Mixing Energizer nickel-medal 2000;2300;2450mAh

peter c. · August 5, 2012

Do I risk damage if using a lower mAh battery with 3 higher mAh batteries in my 580Ex II? Example 3 - 2450 mAh and a 2000 mAh? Thanks

Pete

scott_ferris · August 5, 2012

Yes you do, mixing battery capacities is a big no no.

bob_sunley · August 5, 2012

No damage likely, or even possible. Your run time is limited by the lowest capacity battery. So if one of your 2400mah batteries has 1000mah left in it, that is all you will get when it discharges and the other three still have some reserve.

Same thing happens when you have a "bad cell".

scott_ferris · August 5, 2012

That is not correct Bob, once the lower set discharge the higher capacity set will effectively try to charge them. In a best case scenario you will kill the lower capacity set once they discharge, in a worse case scenario the batteries will catch fire, burst, out gas, and or overheat.

If it was a $20 item then it is worth the risk, in a $450 flash that is prone to overheating, not so much.

bob_sunley · August 5, 2012

Scott, can you please explain how you can "charge a set" of cells when they are in series with a load? You have a set of four cells in series, if one of them is almost discharged, you don't get much out of the "battery".

Same thing with the battery in your car, there are six 2.2 volt cells in that housing, if one of them won't take a full charge, you cant' start your car. No possibility of fire or whatever in a $100k Lexus. Your $400 flash is no different.

William Michael · August 6, 2012

". . .can you please explain how you can "charge a set" of cells when they are in series with a load? You have a set of four cells in series, if one of them is almost discharged, you don't get much out of the "battery"."

</blockquote>

It is very different to the Lexus' car battery.

Firstly, it is most likely that is a typo in the header and that the OP is using NiMH batteries - certainly I expect that Scott assumed this also.

Not butting in on Scott's question - but I had already written this:

Most, if not all Photography equipment which can use NiMH batteries will use them connected in Series. Ideally, all NiMH Batteries connected in series should deliver the same amount of current to the total load and all should approach "empty" at about the same time. IF there is a lower capacity battery in that series as that battery drops and reaches ‘empty’ - AND all the other cells have enough to allow the device to continue to function (i.e. the Device does NOT automatically cut out due to “Low Battery”), the device will continue to draw current. Since all the cells are connected in series the current flows through the "empty” battery also and actually starts charging it: in reverse polarity.

Some manufacturers state that NiMH batteries will cope with a small amount of reverse charge: but it is my understanding that any NiMH battery under reverse charge will be damaged and does have a potential to Vent if any reverse charging continues is beyond a very small amount.

Electrolyte leakage may result because of Venting, which leads to a decrease in the capacity of that battery, (i.e. this practice potentially sets up a cycle whereby the lower capacity battery becomes even a lower capacity battery). Obviously all this makes the process happen even earlier in future discharge cycles.

Also as a result of reverse charging the NiMH battery might bulge because of internal gassing.

Combine battery venting in a small chamber (such as the battery compartment of a Flash Power Supply) and also the local heat generated by rapid use / recycling it is not beyond reason to consider explosion and / or fire. This may also a problem even with matched cells connected in series, because they can become mismatched with time.

Well designed equipment using a few (e.g. two or four) SAME CAPACITY – GOOD CONDITION NiMH batteries in series, will likely power down before the voltage of any one battery drops significantly to begin reverse charging for an excessive period of time: however, with age, use and or a large number of batteries used in series, it is possible for this situation to occur more often.

Obviously, best practice is to buy same capacity NiMH in sets and label them as a SET and to use and charge them, in those sets.

WW

craig_meddaugh · August 6, 2012

As for damaging the flash, Bob is correct in this case. The low voltage, limited stored energy, and the internal resistance of NiMH guarantees that there is no way one of the higher-capacity batteries could run enough current through the lower-capacity batteries to cause any adverse consequences.

As for the batteries, the smallest capacity battery determines the capacity of the entire system, so if you are trying to maximize flash life, this is the wrong way to go. Additionally, the lower-capacity batteries will be subjected to a greater net discharge which is not good for their lifespan.

Personally, I mix and match NiMH all the time with no problem. Also, just because a battery claims it has xxxx mAh doesn't mean this is actually the case. They have substantial variance (+-) 200 mAh out of the box and, after some use, I find that the max capacity has often dropped by 25-40%. So even if you "match" stated capacity, all of us mismatch actual capacity all of the time.

