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12-28-2021, 04:33 AM   #1
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Lithium batteries for old flash unit

I have several old (30 years?) flash units of which the capacitors ar no doubt past their best. They charge up tolerably with fresh AA alkaline batteries, but once the battery voltage drops to less than about 1.4v they take for ever (20-30 seconds anyway) to do a full charge. With NiMH rechargeable batteries (1.2v) they take minutes to charge, or simply don't.

So I am thinking of trying 1.5V lithium iron disulphide AA batteries. Not rechargeable but said to have 7x the life of alkaline and a long shelf life. Does anyone have experience with them in flash units? Wikipedia says they are not popular in the West, although they account for 28% of non-rechargeable sales in Japan. They are available in the UK although I don't think the Royal Mail will carry them. Wikipedia also reckons that ones sold to consumers (like these below) have internal protection against short-circuiting.

https://cpc.farnell.com/energizer/629611/battery-ultimate-lithium-aa-4pk/dp/...?ost=bt0393887

12-28-2021, 07:04 AM - 1 Like   #2
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I have used those in my old *istD where they worked very well. The higher voltage than rechargeables should make them useful for flash use too. I did try them in my AF360 some years ago but only because I had some lying around at the time. The higher price makes them less desirable but that is their only downside.
12-28-2021, 07:39 AM - 1 Like   #3
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I have used them. I kept a set in my bag in case the rechargeable batteries were dead. The long shelf life is a plus.
12-28-2021, 12:13 PM - 1 Like   #4
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Have you tried to fire off a series of full power test flashes to see if the charging speed improves? In my old Vivitar 283 manual, I think this was referred to as "forming" the capacitor. Not sure if that will help here depending on the age of the flash but also worth noting good quality rechargeable batteries help (such as eneloops or the equivalent ikea Ladda).

My 283 and an AF240T are still working well and both are probably 30-40 years old.

12-28-2021, 12:18 PM   #5
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I use to use them in my Vivitar 285HV flashes and they worked great. I now use eneloops and laddas in the flashes and haven't had any issues and they are a lot cheaper in the long run than those energizers. However those energizers could take a beating and still work and I never had problems with them, even when really using the flash hard like at a scout event where I was cycling the flash at full power as soon as it recharged. The batteries got really hot but never had an issue with bursting or leaking. I also use to use them in my K2000 until they were replaced by eneloops and laddas. The only time I really use them now is if I am going to be out in the really cold shooting with my K-500 or flashes as they do better in sub 0 temps than the rechargeable ones. I do keep a set or 2 in my photo bag just in case as they do have a long shelf life.

I do like the AAA ones of these for things that I just want to work without issue and will use those exclusively in my headlamps and O-GPS1.
12-28-2021, 07:08 PM   #6
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The large capacitor is probably suffering from age, and the electrolyte has dried up. The smaller electrolytic capacitors are probably also suffering the same problem. If repairs aren't doable, then letting it sit charging up for hours is sometimes worthwhile - when the caps get a charge, over time they may recover somewhat. Be kind to it, so NiCd or NiMh which are a bit lower in voltage will take longer to top up, but that might help it.
The Li batteries tend to be higher voltage when new (1.6V/1.65V) and that may put a bit more stress on the old flash circuits.
12-28-2021, 09:12 PM   #7
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The Quantum battery packs I used in the 1980's used a sealed lead-acid battery and had plenty of oomph for quick recharge times on the Vivitar 283. These batteries are used in emergency lighting fixtures and UPS devices. Rechargeable, though you want a charge that will switch over to trickle charging to keep the battery topped off and in best condition.

You'd have to make an adapter but that isn't that difficult. I made one out of primarily wood dowels and nails.

You should be able to find a local source but these are what I'm talking about:
https://www.batterymart.com/c-03-6-volt-sealed-lead-acid-batteries.html

12-28-2021, 10:03 PM   #8
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I've used the lithium batteries you mention, they seem fine, and are easy to get in the US, even if they aren't so popular.

But it seems like your real problem is the capacitors, as others have suggested.
01-11-2022, 04:32 PM   #9
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Well I obtained the lithium AA batteries and they definitely speed up flash unit charging.

I have just run some tests with a Pentax AF280T flash unit, which takes four AAs. I compared alkaline batteries, NiMH batteries, a bench power supply, and the new lithium batteries. With each source, I fired a few full power flashes first, then timed how long it took from firing a full flash for the READY light to come back on.

The slightly tired alkalines (1.4v off-load) re-charged it in 20 seconds, the NiMH (1.2v off-load) in 13 seconds, the bench power supply (6v off load, like 4 x 1.5v) in 8 seconds, and the lithiums took 6 seconds.

Interestingly the bench power supply, being design limited to 3 amps, was flat out at 3 amps for about the first 6 seconds, with its voltage reduced below 6v until then. The fact that the lithiums beat it shows they must have been running at maybe 4-5 amps at the start, maintaining higher voltage, nearer to or at 6V.

Also interesting is that the bench power supply's ammeter showed it was still putting significant current (2 amps and declining) into the unit after the ready light had come on, showing that the READY light comes on well before full charge is reached.

I also tested with a big old Sunpak Hammerhead 555 (or G4500DX) which takes 6 AAs. This is what I really want the Lithiums for, The NiMH would not charge it at all (!), but the bench power supply (at 9V) did it in 10 seconds, and the Lithiums in 5 seconds - which is almost as good as the 4 seconds that the manual claims with NiCads. The 555 has a Guide Number of 45m so those lithiums must be working really hard.

QuoteOriginally posted by ProfessorBuzz Quote
The large capacitor is probably suffering from age, and the electrolyte has dried up.
I did look into replacing capacitors but could not source one that would fit in the space and have a reasonable capacity. The handles of the Sunpak hammerheads I have were obviously designed around the main capacitor (or vice-versa) - see picture. I could have accepted some reduction in nominal capacity because the new capacitor would nevertheless probably have more actual capacity than the old one anyway, but I could not find anything suitable that was anywhere near.


QuoteOriginally posted by ProfessorBuzz Quote
The Li batteries tend to be higher voltage when new (1.6V/1.65V) and that may put a bit more stress on the old flash circuits.
Yes, I was surprised to measure the off-load voltage of the Lithiums at 1.7V, though nominally 1.5V. Knowing they have very low internal resistance it is a bit scary handling them, like if accidentally short-circuiting them in the battery holder would they catch fire? However I believe that they incorporate an internal fuse and the Energiser (maker) spec sheet says :
QuoteQuote:
Accidental short circuit for a few seconds will not seriously affect the battery. Prolonged short circuit will cause the battery to lose energy, generate significant heat and can cause the safety release vent to open.
01-12-2022, 07:43 AM   #10
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Capacitors have made huge improvements Iím surprised you canít find something larger capacity in a smaller size. What are the specs of that one (volts, micro farad capacity, etc?)
01-12-2022, 10:19 AM   #11
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QuoteOriginally posted by UncleVanya Quote
What are the specs of that one (volts, micro farad capacity, etc?)
2000 microfarads and 350 volts. Mine is no longer disassembled, but I estimate the available cylindrical space for it is 32mm diameter and 70mm long. In fact the picture I posted above is co-incidentally close to full size (on my 1600x900 20" monitor). BTW, I don't recommend disassembling these things to anybody! The space is packed, so the re-assembly is the hardest part and you really need to grow five or six hands.


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