batteries left inside will not be subject to a rather destructive charge!?

[strmrdr]

Originally Posted by DocFrankenstein

Just keep in mind that I fried two vivitars that way.

If I were to do it again, I'd feed it off FOUR D batteries.

unless the circuit is designed for the higher input voltage it can over volt the capacitors causing them to short out and even explode.
A feedback circuit is used to prevent this in some designs but adds cost so its not always present.
4 D, C or even sub-c cells is what I would do.

[mbellot]

Originally Posted by Goonish

Great idea. I've actually thought about doing this with some AC adapters so I can make a portable studio setup with a couple of cheaper flashes and have multiple slave flashes mounted semi-permanently on stands. The AC adapter of course will provide a permanent power source.

I would strongly advise against AC adapters. Most of the cheap "wall warts", and even some of the more expensive ones do not regulate their output voltage. They are specified for a certain output voltage at one certain load current. Reduce the load (flash is fully charged) and the voltage will go up. I've seen 5-6 volt adapters put out over 10 volts with small loads.

Originally Posted by Lotto

If anything, I would reverse the +/- lead at the jact. It's safter not to expose the hot lead to the outside, I think.

Agreed. Barrel negative/ground is almost a standard. There are a couple oddballs that still do barrel positive, but just a few.

Originally Posted by olly_k

Nice mod, but thinking on would it not be better to have a switching jack so that should a power supply be plugged in, any batteries left inside will not be subject to a rather destructive charge!?

I had suggested a blocking diode on the internal batteries in Vermin's original thread, but looking at the internals a switching jack makes loads more sense.


Vermin: Nice looking work for someone who claims to have little electronics knowledge.

I would give serious consideration to the switching jack idea olly_k put forth. It would let you keep batteries in the flash but prevent any possible damage to internal or external batteries if they had drastically different charge levels. I know you want combined usage like the 580EX, but I just don't know if you can do it safely with the Sigma since it was never designed for an external power source.

[René Damkot]

Originally Posted by olly_k

I would give serious consideration to the switching jack idea olly_k put forth.

Quoted for truth...

Also, AFAIK the only reason the Canon flash has to use the batteries when using the CP-E2 or CP-E3, is to feed the electronics. The pack plugs into the high voltage circuit...
That's an entirely different concept then what you are doing here.
Units like the Quantum Batteries (non Turbo) use a dummy that fits in the battery compartiment of the flash.

[Vermin87]

Hmmm...Actually, the coaxial jack I bought was a switching jack, but was thinking I could use the internal batteries as well, like mbellot said. This is *essentially* the circuit I was going to make (These were done in Paint):

But if I were to do the switching jack setup, is this correctly how to wire it?


Thanks for the input guys.

[mbellot]

Originally Posted by Vermin87

Hmmm...Actually, the coaxial jack I bought was a switching jack, but was thinking I could use the internal batteries as well, like mbellot said. This is *essentially* the circuit I was going to make (These were done in Paint):

But if I were to do the switching jack setup, is this correctly how to wire it?


Thanks for the input guys.

In words (since I'm no artist)

The center pin is connected to both (internal) battery negative and circuit negative. This should require no modification since you already have the negative leads paralleled.

The barel pin gets the orange wire that goes into the guts of the flash.

The switch pin gets the red wire and is routed to the (internal) battery positive.

Just be sure to verify with a multimeter that the barrel is in fact whats being switched in and out (most likely it is).

[mbellot]

After looking at your pictures some more, its really pretty simple to modify your existing setup.

First, move the red wire on the connector from the barrel terminal to the switch terminal.

Second, move the orange wire from the battery pack to the barrel terminal on the connector.

Done.

[Vermin87]

Wait, we were trying to make the inside barrel of the plug hot right? not the outer shell? so it would be reversed...hot leads on the center pin so that on the plug it is inside, then negative ones on the switch and the shell.

[Vermin87]

Upon request, I added the switch jack configuration. Thanks for the input guys

Adding a switching jack

The connections under question for modification are the orange and black ones indicated by the red circles. Remove the wire completely.

Here it is all completely wired and placed back in the flash

Here's a schematic drawing of the ciruit

So now, when the plug is inserted into the jack, the flash doesn't get power from the internal batteries. This way, the internal batteries aren't in risk of being ruined when the battery pack is used. Then when the plug is out, the internal batteries are connected and used for the flash.

[mbellot]

Originally Posted by Vermin87

Wait, we were trying to make the inside barrel of the plug hot right? not the outer shell? so it would be reversed...hot leads on the center pin so that on the plug it is inside, then negative ones on the switch and the shell.

Since you already had it wired for barrel positive it seemed easiest (less work) to just leave it that way.

To do it with center pin positive you would hook the red from the internal battery and orange from the flash circuit to the center pin and then put the black from the internal battery to the switch contact and the black from the flash circuit to the barrel contact.

With the jack wired up safely now I'd say put five fully charged NiMH batteries in series and check the voltage.

As long as you are below ~ 6.4 volts (standard alkaline batteries can have an initial voltage as high as 1.6v, so four would be 6.4 volts) you should be safe to use the five battery version. If you are over 6.5 volts I would stick with packs of four.