However batteries can be funny, science be damned. I once had a SLA (a modern one) blow up on me when I tried to start my truck. Should be impossible, but it happened anyway. Put a very nice dent in my hood and the cloud of gas was very impressive.

If you want to worry about batteries and cameras, worry about the lithium-ion cells that power the camera. People toss those about all of the time, but short the leads and the result is impressive!

scott_ferris · August 6, 2012

Thanks William, you saved me a lot of typing.

OK, real world experience, I have killed two 550EX Speedlites by mixing battery capacities that caused leaks surprisingly quickly.

I have also dealt with two fires on multi-million dollar yachts that had mismatched capacity batteries in their house banks that directly caused those fires. A different situation to a camera flash I agree, but more relevant than a cheap car's battery.

If you want to mix and match be my guest, I won't.

zensphoto · August 6, 2012

I have used NiMH in my 320EX and now I only use the Energizer Lithium, sure they cost more, but I need batteries that go and go and go. The Lithium batteries are a lot lighter especially when you have a long distance to hike. No I can't recharge them, but they are very reliable. I have had a lower mAh mixed in with higher ones you just don't get the total mAh length you would get if all 4 are the same. I have never experienced any damage with my 320EX mixing the mAh NiMH's. For me all works well.

bob_sunley · August 6, 2012

Large capacity batteries in series/parallel connections are in no way relevant to 4 AA NiMH cells in a series setup. Even a small 100AH 24volt ni-cad tray can cause a nice fire when it's shorted.

My experience with the AA type NiMH cells is the same as Craig's, they vary in capacity from 5-20% out of the package and get better and worse as they age. Unless you have a load tester you can't even guess how close they are even when new.

BTW they can leak even when new and unused in a sealed package, just like any other sealed cell.

William Michael · August 6, 2012

I also have mixed varying capacity NiMH and used that (mixed) set of four in a Canon 580 Flash and also a mixed set of six NiMH in my Metz Units and always with no apparent problems of: overheating, swelling or leaking.

But my having done so thus far, without any apparent problems, does not makes the practice correct; nor lessen the chance of a problem or damage to a device in which the batteries are being used, if a problem because of this practice with one of the batteries arises.

As to Craig’s statement: “As for damaging the flash, Bob is correct in this case. The low voltage, limited stored energy, and the internal resistance of NiMH guarantees that there is no way one of the higher-capacity batteries could run enough current through the lower-capacity batteries to cause any adverse consequences.” That’s a big call, IMO.

And, Bob of course a NiMH can leak at any time even without being used – but we are not really discussing how possible that might be or the causes of it.

So I guess we will have to agree to disagree on what is possible and not possible; and also as to why it is possible or not possible.

WW

William Michael · August 6, 2012

As to answering the OP – my comment – considering equally all the input:

It would be safer to be conservative and not mix them up – but on the other hand it might be more adventurous to give it a go and just see what happens.

So what is it Peter - Conservative or Adventurous?

WW

mbkissel · August 6, 2012

I would have to agree with Scott and William. At a minimum, you may only damage the discharged cell permanently such that it can't be recharged. On the other hand, the consequences of a ruptured cell is much more likely to cause significant damage to your flash.

I use a Powerex smart charger that reports the mAh capacity during and after charging. Since I have several "sets" of Eneloops, I group them to minimize the differences in their reported capacities.

I don't know if a 580EX-II has a shutdown on minimum voltage capability. If it does, it may prevent battery damage (and damage to itself) before a single cell reaches its exhausted state. As William says, is it worth the risk to you?

peter c. · August 6, 2012

Thanks for all of your responses. I have started to sort by capacity and now want to buy the Powerex smart charger mentioned by Mark Kessel. Are there other chargers that I should consider? I have several and some are worthless. All of you understand the importance of not compromising as we strive for the best photo shoots.

peter c. · August 6, 2012

Thanks for all of your responses. I have started to sort by capacity and now want to buy the Powerex smart charger mentioned by Mark Kessel. Are there other chargers that I should consider? I have several and some are worthless. All of you understand the importance of not compromising as we strive for the best photo shoots.

craig_meddaugh · August 6, 2012

William,

That's not that big of call. Simple science determines the typical outcome of the situation in question. Now of course, all sorts of unusual things can happen in batteries (see my experience with a SLA that should have never have done what it did) that mess up the simple science and create a vast array of complicated, dangerous, but rare situations, but the vast majority of the time, nothing catastrophic can happen with the low capacity/voltage cells used in camera flashes.

