Battery characteristics: Lithium, Ni-Cad and Ni-MH

[Nick Odell]

I have some cameras from 1989 which have alternative power packs: one for a 6v Lithium cell and the other is for a set of 4 alkaline AA cells.

Printed inside the AA pack and in the instruction manual it reads "Do not use Ni-Cad cells."

I'm familiar with the concept of a known voltage being used as a reference for metering and shutter operation and can usually compensate for higher or lower voltages in the ISO/ASA settings and I'm wondering if incorrect exposures is the only reason I'm being warned off Ni-Cads?

Is there anything about the characteristic discharge of a Ni-Cad cell or anything else about it that could damage the circuitry of a 1989 camera? What about Ni-MH cells which have more-or-less completely replaced Ni-Cads now? Would it be safe to use much more convenient rechargeable Ni-MH cells or should I just stick with Lithium or alkaline?

Any thoughts appreciated.

Thanks,

Nick

[Archibald Tarquin Blenkinsopp]

Nicads as you surmise are lower Voltage 4.8 for a pack as opposed to 6

Flash units were often adorned with warnings about nicads being unsuitable. Possibly because the current drawn is high leading to a very short period of us for rechargeables. The additional problem may be that the current being very high used the batteries internal resistance to limit it to safe values. A nicad giving its full whack of current is a lot more spectacular than an alkaline equivalent :-)

AB

[tabbypurr]

There are 2 problems with using NiCd or NiMH in this app.

1. Flash units often relied on the battery to limit charge current. Without that limit it dies.
2. Terminal voltage. Old cameras often shut down with most of the charge still in the battery if NiCd or NiMH are used. That's not a problem if you can use 5 rechargeables in lieu of 4 alkalines.

Presumably a suitable power resistor might solve 1, but I don't know of what value & haven't tried it.

NT

[Brian Gaff]

I think you need to find out what voltage its made to use. Normally using nicad or the newer equivalent you end up with nominally 1.25v per cell, I have noticed that some circuits simply indicate low battery if you shove rechargeable into them. Depends very much on the design. Brian

[Brian Gaff]

Yes there is that. For example if its a film winding system. the jam which occurs at the end is current limited on alkaline but on rechargeable it can easily cause heating of motor and anything else. Also of course as I said before they may see 4.8v as end of life for the battery, in which case it just wont operate.

I had a Pentax that was like this. A cannon was not very fussy however. Brian

[whisky-dave]

Well I have an old canon winder that can go at 5FPS and takes 12 AA batteries they supply a differnt holder for AA and ni-cds. The Alkaline holder has a label on it indicating that ni-cds can't be used.

Here in the lab we have a fujifinepix camera that can take 4 AA alkalines of Ni-MH cells but you need to indiocate what ones you;ve inserted by settign one of the menu options, which seems a bit primative for a digital camera....

[Nick Odell]

These cameras are Pentaxii (what's the plural of Pentax anyway?) and I think the current limiting characteristic is probably spot on. One of the cameras let out its magic smoke and as the camera was new to me, I wasn't sure if it had just expired due to old age or due to my disregard of the battery warning. Everything still works except the flash unit. The eyepiece has smoked up - which makes it handy for taking pictures of the sun, wouldn't you say?[1]

Nick [1]Joke!

[Nick Odell]

I've got a Finepix S-series camera like that. It might be a little bit primitive but at least it doesn't a) fry the electrics when you try to use it or b) shut down due to low voltage after five shots. Or a) and b).

Nick

[Nick Odell]

I could probably do that: there's plenty of room in the battery pack. But I probably won't and will just keep some alkali cells in reserve in case the Lithium battery pack runs down.

Supplementary question if I may: can I presume that rechargeable Li-on are safe to use in this context or do they share the characteristics of Ni-MH etc? As well as single-use 6v Lithium cells I've got some rechargeable ones and it would be quite handy to use these in those cameras.

Thanks,

Nick

[Theo]

You might get away with it with a couple of LiFePO4, nominal voltage 3.2v per cell, max about 3.6v Lithium ion (nominal 3.6-3.7v, max 4.2v) would likely be too low for one cell and too high for two.

If you're going to do that, get cells with integral protection, because the camera could discharge them beyond a safe voltage (about 2.5v per cell).

They can give a lot of current, so if the application relies on the cells self-limiting they might not be ideal.

Theo

[Nick Odell]

Thanks

The 6v cell is a 2CR5 and I've got some "protected" rechargeable 3v Lithium ones (123???) To swing this onto a D-I-Y theme, I've been making my own rechargeable 2CR5s by taking out the old cells from the battery case and soldering in new contacts.

Good to know that they are (probably) safe to use in these cameras.

Nick

[Theo]

The idea of a 3.0v lithium rechargeable puzzled me for a minute - LiFePO4 are 3.2v and lithium ion are 3.6v, so how do you get 3.0?

However it turns out that the 3.0v ones are 3.6v lithium ion with a series diode to drop 0.7v. So I suppose that would work, if you don't mind wasting

20% of the energy...

Theo

[tabbypurr]

No & no. Lithium have very different characteristics to alkaline, NiCd and NiMH. Terminal voltage varies widely in use, starting much above nominal voltage.

NT

[Nick Odell]

replying to Nick Odell, Nick Odell wrote: Grovelling apologies for turning up under HomeOwnersHub: I was using Google to search for this old thread and HomeOwnersHub is what it served me.

Another piece of camera equipment: this time a motor drive with an operating voltage range between 9-12v. Again it dates back to the eighties but this time the manual specifically says to use either alkaline or NiCad cells. Of course NiMh cells didn't exist in those days so I want to know: if NiCads are okay, will NiMh cells do too?

Thanks,

Nick

[The Natural Philosopher]

yes. they are, excpet with respect to charging, interchangeable with NiCd.

But Id use a 3 cell lithium ion with that voltage

[Nick Odell]

Thanks for that.

It's got eight slots -in two banks of four - for AA cells so I'd need to perform some jiggery pokery to do that. Or use the socket for an external power source which would reduce the portability even more: as it is you need to do a course of weight training before you can lift the blessed thing. (Bronica ETRS with all the bells and whistles)

Nick

[tabbypurr]

yes usually. NiCd hung on for years due to ability to kick out more current, so if the cells are very hard pressed you might find NiMH feebler.

Charging is similar but not identical. A NiMH charger will keep them lasting longer than the old NiCd trickle charger, and charge faster

NT

[The Natural Philosopher]

Oh well cheap and cheerful NiMh it is then

[Nick Odell]

Thanks!

Nick (Back on Eternal September now I've found the thread again)