I'm working on a battery-powered bit of kit for a client. His old system was powered by lead-acid batteries, and while we don't feel a need to retain continuity for continuities sake, we should think before we step away from what's been done.
Does anyone happen to know what the deal is with RoHS and lead-acid batteries? Do you get a pass on that, or is there some well-structured way that you can use them in a product 'cuz they're rechargeable and therefore "green"?
If lead-acid batteries are considered to be Evil by the RoHS community I guess I'll be driven to NiMH or LiPo cells -- but those each have their technical and/or regulatory problems.
We need about 10kJ of energy storage (500mAh at 5V, more or less). Something that works from freezing to +55C is essential.
Comments & suggestions welcome.
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Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Some leftist will have to tell us when lead is not lead >:-} ...Jim Thompson
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| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
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| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
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I love to cook with wine. Sometimes I even put it in the food.
Inertia. The previous generation used sealed lead acid, therefore ...
Our energy needs may go up: we haven't finished dreaming up all the bells and whistles yet, but I think we can keep the energy usage low.
My personal preference would be LiPo, as long as a user can put this thing into checked baggage and fly with it, but the customer is pretty active in decisions like this, and I like to come to the table with at least all options considered.
(I like this customer -- he's active about this stuff in a good sort of way, that makes me look better. He doesn't make arbitrary decisions just because that's how it was done before, or that's what's in the latest Omni. He does sometimes disagree with me, but he usually has good reasons. We pull in slightly different directions but we both believe in studying up before we jump up and down in disagreement -- and as a consequence, his product gets better.)
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Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
I assume you need a recycling, do not throw into the waste stream instructions on the battery, compartment and manual. I think thats all that is required for REACH compliance.
I wouldn't build Sparkfun stuff into a product, but I've got some of their tools on my bench, and their USB to TTL-level serial devices are nifty. And I often look at what they're doing for inspiration.
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Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
0.5Ah is a rare SLA. Are you using such thiny things, or is it power sharing from a bigger battery?
My kneejerk reaction would be NiMH. At that sort of capacity its very cheap, and you get lots of cycles. I know they manage 55C, but don't know what effect it has on life expectancy. SLA is fussier, so more product use restrictions if you want decent life.
I can't cite chapter and verse, but: I don't think RoHS bans lead-acid batteries totally. If you use one, you probably have to at least put the "crossed out trash can" and "Pb" on the label somewhere. I think there might be some language to the effect of "please don't use one if you don't really need it", but I don't know if you have to justify your choice in some way.
My first thought was one or two Eneloop AA NiMH batteries. One is almost enough (1.2 V, 1900 mAh minimum) and two should be plenty. They almost meet the temperature spec (charge 0 to 40 C, discharge 0 to 55 C), and they are shipped at about 75% charge. Install them with one of those plastic tabs that hangs out of the battery door with "pull here please" written on it and your gadget will be ready to go as soon as the end customer gets it. You may or may not need this feature, but this also gives the customer the ability to stick a couple of alkaline AAs in it if they have a dire need. (You either have to buy a charger chip that's smart enough to not charge alkalines, or put in some kind of overvoltage cutoff so that alkalines won't work.)
I have run Eneloops in my pointy-shoot digital camera for about 3 years now and they seem to perform as advertised.
I'd bet a nickel that they are currently using something like an Enersys (formerly Gates and Hawker) "Cyclon" sealed lead-acid cell - the ones that look like fat D cells with two tabs on the top. (These seemed to be real popular from maybe the mid-80s to the mid-90s.) You can get those in 2 V increments and in 2.5 Ah to 25 Ah sizes, and they work from -65 C to 80 C.
One drawback here is that I think you have to ship batteries like this disconnected from the product (an off switch may not be enough), and you may have to put huge "nonspillable battery" labels on the packaging. If the customer is used to hooking up the battery on receipt, then shipping it disconnected is not such a big deal.
I haven't run Cyclons in anything, but I used to work with the (mechanically different) Genesis batteries from Enersys, and they really did do what they said, in traction service.
Standard disclaimers apply: I don't get money or other consideration from any companies mentioned.
Lead is perfectly fine when it is used in large sheets to channel the acid rain off a church roof. It only becomes toxic when you plate it onto the ends of an 0402 surface mount capacitor. Similarly if you mix lead into steel for better machining properties then when the steel rusts in a ditch, the lead turns into rainbows and flowers, because the steel wasn't electronic.
Shouldn't, but is. Try taking an iphone to a post office or courier in Australia and sending it overseas. The post office will flatly refuse, but some couriers will agree, provided you let their special export packer pack it for you, with the corresponding fee. Same goes for single primary lithium coin cells that were perfectly fine all through the 80s and 90s but are now almost treated as WMDs. Whilst there are probably regulations that say that the lithium batteries are fine, and Apple and Samsung would know how to make use of the exemptions, for a small business it is easier to design out the lithium battery, or just refuse to deal with Australian customers. Unfortunately there are probably other countries with similar rules. So far they haven't thought of over-regulating the transport of supercaps, but I'm sure there will soon be a mandatory Certificate of Dischargement that you'll have to buy from a special discharging inspector, whose place of inspection is conveniently located slightly further away than wherever you wanted to send the device to.
I ordered a replacemnet laptop battery from a HK supplier on Alibaba price was good, delivry was "60 days" by post, it arrived in a box with the usual red "lithium battery" warning label label, the box was inside a padded envelope with no warnings on it.
Ok, maybe the crap only occurs shipping FROM Australia, or maybe they had the right paperwork to convince HK post that it was fine, or maybe the padded envelope with no warning labels on it did the trick. Probably within Australia putting false information on the declaration form would get it through, but you might also get in trouble.
Still, if the battery is just a small part of a much more expensive and urgently needed item, e.g. the real time clock of a server or something, then it could be a hassle. It has greatly inconvenienced me when trying to send something to an overseas test lab.
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