Posted on 30. April 2010 09:51 by jr
Just a quick post of my new homemade 6 volt battery for my small portable flashes (Canon 430, 550, 580, 580 EX II, Nikon Sb-24, SB-26, Sb-28 etc)
The battery
The battery is made of an empty aluminum case measuring 153 x 82 x 50 mm. Inside I put a single 6 volt 4Ah lead battery. Since batteries like these can carry a lot of current - enough to melt the wires and perhaps start a fire if shorted, I put in a 5 amp fuse as close to the + side of the battery as I could. From there the wires go to the on/off button and from there to the male recessed plug. The other pin of the male recessed plug goes to the battery's minus side. I believe this type of plug is ordinarily used for microphones, but I'm not sure. I chose them because the plug is recessed so there is little risk that the + and - will be shorted and the female and the male are screwed together so they don't get loose by accident. The plug also has a small groove so I don't accidently put the female plug in the wrong way (hint: very bad for your flash if the plus and the minus poles are reversed). At the back of the case I screwed in small metal ring-thingy ordinarily used on boats. A small strap like the one you get with a cell phone is used let the battery hang. I drilled all holes using a stepping drill ment for metal (damn expensive, but I already had it lying around). Luckily aluminum is quite soft to drill in.
Cabling
I then used a spiral cable with a max length of 2 meters when stretched and only 50 cm when rolled up. I put a female plug at one end and a male plug at the other end.
Now it was time to create the fake batteries for the flashes. I used a round wooden stick which had similar diameter to an ordinary AA battery and cut two small pieces out of it - one a little shorter than the other. They didn't fit completely so I rolled a little gaffers tape around them to make them fit perfectly inside the flash. I used a small piece of cable with a female plug at one end as the wire going from the flash. The other end I split in two and put each wire inside one of the wooden pegs (I drilled a hole completely through in each of them first). I put a thick screw inside the hole of each wooden peg. this both acts as a conduit for the current and as a means of securing the wires. I used a small plastic strip as a relief for the tension, should the cable be pulled hard. I then used a dremmel to drill a small hole in the side of the flash so the cable could run out.
Remember that you must use cables that can handle the current drawn from the flash. I don't know exactly how much if will gooble up at any given time, but to be on the safe side I chose "1.5 kvadrat" (that's what it's called in Danish). In the US I believe you call it gauge. The wire would have an AWG of 15, meaning that the diameter in inches would be 0.0571.
Assembly
Just solder the wires inside the case according to the above mentioned sequence. My soldering skills are so damn poor and the wires almost too thick for the small holes in the plugs, button and fuse holder, but I managed. It ain't pretty, but it's all hidden so who cares :)
Make sure that all wires and soldering inside the case and inside each plug is shielded from the metal casings with electrical tape or likewise.
Word of warning!
If you put + and - in the flash the wrong way, the flash is toast! I mean instantly. No warning! It's just dead and cannot be recovered. So make sure you know what you're doing. I only tried this with my SB-26 and SB-28's. There is only one place the plus side can be attached correctly and one place the minus side can be attached correctly. It is not the same place from flash model to flash model. In the case of the SB-26 and SB-28, the plus side must be pointing downwards in the slot closest to the base of the flash, while the minus side must be pointing downwards in the slot closest to the top of the flash. also make sure you test and retest and then test again that plus is running the correct way all along all your wires - and don't test it with the battery connected. Ordinary multimeters will not like the strong current from the battery. Unplug the battery while testing with a multimeter (not sure what it is called in English, but it's used to test current, conductivity etc.)
Performance
I made two of these and will most likely make one or two more soon. They look almost professional and they work great. They cut recharge time with about 1 second on a full 1/1 power pop from the flash. They hold approximately twice the power of 4 of the best NiHM batteries out there. They take max 2-3 hours to recharge with a CTEK XC 800 lead battery charger. If you use an intelligent charger like that, the battery will last longer. Batteries like these last approximately 2-3 years depending on use, but they cost very little to replace.
Prices
Prices in Danish Kroner (remember we have a horrible tax on all goods, so this might be a lot cheaper where you come from):
· Charger: 399 DK Kr. (71 USD)
· Aluminum box: 85 DK kr. (15 USD)
· Plugs, on/off button and fuse holder: 123 DK Kr. (22 USD)
· Spiral cable: 100 DK Kr (18 USD)
· Battery: 119 DK kr. (21 USD)
Total for one complete battery without charger: 427 DK kr. (76 USD)
Wires, soldering iron etc. I had lying around. Shipping for the parts are not shown in the calculation (although the spiral cable's price is with shipping included).
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