Flash Output

[RalphLambrecht]

stick with me,I need to explain my question in a bit of detail: I own and love a Hensel portable flash system. The only thing I'm a bit dissatisfied with is the number of flashes per charge,which Hensel claims to be in the hundreds(I get far less;maybe 50-100). I'm a mechanical engineer and very comfortable with ISO units and their conversions but know little to nothing about electro/electronic mathematics.Nevertheless, I gave this a try and now, I need somebody are familiar to tell me if I'm close or simply off my rocker.Here it goes: the unit is powered by a 12V battery rated at &Ah.As far as I remember W=V*A,so,I calculated12V*7A makes84Wh* 3600s makes302,400Ws. If every flash pop requires 1200 Ws as is specified,that should give me252 flashes per charge, ignoring inefficiencies and power to control the unit(display,wirelessreceivertec). As I said, I get far less. Is my calculation reasonable or should I stick to mechanical engineering;be kind;I'm trying here.

 

[tedr1]

the unit is powered by a 12V battery rated at &Ah

there seems to be a typo here?

The basic power calculation is correct. The "inefficiencies" factor may be a biggie, which needs the special knowledge of a flash engineer to understand and answer.

PS the charge storage bank may be capacitors, some of these fall in value with time, especially when they operate at elevated temperatures, your calculation would be correct for the equipment when new.

 

[Leigh B]

Hi Ralph,

You'll find wide variations in battery quality depending on where it's made.
Batteries are not unique in this scenario.
If anything, they're worse than many other products.

Also, how old are the strobes? I never heard of that brand.

All strobes that I know of have electrolytic capacitors that actually power the tube.
Electrolytics deteriorate with age and develop leakage.
That leakage current comes from the battery, reducing its usable capacity.
The only solution is to have the head serviced to replace the capacitors.

- Leigh

 

[mgb74]

Also, if it's a sealed lead acid battery, it has certain lifespan (just like your car battery). It will degrade in capacity over time. If its a relatively recent LiOn battery, it's subject to the variations Leigh described. Though if it's the Hensel brand power pack, then I would think they would use quality components.

And of course marketing materials tend to be optimistic, so their claim of hundreds may be based on the most advantageous conditions.

But if its a new Hensel battery pack and you're getting a fraction of the claimed performance, I'd argue that the battery (or flash) is deficient.

 

[wiltw]

Well, P=VI, POWER = Volts * Amps, and power is not associated with the Time element. We do not know the Capacity of your source, we only know the Power it can output!

Do you have a spec on the stated Amp-hour capacity of the battery which is in the Hensel supply? I see in a photo of one Hensel battery that it is 12Amp-hour...is that the one used in your unit?

 

[spijker]

Here it goes: the unit is powered by a 12V battery rated at 7Ah. As far as I remember W=V*A, so, I calculated 12V*7Ah makes 84Wh * 3600s/h makes 302,400Ws. If every flash pop requires 1200Ws as is specified,that should give me 252 flashes per charge, ignoring inefficiencies and power to control the unit (display, wireless receiver etc).

I corrected the quote a bit here and there.

I'm an electrical engineer and your calculation is correct. As others said, the 7Ah is the wildcard. The battery is older and capacity drops over time with charging. You may want to check with Dead Link Removed if you could get the actual battery replaced.

 

[Chan Tran]

Of course the efficiency has something to do with it. Assuming 50% efficiency which I don't think it's that low. That should still give you 125 flashes or so. I suspect that your 7AH battery isn't 7AH. Its capacity has been greatly reduced due to age I think. Also capacitor leakage could be the problem too.

 

[RalphLambrecht]

there seems to be a typo here?

The basic power calculation is correct. The "inefficiencies" factor may be a biggie, which needs the special knowledge of a flash engineer to understand and answer.

PS the charge storage bank may be capacitors, some of these fall in value with time, especially when they operate at elevated temperatures, your calculation would be correct for the equipment when new.

Yes, my finger was stuck on the shift key.the battery is 12Vrated as 7Ah.

 

[RalphLambrecht]

Hi Ralph,

You'll find wide variations in battery quality depending on where it's made.
Batteries are not unique in this scenario.
If anything, they're worse than many other products.

Also, how old are the strobes? I never heard of that brand.

All strobes that I know of have electrolytic capacitors that actually power the tube.
Electrolytics deteriorate with age and develop leakage.
That leakage current comes from the battery, reducing its usable capacity.
The only solution is to have the head serviced to replace the capacitors.

- Leigh

Hensel is a well known and highly -regarded manufacturer of professional lighting equipment in Germany.my unit shipped with a lead-gel battery and Hensel is now offering a lithium-ion replacement but that needs another charger and together,they are asking for 1,000 Euros. Incidentally, a mains adapter is about the same and I would use the portability. I think my problem was that I used it too infrequently with long idle times(weeks) in between.

