Battery question (DIY, electronics)

[Dmitri]

I am looking at building a battery pack for my vivitar 285HV to hopefully reduce recycle times. I found some nice ones, but I was wondering if using a 12v battery might be better than a 6v? Since it's the HV version instead of the regular 285, would this be acceptable?

I know 0 about electronics and I'm a bit confused by this. I did read somewhere that the HV can handle higher voltages (and can get like 1 sec recycle time at full power, for short bursts).

Anyone with know-how know?

 

[behanana]

Dmitri, I don't know if I can help or not, however can you send or attach a link to what you are looking to build. I looked up the battery pack idea and my initial thoughts are this; Understanding Ohm's law that Volts=Amps x Resistance, the question you posed of "if a 12v battery would be better than a 6v battery?" is hard to to give a simple anwser too. The flash bulb is going to be the resistance of the circuit (I'm not looking at all the wiring and electronics inside the flash assembly), this will not change reguardless of the battery, due to this the required amps to set the flash off will change, the voltage is how fast the amps get through the circuit. This is where the 12v comes into play, now the initial thought is "YES" however, with all things there is always a catch, by allowing the amps to flow faster flow this will cause heat to build up faster, this may cause "thermal events" to happen. Like I said, there is no good Yes or No anwser to your question.

If it was me, I would probably get better rechargable AA batterys. If you are going to do this, I would try to contact someone who has done it and see how it's worked, and how long they have been using the flash. A fast recycle time will only be beneficial if the flash lasts longer than 30 shots and doesn't melt into a blob.

 

[RockstarPhotography]

A battery pack is a fairly simply mod that can be done to a flash. You do NOT want to change the voltage going into the flash. A good understanding of circuits and wiring is needed. You have to understand how you voltages and ohms change depending on if you wire the batteries in series or parallel. Here's a basic rundown on how I build mine. D batteries are the same voltage as AAA. at radio shack you can buy holders for 4 D batteries. pick up one of them and a couple of 3 way "power plugs" both female and male. Do a search on how to wire the plug into your flash. With a 3 way plug, the flash will run off the AAA batteries in the flash until you plug in the batter pack, then it will bypass the AAA and run of the pack. you can mount the D cells in a cheap pencil case, or whatever you want. make sure the wire is of sufficient gauge to handle the current. I'm buying a couple for flashes soon and will be doing a tutorial on this.

 

[nick_cool]

The manual do not say what is consider HV, and if it is applied directly to the power input, so 6V is the limit.

You can use a bigger external 6V battery (4 big NiMh, Pb Acid, NiCd, etc.), but I prefer to have an extra fresh NINh pack and change it when the first start to fall.

The pack quality and capacity of discharge are things to consider too.

 

[Dmitri]

The problem with better AA, even brand new NiMH is that you still get a 6-10 second recycle time at full power. I know that external battery packs will increase the number of shots taken before the battery dies, but I think that 6v will still only increase the recycle time by a small amount.

But as behanana says, too much voltage will melt the flash - but it should be awesome for short bursts, no? For example, 1 second recycle time but careful not to pop more than 6 before letting it cool a bit?
I wish I paid more attention in school! Thanks all.

 

[Ginu]

I'm not a engineering wizz but wow this is pretty funny.

The voltage has nothing to do with the recycling time of the flash... the recycling time is due to how fast the capacitors can recharge back up (if you pump more voltage through it, they will simply burst or melt) and the actual flash bulb can take so much abuse b4 heating up to the max and burst.
Want a faster recycling time get a better flash. Make sure you dont use alkaline batteries and use NiMH and it will recycle faster and will also have a longer lifetime.

Decent rechargeable batteries are not expensive (get a charger and 4 batteries for 20-30$; make sure the rechargeables are 1.5v not 1.2v which is the standard).


Out of curiosity, do you think your car is faster by simply using higher octane gas?

 

[Garbz]

The voltage has nothing to do with the recycling time of the flash... the recycling time is due to how fast the capacitors can recharge back up (if you pump more voltage through it, they will simply burst or melt) and the actual flash bulb can take so much abuse b4 heating up to the max and burst.