Of course, something could happen, but as I pointed out, we always mismatch batteries, and even if you treat them as a set, all batteries age differently. Even if you use a high-end charger, there is still a possibility for internal crystal growth to occur that will short a battery, with rare but disastrous consequences. However, given what you would have to do (discharge and recharge batteries prior to every use) to avoid these rare situations, it is hardly worth worrying about.

As for the yacht experience, that is perfectly plausible, but only due to the wiring between the batteries. Given the power capacity of house batteries on a boat and the typically corroded or mis-wired connections between the batteries, inadvertent current flow due to the uneven charge state of multiple batteries can certainly cause a fire by overloading the wires or other electrical devices separating battery banks. I've never had a fire, but have come close (wires boiling off insulation is never a good thing!). However, given the vastly different current capacities in the two scenarios, this is an apples/oranges comparison.

William Michael · August 6, 2012

"Simple science determines the typical outcome of the situation in question"

</blockquote>

Yes I agree, science will indicate typical outcomes. And science will indicate possible outcomes and the probability thereof.

Simple science will determine if mixing different capacity NiMH Batteries will increase the chance of venting - and the answer is; yes it will. Simple science will also determine whether a NiMH battery venting in an enclosed area will increase the risk of damage to the device in which it is enclosed: and the answer is yes it will.

And that is what the OP asked.

And these facts - based upon simple science - means there is an increased risk of damage (not a catastrophe) - but just 'damage' – ergo statements like ‘there is no way’ . . . are a big call. But we shall agree to disagree on that also: because whether it is a big call or not - is only an opinion and not based on science: so let’s not confuse the two.

As to whether one worries about mixing different capacity NiMH batteries: that’s a personal choice.

WW

david_john_appleton · August 6, 2012

you will find the best branded battery's will have a 10% varying capacity any place..and when they get older its probably more like 50% ...cheaper battery you can take off 30% what it say on the side ...so them bargain 3000ma battery's off the bay will probably test out to be 2000ma so best to keep in matched sets as 2 batters of say 2700ma of different make may say 2700ma but not be

What is important if you mix capacity's is do not run them dead flat as the lowest capacity battery will run to below flat which will reverse polarity (only with nimh) then when you put it in a smart charger it will register as faulty ..

This can be fixed by charging in a old unsmart charger for a short time and then putting back in the smart charger

I find 90% of nimh battery's that show up as faulty in a smart charger are fine once the have had a bit of charge put back in them

Marcus Ian · August 6, 2012

I used Energizer NiMH exclusively for several years in my flashes - They varied from 2300-2500 mAh per battery (as printed on the side). They occasionally got mixed up with no ill effects.

That said, I did take time to organize them into 'groups' and label them appropriately (same as my camera batts). I figured that the differences in labeling usually comes from slight changes and revisions in the manufacturing process, designed structure, and/or tweaks in the chemistry (the addition of trace elements for example), and that while the net differences probably wouldn't be enough to cause any significant problems, it was best to play it safe. As pointed out, the interior of an operating flash is a confined, hot place.

However, of far greater importance is the quality of the charger. The Maha Powerex 8 cell is my primary unit of choice, w/ a smaller Duracell 4 cell unit as a backup/supplemental unit. Both address the two critical features of a modern NiMH charging unit. 1) charge time/power/algorithm - a fast charger is a requirement to optimize the life and charges of your NiMH batts (slow niCad chargers will kill them dead - quite rapidly) - 'dumb' chargers may not as fast, but will still kill them, The algorithm is critical because it varies the charge amount as the cell's voltage increases - very important. 2) individual cell circuits - So if you have a bad cell, it doesn't kill other batts, and the algorithm can be applied to each cell individually - allways less stressful on each batt. (for example with a series charger - bad - the charge is applied across all the batts, and the charger only reads the 'total' voltage - so a bad (low) cell makes the other batts take a higher charge (bad))

craig_meddaugh · August 7, 2012

William W,

I hate parsing posts, but science is nothing more than a collection of opinions hopefully rooted in truth (too often this turns out not to be the case, but this is hardly the forum for that sort of thing).

I do apologize for my lack of nuance and you are completely correct in asserting that mixing capacity will increase the risk of some undesirable outcome. However, this increased risk is so low as to be absolutely nothing to worth worrying about as the cost of reducing the risk far outstrips the cost of a new flash multiplied by the very, very low probability that something unfortunate happens.

