Charging batteries inside an appliance

Why would you want to butcher a camera to slow charge standard AA's inside?? Why not just take them out and sit them on a commercial trickle charger? Put some Alkalines in the camera in the mean time to keep the time/date going.

Cameras that have a docking cradle will often let you recharge the batteries in-situ. Does your camera support this?

There is essentially no difference between the two chargers. You can use a Nicd charger to charge NiMH's.

Yes, the camera takes an almost unmeasurable amount to keep the time/date clock going. A pair of Alkaline AA's in there will probably last half the shelf life.

I can't see why you want to do this, why not just take the batteries out? Keep them on a wall trickle charger next to the camera and simply pick them up when you want to use the camera. A few seconds to insert them and away you go.

Dave :)

Hi Dave or whoever can help,

Thanks for the reply.

With the digital camera I have it is very hard and time consuming to open the battery case. It is a very tight fit. Also it is very easy to forget to put the batteries in if they are taken out. Having to put them in would take crucial time if the photograph had to be taken urgently. For example, I plan to take weather phenomenon that can only occur for a few seconds at times without notice.

There are some cameras that charge the batteries internally but they are rare and may not do what I want.

On my Nickel Cadmium charger they warn that it can only be used for Nickel Cadmium batteries.

Do you know of any suitable charger?

Regards Richard.

David L. J> > Hi

In that case I would seriously consider primary batteries. Alkalines are fine if you don't take too many shots, otherwise the new Lithium AA's are the go. Quite expensive, but if you only use infrequently then probably OK. They have the advantage of working in cold climates too if that is an issue. With rechargables you can always forget to charge them, but with primaries you will always be ready to go.

I keep a pair of AA Alkalines in my old camera in the glove box, always ready to go no matter what.

Ignore it, that is typical manufacturer rubbish. It will work fine with NiMH's.

Without knowing your camera I am hesitant to suggest anything.

Incidently, how are you going to modify the camera to take the connector, sounds real messy...

BTW, if it's crucial that you know the batteries are charged, you'd better have a charge indicator light on the charger that detects actual trickle charge current. Otherwise if your custom fitted socket gets a loose contact, you won't know if the batteries are charged or not.

Dave :)

Please don't make stuff up and present it as fact if you don't know the answer. Your answer couldn't be further from the truth, and if followed, will likely cause the original poster to needlessly shorten the life of his cells. NiMh cells do not tolerate over charging, and most NiCd chargers will overcharge NiMh cells.

However, *generally* an NiMh charger will work for both cell types.

If you want the technical details of why this is the case, just ask. Or check out the web sites of any manufacturer of NiCd and NiMh cells.

Regards, Peter

Hi

What if I connected the NiCd charger to a common electric timer that perhaps left the charger on for half an hour and one hour off in repeated regular cycles? Perhaps the charger could be turned on for less time and done less frequently.

I plan on buying another camera as the one I have is a little old. I am trying to decide on which one.

People who sell the cameras do not recommend AA Alkalines as they say that they do not last long and are too low an amperage.

Regards Richard.

I'm not making stuff up, what I said is perfectly correct for the slow charging the OP is after. Perhaps I should have made that point clear. We are not talking about a fast charger here, or even a regular charger, the OP wants a slow charger to avoid heating the cells while inside the camera. Most NiCD chargers are just a constant current source (with cutoff functions), and CC is a pefectly valid way to charge a NiMH. The life won't be shortened at all if the OP uses a sufficiently low NiCd trickle charger on a NiMH. The OP will be forced to use a very slow trickle charger unless he wants to put a temp sensor in the camera as well.

I know all about it already thanks.

Dave :)

Not a good idea, you'll almost certainly overcharge the cells and shorten their life, unless you use a very low current "trickle" charger. You really need a temperature sensor inside the camera to detect if the cells are being over charged. It's all looking like a pain in the butt really.

Problem solved then, get one with a charging cradle and you can leave it charging indefinitely.

Correct. For high drain devices like cameras the capacity of standard Alkalines is very poor compared to 2500mAh NiMH. In most cases you are lucky to get half the number of shots you get with the NiMH's. Energizer for instance quote the AA 2500mAh NiMH capacity rated at

500mA drain (to 1.0V), where as the AA Alkalines are rated at 25mA drain to 0.8V. At 500mA drain the Alkalines capacity is only about 1400mAh, and that's to 0.8V, not 1.0V. Most cameras are designed for NiMh use, so they won't drain down to 0.8V, so you loose even more capacity there on Alkalines. That's why you'll get roughly half the number of shots on Alkalines. Lithium AA's on the other hand are rated at 3000mAh at 250mA drain to 1.0V, so you'll get similar performance to the NiMH's. They are much more expensive though, but it means you can leave the camera lying around for years without being charged and it will be ready to go when needed, guaranteed.

