I once had an electric outboard motor for a canoe, and was told that it needed a deep-cycle battery, that was designed to be fully discharged and then re-charged. In this it differed from a car battery, which is meant to be kept near full charge all the time. I can see the logic in this. My Wildview motion-sensing camera, which runs off four C-cells can also be powered by an external 12Volt battery, which can be had from the U.S. at enormous expense. I occurs to me that I could use a motorcycle battery or perhaps a battery from a powered golf-buggy. It seems to me that the Wildview is used in such a way that a deep-cycle battery would be more appropriate than a motorcycle battery. Is this the case, and if so, is a golf-buggy battery a deep-cycle battery? Or, is there a better option? The camera is left out in the bush for a day or two at a time.
Regarding "standard" and "deep cycle" versions of batteries, the battery technologies are basically the same, they just fiddle with the chemical and physical makeup a bit to ensure it will stand up to deep cycle abuse better. And you pay a premium for this.
Hmm, I imagine it's just deep cycle lead-acid of some specific size, or within some specific connector that "mandates" purchase at great expense from the manufacturer in question. In other words, it's ripe for options.
Yes and no. They are wet type lead-acid batteries, and while that doesn't stop them from working of course, the risk of spillage during transport and handling will lean you towards some flavour of non-spillable battery instead.
Maybe. However, if you're salvaging a battery from a buggy, the fact that you CAN salvage the battery probably means it's done it's life already.
Though if the buggy battery is free, I'm quite sure you can't complain about battery life.
You have a number of options:
Lead acid (sealed or otherwise, deep cycle or otherwise) might not be the "best" battery technology choice for the job, but it certainly is the cheapest. In the shorter term anyway. Remember, you have to factor in the cost of the charger too!
NiCad has a decent enough charge storage life and is reasonably cheap. But contains cadumium which is damaging to the environment. If you care about that. (If they keep selling them, it means people keep buying them).
NiMh is not as good as NiCds as far as battery life storage life goes, but it makes up for it in capacity per volume. And costs a bit more than NiCd.
LiIon has a terrible charge shelf life, but again, it more than makes up for it with obscene storage per unit volume. It's also so expensive that it'll make your wallet run for cover. LiIon also doesn't cater for Joe-Average either as far as "a black box that puts out 12v" goes. Great for DIY engineers who eat this stuff for breakfast, (because you have to design the charger yourself as well) but little available off the shelf.
Plus apparently identical NiCd cells are in fact horribly variable in their self discharge rate and change over time and with usage. If ever a NiCd cell is significantly heated by over charging, its self discharge rate goes through the roof.
The above two facts account almost entirely for the mysterious but non-excitant "memory effect " so often complained of with NiCds.
** Shame you dipped your brush in a bucket of diarrhoea.
** My remarks apply to all NiCds - even the best ones like Sanyo.
** They mean that there is actually a gradual loss of max capacity over several years, instead of self-discharge, ie internal current leakage.
What's the battery life with the existing C cells? Alkaine D cells would offer improved capacity. You could make up a pack that connected to the 12V battery connector (mindful of the operational voltage range on that connector of course).
In that case a 12V pack of Alkaline D cells might give you very roughly, about 8 times that life, say 16 days. If you only used it say that many days a year, a non-rechargable solution like Alkaine may be better. Also other factors like charging can be annoying if you forget for instance. Also, you don't know how efficient (or ineffecient) the internal converter is, it needs to drop the external 12V to whatever is required by the internal circuitry. That will have an impact on whatever solution you choose.
I know, I'm sure I replied to Phil's first post, but it seems lost somewhere. (where do all those bits go?)
I had read, seen or heard (can't remember for the life of me) a bazillion years ago that LiIons were not that great on the self-discharge area. And never having to work on them, I never bothered to actually check that. :-\\
On Sat, 21 Feb 2009 12:42:01 +1100, John Tserkezis wrote: (snip)
John, you are waaaay off track if you actually believe that.
Back during the evaluation of a commercial Li-Ion charger I designed back in (crikey!) 2003 I did some cyclic charge/discharge working on packs comprising
18650 size cells. They are still sitting on the workshop shelf where they finsished up charged to 4v20/cell on 23 Feb 2003.
I routinely check them about once a year, in case they drop below the 3v0 protection module cutoff.
Just checked - all cells still around 3v85.
Let's see - about 30% in 9 years, or 0.3% per month, and that's with the minute but measurable parasitic load of the pack protection module. Beats the hell out of lead-acid or any Nickel chemistry I've seen.
I'm pretty sure it uses a bit of power to keep up a clock, and empheris data and perhaps other crap like l^Huser setup and such. Though this is not exactly a high energy application, so a week does seem a bit short. Bad design dare I say it? Have I mentioned I'm not fond of TomTomTom?
Yep, depends heavily on design as far as I've seen, some devices keep an lcd display on all the time, and still last quite a significant time (some months for my slr camera), and other things that barely keep up a clock can't seem to last a week or two.
My embedded GPS module uses 2 AA batteries for empheris data upkeep. I can't remember the current draw details (long time ago), but I do remember it was a tossup between shelf life of the alkaline batteries and enough current draw to battery depletion. Basically, I knew that once I put them in, they weren't coming out.
Adding a clock to the mix really can't be too much worse, and perhaps some more sram for general user data storage (additional points, stored routes, tracks etc).
On the other side, I've seen some car clocks that are quite rude with their power consumption. Three lines, ground, +12v, and another +12v to actually light up the display, thus allowing a low power mode when otherwise off. The "low" power mode took several tens of milliamps. I don't care who says what, that's just not on.
If it isn't in the microamp range, they've done something very, very wrong.