As we all agree, cells vary substantially as to their actual capacity. This is true out of the box and certainly true after more than a couple cycles of use, even when used together as a "set." Thus, if you or anyone else is truly concerned about the issue of mismatched cells, your only choice is to buy several charger/testers (even the fastest take about an hour for discharge/recharge cycle) to manage all of your batteries. This has to be done prior to every shoot and each battery will somehow need to be labeled with its actual capacity and grouped in such a way that you don't inadvertently mix things up when pulling new batteries from your vest.

This sounds like a lot of work to reduce an already tiny risk.

Just as a general note I actually played with some batteries today and the best I could do was to get a discharged low capacity battery slightly warm by pairing it with three fully charged higher capacity batteries. I'll experiment with different loads on the circuit tonight, to see what it takes to create problems. Also, just for grins, I'll also be testing some batteries to destruction to see what sort of current flow is necessary to get a cell to actually vent.

As a note, I tested a selection of my cells last night and I found a lot of cells that were well down from specs (a couple were no longer holding 1000 mAh... these will be the subjects for tonight's experiment) and a lot of cells that remained at spec. I've been mixing and matching these in multiple flash setups (typically with external high voltage packs) for years with no problems. Again, we mismatch cells, intentionally or not, all of the time and I haven't seen or heard very many horror stories.

William Michael · August 7, 2012

Two notes:

I also am not generally keen on dissecting the words either – and I did not do so to either elicit an apology nor to criticise your commentary – but to make my point clear and because I believe my point (more importantly the point of the difference) is important.

Hopefully Science’s opinions are as a result of best practice trials and observations.

.

My response:

Craig,

I understand that you are stating there is ‘minimal risk’: that was understood from the beginning; I mentioned I have mixed batteries of different capacities; I also understand that these AA NiMH batteries age differently and there are manufacturers’ tolerances for the ‘bought new’ battery anyway...

.

I appreciate your testing – I really do. I would conclude and concur with you that your tests (and your experiences) add weight to a ‘scientific opinion’ that there is not much to worry about.

On the other hand (and by co-incidence peculiar to the 580MkII): I have knowledge of three 580MkII’s frying and several overheating but cutting out before frying. One 580MkII (not mine) I have seen fry.

I had one 580MkII (and sold it) and I could make mine overheat and cut out quite easily: there are quite a few threads about this phenomenon of the 580MkII getting hot and cutting out ‘more easily’ than the 580 (original).

The 580MkII which fried in front of my eyes, upon a cursory look, did not seem to have any battery damage – though the batteries were quite hot – and I do not know if the batteries were mixed capacity or not: the main task was to get a back-up unit operative and to keep shooting.

I am NOT suggesting that the three 580MkII’s which I know fried were a result of mixed capacity batteries venting – I am saying that Flash Units can, (depending upon how the Flash is used) get hot and the batteries inside also can, (depending upon how the Flash is used) get hot – and the batteries are in a confined space.

And I am also saying that the overheating & cut out circuitry of flash units generally, could fail.

Also I am NOT saying the OP will use a 580MkII with HSS and plant his index finger on the shutter release until the 580MkII shuts down (or fries).

I am just saying there are variables: and I now the smell of a burnt Flash Unit and the feel of hot batteries.

On the issue of being very concerned and testing battery capacity each night and buying a laboratory full of gear to do that testing – I admire your wordsmithery: it was a good read and taking an extreme is an easy and colourful way to make good a point of view.

But, if you re–read all which I have written on this thread I was never suggesting any of that every night testing – but rather as making the very precise point that mixing battery capacities makes the risk of a mishap, greater.

Regarding the salient point about the amount of effort required and if it is, or is not worthwhile – this is my response:

To buy batteries in sets of four and label them and keep using them in those sets of four is really pretty simple to do – there is NOT that much effort involved, especially for use in a Flash which uses four batteries. Also there is not all that much effort required to use a good quality charger, either.

So taking all that into consideration and whilst acknowledging that there is an initial minimal risk of damage anyway; the two questions I believe that this tread is all about are:

1. Can mixing Battery Capacities risk damage (or raise the risk of damage)? – the (technical and factual) answer is that question is -

“Yes”

2. Is it worthwhile to buy and then to keep my batteries in equal capacity sets of four for use in my 580MkII? – (my opinion based upon all I have written in several posts here) is:

"sure is and why not do that anyway? - it is pretty easy to do and is more than a modicum of best practice, anyway."

WW

William Michael · August 7, 2012