 

[RalphLambrecht]

stick with me,I need to explain my question in a bit of detail: I own and love a Hensel portable flash system. The only thing I'm a bit dissatisfied with is the number of flashes per charge,which Hensel claims to be in the hundreds(I get far less;maybe 50-100). I'm a mechanical engineer and very comfortable with ISO units and their conversions but know little to nothing about electro/electronic mathematics.Nevertheless, I gave this a try and now, I need somebody are familiar to tell me if I'm close or simply off my rocker.Here it goes: the unit is powered by a 12V battery rated at &Ah.As far as I remember W=V*A,so,I calculated12V*7A makes84Wh* 3600s makes302,400Ws. If every flash pop requires 1200 Ws as is specified,that should give me252 flashes per charge, ignoring inefficiencies and power to control the unit(display,wirelessreceivertec). As I said, I get far less. Is my calculation reasonable or should I stick to mechanical engineering;be kind;I'm trying here.

thanks for all replies; I will check with Hensel USA for further action.good to know the basic math was correct.

 

[Leigh B]

Hensel is now offering a lithium-ion replacement but that needs another charger and together,they are asking for 1,000 Euros.

I believe this is only a 7 amp-hour battery. I didn't realize they made them that small.

Check out batteries available from reputable electronic distributors like Mouser or Newark.
Dead Link Removed
www.newark.com

- Leigh

 

[AgX]

Also, how old are the strobes? I never heard of that brand.

As Ralph already said, Hensel is a well known manufacturer in Europe, and they are marketleader in Germany.

 

[John Koehrer]

What would it cost to have the pack rebuilt with Lithiums? Batteries plus comes to mind. Don't forget a new charger.

 

[mgb74]

12v 7ah Sealed Lead Acid batteries are commonly used in security systems and similar applications. I think you got it right with "I think my problem was that I used it too infrequently with long idle times(weeks) in between.".

For example, the instructions for the early Quantum power packs, that used SLA batteries, say:

Always recharge the Quantum Battery immediately after using it. Do not wait. If a battery is stored in an
uncharged condition it could permanently lose some or all of its capacity.

1. Turn the Quantum Battery switch off.
2. Plug the QB26 charger into a 115 volt AC outlet and into the Quantum Battery.
3. The CHG (yellow) indicator will light.
4. Charge for 16 hours or longer.​

and

• If the Quantum Battery is not used for long periods of time give it a charge every 3-6 months to maintain maximum
recharge life.​

You didn't say whether you acquired the power pack new and, if so, it performed better then.

It's likely, but not certain, that the 12v 7ah battery is a commercially available off the shelf item. While the specs may be 12v 7ah, the form factors and terminal types can vary. My first thought would be to a) ask Hensel for the specific battery model used or b) open it up and see. This will give you an idea of the variations. It's my understanding that going up in capacity (i.e. replace 7ah with 8ah) will do no harm - assuming it fits.

 

[mgb74]

What would it cost to have the pack rebuilt with Lithiums? Batteries plus comes to mind. Don't forget a new charger.

Couldn't the discharge rate of lithiums vs. SLA be a factor (unless the pack electronics were changed)?

 

[RalphLambrecht]

12v 7ah Sealed Lead Acid batteries are commonly used in security systems and similar applications. I think you got it right with "I think my problem was that I used it too infrequently with long idle times(weeks) in between.".

For example, the instructions for the early Quantum power packs, that used SLA batteries, say:

Always recharge the Quantum Battery immediately after using it. Do not wait. If a battery is stored in an
uncharged condition it could permanently lose some or all of its capacity.

1. Turn the Quantum Battery switch off.
2. Plug the QB26 charger into a 115 volt AC outlet and into the Quantum Battery.
3. The CHG (yellow) indicator will light.
4. Charge for 16 hours or longer.​

and

• If the Quantum Battery is not used for long periods of time give it a charge every 3-6 months to maintain maximum
recharge life.​

You didn't say whether you acquired the power pack new and, if so, it performed better then.

It's likely, but not certain, that the 12v 7ah battery is a commercially available off the shelf item. While the specs may be 12v 7ah, the form factors and terminal types can vary. My first thought would be to a) ask Hensel for the specific battery model used or b) open it up and see. This will give you an idea of the variations. It's my understanding that going up in capacity (i.e. replace 7ah with 8ah) will do no harm - assuming it fits.

I bought the pack new and had the battery replaced once already.It always performed well with a new battery but after a year or so capacity is down dramatically. Hensel has a Lion battery replacement but it is very expensive and requires a new also very expensive charger; not going there;my problem is that I really like the way the unit works when it works;two heads, individually changing light output and overall output adjustable in 0.1 stops ideal for my work.Before I had a very robust Stroboframe unit with only very rough adjustments1/4,1/2, full and far too powerful

 

[RalphLambrecht]

I'm coming to the conclusion that I'm dealing with a badly treated battery in combination with aging capacitors and that I probably chose the wrong unit for the application.I don't need a portable unit;I 'd probablybe better off with two mono heads.