The biggest problem everyone here is making is assuming that this is a simple circuit, it's not. The batteries are hooked to a flyback converter. This allows you to generate a large regulated voltage which charges a capacitor and sits across the flash tube. An ignition transformer then generates a spark at about 4000V which ionises the space in the flash tube. This changes the electrical properties in the tube and the bright flash is sustained by the voltage stored in the capacitor till either a timing circuit quenches this connection or the capacitor is discharged and the flash can no longer sustain.

Ok so that's the basics out of the way. A higher voltage CAN make the flash charge faster. In fact this is how the Nikon SB-800's additional battery works. It just boosts the voltage by 1.5V at the input to the flyback regulator allowing it to sustain a larger current in the inductors which transfer power to the high voltage side of the regulator. The risk you run is one of input compliance. Just because the SB-800 charges 1 second faster with 1.5V doesn't necessarily mean it can handle 3V or even higher without damaging some part of the regulator.

Also note the key word regulator. It regulates. Whatever you do to the input won't affect the output on any properly designed circuit. The flash charges to 300V regardless of the voltage on the input so there's no risk in damaging the flash bulb. There IS however a risk that you can overheat your bulb as the additional recycle speed means your flash doesn't have as much time to cool down between shots, and that can damage the bulb.

Cars don't run faster by using high octane gas, but you can increase the compression ratio of the engine with high octane gas which will generate more power. Your analogy is actually quite fitting here, and think of the regulator as a modern engine which will ramp back when the knock detection starts going off. Some cars just like some flashes actually do go faster simply by using higher octane gas.


In summary, don't do it without knowing the limits. Unlike your car analogy you can break your flash with a higher voltage. Find some concrete numbers unless you're a tinkerer who is comfortable with potentially having an expensive paperweight. Oh and 12V will almost definitely be too high.

 

[sierramister]

I have to agree with Garbz. When I put my batteries in fresh, I have 6V total from 4 AA's. After 200 flashes, the recycle time is much slower and the batteries now have less than 6V. Therefore, there is a direct relationship between voltage and recycle time.
Vb = IR + Q/C.

I
The voltage has nothing to do with the recycling time of the flash...
Out of curiosity, do you think your car is faster by simply using higher octane gas?

 

[nick_cool]

If you are eager to try, you can connect a 7,4v 3700mahr Lipo like this:

HobbyKing Online R/C Hobby Store : Rhino 3700mAh 2S 7.4v 25C Lipoly Pack

Do not forget to buy the charger too.

 

[RockstarPhotography]

The voltage has nothing to do with the recycling time of the flash... the recycling time is due to how fast the capacitors can recharge back up (if you pump more voltage through it, they will simply burst or melt) and the actual flash bulb can take so much abuse b4 heating up to the max and burst.

The biggest problem everyone here is making is assuming that this is a simple circuit, it's not. The batteries are hooked to a flyback converter. This allows you to generate a large regulated voltage which charges a capacitor and sits across the flash tube. An ignition transformer then generates a spark at about 4000V which ionises the space in the flash tube. This changes the electrical properties in the tube and the bright flash is sustained by the voltage stored in the capacitor till either a timing circuit quenches this connection or the capacitor is discharged and the flash can no longer sustain.

Ok so that's the basics out of the way. A higher voltage CAN make the flash charge faster. In fact this is how the Nikon SB-800's additional battery works. It just boosts the voltage by 1.5V at the input to the flyback regulator allowing it to sustain a larger current in the inductors which transfer power to the high voltage side of the regulator. The risk you run is one of input compliance. Just because the SB-800 charges 1 second faster with 1.5V doesn't necessarily mean it can handle 3V or even higher without damaging some part of the regulator.

Also note the key word regulator. It regulates. Whatever you do to the input won't affect the output on any properly designed circuit. The flash charges to 300V regardless of the voltage on the input so there's no risk in damaging the flash bulb. There IS however a risk that you can overheat your bulb as the additional recycle speed means your flash doesn't have as much time to cool down between shots, and that can damage the bulb.