Dave :)

Hi

Thanks for the letter.

How slow a battery charger would I need and what output should it have? I think the NiCad one that I have takes about 16 hours to charge the batteries.

Why wouldn't the common electronic timer work because if it switches the charger off for periods, wouldn't it have the same affect as a slower charger if it does not remain on for long? The timer could even only switch the charger on for half an hour a day if that is best.

It is unlikely a camera with a charging cradle would have the features I want as they are rare.

I heard that cameras do drain a small amount of power from the battery even when they are switched off. This is for the clock etc. So I doubt that the batteries would last years even for a lithium battery from what I have read others say.

What do you think about the below non rechargeable battery? They cost about 10 dollars a pair.

AA Size Lithium Long Lasting Batteries 1.5V - Pk. 2

The worlds longest lasting AA battery. The perfect power source for high drain appliances, such as cameras, camcorders, personal stereos, mobile phones, palm top computers and TV's.- Up to 3 times the life of any alkaline battery.- Up to 10 times the life of ordinary carbon zinc battery- Guaranteed shelf life up to 10 years.- 1.5V, 1.4Amp hour.- Pack of 2

Your help is appreciated, Regards Richard.

It would need to be designed for 2 series AA's (i.e. about 2.4V), and off the top of my head I would say about 50mA would be fine if you are going to pulse it on and off as you suggest, then it'll take a few days to full charge from flat. If you use higher current you have to be a lot more careful with cycle times. Your problem is you won't really know how much charge is left in the batteries and without overcharge protection you could damage the batteries. Like I've said, it's getting messy, I really wouldn't bother doing it. Have you even thought about how you are going to *reliably* modify the camera to take a socket and internal wiring to do this? If reliability and instant readiness of your camera is the #1 priority then the last thing I would do is modify the battery connections.

Yes, that can be made to work given the right current.

I would hardly say they are rare. A lot of cameras with Li-Ion batteries will have internal charging features. What features do you need?

They should last for years. The clock takes in the order of microamps of current. Measure it with a meter if you want to be sure. My Fuji for example takes about 30uA, so the batteries will last for essentially the shelf life. Actually, the camera takes a "gulp" when the bateries are first inserted, this is to charge the super cap that retains the clock power while the batteries are replaced.

Like I said in my other post, Lithium AA's will last as long or longer than fully charged 2500mAh NiMH's. Modern cameras can get hundreds of shots from such a set. 500+ shots is not uncommon. If you only take a few shots here and there then they should last a very long time and will be the best option. If you take hundreds of shots in one sitting then you'd have to replace them after every use.

Dave :)

Hi Dave

Thanks for the letter.

I heard that Li-Ion batteries are very expensive and may only last 2 years and that AA would be more economical. So buying a camera with a charging cradle may be expensive to maintain.

I can try the batteries I described in my last post but it is just the camera experts recommend rechargeable so I thought I could try both.

You state: "Your problem is you won't really know how much charge is left in the batteries and without overcharge protection you could damage the batteries." Wouldn't this problem be overcome if I use a Nickel Metal Hydride charger as they are specially made for these batteries and are not supposed to over charge them.

Your help is appreciated, Regards Richard.

Li-Ion are expensive only if you buy the name brand from the camera houses. Li-Ion batteries for my Canon are about $2ea on eBay from the US for a generic brand, and they work pretty well. You should get more than 2 years use out of a Li-Ion.

I'm a big fan of AA's for all of my gear. It means that I can share batteries between my camera, GPS, UHF radios, torch etc. Essential when you are out in the field.

But for other people Li-Ion and a charging cradle is the way to go, as it's a "no-fuss" solution. Look at *your* needs and how you will use the camera and then determine what is best for you. Don't let anything you read about the pros or cons a battery technology drive your decision, NiMH and Li-Ion are both mature and excellent solutions for camera use.

Of course they recommend rechargables, that's because primary Lithiums are expensive, and for the average user it's much cheaper and better to use NiMH. Don't listen to the generic recommendations from the "camera experts", look at *your* usage pattern and determine if Lithiums would be a better solution. I recon there is a very good chance they would be best for your "emergency use" application.

