Checked with our radio guy for our solar sites. He's kind of a battery nut. Lead-calcium, Lead-Lead, and Lead-Antimony, constant current, constant voltage and "smart" chargers. He and I also have an old ford tractor farm upbringing, generators, relays, and the new fangled stuff. In the 15 years here I've been involved in our remote telemetry sites I've soaked up more bad information than you can believe. I'll try to put what we "believe" to be somewhat true. You millage will vary, too much religion in the battery trade for me. Car batteries. Lead antimony older, and lead calcium later in years. The calcium containing batteries really have a poor tolerance regarding discharge. And they put up with being charged in a brutal environment at rates that make a welder blush. The plates shed and swell, causing flaking, and in extreme case, plate cracking during the charge discharge cycle. The plates are thin, the separators are thin, to get more plates per pound for cold cranking amps and really fast charging for mom's trip to the store. Quality of the calcium auto batteries is almost always plate thickness and separators. Even a controlled discharge to %25 remaining charge and immediate recharge at a slow rate will damage the capacity of most of the calcium batteries, as much as reducing the capacity %25 or more. I "believe" that the average car battery design is all about $$ and environmental impact. Not so much about life, or robustness. Very hi discharge for a very small % of capacity, and a really fast rec harge. Lead antimony plates. Not sure, but I think it was more when and how thick the plates were, but anyway, they were more robust, did not shed as much during the charge/discharge cycle, and could be (can be) discharged much deeper and recover %100. I've read somewhere in my lost memory that the plates did not shrink/grow as much as the calcium containing plates. Lead plates. Don't know much about them. We've had some, last a long long time, heavy and low capacity per weight. Old information, don't know much about the new thin ones with starved electrolyte. (gassing control) Chargers. Old chargers were current limited constant voltage at around 14.6. Boiled the batteries, add water as needed. New alternator systems are a really mixed bag. Some are current limited constant voltage, some have a current limit and when the voltage exceeds the 14.6 range they "knee" back to something a bit less than 14 volts. The smarter chargers will charge current until the voltage reaches a temperature dependent point (14.8?), and then go back to something about 13.6 or 13.8 depending. Some of the better smart chargers are a constant current, with a trip point at something around 14.6 or so to drop back to a float (constant voltage). The best charger I've seen for starved electrolyte lead cells did a temperature, time, smart charge thing. Charge at something like the 20 hour rate until the voltage increased to a set point, then did a constant current charge for %40(?) of the cell capacity, over and above the "full charge". Then did a float at 13.4 or some lower number. Expensive, but with the "gel cells" type starved electrolyte he could get very close to %85/90 useful capacity for his glider The cells we've been using as of late for the remote sites are still the Delco 2000 series. The new cells are a lot different, and don't seem to last quite as long as the older ones, but trying to stay affordable at some level. Someplace I've got the pdf of this cell,,, can't find it, but I think the 2000 was a mixed plate. Cornell university had a nice paper on deep discharge "off grid" battery information. They had the three stage charge graph, I think they called it load, soak and float or something silly like that. -----Original Message----- >From: Marcel Duchamp >Sent: Oct 6, 2008 6:19 PM >To: "Microcontroller discussion list - Public." >Subject: Re: [EE] Lead-calcium batteries > >Brent Brown wrote: >> On 7 Oct 2008 at 10:12, Jinx wrote: >>> So car batteries with calcium certainly do exist. In fact it may be that >>> most automotive batteries sold will be lead-calcium or hybrid >>> >>> If that is so, then what confuses me slightly are the charging voltage >>> figures. AFAICT, no battery I've looked at so far has a "Recommended >>> Charge Voltage" figure on the label, so you may be innocently over- or >>> under-charging >> -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist