What exactly is meant when the batteries warn you that they may explode if you mix them with other types? Does that mean a Duracel and an Eveready?
Also, has there been a test done on the ratio of power to cost for different batteries that would answer the question, “Should I buy fewer expensive ones or more cheap ones?”
Don’t know about your first question, but I did find something comparing the cheaper batteries to the more expensive batteries once. I couldn’t find it now for the lif of me, but it said that brands such as Duracell and Energizer do last longer than the cheaper brands, but not by much, and that buying more of the cheaper brands is a good idea.
It may refer to the fact that if you mix batteries, not only brands but, more importantly, exhausted ones with new ones, the dead ones will be polarized in reverse by the new ones.
Regarding cost per unit of power, I believe Consumer reports did a study a few months ago. I have done my own tresearch on this and it is difficult to say because, while the price is easy to establish, the amount of power you get is not disclosed and is subject to many variables.
In general terms though, size does make a difference. In general I have found:
Sizes AAA and AA tend to cost about the same. Obviously, Siza AA has more energy. Likewise, sizes C and D tend to cost about the same and size D has more power.
In a study I did recently with Duracell batteries I determined size AA costs 40 cents per Ah and size D costs 10 cents per Ah. Not only that but you will get more than the rated Ah from a bigger battery than from a smaller one. My digital camera eats AA batteries like they’re free so I have prepared an exteernal battery pack with D size batteries and I carry it in a belt pouch. It works great. In general gadgets have batteries that are too small for them because if they had bulky, heavy batteries, people would not buy them.
I could be totally off base here, but I don’t think there’s an explosion hazard if you mix alkaline and zinc batteries, since a) both have the same nominal cell voltages, b) the energy density for either is not very high, and c) the internal resistance for either is not untra-low, thereby limiting the current if short-circuited. Now with NiCd or NiMH it’s a different story… all I know is that you never want to short one out, as lotsa current will flow due to its low internal resistance. Since P = R*I^2, the battery will rapidly heat up, which is not a good thing to put it mildly.
As far as safety goes, the batteries that concern me the most are lead acid. I think they’re flat out dangerous.
As regards the use of cheap/expensive batteries.
No easy answer, batteries are designed for differant outputs over differant timescales, so one battery might be able to put out lots of power in a short time, and another might put out less power over a longer time, but the total energy output of both may be the same.
Dry cell batteries contain chemicals called depolarisors, which clear up oxides that are deposited on the electrodes during use, but if you use the battery too hard then those oxides will form a thicker insulating layer over the electrodes, reducing output and the depolarisors cannot cope, often it is not the fact that the electricity producing chemicals have been used up that limits the life of a dry cell, instead it is either using it in the wrong application or using up the depolarisor chemicals.
Generally it is best to use any dry cell in low current applications and leave a longish break between uses, my radio/alarm goes off every day and runs the radio for maybe half an hour and yet the battery lasts for months, the 24 hour break between uses allows the depolarisors to do their stuff.I use alkaline cells for this purpose.
Things like camera auto-winders and flashes present problems because they may be stored for many months and then called on for an intense short period of use, and then stored again for months.It is a good idea to use lithium cells for this.
Lithium cells are expensive but they have a very long shelf life and are sometimes used in c-mos memory power backups.
There are units that ‘recharge’ chemical dry cells, in fact what they do really is to assist depolarise them which increases their life by allowing them to use up their ‘fuel’ more fully.
Mixing differant types of cell or cells with differant ages is a bad idea.
Batteries have an internal resistance(due to the polarisation of the terminals - yes its that important) which increases as the cell ages.The internal resistance limts the current that can be produced, and if a short circuit should occur then this will prevent the cell overheating and possibly exploding or at least leaking out chemicals inside the appliance.
When you mix differant types of cell, some of them may be designed to withstand the higher current, but others may not and these are the ones that can overheat.
Mixing the ages of cells means that you may end up with a cell in position long after its useful life, and although the appliance may be operating from the good cells, the old one may be leaking unkown to the user.
You can get information about the power available from a dry cell(usually in trade catalogues or in, say, Radio Shack catalogue), it will be in the form of X amps for X time, or more rarely in joules, obviously the bigger the number the better, but…
There will also be information upon the maximum discharge current too, so even if a battery is rated at 1Amp/Hour the maximum discharge rate may only be 200milliamps so in theory it should last 5 hours at that rate, but of course using it at that level may mean that the depolarisors will not work as well, you may then get a much shorter life out of it.As a general rule you do not wnat to use a dry cell at more than 2/3rds its maximum current, and remember to give it a rest too.
Crafterperson
Nowt at all wrong with lead-acids in the hands of those who know, and the safety precautions are not that onerous.
Put any equipment in an environment among the uninformed, or just plain stupid and accidents will occur, one has to take responsibility for oneself by making sure of the facts, seems to be a dissappearing philosophy in an increasingly litigious society but it has worked for me up to now.
I think sailor had it with mixing old and new batteries. The new battery would be doing more of the work and heat would
build up over time. “Explosion” is probably too extreme a word, it would probably just be the expanding electrolyte cracking
the case and leaking, but it’s still not a good thing…
But “exploding batteries” gives me a chance to pass on a warning - a few months back I put my key in the ingnition, turned
it, and was greeted with a loud pop and smoke coming from under my hood. At first I wondered if someone had rigged a firecracker
to my engine, but after popping the hood I found one of the caps blown off my battery and the casing cracked. When I went
to the auto supply shop, the guy at the counter said this was not an unusual occurance in Texas in the summer. Apparantly
water will evaporate and seep out, and eventually if a cell gets completely dry, with no acid to transmit the charge, the
resultant spark will set off the remaining gasses.
So, if you are driving a car in a warm climate, and you’re not using a sealed battery, watch that water level!
Consumer reports looked into if name brand batts were worth it - their conclusion was no - go w/ the cheapest alk. as long as it is fresh.
For AA - visit some PDA forumns- they go into discussions of how long various batts last. The short of it is:
1 lithimn is the best but most expensive and the extra run time doesn’t justify te cost.
2 Ultras do not give you longer run time in pda’s (some claim they do but most claim otherwise) - they are designed for high drain devices.
3 hi opal
4 No name alks will have a slightly shorter run time perhaps 1 hr in 20hrs - but also greater variation (name brand will work on average 20-21hrs while no name brand will last 18-21 hrs).
5 Nimh rechargables (1600 mah) will last about 2/3 the life of alks in low drain devices but will actually last longer in high drain devices.
6 NiCd (650 mAh) will last about 1/2 that of Nimh’s in low drain devices. (remember the rating is under certain conditions actual device conditions will give you diffrent mAh runtime)
7 Rechargable Alk’s gives you alk voltages and about 1/2 the run time of normal alks. You get about 10-20 recharges before they can’t be recharged.
If the price per unit runtime is all that matters, Here’s the order (again assuming low drain):
Nimh<NiCd<Rechargable alk<no name alk<name brand alk<lithimn
NiCd and Nimh are about the same though and much cheaper then any other. Carbon zinc I would guess would fall between no name alks and name brand alks - not many pda users use them. And the above does include in the price a decent charger and assumes numerous recharges for NiMh and Nicd and max recharges for rechargable alks including replacement cells used in hte charger.
Agian most of this is from memory so I’d advise you to check for your self.
As an ex-Radio Shack Manager I would advise you to purchase your batteries from a busy Radio Shack as they are likely to be about the freshest you can get (this assumes the manager is competent and brings batteries forward on the peg if a new shipment arrives)
With respect to smaller batteries exploding this does happen but typically with the higher voltage small batteries. Once, after hours, I was in the back office and heard an explosion that sounded like a firecracker going off. It was a used dog collar “shock” battery that had been left on the counter when the customer came in to buy a new one. It had literally exploded like a firecracker all over the front counter area. I suspect the customer might have put the battery in backwards for some time before he removed it.
I bought a couple of packages of Panasonic AA batteries at the dollar store (3 batts for a buck) once. Found that the old adage “ya get what ya pay for” is quite true with cheap batteries. Used them in our 2-way radios on a birdwatching trip, the cheap batteries barely lasted 3 or 4 hours on standby before I got the “bat low” beep, whereas with expensive energizers, I’ve gotten 20-30 hours of standby, an entire weekend’s use.
Now I only buy fresh top of the line batteries and also I store them in the fridge before use, as I have been told that keeping them cold extends life.
gingersnap I would guess you got either very old ones or not alkaline (carbon zinc).