That's not the complete story. A proper NiMH charger will have over-temperature protection as an additional (and fail-safe) measure of battery overcharging, and this is built into the charger cradle. When charging external batteries this means you would need to install a temperature sensor inside the camera next to the batteries. Not a trivial thing to do.

Have I convinced you to give up the idea yet? ;->

Dave :)

Hi

I think I was quoted about $70 for a Li-Ion battery and not a great deal less for a generic one. So I would be surprised if something about the cost you stated would be any good or be the correct battery for the purpose.

I can't see how the battery would overheat if a proper charger is used and it is at a very slow rate. The temperature could be measured with a thermometer. I should think that the temperature would be consistent. What is the highest temperature that would be acceptable and is the main temperature risk to do with the camera?

So do you think that I should try the below battery first as they are from a company I plan to order from? They cost about 10 dollars a pair.

AA Size Lithium Long Lasting Batteries 1.5V - Pk. 2 The worlds longest lasting AA battery. The perfect power source for high drain appliances, such as cameras, camcorders, personal stereos, mobile phones, palm top computers and TV's.- Up to 3 times the life of any alkaline battery.- Up to 10 times the life of ordinary carbon zinc battery- Guaranteed shelf life up to 10 years.- 1.5V, 1.4Amp hour.- Pack of 2. Your help is appreciated, Regards Richard.

What's the battery model number? You can almost certainly get it a lot cheaper on eBay. Where did you get the quote from?

I've said it numerous times before, if the current is low enough then yes, you can continously charge the batteries without a problem. But the charge current will be so low (less than 1/10th C) that it will take many days to fully charge the battery. If that is acceptable to you then great, go for it.

But if you want the batteries to be charged at a reasonable rate and then have the charger switch to "trickle charge" mode, you will most likely need the temperature sensor inside the camera and hooked up to the charger. The charger uses the rapid rise in temperature to detect that that the battery is full. If you want to use a charger without a temp cutoff and only relies on voltage detection then you run the risk of damaging the batteries.

It's a bad idea all round, and you haven't even addressed the reliability issue I raised!

For god sake, yes, try them, they are purpose designed for high drain devices like cameras! Dave :)

they bdon't want you using it primary cells. (dray cells, alkalines etc)

I got one labeled "lenmar nomem pro" it's a fast-charger with a 12V plug pack and a car adaptor, it'll charge 1000maH AA nicads in 100 minutes and NiMHs in proportianately longer (and shut off automatically)

--

Bye.
   Jasen

Here's a quote directly from the Panasonic web site: "Trickle charging cannot be used with NiMh batteries."

Trickle charging NiMh cells *will* reduce their service life. I really do suggest that you might like to update your knowledge with a visit to the web sites of a few battery manufacturers.

It's hard to be clearer than the quote above, directly from one of the most respected battery manufacturers. Here's a link to the application note that the quote is from:

Regards, Peter

The next paragraph says: "However, after applying a refresh charge using a rapid charge, use a trickle charge of 0.033CmA to 0.05CmA" It also goes on to recommend a timer just in case. So it's actually telling you to use a trickle charge. The quote not to use it is most likely referring to traditional NiCd levels. The guy who wrote it probably got a bit confused.

Take a look at the Energizer application note:

Page 19: "For charging schemes that then rely on a timed "topping' charge to ensure complete charge, a rate of 0.1C appears to balance adequate charge input with minimum adverse effects in overcharge. Finally a maintenance (or trickle) charge rate of 0.025C (C/40) is adequate to counter self-discharge and maintain cell capacity."

and Duracell:

Page 16: "A number of applications require the use of batteries which are maintained in a fully-charged state. This is accomplished by trickle charging at a rate that will replace the loss in capacity due to self-discharge. In these applications, a trickle charge at a C/300 rate is recommended. The preferred temperature range for trickle charging is between 10=B0C to 35=B0C (50=B0F to

95=B0F). Trickle charge may be used following any of the previously discussed charging methods."

So Energizer and Duracell fully endorse trickle charging, just like many other manufacturers, and just like professional charger systems have.

So it's perfectly OK to use a trickle charge, just make sure it's very small, smaller than for NiCd.

BTW, I'd be willing to bet big time that Panasonic brand NiMH chargers have a trickle charge mode too.

I have, and it's you who should update your knowledge. You take one quote from one manufacturer that actually contradicts itself in the next paragraph, and you take it as gospel.

Common industry knowledge is that NiMH's can be trickle charged, and I've designed charging systems myself like this without any measurable loss of capacity. There are many other factors which are more detrimental to the service life of a NiMH than a high trickle charge rate.

Energizer and Duracell are respected manufacturers, and both of them say I am right and you are wrong. I'd suggest you check out a few more references next time before you go taking one manufacturers quote as gospel.

Regards Dave :)

C30 to C50 is a maintenance charge, not the typical C10 trickle charge used with NiCds. A maintenance charge is intended to keep a cell charged, not to charge it. The purpose is to simply counter self-discharge, which is about three times higher with NiMh compared to NiCd.

In fact, that's exactly what your energizer and duracell quotes are saying too.

No, they are endorsing a maintenance charge, at a much lower rate than a typical C10 NiCd trickle charge rate. In fact, duracell is saying C300, which will never charge a cell.

No, read it your quotes again. Maintenance, not trickle charge. And at a much lower level than a NiCd trickle charger.

I'll take that bet. Cash or chocolate only, please.

Maintenance, possibly. Trickle, never.

There is no contradiction. Instead, you appear to be confusing trickle charging with maintenance charging. Your own quotes show this.

Your own quotes do not support your statement - they are clearly talking about maintenance, not trickle charging. It appears that you cannot see the difference.

From the Duracell data sheet you quote, at the bottom of page 19:

"Finally a maintenance (or trickle) charge rate of 0.025C (C/40) is adequate to counter self-discharge and maintain cell capacity."

Clearly, what they're saying is that this "trickle" charge (to use the word you like, and the word they add for people who don't understand "maintenance" :-) is not *charging* the battery, but merely overcoming self-discharge. Again, they say the same thing on page 21, near the top.

On your "techbull.pdf" file (what a great filename, lol), Duracell are saying exactly the same thing (top of page 17), but they are using your term "trickle charge", when it's really just overcoming self-discharge. They even say these exact words. C300 will never *charge* a cell, so saying that this is trickle charging the cell is just plain silly.

A typical NiCd C10 trickle charger will fully charge a NiCd cell in about 12-14 hours. Connect this same C10 charger to a NiMh cell for the same time, and you'll probably not cause any problems.

*HOWEVER*, a typical NiCd C10 trickle charger does not have a timer, and is often left on (by the user) for longer than 14 hours. At the C10 rate, you can virtually charge a NiCd cell forever without causing any problems. Not so with NiMh cells. As you'll read in the data sheets you quote, C10 for more than about 12 hours *will* overcharge a NiMh cell, and NiMh cells *will* suffer a reduction in capacity because of this overcharging. Measurable, and definite. *AND* is says so in the data sheets.

Peter

So this "maintenance" charge value is such a precisely engineered value that it *just* counteracts the self discharge? What if you go 0.01C over the quoted maintenance rate, are you going to eventually damage the cell? The answer of course is no.

I was not implying you use those exact figures to trickle charge the cell.

Now this is just playing around with words and specific numbers.

Yes, a NiMH cell may have its service life reduced by a normal 0.1C charger, due to overcharge, but you are talking specific values now.

It is possible to "trickle charge" a NiMH cell (at some rate between

0.1C and the "maintenance" charge rate for arguments sake) to eventually fully charge a NiMH cell and not damage it. That's what I've been saying all along.

You can dick around with exact C numbers all you like, the fact is in practice you can do it sucessfully. I know, I've done it myself. If you get too high a trickle charge rate you might shorten the life of the cell, but even then it's not a big deal in many applications, you can still get a good service life for your money.

Not everything is black and white as per the data sheet you know, not all cells are the same either, nor are any two systems alike. Build some real systems, test some real batteries, you'll find out.

Dave :)

No it's not - the figures are from your data sheets.

Yes, specific because C10 is the typical rate used to trickle charge NiCd.

Surely now *you're* just "playing with words and specific numbers" :-)

Your original statement was this:

Patently, that's untrue. And now you appear to even be agreeing that you need to charge at a specific rate.

The fact is, unless you "dick around with exact C numbers", you're in danger of overcharging NiMh cells, and therefore reducing their service life. Which is exactly what your data sheets all say, many times over.

I've probably built more that you can imagine, Dave.

Peter