long lasting battery

----- Original Message ----- From: "Robert Baer" Newsgroups: sci.electronics.design,sci.chem.electrochem.battery Sent: Monday, February 26, 2007 10:31 PM Subject: Re: long lasting battery

Off the top of my head :) which is why I left the current draw as a variable, since I didnt know what type of converter he would be using to get his target output.... And I assumed that there would be at least a fair amount of current draw because he mentioned AC mains power as his primary power source... we found out later that the load was 1/2 watt or so, which makes some of the features I tossed in unneccessary -- but the overall architecture of the system still applies to his application. And for his specifications.. he still needs a system that can deliver 100 watt/hours ... which, in my opinion, still puts him in SLA territory based on the costs for the large quantity of cells needed to provide the capacity with other battery technologies.

it depends how much power you need, it's conceivalble that a 6V alkaline lantern battery would last the distance.

Otherwise you're looking at some sort of rechargable, and lead-acid of some sort will be the cheapest way to go - probably a sealed or gel type.

On Feb 26, 3:20?pm, "John Barrett" wrote: solar?

I agree. Recognizing we don't yet have enough from the original poster to go on.... Solar power, when done correctly, is about as reliable as anything else I've seen. Unless you have a constant source of sunlight (or equiv), then yes, you would still need a storage mechanism (batteries, caps, etc..)

Our own product uses solar. Other than the occasional dead panel that arrives from China, we have ZERO problems in the field. (That includes ice and snow, BTW) AND, our design can run simultneously via a wall-wart, though it is never necessary to do so. There's a blocking diode in the panel, so it's rather trivial to parallel them with a switcher, etc... You put the regulator downstream. No big deal.

Note to OP: For onesiew-twosies, try

HOWEVER, if the poster's application is outdoors, you have other more important things to worry about which may not be immediately obvious:

#1 - Lightning Damage - which small solar panels definitely do a better job with IMO. #2 - Local building codes would likely require a GFCI breaker or outlet to "wet" locations (i.e., outdoors). Anyone whose played with these knows about nuisance tripping. (A solar panel overcomes this.) #3 - It is often much cheaper to install solar. No electricians, no permits (usually), etc...

Not to mention, over the long term, it might even be environmentally friendly! So, with that said, don't be so quick to rule out Solar.

(I do admit however, that none of this addresses the issue of a 10- year storage battery.)

-mpm

NiMH does not last 10 years, just because of alloy electrode corrosion, even if you don't do any cycling.

Regards, Evgenij

LiPo - 10 years service? You must be kidding. It will be down by 30% of useable capacity in 2-3 years. The only real shot at 10 years service he has are special grade lead-acid batteries, assuming they will be most of the time in charged state, and occasionally maintained by adding water (although glass-mat or gel cells might work even without maintenance).

Regards, Yevgen

NiCd - at least many of them - lasts 10 years.

I'd first ask if the 'sensor' really needs 400mW all the time. Or if it'd work for 400mW, 1 second a minute.

That entire post is just *so* wrong I wouldn't know where to start to put it right.

At a guess i'd say as a metal hydride :)

Bye. Jasen

And for NiMH you'd be right. How 'bout in the Ni-H2 of spacecraft- literature mention though -- is that the same thing? I'd guess it likely is, but couldn't confirm it.

Best, James Arthur

It is not. They could not afford to carry heavy metal-hydride (and good alloys were not available at that time). So they just used H2 pressurized in a cylinder. It was half-fuel cell, half battery. Anode was porous, set with Pd catallyst and exposed to H2, while anode was NiO(OH)2. These batteries are awesome in terms of longevity, but rather expensive due to catalyst and overall balance of plant (BOP) - cylinder, pipes, manometers etc that handling of high pressured H2 requires.

Regards, Evgenij

^^^^^^cathode

NiCd lasts when really really deep cycled (discharged 99%) at least 50% of the time. Of course if your transponder must stay up, you need two battery packs and sufficient recharge capability for the deep cycling required.

NiMH handled similarly might last as long.

LiPoly (phosphate) a relatively new battery type may be the ticket, but they are very expensive and do not tolerate discharge below 60% very well.

Not by track record; see "battery university".

Not true. Maximum life from NiCd comes from deep cycling every cycle. My dad did the reliability studies 40 years ago. A lot of existing sattelites use two banks of of NiCd this way.

NiMH questions? Google for it.

Yep, that is their forte. Possibly in a decade some variation on Lithium will beat it is watt-hours per pound-year life.

Thanks for that concise, lucid clarification.

Best wishes, James Arthur

I'm not an expert, I'm simply repeating what I've read. For example, the table on page 4:

Since you're the second person to misinterpret my remark, I'll explain it: I wasn't sure how Ni-H2 cells stored their hydrogen, whether as a metal hydride--as NiMH cells do--or some other way. With help from my internet friends, it turns out "some other way" is the case: Ni-H2 NiMH.

Best regards, James Arthur

I had seen a reference before; this made me look. The technology is completely different. NiH2 requires pressure vessels that will hold at least 900 psi (65 bar). Eagle Picher is a manufacturer.

Bless Google, it makes learning things easier (by finding the information fast) and richer (by finding the contrary information just as fast).

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Lead Acid car batteries often last 7 to 10 years or more here in our abusive Canadian climates.