Cars don't run faster by using high octane gas, but you can increase the compression ratio of the engine with high octane gas which will generate more power. Your analogy is actually quite fitting here, and think of the regulator as a modern engine which will ramp back when the knock detection starts going off. Some cars just like some flashes actually do go faster simply by using higher octane gas.


In summary, don't do it without knowing the limits. Unlike your car analogy you can break your flash with a higher voltage. Find some concrete numbers unless you're a tinkerer who is comfortable with potentially having an expensive paperweight. Oh and 12V will almost definitely be too high.

Higher octane gas does not make your compression go up. lol. Higher octane burns faster and cleaner which creates more power. Compression in the cylinder is based on how much room there is left in the cylinder when the piston is a TDC. Domed pistons, small chamber heads, will both increase compression. What gas you put in it does not matter. You may be confused, in if your running I high compression engine, with low octane fuel, you will get a pinging noise because the cylinder is pre-detonating.

 

[Garbz]

Didn't say it does. I said you can increase the compression of the engine if you are using higher octane gas without fear of predetonation, i.e. modify the engine. I can't however increase the compression ratio and stay on low octane fuel as the engine will destroy itself through knocking. And most modern high compression engines will limit performance by altering fuel air mixture if knocking is detected on the fly which is why high octane petrol will often increase performance of many modern cars.

In any case the point of the thread is higher voltage at the input CAN and often does improve the cycle time of a flash.

 

[epatsellis]

...Higher octane gas does not make your compression go up. lol. Higher octane burns faster and cleaner which creates more power. Compression in the cylinder is based on how much room there is left in the cylinder when the piston is a TDC. Domed pistons, small chamber heads, will both increase compression. What gas you put in it does not matter. You may be confused, in if your running I high compression engine, with low octane fuel, you will get a pinging noise because the cylinder is pre-detonating.

Actually, higher octane fuels burn more slowly. It's part of the definition of the octane rating in fact.

 

[mikehaugen]

and compression is actually a ratio of how much room there is when the piston is at bdc in comparison to tdc, not just tdc alone. but this is a photography forum so who cares.

 

[Ginu]

I have to agree with Garbz. When I put my batteries in fresh, I have 6V total from 4 AA's. After 200 flashes, the recycle time is much slower and the batteries now have less than 6V. Therefore, there is a direct relationship between voltage and recycle time.
Vb = IR + Q/C.

I
The voltage has nothing to do with the recycling time of the flash...
Out of curiosity, do you think your car is faster by simply using higher octane gas?

I was referring to doubling the voltage as the OP stated from 6V to 12V not the difference in between charged 6V batteries and slightly used 1.3V per battery generating a total of 5.2V...
Obviously the circuit is designed for 6V so dropping the voltage to 5.2V will slow the recycling time, however nothing more than 6V will increase the recycling time of the flash unless it is build for it. Think about the difference of the spark from a set of fresh 6V batteries peaking a spark at 4000V vs slightly discharged batteries holding 5.2V producing around 3000-3500V off the spark meaning it would take roughly 10-30% extra time to reach that required 4000V spark which hits the bulb for 100% power.

In easier terms, imagine a brand new car shock vs a used shock... the used shock will take longer and will not be able to take those sharp hits as well as a brand new shock which is much more responsive. Both situations will get you to the same point when the car is at a still, but lose performance when the shock is required to work.
Now doubling the PSI to double will most likely burst the shock as it is not designed to withstand such pressure.

 

[Garbz]

unless it is build for it.

This is ultimately what it all comes down to. Switch mode regulators on the whole can be designed to take a wonderfully large range of inputs and provide a stable output. Take a look at your mobile phone charger. It likely says 100V-260V AC 50-60Hz on it. Wonderful thing. Linear powersupplies like the one in my poweramp drops out when there's a sizable power dip in the house.

The only problem we really have here is a lack of detailed knowledge of the circuit's capabilities. The OP's 12V boost may work marvelous. It may let the magic smoke out of the electronics. Who wants to be the first to try it?