DIY External battery pack design, please verify.

I've decided that i need a battery pack for my Sigma 530 DG Super. The rechargeable batteries are great and all, but I want to punch it up just a bit more.

In order to do this I searched the web and found a few good articles. The real key is to determine which leads in the flash are taking the power in. I've determined the the positive and negative terminals for the flash are found on the battery spots closest to the back of the flash when shoe mounted to your camera. This tells us where the power from the pack needs to go.

My idea is to use a 6v 1.2-4 amp battery. The battery will connect to a coiled cord using a quick connect/disconnect molux style connector. The coiled cord will have a diode (5 amp???) inline with it. A diode prevents the backwards flow of electricity, for those un-aware. This prevents me from hooking up and having the electricity flow back into the battery incorrectly. The coiled cord will have a quick connect at the top that connects to a flat cable that passes through the battery door to the "dummy batteries". Two of the dummy batteries have nothing in them, and are only used as space holders. The negative terminal battery ( on bottom in back) is a straight pass through wire. The positive (on top in back) will have a 5-15 amp fuse in it in order to prevent any other damages. My plan is to heat shrink and finish it off, as well as find a nice case for the battery to hook to my belt.

If anyone has any input or suggestions on component ratings, it would be more then welcome. Of course plans parts and images along the way will be posted once final design has been accomplished.

Attached is a quick diagram I drew:

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So what is a dummy battery ? I hope that you will not take the actual battery and try to modify it. Probably a plastic rod with glued/welded in battery caps would work.
Secondly why do you need a diode ? You need the connector that can be plugged in only in the right polarity. That takes off a confusion why the flash does not work.

As said above ,use a connector that is polarity protected.A diode will cause a voltage drop of 0.6 volt and will slow the discharge time a little.

Of course I would not modify a real battery, My plan is to use a fake battery size case with the appropriate metal tip for my scenario. I thought about the voltage drop as well, but was concerned that a possible faulty discharge could fire back to the battery, In all honesty if that happened with out a battery pack, it would hit the AA's and cause damage to them. I'll drop the Diode out.

I think a 5 amp inline fuse will work fine. since it is a series circuit and there is no other power source, i shouldn't lose anything with the fuse. Yes I will also use a polarity protected connector, and the coiled cable will be 4 internal cables and I will use a pair for both polarities, for redundancy in the cable.

What i really want is a professional look and feel so i don't look like a dork with a ghetto battery pack, oh and a rapid recharge rate. Something reproducible as well would always be nice eh?

Maplin in the UK used to sell excellent dummy AA batteries as pictured here (with the cover removed):

http://lionels.orpheus​web.co.uk …-Bit/Master128/Dummy.jp​eg

Not sure if they're still available.

Dave F.

I use wooden dowel, just cut a slot down the length for the wire. Put a screw in the end for a contact. works great.

The dowel method is probably cheaper, but if you want a plastic tube so that you don't have to cut a slot for the wire, McMaster-Carr (mcmaster.com) is a decent source.
Looks like AA batteries are .553" in diameter, so 1/2" OD tubing would work pretty well. Seems like item #1859T12 would work:
Black Polypropylene Tube 1/2" OD X 1/4" ID
$2.40/ft cut to length

With a 1/4" ID, one could just connect a wire to a 10-24 or 1/4"-20 screw, drop it in the center of the tube with a little drop of epoxy, and voila!

tetrode wrote in post #7558883
Maplin in the UK used to sell excellent dummy AA batteries as pictured here (with the cover removed):

http://lionels.orpheus​web.co.uk …-Bit/Master128/Dummy.jp​eg

Not sure if they're still available.

Dave F.

Thats exactly what I was looking for. If this was just a one time thing for me, I'd use dowels, but I'd like to step it up to the point were I'd feel comfortable selling it to a stranger.. In the sense that is should look , feel, and operate with a certain level of reliability and appearance.